2024/10/08 更新

写真a

ノノムラ タク
野々村 拓
NONOMURA Taku
所属
大学院工学研究科 航空宇宙工学専攻 空力・推進 教授
大学院担当
大学院工学研究科
学部担当
工学部 機械・航空宇宙工学科
職名
教授
外部リンク

研究キーワード 5

  1. 縮約モデル

  2. 流体音響学

  3. 流体力学

  4. 流体制御学

  5. 実験空気力学

研究分野 1

  1. フロンティア(航空・船舶) / 航空宇宙工学  / 空気力学

現在の研究課題とSDGs 3

  1. データ駆動型スパース流体制御

  2. 大規模自由度場のセンサ・アクチュエータ位置最適化

  3. 高速流体場の時空間超解像計測

経歴 5

  1. 東海国立大学機構 名古屋大学   大学院工学研究科   教授

    2023年11月 - 現在

      詳細を見る

    国名:日本国

    researchmap

  2. 東北大学   大学院工学研究科   准教授

    2016年8月 - 2023年10月

      詳細を見る

  3. 宇宙航空研究開発機構   助教

    2011年4月 - 2016年7月

      詳細を見る

  4. 宇宙航空研究開発機構   プロジェクト研究員

    2009年4月 - 2011年3月

      詳細を見る

  5. 宇宙航空研究開発機構   日本学術振興会特別研究員

    2008年4月 - 2009年3月

      詳細を見る

学歴 2

  1. 東京大学   工学系研究科   航空宇宙工学専攻

    - 2008年3月

      詳細を見る

    国名: 日本国

    researchmap

  2. 名古屋大学   工学部   機械航空工学科

    - 2003年3月

      詳細を見る

    国名: 日本国

    researchmap

所属学協会 6

  1. 計測自動制御学会

    2021年12月 - 現在

      詳細を見る

  2. 可視化情報学会

    2019年1月 - 現在

      詳細を見る

  3. アメリカ航空宇宙学会

      詳細を見る

  4. 日本航空宇宙学会

      詳細を見る

  5. 日本流体力学会

      詳細を見る

  6. 日本機械学会

      詳細を見る

▼全件表示

委員歴 9

  1. American Institute of Aeronautics and Astronautics   Fluid Dynamic Technical Committee  

    2020年3月 - 現在   

      詳細を見る

    団体区分:学協会

    researchmap

  2. 日本流体力学会   理事  

    2024年4月 - 2026年3月   

      詳細を見る

    団体区分:学協会

    researchmap

  3. Editorial board of Transaction of Japan Society of Aeronautics and Space Science   Editor in Cheif  

    2023年5月 - 2025年3月   

      詳細を見る

    団体区分:学協会

    researchmap

  4. 日本航空宇宙学会   編集理事(論文)  

    2023年4月 - 2025年3月   

      詳細を見る

  5. 日本航空宇宙学会   論文編集委員会  

    2021年4月 - 現在   

      詳細を見る

  6. 日本機械学会   流体工学部門委員  

    2021年4月 - 2023年3月   

      詳細を見る

  7. 日本機械学会   宇宙工学部門委員  

    2020年4月 - 現在   

      詳細を見る

  8. 可視化情報学会   可視化情報学会誌編集委員  

    2020年3月 - 現在   

      詳細を見る

    団体区分:学協会

    researchmap

  9. 日本流体力学会   ながれ編集委員  

    2017年5月 - 現在   

      詳細を見る

    2021.5より学術担当幹事

    researchmap

▼全件表示

受賞 19

  1. 一般表彰(貢献表彰)

    2023年7月   日本機械学会流体工学部門   PA研究会主査;幹事

    瀬川武彦, 深潟康二, 松野隆, 野々村拓

     詳細を見る

  2. NASA Group Achievement Award

    2023年4月   NASA  

    STMD Early Career, ROAMX Team

     詳細を見る

  3. 最優秀賞 流体力学部門

    2022年11月   日本航空宇宙学会/航空宇宙数値シミュレーション技術シンポジウム   圧縮性低レイノルズ数流れにおける平板上の層流剥離泡および乱流遷移に対するマッハ数効果の数値的研究

    永田貴之, 野々村拓

     詳細を見る

  4. 日本流体力学会論文賞

    2022年9月   日本流体力学会   Unified mechanisms for separation control around airfoil using plasma actuator with burst actuation over Reynolds number range of 103 –106, Physics of Fluids, Vol. 32, 025102 (2020)

    Makoto Sato, Koichi Okada, Kengo Asada, Hikaru Aono, Taku Nonomura, Kozo Fujii

     詳細を見る

  5. 可視化情報学会 第33期 学会賞 論文賞

    2022年8月   一般社団法人 可視化情報学会   非定常せん断応力の可視化計測にむけた蛍光油膜法の開発

    Chungil Lee, Taekjin Lee, 遠藤幹太,齋藤勇士,Chen Lin, 野々村拓,浅井圭介

     詳細を見る

  6. アメリカ航空宇宙学会 アソシエイトフェロー

    2022年1月   アメリカ航空宇宙学会  

    野々村拓

     詳細を見る

  7. 日本機械学会流体工学部門 一般表彰 フロンティア表彰

    2021年11月   日本機械学会流体工学部門  

    野々村拓

     詳細を見る

  8. 日本機械学会部門計算力学部門 部門賞 業績賞

    2021年9月   日本機械学会計算力学部門  

    野々村拓

     詳細を見る

  9. 可視化情報学会 第31期 学会賞 奨励賞

    2020年9月   一般社団法人 可視化情報学会   Denoising the Pressure Sensitive Paint Measurement of Unsteady Low-Speed Flow using Extended Kalman Filter Based Dynamic Mode Decompisition

    野々村拓

     詳細を見る

  10. Outstanding Reviewer award of Fluid Dynamic Research

    2020年4月  

    Taku Nonomura

     詳細を見る

  11. ディスティングイッシュトリサーチャー

    2020年4月   東北大学  

    野々村拓

     詳細を見る

  12. 日本流体力学会竜門賞

    2019年9月   日本流体力学会   高速流からの音響波解析のための高次精度重み付き差分法の研究

    野々村 拓

     詳細を見る

  13. 最優秀賞 流体力学部門

    2019年9月   日本航空宇宙学会/航空宇宙数値シミュレーション技術シンポジウム   遷音速バフェットオンセット付近における旅客機翼上の非定常圧力場

    杉岡洋介, 中北和之, 小池俊輔, 中島努, 野々村拓, 浅井圭介

     詳細を見る

  14. 文部科学大臣表彰若手科学者賞

    2019年4月   文部科学省   高精度数値解析による超音速噴流からの空力音響波予測の研究

    野々村 拓

     詳細を見る

  15. AIAA 2018 Aerodynamics Measurement Technology (AMT) Best Paper.

    2018年6月   American Institute of Aeronautics and Astronautics   First Results of Lifetime-Based Unsteady PSP Measurement on a Pitching Airfoil in Transonic Flow

    杉岡洋介, 野々村拓, 浅井圭介, 中北和之, 斎藤健一

     詳細を見る

  16. 所長賞

    2015年12月   宇宙航空研究開発機構宇宙科学研究所   超小型深宇宙探査機(PROCYON)の開発

    超小型深宇宙探査機技術実証チーム

     詳細を見る

  17. 日本航空宇宙学会若手優秀講演賞

    2015年4月   (一社)日本航空宇宙学会   「乱流遷移する超音速ジェットからの音響波の定量予測」

    野々村 拓

     詳細を見る

  18. 第27回数値流体力学シンポジウムベストCFDグラフィックス・アワード第2位

    2014年12月   (一社)日本流体力学会   「回転するタイヤ周りに発生する空力音の数値解析(Re=100,000)」

    阿部圭晃, 野々村拓, 近藤勝俊, 飯田大貴, 渡辺毅, 池田俊之, 小石正隆, 山本誠, 藤井孝藏

     詳細を見る

  19. 第21回数値流体力学シンポジウムベストCFDグラフィックス・アワード第一位

    2007年12月   第21回数値流体力学シンポジウム実行委員会   「ロケット音響予測に向けた超音速ジェットからの音響特性の解析 i〜検証および周波数特性〜」

    野々村 拓

     詳細を見る

▼全件表示

 

論文 226

  1. Unsteady large-scale wake structure behind levitated free-stream-aligned circular cylinder 査読有り

    Yokota, S; Nonomura, T

    JOURNAL OF FLUID MECHANICS   982 巻   2024年3月

     詳細を見る

    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Fluid Mechanics  

    The relationships between characteristic large-scale wake structures appearing behind a free-stream-aligned circular cylinder are investigated and discussed from the velocity field obtained by wind tunnel tests. The tests were conducted under a supportless condition using a magnetic suspension and balance system and stereo PIV measurements at a Reynolds number of 3.46 × 104. The velocity fields were analysed with a modal decomposition combining azimuthal Fourier decomposition and proper orthogonal decomposition. The wake behind the free-stream-aligned circular cylinder with three different fineness ratios of 1.0, 1.5 and 2.0 was investigated, and the wake structures in a non-reattaching flow formed by the cylinder at a fineness ratio of 1.0 are mainly discussed in the present study. Four characteristic large-scale wake structures of the recirculation bubble pumping, azimuthal shear mode, large-scale vortex shedding and streaks are identified and mainly focused on in the present study. The state of the vortex shedding is classified into three: anticlockwise/clockwise circular and flapping patterns. Each state has a relationship with the azimuthal shear mode and it tends to appear when the state is circular. Furthermore, from the analysis of the relationship between modes, the recirculation bubble pumping is found to be related to the vortex shedding position in the radial direction and the strength of the streaks. Particularly, analysis of causality shows that the recirculation bubble pumping is affected by them in the low-frequency range.

    DOI: 10.1017/jfm.2024.93

    Web of Science

    Scopus

    researchmap

  2. Super-resolution of time-resolved three-dimensional density fields of the B mode in an underexpanded screeching jet 査読有り

    Lee, C; Ozawa, Y; Nagata, T; Nonomura, T

    PHYSICS OF FLUIDS   35 巻 ( 6 )   2023年6月

     詳細を見る

    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    The estimation of time-resolved three-dimensional (3D) density fields of an underexpanded jet at the nozzle pressure ratio of 2.42, a so-called "spatiotemporal super-resolution"was conducted using non-time-resolved three-dimensional background-oriented schlieren (3D-BOS) and time-resolved microphone measurements. This approach aims to reconstruct three-dimensional density fields associated with the intermittent and switching behavior of the B mode of a screeching jet from the microphone data by constructing a linear regression model. An azimuthal Fourier decomposition is applied to the 3D-BOS and microphone data, and the proper orthogonal decomposition (POD) is performed for each of their azimuthal Fourier modes. The m = 1 azimuthal Fourier mode is dominant in both cases, and the leading two POD modes in the m = 1 azimuthal mode of the microphone data are associated with the B mode. The linear regression model is constructed from the POD modes of the m = 1 azimuthal 3D-BOS data and the first two microphone POD modes of the m = 1 azimuthal mode of the microphone data. The three-dimensional density fields reconstructed from each POD mode of the m = 1 azimuthal mode of the microphone data have helical structures with opposite rotation directions. The amplitudes of those POD modes change with time, and the azimuthal structure associated with the B mode is determined depending on those amplitudes. The present result showed that intermittency in the flapping to helical structures and their strength can be interpreted by the temporal changes in the strengths of two rotating helical structures with opposite rotation directions.

    DOI: 10.1063/5.0149809

    Web of Science

    Scopus

    researchmap

  3. Proof-of-concept study of sparse processing particle image velocimetry for real time flow observation 査読有り

    Kanda, N; Abe, C; Goto, S; Yamada, K; Nakai, K; Saito, Y; Asai, K; Nonomura, T

    EXPERIMENTS IN FLUIDS   63 巻 ( 9 )   2022年9月

     詳細を見る

    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: In this paper, we overview, evaluate, and demonstrate the sparse processing particle image velocimetry (SPPIV) as a real-time flow field estimation method using the particle image velocimetry (PIV), whereas SPPIV was previously proposed with its feasibility study and its real-time demonstration is conducted for the first time in this study. In the wind tunnel test, the PIV measurement and real-time measurement using SPPIV were conducted for the flow velocity field around the NACA0015 airfoil model. The off-line analysis results of the test show that the flow velocity field can be estimated from a small number of processing points by applying SPPIV, and also illustrates the following characteristics of SPPIV. The estimation accuracy improves as the number of processing points increases, whereas the processing time per step increases in proportion to the number of processing points. Therefore, it is necessary to set an optimal number of processing points. Furthermore, the number of modes should be appropriately selected depending on the number of processing points. In addition, the application of the Kalman filter significantly improves the estimation accuracy with a small number of processing points while suppressing the processing time. When the flow velocity fields with different angles of attack are used as the training data with that of test data, the estimation using SPPIV is found to be reasonable if the difference in angle of attack between the training and test data are equal to or less than 2 deg and the flow phenomena of the training data are similar to that of the test data. For this reason, training data should be prepared at least every 4 deg. Finally, the demonstration of SPPIV as a real-time flow observation was conducted for the first time. In this demonstration, the real-time measurement is found to be possible at a sampling rate of 2000 Hz at 20 or less processing points in the top 10 modes estimation as expected by the off-line analyses. Graphical Abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-022-03471-0

    Web of Science

    Scopus

    researchmap

    その他リンク: https://link.springer.com/article/10.1007/s00348-022-03471-0/fulltext.html

  4. Optimization of sparse sensor placement for estimation of wind direction and surface pressure distribution using time-averaged pressure-sensitive paint data on automobile model 査読有り

    Inoba, R; Uchida, K; Iwasaki, Y; Nagata, T; Ozawa, Y; Saito, Y; Nonomura, T; Asai, K

    JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS   227 巻   頁: 105043 - 105043   2022年8月

     詳細を見る

    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Wind Engineering and Industrial Aerodynamics  

    This study proposes a method for predicting the wind direction against the simple automobile model (Ahmed model) and the surface pressure distributions on it by using data-driven optimized sparse pressure sensors. Positions of sparse pressure sensor pairs on the Ahmed model were selected for estimation of the yaw angle and reconstruction of pressure distributions based on the time-averaged surface pressure distributions database of various yaw angles, whereas the symmetric sensors in the left and right sides of the model were assumed. The surface pressure distributions were obtained by pressure-sensitive paint measurements. Three algorithms for sparse sensor selection based on the greedy algorithm were applied, and the sensor positions were optimized. The sensor positions and estimation accuracy of yaw angle and pressure distributions of three algorithms were compared and evaluated. The results show that a few optimized sensors can accurately predict the yaw angle and the pressure distributions.

    DOI: 10.1016/j.jweia.2022.105043

    Web of Science

    Scopus

    researchmap

  5. Computational study on aeroacoustic fields of a transitional supersonic jet 査読有り

    Nonomura, T; Ozawa, Y; Abe, Y; Fujii, K

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   149 巻 ( 6 ) 頁: 4484 - 4502   2021年6月

     詳細を見る

    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of the Acoustical Society of America  

    Aeroacoustic fields of a supersonic free jet at the Mach and Reynolds numbers of 2.1 and 70 000, respectively, of the transitional conditions are computationally investigated by large-eddy simulations. The supersonic transitional jets of different shear layer thicknesses without disturbances and those of the fixed shear layer thickness with disturbances are computationally investigated, and the effects of the shear layer thickness and the disturbance are discussed. The position of the transition and the turbulence intensity in the vicinity of the transition are clearly affected by those parameters. The turbulent fluctuation along the shear layer and the resulting intensity of the generated Mach waves are substantially attenuated by decreasing the shear layer thickness or adding the disturbance. A 5 dB increase in the sound pressure level is observed. This relatively lower increment in the sound pressure level compared with the 10-20 dB increase in the subsonic jet case is discussed as being due to the transition process promoted by the spiral mode in the supersonic jet case, unlike the axisymmetric case in the subsonic jet case. This point is confirmed by the linear stability analysis, the proper orthogonal decomposition analysis, and the visualization of vortex structures in the transition region.

    DOI: 10.1121/10.0005313

    Web of Science

    Scopus

    PubMed

    researchmap

  6. Quantitative evaluation of predictability of linear reduced-order model based on particle-image-velocimetry data of separated flow field around airfoil 査読有り

    Nonomura, T; Nankai, K; Iwasaki, Y; Komuro, A; Asai, K

    EXPERIMENTS IN FLUIDS   62 巻 ( 5 )   2021年5月

     詳細を見る

    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: A quantitative evaluation method for a reduced-order model of the flow field around an NACA0015 airfoil based on particle image velocimetry (PIV) data is proposed in the present paper. The velocity field data obtained by the time-resolved PIV measurement were decomposed into significant modes by a proper orthogonal decomposition (POD) technique, and a linear reduced-order model was then constructed by the linear regression of the time advancement of the POD modes or the sparsity promoting dynamic mode decomposition (DMD). The present evaluation method can be used for the evaluation of the estimation error and the model predictability. The model was constructed using different numbers of POD or DMD modes for order reduction in the fluid data and different methods of estimating the linear coefficients, and the effects of these conditions on the model performance were quantitatively evaluated. The results illustrates that forward (standard) model works the best with two to ten significant DMD modes selected by sparsity promoting DMD. Graphical abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-021-03205-8

    Web of Science

    Scopus

    researchmap

  7. Randomized Subspace Newton Convex Method Applied to Data-Driven Sensor Selection Problem 査読有り

    Nonomura, T; Ono, S; Nakai, K; Saito, Y

    IEEE SIGNAL PROCESSING LETTERS   28 巻   頁: 284 - 288   2021年

     詳細を見る

    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Signal Processing Letters  

    The randomized subspace Newton convex methods for the sensor selection problem are proposed. The randomized subspace Newton algorithm is straightforwardly applied to the convex formulation, and the customized method in which the part of the update variables are selected to be the present best sensor candidates is also considered. In the converged solution, almost the same results are obtained by original and randomized-subspace-Newton convex methods. As expected, the randomized-subspace-Newton methods require more computational steps while they reduce the total amount of the computational time because the computational time for one step is significantly reduced by the cubic of the ratio of numbers of randomly updating variables to all the variables. The customized method shows superior performance to the straightforward implementation in terms of the quality of sensors and the computational time.

    DOI: 10.1109/LSP.2021.3050708

    Web of Science

    Scopus

    researchmap

    その他リンク: https://dblp.uni-trier.de/db/journals/corr/corr2009.html#abs-2009-09315

  8. Dynamic mode decomposition based on expectation–maximization algorithm for simultaneous system identification and denoising

    Iwasaki Y., Sasaki Y., Nagata T., Kaneko S., Nonomura T.

    Mechanical Systems and Signal Processing   223 巻   2025年1月

     詳細を見る

    出版者・発行元:Mechanical Systems and Signal Processing  

    The present study proposes a novel dynamic mode decomposition (DMD) that can simultaneously estimate the reduced-order model, the original signal, and the system/observation noise model only from the noisy data. An expectation–maximization (EM)-algorithm DMD (EMDMD) combines DMD and the parameter adjustment of the linear dynamical system (LDS) based on the EM algorithm. The initial parameters based on the linearity of the reduced-order data are set by using DMD. Subsequently, the log-likelihood of the complete data is maximized by adjusting the LDS parameters while separating the noise. The proposed algorithm is applied to the benchmark data of the short-fat and tall-skinny data matrices with different noise and the time-series velocity fields of the flow around a circular cylinder and the separated flow around an airfoil. The performance of EMDMD in terms of system identification and noise separation from the noisy data is evaluated, and the EMDMD shows the highest system identification and noise separation performance in all data.

    DOI: 10.1016/j.ymssp.2024.111864

    Scopus

  9. Measurement of pressure fluctuation distribution on a flat wall behind supported square cylinder with pressure-sensitive paint 査読有り

    Matsui, A; Kawase, C; Sugioka, Y; Asai, K; Nonomura, T

    EXPERIMENTAL THERMAL AND FLUID SCIENCE   157 巻   2024年8月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experimental Thermal and Fluid Science  

    The pressure fluctuation distribution on the floor surface behind a supported square cylinder in a turbulent boundary layer was measured by using pressure-sensitive paint (PSP). Specifically, the accuracy and frequency response of PSP at a Mach number around M = 0.3 were examined. Four square cylinders with different dimensions were investigated in the same turbulent boundary layer, and the detailed relationship between these conditions and Kármán vortex shedding structures was discussed. The values measured with PSP had a similar trend to those measured with a pressure transducer at up to 5 kHz. The peak power spectral density (PSD) of the pressure fluctuations due to Kármán vortex shedding was observed within an error of approximately 30 % at up to frequencies greater than 3 kHz. Moreover, the peak frequency of Kármán vortex shedding was found to decrease with the cylinder height in a manner similar to a previous empirical equation for the Strouhal number. The peak PSD value for the shortest square cylinder (h/w = 3.5, h/δ = 1.1) was twice as high as that for the other cylinders; also, the high-pressure fluctuation area in this case did not spread downstream, which suggests that the flow from the top of the cylinder affected the Kármán vortex shedding generated from the cylinder's sides. One contour of the two main modes extracted for the highest PSD via the right singular vector vi at the Kármán vortex frequency had an asymmetric distribution behind the supported taller square cylinders (h/w ≥ 7.0, h/δ ≥ 2.3). This result is considered to be derived from the Kármán vortex shedding being mainly generated from the mainstream rather than the boundary-layer flow.

    DOI: 10.1016/j.expthermflusci.2024.111226

    Web of Science

    Scopus

    researchmap

  10. Improved estimation of yaw angle and surface pressure distribution of Ahmed model with optimized sparse sensors by Bayesian framework based on pressure-sensitive paint data 査読有り

    Inoba, R; Uchida, K; Iwasaki, Y; Yamada, K; Jebli, A; Nagata, T; Ozawa, Y; Nonomura, T

    EXPERIMENTAL THERMAL AND FLUID SCIENCE   156 巻   2024年7月

     詳細を見る

    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experimental Thermal and Fluid Science  

    The present study provides a Bayesian framework for the estimation of the yaw angle and the pressure distribution on the surface of the vehicle from the spatially sparse pressure measurements obtained by optimized sensing locations and data-driven models. The framework is demonstrated on the Ahmed model which is the simplified car model. The yaw angle and the pressure distribution on the top surface of the Ahmed model are estimated based on the sparse pressure measurement on the top surface. The estimation models are constructed based on the time-averaged pressure distribution on the top surface of the car model with various yaw angles obtained by a pressure-sensitive paint technique. The estimation model for the yaw angle was constructed as the linear regression between the yaw angle and pressure at the sensing locations, and the estimation model for the pressure distribution was constructed from a POD-based reduced order model. The Bayesian estimation was newly adopted for the mode coefficient estimation of the reduced-order model of the pressure distribution, and the optimization method of the sensing locations for the Bayesian estimation was adopted. The performance of the present Bayesian method was compared with previously proposed methods, and the results showed that the Bayesian method provides the best performance under most conditions on the yaw angle estimation and the pressure distribution reconstruction. In addition, various combinations of the estimation method and sensing location optimization method were tested, and the impact of estimation and sensing locations was discussed.

    DOI: 10.1016/j.expthermflusci.2024.111210

    Web of Science

    Scopus

    researchmap

  11. Indexes for evaluation of dynamic characteristics of pressure-sensitive paint based on pressure sensitivity and frequency response 査読有り

    Kasai, M; Nagata, T; Nonomura, T

    MEASUREMENT SCIENCE AND TECHNOLOGY   35 巻 ( 6 )   2024年6月

     詳細を見る

    担当区分:最終著者   記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Measurement Science and Technology  

    Two evaluation indexes were proposed to select the optimal PSP for unsteady pressure measurement from various PSPs with different pressure sensitivity and frequency response. An effective sensitivity coefficient calculated by pressure sensitivity and gain attenuation due to the response delay was proposed. Furthermore, an effective amount of intensity change was recommended, which takes into account the emission intensity and the effective sensitivity coefficient, because the magnitude of the intensity of a PSP is also important for unsteady-pressure measurement with high-speed sampling. A total of five types of PC-PSPs developed in previous studies were compared: two types of fast-response PC-PSPs using Pt(II) meso-tetra (pentafluorophenyl) porphine (PtTFPP) with poly(isobutyl methacrylate) (poly(IBM)) and ruthenium complex with RTV silicone, respectively, and three types of PC-PSPs using PtTFPP with poly[1-trimethylsilyl)-1-propyne] (poly(TMSP)). A comparison was made using the proposed evaluation indexes under various pressure ranges. The results shows that poly(TMSP)-based PC-PSP has a high effective sensitivity coefficient at pressures less than 20 kPa. On the other hand, poly(IBM)-based PC-PSP has the highest effective sensitivity coefficient at a pressure of 100 kPa. The effective amount of intensity change of poly(TMSP)-based PC-PSP is the highest at 2 kPa, but that of poly(IBM)-based PC-PSP is the highest at a pressure higher than 5 kPa among the evaluated PC-PSPs due to its high luminescence intensity. A PSP with high emission intensity will provide high performance in terms of fluctuation of emission intensity detected by the photodetector when the excitation intensity and the exposure time are limited due to limitations of optical equipment or high-speed sampling.

    DOI: 10.1088/1361-6501/ad2b41

    Web of Science

    Scopus

    researchmap

  12. Dual-luminophore pressure-sensitive paint measurement using three-gate lifetime method with photodegradation correction 査読有り

    Uchida, K; Nakakita, K; Sugioka, Y; Asai, K; Nonomura, T

    REVIEW OF SCIENTIFIC INSTRUMENTS   95 巻 ( 6 )   2024年6月

     詳細を見る

    担当区分:最終著者   記述言語:英語   出版者・発行元:Review of Scientific Instruments  

    In this paper, we propose a photodegradation correction method for the dual-luminophore pressure-sensitive paint (PSP) measurement using lifetime-based imaging, which was proposed for correction of the temperature-induced error but has suffered from photodegradation in the previous studies. We introduced a parameter that characterizes the photodegradation of a dual-luminophore PSP as the intensity ratio between the two luminophores. The changes in the calibration coefficients for the pressure and the temperature due to photodegradation were corrected based on this parameter. In this study, a coupon-based calibration test was performed, and the luminescence characteristics of the dual-luminophore PSP including photodegradation were investigated. Then, the proposed method was applied to a coupon-based validation test and a jet impingement test, and the effectiveness of the method was evaluated by comparing results with and without correction. The pressure measurement accuracy was significantly improved by photodegradation correction.

    DOI: 10.1063/5.0194749

    Web of Science

    Scopus

    PubMed

  13. High-efficiency sound source localization using data-driven sparse sampling with validation using monopole laser sound source 査読有り

    Kaneko, S; Ozawa, Y; Nakai, K; Saito, Y; Asai, K; Nonomura, T; Ura, H

    AIP ADVANCES   14 巻 ( 6 )   2024年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIP Advances  

    This study proposes a framework that reduces the calculation cost of sound source localization with the Amiet model, using a data-driven sparse sampling method. This method accelerates the calculation of the steering vector used in conventional beamforming. An aeroacoustic wind tunnel test was conducted in a 2 × 2 m2 low-speed wind tunnel, and the proposed method was verified. During the test, a monopole laser sound source, which does not interfere with the flow, was used, and its acoustic signals were measured using a microphone array. Next, steering vectors were reconstructed by discovering dominant modes and optimized sampling points from the training data based on the Amiet model and the modified data-driven sparse sampling method. Finally, the sound-source positions when the steering vector of the proposed model was used were compared with the positions observed when the steering vector of which all the grid points were calculated was used. The error was less than 2 mm when 16 modes were used, and the calculation time was reduced to ∼1/33 of that of the previous Amiet model.

    DOI: 10.1063/5.0205567

    Web of Science

    Scopus

    researchmap

  14. Experimental Parametric Study on Flow Separation Control Mechanisms around NACA0015 Airfoil Using a Plasma Actuator with Burst Actuation over Reynolds Numbers of 10<SUP>5</SUP>-10<SUP>6</SUP> 査読有り

    Kubo, N; Bhandari, S; Tanaka, M; Nonomura, T; Kawabata, H

    APPLIED SCIENCES-BASEL   14 巻 ( 11 )   2024年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Sciences (Switzerland)  

    Dielectric barrier discharge plasma actuators (DBD-PAs) have the potential to improve the performance of fluid machineries such as aircrafts and wind turbines by preventing flow separation. In this study, to identify the multiple flow control mechanisms in high Reynolds number flow, parametric experiments for an actuation parameter (Formula presented.) with a wide range of Re values (105–106) for NACA0015 airfoil was conducted. We conducted wind tunnel tests by applying a DBD-PA to the flow field around a wing model at the leading edge. Lift characteristics, turbulent kinetic energy in the flow field, shear layer height, and the separation point of the boundary layer were evaluated based on pressure distributions on the wing surface and velocity of the flow field, with the effect of DBD-PA on the post-stall flow around the wing and the mechanism behind the increase in the lift coefficient (Formula presented.) analyzed based on these evaluation results. The following phenomena contributed to the increase in (Formula presented.) : (1) increase in turbulent kinetic energy; (2) increase in circulation; and (3) acceleration of the flow near the leading edge. Thus, this study effectively investigated the dependence of the increase in lift on (Formula presented.) and the lift-increasing mechanism for a wide range of Re values.

    DOI: 10.3390/app14114652

    Web of Science

    Scopus

  15. Modal analyses of double pulsed pressure-sensitive paint data of impinging supersonic jet

    Li, EHR; Oka, Y; Ozawa, Y; Nonomura, T

    JOURNAL OF VISUALIZATION     2024年5月

     詳細を見る

    出版者・発行元:Journal of Visualization  

    The surface pressure field generated by a supersonic impinging jet on a vertical flat plate was measured using a pressure-sensitive paint (PSP) and a double-pulsed laser. The Mach number of the jet was Mj = 1.23 and the position of the flat plate was h/D = 4.5. A significant peak at St = 0.41 (15.2 kHz) was observed in the spectra measured by a microphone, and unsteady pressure transducers. The feedback loop involved in the acoustic loading occurred at this frequency. Coherent structures of the flow were extracted by applying the azimuthal Fourier decomposition and the dynamic mode decomposition (DMD) to PSP images on the impingement plate. Axisymmetric modes expanding outward from the impingement point of the jet were observed for the azimuthal mode m = 0. Two helical modes related to the feedback loop were identified for |m| = 1. It was confirmed that the RMS values of the amplitudes of these DMD modes were larger than the other modes. The frequencies of these DMD modes were St = 0.39 (14.3 kHz) and St = 0.37 (13.7 kHz), respectively. Coherent structures associated with phenomena faster than 10 kHz were successfully extracted from PSP measurement data. Graphical abstract: (Figure presented.)

    DOI: 10.1007/s12650-024-01000-1

    Web of Science

    Scopus

  16. Spatial superresolution based on simultaneous dual PIV measurement with different magnification

    Ozawa Y., Honda H., Nonomura T.

    Experiments in Fluids   65 巻 ( 4 )   2024年4月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    A reconstruction framework based on proper orthogonal decomposition and the Bayesian estimation was designed for the spatial superresolution of a subsonic jet, and the simultaneous two PIV measurements of a subsonic jet with different magnifications were conducted for training and testing the framework. The measurement system successfully acquired paired particle images of broad and close-up views of the jet in the same plane, and low and high-resolution velocity fields were obtained. The artificial low-resolution velocity fields were also generated by average pooling of the measured high-resolution velocity fields, and the performance of the reconstruction framework was evaluated. The estimation accuracy of the proposed framework was compared with that of bicubic interpolation and machine learning-based reconstruction methods: convolutional neural network and downsampled skip-connection/multi-scale methods. The framework successfully reconstructed the high-resolution velocity field from the low-resolution velocity field of the artificial one and actually measured one. The minimum reconstruction error of the Bayesian estimation using actually measured low-resolution velocity field was 63%, outperforming bicubic interpolation. Although this reconstruction error of the proposed framework is almost the same as (slightly worse than) that of the neural network methods, its reconstruction process is clearer and simpler than the neural network method. The power spectra of turbulent kinetic energy showed that the proposed framework can accurately recover the original velocity field in a wide waveband compared to the other methods. Therefore, the proposed framework can be a superresolution method of experimental fluid dynamics.

    DOI: 10.1007/s00348-024-03778-0

    Scopus

    researchmap

  17. Data Assimilation of Ideally Expanded Supersonic Jet Using RANS Simulation for High-Resolution PIV Data

    Ozawa, Y; Nonomura, T

    AEROSPACE   11 巻 ( 4 )   2024年4月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Aerospace  

    Data assimilation using particle image velocimetry (PIV) and Reynolds-averaged Navier–Stokes (RANS) simulation was performed for an ideally expanded supersonic jet flying at a Mach number of 2.0. The present study aims to efficiently reconstruct all the physical quantities in the aeroacoustic fields that match well with a realistic, experimentally obtained flow field. The two-dimensional, two-component PIV measurement was applied to the jet axis plane, and the time-averaged velocity field was obtained using single-pixel ensemble correlation. Two-dimensional axisymmetric RANS simulation using the Menter shear stress transport (SST) model was also performed, and the parameters of the SST model were optimized via data assimilation using the ensemble Kalman filter. The standard deviation of the observation noise (Formula presented.), which is a parameter of the ensemble Kalman filter, is estimated by the previously proposed method (Nakamura et al., Low-Grid-Resolution-RANS-Based Data Assimilation of Time-Averaged Separated Flow Obtained by LES. Int. J. Comp. Fluid. Dyn., 2022), and its effectiveness was investigated for the first time. This method effectively estimated the magnitude of (Formula presented.) at each generation without tuning the hyperparameters. The assimilated flow fields exhibited similar flow structures observed in PIV such as the potential core length or shear layer. Therefore, the present framework can be used to estimate time-averaged full flow fields that match well with experimentally observed flow fields, and has the potential to construct a database for the Navier-Stokes-based stability analysis that requires a full flow field.

    DOI: 10.3390/aerospace11040291

    Web of Science

    Scopus

    researchmap

  18. Experimental Investigation of Control Effects of Flapping Jets on Supersonic Cavity Flow

    Oka, Y; Ozawa, Y; Handa, T; Nonomura, T

    AIAA JOURNAL   62 巻 ( 3 ) 頁: 928 - 939   2024年3月

     詳細を見る

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.2514/1.J063448

    Web of Science

    researchmap

  19. Base pressure fluctuations on levitated freestream-aligned circular cylinder

    Yokota, S; Nagata, T; Kasai, M; Oka, Y; Nonomura, T

    PHYSICS OF FLUIDS   36 巻 ( 1 )   2024年1月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    Base pressure fluctuations associated with the large-scale wake structures behind a freestream-aligned circular cylinder and aerodynamic force fluctuations related to them are experimentally investigated in the wind tunnel tests. Measurements at R e D = 6.97 × 10 4 and 1.04 × 10 5 were conducted using pressure-sensitive paint (PSP) and a magnetic suspension and balance system (MSBS) for creating a supportless condition. The obtained pressure fields were mainly analyzed by a modal decomposition combining azimuthal Fourier decomposition and proper orthogonal decomposition (POD). The pressure fluctuations caused by large-scale vortex shedding were observed from the results of frequency analysis for mode coefficients. The states of the fluctuations were classified into three patterns, which are anticlockwise/clockwise circular and flapping patterns. These patterns have been observed in the previous studies for velocity fluctuations in the wake of a freestream-aligned circular cylinder. The conditional sampling analysis revealed that the trend in the amplitude of the pressure fluctuations is different by the state, and the flapping pattern causes a large pressure difference across the cylinder axis. Furthermore, the relationship between the antisymmetric pressure fluctuations and lift fluctuations, which act in the lateral direction of the cylinder, is confirmed.

    DOI: 10.1063/5.0179847

    Web of Science

    Scopus

    researchmap

  20. Robust and multiresolution sparse processing particle image velocimetry for improvement in spatial resolution

    Abe C., Kanda N., Nakai K., Nonomura T.

    Journal of Visualization     2024年

     詳細を見る

    出版者・発行元:Journal of Visualization  

    In this study, robustness of sparse processing particle image velocimetry (SPPIV) of high spatial resolution was improved, and the flow velocity field was measured in real time by improved SPPIV, whereas SPPIV estimates the entire flow field from limited results of sparsely located PIV analysis interrogation windows in real time but suffers from estimating high spatial resolution field because of outliers appearing in the cross correlation analysis. The high-resolution velocity field estimation was conducted by reducing the interrogation window size from 32×32pixel2 to 16×16 and 8×8pixel2, and the robustness of the improved SPPIV was investigated. We developed two methods of high-resolution SPPIV which is capable of real-time flow field measurement. One is robust SPPIV which incorporates with robust Kalman filter and eliminates the outliers, while the other is multiresolution SPPIV which adopts the large interrogation area for real-time measurements and projects it into the high-resolution velocity fields. Robust and multiresolution SPPIV can estimate the velocity fields more accurately than high-resolution standard SPPIV with 16×16 or 8×8pixel2 interrogation windows. The detailed discussion and comparison of those two methods are conducted. In addition, the sensor optimization is compared in the present framework and it shows that the sensors optimized by the Kalman filter index are better than those by the snapshot-to-snapshot index for SPPIV application. Graphical abstract: (Figure presented.).

    DOI: 10.1007/s12650-024-01016-7

    Scopus

  21. Assessment of Sensor Optimization Methods Toward State Estimation in a High-Dimensional System Using Kalman Filter

    Nagata T., Sasaki Y., Yamada K., Watanabe M., Tsubakino D., Nonomura T.

    IEEE Sensors Journal   24 巻 ( 11 ) 頁: 18012 - 18023   2024年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Sensors Journal  

    The characteristics of the sensor selection method based on various algorithms for state estimation in a high-dimensional system using the Kalman filter were investigated. Sensors were selected based on the error covariance matrix of the Kalman filter. The performance of the sensor selection methods based on different algorithms, semidefinite programming (SDP), approximate convex relaxation, and greedy algorithm, including newly formulated methods, were compared by varying the number of potential sensor locations and the number of sensors to be selected under several noise ratio conditions. Two sensor selection methods for state estimation in a high-dimensional system using a Kalman filter were newly proposed based on the SDP with gain formulation and approximate convex relaxation, and the characteristics of the method including the previously proposed method were compared in a high-dimensional system. Although the condition was limited at n < O(103) , the approximate convex relaxation method and its randomized method are effective in terms of computational time and objective value for a small-scale problem. The objective value obtained by the greedy method shows the best performance compared to the other methods in almost all investigated conditions. Particularly, the greedy method outperforms other methods when the number of selected sensors is small. In addition, only the greedy method can handle the large-scale problem of n> O(104). Overall, the greedy-based method is found to be favorable in large-scale problems in terms of computation time and the performance of the obtained sensor set.

    DOI: 10.1109/JSEN.2024.3388849

    Scopus

    researchmap

  22. Polarization Analysis in Time-Frequency Domain by Complex Spectral Matrix: Application to Various Phases of Seismogram

    Nagata, T; Mukuhira, Y; Sun, JY; Moriya, H; Shiina, T; Nonomura, T

    IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING   62 巻   頁: 1 - 15   2024年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Transactions on Geoscience and Remote Sensing  

    The detection and analysis of low signal-to-noise-ratio (SNR) events are valuable for a better understanding of various physical processes in underground reservoirs. The spectral matrix (SPM) analysis for detecting low-SNR P-wave arrivals, which is a previously proposed templateless detection method, is extended. The introduction of time-delay components increases the rank of SPM and makes it possible to characterize various polarized waves and detect further low-SNR events by a complex SPM analysis. In a P-wave detection problem, a new weighting function based on the phase information of the first eigenvector was proposed, and the polarization evaluation of the P-wave arrival was further improved. The results with the synthetic waveform showed that the separation of signal and noise is improved by the proposed method. In addition, detection experiments were performed with the waveforms recorded at the Groningen gas field in the Netherlands, and the proposed method newly detected two low-SNR events that were not detected by existing methods. The proposed method is robust to noise and shows the potential to detect low-SNR coherent signals and to characterize comprehensive polarized waves efficiently. Furthermore, we tested the proposed method on the whole seismogram of microseismicity and intermediate-depth earthquakes. We could identify the different phase arrivals by combining the magnitude of the first eigenvector. The contribution of the present work is an extension of the SPM analysis itself. Users can design appropriate indices based on three complex eigenvectors and eigenvalues.

    DOI: 10.1109/TGRS.2024.3352817

    Web of Science

    Scopus

    researchmap

  23. Sensor Selection With Cost Function Using Nondominated-Solution-Based Multiobjective Greedy Method

    Saito, Y; Nakai, K; Nagata, T; Yamada, K; Nonomura, T; Sakaki, K; Nunome, Y

    IEEE SENSORS JOURNAL   23 巻 ( 24 ) 頁: 31006 - 31016   2023年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Sensors Journal  

    In this study, a new greedy sensor selection algorithm with a cost constraint is proposed based on a nondominated-solution-based multiobjective greedy (NMG) method, and its performance is investigated by comparing it with a previously proposed method. The cost function is simultaneously considered with the D-optimality criterion, and the sensor set is selected based on the idea of the nondominated solution. Although a multiobjective optimization method for sensor selection with a cost constraint was previously considered based on the linear combination of the objectives, it requires a hyperparameter that determines the balance between the actual objective and the cost of the optimization. On the other hand, the proposed algorithm can obtain the Pareto solution without tuning the balance between the actual objective and the cost. We demonstrate the effectiveness of the proposed algorithm on the three different real datasets that are related to the sea surface temperature field, the flowfield around an airfoil, and the combustion field in a rocket chamber. A binary cost function is virtually imposed for each potential sensor location, and a sensor selection problem with a cost constraint is simulated. The results of the numerical experiments demonstrated that the NMG method could field a Pareto solution, and the objective values of almost all the sensor sets at a certain cost selected by the proposed method are superior to those selected by the previous method.

    DOI: 10.1109/JSEN.2023.3328005

    Web of Science

    Scopus

    researchmap

  24. Seismic wavefield reconstruction based on compressed sensing using data-driven reduced-order model 査読有り

    Nagata, T; Nakai, K; Yamada, K; Saito, Y; Nonomura, T; Kano, M; Ito, S; Nagao, H

    GEOPHYSICAL JOURNAL INTERNATIONAL   233 巻 ( 1 ) 頁: 33 - 50   2023年11月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Journal International  

    Reconstruction of the distribution of ground motion due to an earthquake is one of the key technologies for the prediction of seismic damage to infrastructure. Particularly, the immediate reconstruction of the spatially continuous wavefield is valuable for decision-making of disaster response decisions in the initial phase. For a fast and accurate reconstruction, utilization of prior information is essential. In fluid mechanics, full-state recovery, which recovers the full state from sparse observation using a data-driven model reduced-order model, is actively used. In this study, the framework developed in the field of fluid mechanics is applied to seismic wavefield reconstruction. A seismic wavefield reconstruction framework based on compressed sensing using the data-driven reduced-order model (ROM) is proposed and its characteristics are investigated through numerical experiments. The data-driven ROM is generated from the data set of the wavefield using the singular value decomposition. The spatially continuous seismic wavefield is reconstructed from the sparse and discrete observation and the data-driven ROM. The observation sites used for reconstruction are effectively selected by the sensor optimization method for linear inverse problems based on a greedy algorithm. The proposed framework was applied to simulation data of theoretical waveform with the subsurface structure of the horizontally stratified three layers. The validity of the proposed method was confirmed by the reconstruction based on the noise-free observation. Since the ROM of the wavefield is used as prior information, the reconstruction error is reduced to an approximately lower error bound of the present framework, even though the number of sensors used for reconstruction is limited and randomly selected. In addition, the reconstruction error obtained by the proposed framework is much smaller than that obtained by the Gaussian process regression. For the numerical experiment with noise-contaminated observation, the reconstructed wavefield is degraded due to the observation noise, but the reconstruction error obtained by the present framework with all available observation sites is close to a lower error bound, even though the reconstructed wavefield using the Gaussian process regression is fully collapsed. Although the reconstruction error is larger than that obtained using all observation sites, the number of observation sites used for reconstruction can be reduced while minimizing the deterioration and scatter of the reconstructed data by combining it with the sensor optimization method. Hence, a better and more stable reconstruction of the wavefield than randomly selected observation sites can be realized, even if the reconstruction is carried out with a smaller number of observations with observation noise, by combining it with the sensor optimization method.

    DOI: 10.1093/gji/ggac443

    Web of Science

    Scopus

    researchmap

    その他リンク: https://academic.oup.com/gji/article-pdf/233/1/33/47386322/ggac443.pdf

  25. Experimental investigation of strut effects on slanted cylinder afterbody and balance

    Tashiro, K; Yokota, S; Asai, K; Nonomura, T

    EXPERIMENTAL THERMAL AND FLUID SCIENCE   148 巻   2023年10月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Experimental Thermal and Fluid Science  

    In this study, strut support effects on a slanted cylinder afterbody were investigated by a magnetic suspension and balance system installed in a wind tunnel. The results showed that the aerodynamic characteristics with respect to the critical Reynolds number where the flow field and aerodynamic forces change significantly. In the cases with the dummy strut, the range of the critical Reynolds number decreases, and the variation depends on the location of the strut. The size of the recirculation region and the separation bubble on the wake center plane also changes depending on the location of the strut. Moreover, additional weak vortices are observed to be formed behind the strut, which changes the wake structure. That change affects the variation of the vortex core wandering, and is a factor in the power spectral density peaks observed in previous studies. It is suggested that the strut support strongly interferes with the flow around the test model and should be carefully considered.

    DOI: 10.1016/j.expthermflusci.2023.110952

    Web of Science

    Scopus

    researchmap

  26. Comparison of Separation Control Mechanisms for Synthetic Jet and Plasma Actuators

    Abe, Y; Nonomura, T; Sato, M; Aono, H; Fujii, K

    ACTUATORS   12 巻 ( 8 )   2023年8月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Actuators  

    This study numerically investigated the mechanisms of separation control using a synthetic jet (SJ) and plasma actuator (PA) around an NACA0015 airfoil at the chord Reynolds number of 63,000. Both SJ and PA were installed on the leading edge with the same order of input momentum ((Formula presented.) – (Formula presented.)) and the same actuation frequencies in (Formula presented.) –30. The momentum coefficient (Formula presented.) is defined as the normalized momentum introduced from the SJ or the PA, and (Formula presented.) stands for the actuation frequency normalized by the chord length and uniform velocity. A number of large-eddy simulations (LES) were conducted for the SJ and the PA, and the mechanisms were clarified in terms of the exchange of chordwise momentum with Reynolds shear stress and coherent vortex structures. First, four main differences in the induced flows of the SJ and the PA were clarified as follows: (A) wall-tangential velocity; (B) three-dimensional flow structures; (C) spatial locality; and (D) temporal fluctuation. Then, a common feature of flow control by the SJ and the PA was revealed: a lift-to-drag ratio was found to be better recovered in (Formula presented.) –20 than in other frequencies. Although there were differences in the induced flows, the phase decomposition of the flow fields identified common mechanisms that the turbulent component of the Reynolds shear stress mainly contributes to the exchange of the chordwise (streamwise) momentum; and the turbulent vortices are convected over the airfoil surface by the coherent spanwise vortices in the frequency of (Formula presented.).

    DOI: 10.3390/act12080322

    Web of Science

    Scopus

    researchmap

  27. Evaluation of characteristics of fast-response pressure-sensitive paint under low-pressure conditions 査読有り

    Kasai, M; Nagata, T; Uchida, K; Nonomura, T; Asai, K; Egami, Y

    MEASUREMENT SCIENCE AND TECHNOLOGY   34 巻 ( 7 )   2023年7月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Measurement Science and Technology  

    In this study, fast-response polymer-ceramic pressure-sensitive paints (PC-PSP) were developed and evaluated for pressure measurement under low-pressure conditions. The PC-PSP using poly[1-trimethylsilyl)-1-propyne] (poly(TMSP)), which has high oxygen permeability under low-pressure conditions, was developed in this study. The static and dynamic characteristics of the developed poly(TMSP)-based PC-PSP were evaluated in comparison with those of conventional poly(isobutyl methacrylate) (poly(IBM)) binder and ruthenium-complex-based PC-PSPs, which have been used for pressure measurements under atmospheric pressure conditions. The particle mass content of titanium dioxide of PC-PSPs with poly(TMSP) was changed from 90 wt% to 98 wt% to increase the frequency response. The critical pigment volume concentration, so called CPVC, of the PC-PSP with poly(TMSP) and hydrophobic particles and hydrophilic particles were 95-98 wt% and 90-95 wt%, respectively. The PC-PSP using hydrophilic particles with poly(TMSP) and a particle mass content of 98 wt% could provide a cut-off frequency of approximately 4.5 kHz and a high local Stern-Volmer coefficient of 0.5 at low pressure of 2 kPa.

    DOI: 10.1088/1361-6501/acc5a0

    Web of Science

    Scopus

    researchmap

  28. Sound-source distribution in the bogie section of a train determined by simultaneous measurement by pressure-sensitive paint and a microphone 査読有り

    Matsui, A; Kasai, M; Sugioka, Y; Asai, K; Nonomura, T

    EXPERIMENTAL THERMAL AND FLUID SCIENCE   145 巻   2023年7月

     詳細を見る

    担当区分:最終著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experimental Thermal and Fluid Science  

    Sound-pressure level of acoustic waves from the flow around a 1/8-reduced-scale simplified train model and pressure-fluctuation distribution of the bottom surface of the bogie were measured simultaneously by a microphone and a pressure-sensitive paint (PSP). A high-pressure-fluctuation area was observed on the upstream side on the bogie bottom surface at the peak sound frequency. The phase distribution of the peak frequency of the PSP data was observed to be uniform in the spanwise direction and delayed in the downstream direction. This result indicates that propagation speed of peak surface pressure fluctuation was 66 % of the freestream wind velocity. Thus, the measured peak sound frequency was found to be the same as the theoretical cavity peak frequency given by the Rossiter equation with that propagation speed as a vortex convection velocity. Therefore, the peak sound is concluded to be generated from acoustic feedback in the cavity, which is the gap between the upstream cavity edge and the bogie. Moreover, the difference between the measured and correlated peak sound levels of the bottom surface of the bogie, was no more than 3 dB, where the correlated sound level was calculated by using the Lighthill-Curle equation with coherent output power data.

    DOI: 10.1016/j.expthermflusci.2023.110885

    Web of Science

    Scopus

    researchmap

  29. Density field reconstruction from time-series schlieren images via extended phase-consistent dynamic mode decomposition

    Shigeta, T; Nagata, T; Nonomura, T

    EXPERIMENTS IN FLUIDS   64 巻 ( 7 )   2023年7月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    The extended phase-consistent dynamic mode decomposition (DMD) method, which reconstructs density fields from density gradient fields in multiple directions, was developed and applied to schlieren images in the low-density wind tunnel tests. Schlieren images were acquired in the Re = 3000, 10,000, and M = 0.15, 0.50 flows around a triangular airfoil, and the density gradient fields were calculated from the calibration of the optical system. The proposed density field reconstruction method adopts the extended phase-consistent DMD principle for the estimation of the DMD modes of the density field. The density field was reconstructed with good accuracy in a numerical simulation for comparison, and the density fluctuation region caused by vortex shedding around a triangular airfoil was visualized by the experimental data.

    DOI: 10.1007/s00348-023-03668-x

    Web of Science

    Scopus

    researchmap

  30. Efficient Sensor Node Selection for Observability Gramian Optimization

    Yamada, K; Sasaki, Y; Nagata, T; Nakai, K; Tsubakino, D; Nonomura, T

    SENSORS   23 巻 ( 13 )   2023年7月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors  

    Optimization approaches that determine sensitive sensor nodes in a large-scale, linear time-invariant, and discrete-time dynamical system are examined under the assumption of independent and identically distributed measurement noise. This study offers two novel selection algorithms, namely an approximate convex relaxation method with the Newton method and a gradient greedy method, and confirms the performance of the selection methods, including a convex relaxation method with semidefinite programming (SDP) and a pure greedy optimization method proposed in the previous studies. The matrix determinant of the observability Gramian was employed for the evaluations of the sensor subsets, while its gradient and Hessian were derived for the proposed methods. In the demonstration using numerical and real-world examples, the proposed approximate greedy method showed superiority in the run time when the sensor numbers were roughly the same as the dimensions of the latent system. The relaxation method with SDP is confirmed to be the most reasonable approach for a system with randomly generated matrices of higher dimensions. However, the degradation of the optimization results was also confirmed in the case of real-world datasets, while the pure greedy selection obtained the most stable optimization results.

    DOI: 10.3390/s23135961

    Web of Science

    Scopus

    PubMed

    researchmap

  31. First lift-off and flight performance of a tailless flapping-wing aerial robot in high-altitude environments

    Tsuchiya, S; Aono, H; Asai, K; Nonomura, T; Ozawa, Y; Anyoji, M; Ando, N; Kang, CK; Pohly, J

    SCIENTIFIC REPORTS   13 巻 ( 1 )   2023年6月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Scientific Reports  

    Flapping flight of animals has captured the interest of researchers due to their impressive flight capabilities across diverse environments including mountains, oceans, forests, and urban areas. Despite the significant progress made in understanding flapping flight, high-altitude flight as showcased by many migrating animals remains underexplored. At high-altitudes, air density is low, and it is challenging to produce lift. Here we demonstrate a first lift-off of a flapping wing robot in a low-density environment through wing size and motion scaling. Force measurements showed that the lift remained high at 0.14 N despite a 66% reduction of air density from the sea-level condition. The flapping amplitude increased from 148 to 233 degrees, while the pitch amplitude remained nearly constant at 38.2 degrees. The combined effect is that the flapping-wing robot benefited from the angle of attack that is characteristic of flying animals. Our results suggest that it is not a simple increase in the flapping frequency, but a coordinated increase in the wing size and reduction in flapping frequency enables the flight in lower density condition. The key mechanism is to preserve the passive rotations due to wing deformation, confirmed by a bioinspired scaling relationship. Our results highlight the feasibility of flight under a low-density, high-altitude environment due to leveraging unsteady aerodynamic mechanisms unique to flapping wings. We anticipate our experimental demonstration to be a starting point for more sophisticated flapping wing models and robots for autonomous multi-altitude sensing. Furthermore, it is a preliminary step towards flapping wing flight in the ultra-low density Martian atmosphere.

    DOI: 10.1038/s41598-023-36174-5

    Web of Science

    Scopus

    PubMed

    researchmap

  32. Reservoir computing reduced-order model based on particle image velocimetry data of post-stall flow

    Iwasaki, Y; Nagata, T; Sasaki, Y; Nakai, K; Inubushi, M; Nonomura, T

    AIP ADVANCES   13 巻 ( 6 )   2023年6月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIP Advances  

    The present study proposes a reservoir computing reduced-order model (RCROM) of the post-stall flow around the National Advisory Committee for Aeronautics 0015 airfoil based on the time series velocity field, and the estimation accuracy of the RCROM is evaluated compared to that of a linear reduced-order model (LROM). The data were experimentally obtained by particle image velocimetry at a chord Reynolds number of 6.4 × 104 and an angle of attack of 18°. The low-dimensional description of the velocity field can be obtained by decomposing the velocity field with a proper orthogonal decomposition (POD) technique and by employing the leading POD mode coefficients as temporal variables of the data instead of the velocity field. Reservoir computing (RC) is adopted as a nonlinear function that predicts several steps ahead of the leading POD mode coefficients. The hyperparameters of RC are tuned by Bayesian optimization, and the optimized RCROM outperforms the LROM in terms of estimation accuracy. The estimation accuracy of the RCROM can be investigated under different numbers of the predicted dominant POD modes and prediction step conditions. As a result, the RCROM shows higher estimation accuracy than the LROM.

    DOI: 10.1063/5.0150947

    Web of Science

    Scopus

    researchmap

  33. Experimental Observations of Transient Flows in Separation Control Using a Plasma Actuator 査読有り

    Viguera, R; Anzai, Y; Sasaki, Y; Nonomura, T

    ACTUATORS   12 巻 ( 6 )   2023年6月

     詳細を見る

    担当区分:最終著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Actuators  

    This paper presents the experimental results of separation and reattachment transient flow processes over a NACA0015 airfoil wing when using a plasma actuator for flow control. In addition, it addresses the flow behavior in the transient processes when the flow control device is activated or deactivated, providing insights for future feedback-based active flow control. This approach offers the benefit of enhanced aerodynamic capabilities. The experiments were conducted at a Reynolds number of 66,000 and an angle of attack of 13 degrees for leading-edge separation without control. The plasma actuator was installed on the leading edge of the wing, with a voltage of 8 kV, base frequency of 30 kHz, and burst frequencies ranging from 100 Hz to 600 Hz. Particle image velocimetry was employed for the flow field velocity measurements, and surface pressure data were obtained using eight piezoelectric pressure sensors. The first proper orthogonal decomposition mode of the transient flow velocity field is the focus of this paper and the flow behavior is quantitatively discussed. The results reveal details about the flow separation and reattachment transient processes such as their flow structures and their evolution over time. It is concluded that the time asymmetry between the separation and reattachment transient processes could be leveraged for further improvements to the efficiency of actuators.

    DOI: 10.3390/act12060218

    Web of Science

    Scopus

    researchmap

  34. Flow instability and momentum exchange in separation control by a synthetic jet

    Abe, Y; Nonomura, T; Fujii, K

    PHYSICS OF FLUIDS   35 巻 ( 6 )   2023年6月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    This study investigates a mechanism for controlling separated flows around an airfoil using a synthetic jet (SJ). A large-eddy simulation (LES) was performed for a leading-edge separation flow around an airfoil at the chord Reynolds number of 63 000 and the angle of attack of 12°. The present LES resolves a turbulent structure inside a deforming SJ cavity with a deforming grid. An optimal actuation-frequency band is identified between the normalized frequencies of F + = 6.0 and 20, which suppresses the separation and drastically improves the lift-to-drag ratio. In the controlled flows, the laminar separation bubble near the leading edge periodically releases multiple spanwise-uniform vortex structures, which diffuse and merge to generate a single coherent vortex in the period of F+. Such a coherent vortex plays a significant role in exchanging a chordwise momentum between a near-wall surface and the freestream away from the wall. It also entrains smaller turbulent vortices and eventually enhances the turbulent component of the Reynolds stress throughout the suction surface. Linear stability theory (LST) was subsequently compared with the LES result, which clarifies the applicability of the LST to the controlled flows. In the optimal F+ regime, both linear and nonlinear modes are excited in a well-balanced manner, where the first mode is associated with the Kelvin-Helmholtz instability and contributes to a quick and smooth turbulent transition, while the second mode shows a frequency lower than that of the linear mode and encourages a formation of the coherent vortex structure that eventually entrains smaller turbulent vortices.

    DOI: 10.1063/5.0148943

    Web of Science

    Scopus

    researchmap

  35. Randomized Group-Greedy Method for Large-Scale Sensor Selection Problems

    Nagata, T; Yamada, K; Nakai, K; Saito, Y; Nonomura, T

    IEEE SENSORS JOURNAL   23 巻 ( 9 ) 頁: 9536 - 9548   2023年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Sensors Journal  

    The randomized group-greedy (RGG) method and its customized method for large-scale sensor selection problems are proposed. The randomized greedy sensor selection algorithm is applied straightforwardly to the group-greedy (GG) method, and a customized method is also considered. In the customized method, a part of the compressed sensor candidates is selected using the common greedy method or other low-cost methods. This strategy compensates for the deterioration of the solution due to compressed sensor candidates. The proposed methods are implemented based on the D-and E-optimal design of experiments, and numerical experiments are conducted using randomly generated sensor candidate matrices with potential sensor locations of 10000-1000000. The proposed method can provide better optimization results than those obtained by the original GG method when a similar computational cost is spent as for the original GG method. This is because the group size for the GG method can be increased as a result of the compressed sensor candidates by the randomized algorithm. Similar results were also obtained in the real dataset. The proposed method is effective for the E-optimality criterion, in which the objective function that the optimization by the common greedy method is difficult due to the absence of submodularity of the objective function. The idea of the present method can improve the performance of all optimizations using a greedy algorithm.

    DOI: 10.1109/JSEN.2023.3258223

    Web of Science

    Scopus

    researchmap

  36. Experimental investigation of the supersonic cavity by spectral-POD of high-sampling rate pressure-sensitive paint data

    Oka, Y; Ozawa, Y; Nagata, T; Asai, K; Nonomura, T

    EXPERIMENTS IN FLUIDS   64 巻 ( 5 )   2023年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    A pressure distribution inside a two-dimensional rectangular cavity with a ratio L/ D= 5.0 of the cavity length L to the depth D over a supersonic flow was obtained using an improved fast anodized-aluminum pressure-sensitive paint (AA-PSP). The freestream Mach number was M∞= 1.9 and the frequencies of the dominant cavity modal phenomena, called “Rossiter” modes, were on the order of 1–10 kHz. The fast AA-PSP using a free-based porphyrin luminophore and a high-frequency-repetition double-pulsed laser were applied, and instantaneous pressure fields were captured. This measurement system has a 60 kHz sampling rate and is suitable for the purpose of a direct measurement of the Rossiter mode phenomena. The result of the power spectral density (PSD) of the PSP measurement showed that this measurement system is capable of observing phenomena of approximately 18 kHz. Time-resolved pressure transducer measurement was also employed, and PSD obtained by the PSP measurement was validated. The frequency spectra and the amplitudes of PSD obtained by the PSP measurement were in good agreement with those obtained by the pressure transducer data. A spectral proper orthogonal decomposition (SPOD) analysis was also conducted, and the symmetric and asymmetric spatial modes were extracted at each peak frequency. In this analysis, the seventh Rossiter mode phenomena of approximately 21 kHz were visualized. The peak frequencies of symmetric modes were in good agreement with those of the Rossiter mode, and lower than that of asymmetric modes. The energy of the symmetric modes at each peak frequency was several times higher than that of the asymmetric mode. The phase of the SPOD mode revealed the propagation direction of the pressure waves. It showed the existence of the upstream propagation waves and standing waves inside the cavity.

    DOI: 10.1007/s00348-023-03648-1

    Web of Science

    Scopus

    researchmap

  37. Observation site selection for physical model parameter estimation towards process-driven seismic wavefield reconstruction 査読有り

    Nakai, K; Nagata, T; Yamada, K; Saito, Y; Nonomura, T; Kano, M; Ito, S; Nagao, H

    GEOPHYSICAL JOURNAL INTERNATIONAL   234 巻 ( 3 ) 頁: 1786 - 1805   2023年4月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Journal International  

    The ‘big’ seismic data not only acquired by seismometers but also acquired by vibrometers installed in buildings and infrastructure and accelerometers installed in smartphones will be certainly utilized for seismic research in the near future. Since it is impractical to utilize all the seismic big data in terms of the computational cost, methods which can select observation sites depending on the purpose are indispensable. We propose an observation site selection method for the accurate reconstruction of the seismic wavefield by process-driven approaches. The proposed method selects observation sites suitable for accurately estimating physical model parameters such as subsurface structures and source information to be input into a numerical simulation of the seismic wavefield. The seismic wavefield is reconstructed by the numerical simulation using the parameters estimated based on the observed signals at only observation sites selected by the proposed method. The observation site selection in the proposed method is based on the sensitivity of each observation site candidate to the physical model parameters; the matrix corresponding to the sensitivity is constructed by approximately calculating the derivatives based on the simulations, and then, observation sites are selected by evaluating the quantity of the sensitivity matrix based on the D-optimality criterion proposed in the optimal design of experiments. In this study, physical knowledge on the sensitivity to the parameters such as seismic velocity, layer thickness, and hypocentre location was obtained by investigating the characteristics of the sensitivity matrix. Furthermore, the effectiveness of the proposed method was shown by verifying the accuracy of seismic wavefield reconstruction using the observation sites selected by the proposed method.

    DOI: 10.1093/gji/ggad165

    Web of Science

    Scopus

    researchmap

  38. Effect of angle of attack on aerodynamic characteristics of levitated freestream-aligned circular cylinder

    Yokota, S; Asai, K; Nonomura, T

    PHYSICAL REVIEW FLUIDS   8 巻 ( 2 )   2023年2月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physical Review Fluids  

    An effect of an angle of attack on the aerodynamic characteristics of a freestream-aligned circular cylinder is investigated and discussed. The experiment without support interference was conducted using a magnetic suspension and balance system (MSBS) which can levitate and support a model. A cylindrical model with a fineness ratio of 1.0 was employed in wind tunnel tests. The Reynolds numbers based on the diameter of the model were 3.3×104 and 6.7×104. The range of the angle of attack is from 0 to 15°. Aerodynamic forces and velocity fields were obtained by the MSBS and particle image velocimetry. The results of the time-averaged aerodynamic force and moment coefficients and the time-averaged velocity field illustrate that the flow reattachment occurs at an angle of 9° or more. The flow reattachment changes the aerodynamic characteristics, especially the lift and pitching moment coefficients and the lift force fluctuations.

    DOI: 10.1103/PhysRevFluids.8.024701

    Web of Science

    Scopus

    researchmap

  39. A platinum-based fast-response pressure-sensitive paint containing hydrophobic titanium dioxide

    Kasai, M; Suzuki, A; Egami, Y; Nonomura, T; Asai, K

    SENSORS AND ACTUATORS A-PHYSICAL   350 巻   2023年2月

  40. Model position sensing method for low fineness ratio models in a magnetic suspension and balance system

    Inomata, C; Kuwata, M; Yokota, S; Abe, Y; Sawada, H; Obayashi, S; Asai, K; Nonomura, T

    REVIEW OF SCIENTIFIC INSTRUMENTS   94 巻 ( 2 ) 頁: 025102 - 025102   2023年2月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Review of Scientific Instruments  

    A new model-position-sensing method for the levitation of models with a low fineness ratio (ratio of the longitudinal length to the diameter) in a magnetic suspension and balance system (MSBS) is proposed. MSBS is an ideal model-support device for wind-tunnel testing, which enables the study of flow fields around blunt bodies without flow disturbances introduced by mechanical support devices, with the aerodynamic forces determined from the magnetic forces using a pre-calibrated relationship. The new method allows wind tunnel experiments without mechanical supports with a low fineness ratio model. This method adopts two line sensors placed parallel to the central axis of the model image and measures the position with a resolution finer than 0.06 mm or deg even for thin model geometries. In addition, measurement errors were reduced by correcting a second-order term in the depth direction of the camera. A low fineness ratio circular cylinder model was levitated following sensor calibration. The model was supported in conditions with and without freestream flow. This position measurement method was also applied to a reentry capsule model. The model was levitated while keeping its position and attitude stabilized near the origin.

    DOI: 10.1063/5.0113806

    Web of Science

    Scopus

    PubMed

    researchmap

  41. A platinum-based fast-response pressure-sensitive paint containing hydrophobic titanium dioxide

    Kasai, M; Suzuki, A; Egami, Y; Nonomura, T; Asai, K

    SENSORS AND ACTUATORS A-PHYSICAL   350 巻   2023年2月

  42. Flow Control around NACA0015 Airfoil Using a Dielectric Barrier Discharge Plasma Actuator over a Wide Range of the Reynolds Number

    Sekimoto, S; Fujii, K; Anyoji, M; Miyakawa, Y; Ito, S; Shimomura, S; Nishida, H; Nonomura, T; Matsuno, T

    ACTUATORS   12 巻 ( 1 )   2023年1月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Actuators  

    In this study, an experimental investigation of separation control using a dielectric barrier discharge plasma actuator was performed on an NACA0015 airfoil over a wide range of Reynolds numbers, angles of attack, and nondimensional burst frequencies. The range of the Reynolds number was based on a chord length ranging from 2.52 × 10 (Formula presented.) to 1.008 × 10 (Formula presented.). A plasma actuator was installed at the leading edge and driven by AC voltage. Burst mode (duty-cycle) actuation was applied, with the nondimensional burst frequency ranging between 0.1–30. The control authority was evaluated using the time-averaged distribution of the pressure coefficient (Formula presented.) and the calculated value of the lift coefficient (Formula presented.). The baseline flow fields were classified into three types: (1) leading-edge separation; (2) trailing-edge separation; and (3) the hysteresis between (1) and (2). The results of the actuated cases show that the control trends clearly depend on the differences in the separation conditions. In leading-edge separation, actuation with a burst frequency of approximately (Formula presented.) 0.5 creates a wide negative pressure region on the suction-side surface, leading to an increase in the lift coefficient. In trailing-edge separation, several actuations alter the position of turbulent separation.

    DOI: 10.3390/act12010043

    Web of Science

    Scopus

    researchmap

  43. Sensor Selection by Greedy Method for Linear Dynamical Systems: Comparative Study on Fisher-Information-Matrix, Observability-Gramian and Kalman-Filter-Based Indices

    Takahashi, S; Sasaki, Y; Nagata, T; Yamada, K; Nakai, K; Saito, Y; Nonomura, T

    IEEE ACCESS   11 巻   頁: 67850 - 67864   2023年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Access  

    Objective functions for sensor selection are investigated in linear time-invariant systems with a large number of sensor candidates. This study compared the performance of sensor sets obtained using three types of D-optimality-based indices as objective functions for sensor selection based on the greedy method. The compared indices are computed based on the snapshot-to-snapshot Fisher information matrix, the observability Gramian and the Kalman filter-based matrix. Both random systems and systems with eigenmodes are considered, indices for selecting the best-performing sensor set for each are identified, as well as computational complexity and corresponding wall clock times. The sensor optimized for each index works best for that index, as expected. We also clarified the trend of the sensor sets selected by the greedy method based on each objective function in terms of the other objective function.

    DOI: 10.1109/ACCESS.2023.3291415

    Web of Science

    Scopus

    researchmap

  44. Photostability Enhancement of Dual-Luminophore Pressure-Sensitive Paint by Adding Antioxidants 査読有り

    Uchida, K; Ozawa, Y; Asai, K; Nonomura, T

    SENSORS   22 巻 ( 23 )   2022年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors  

    Antioxidants were applied to a dual-luminophore pressure-sensitive paint (PSP), and the effects on photodegradation caused by exposure to excitation light were studied. Three types of antioxidants that are commonly used for the photostability enhancement of polymers were added to a dual-luminophore PSP, and degradation rates and pressure/temperature sensitivities were investigated by coupon-based tests. One-hour-long aging tests were performed in a pressure chamber with a continuous excitation light source under dry air and argon atmospheres at 100 kPa and 20 °C. As a result of the aging tests, a singlet oxygen quencher type antioxidant was found to reduce the degradation rate by 91% when compared with the dual-luminophore PSP without antioxidants. This implies that singlet oxygen has a dominant role in the photodegradation mechanism of the dual-luminophore PSP.

    DOI: 10.3390/s22239470

    Web of Science

    Scopus

    PubMed

    researchmap

  45. Unsteady Aerodynamics Around a Pitching Airfoil with Shock and Shock-Induced Boundary-Layer Separation 査読有り

    Oyeniran, ND; Miyake, T; Terashima, H; Seki, R; Ishiko, K; Nonomura, T

    AIAA JOURNAL   60 巻 ( 12 ) 頁: 6557 - 6565   2022年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    This study numerically investigated the characteristics of unsteady aerodynamic forces around a pitching airfoil in the transonic flow regime. The unsteady Reynolds-averaged compressible Navier–Stokes (URANS) equations were solved using a Spalart–Allmaras (SA) turbulence model. The pitching NACA64A010 airfoil at mean angles of attack of 0, 2, 4, and 6 deg with the amplitude of 1 deg and reduced frequency of 0.2 was parametrically simulated. The study found that the trend of the unsteady aerodynamic characteristics around the pitching airfoil, particularly that of the unsteady lift force, significantly changes with the mean-angle-of-attack conditions. The shock-induced boundary-layer separation and reattachment during the pitching oscillation have a crucial role in determining the trend of the unsteady aerodynamic forces, such as the phase-delayed or phase-advanced features for the variation in the angle of attack. The boundary-layer separation during the oscillation, observed at a high mean angle of attack of 6 deg, produces the phase-advanced feature of the lift force. Because the phase-advanced feature is associated with a positive damping effect, the result indicates that the boundary-layer separation may serve as a stabilizing effect on the pitching airfoil motion. The boundary-layer reattachment from separation during the airfoil oscillation, observed at an intermediate mean angle of attack of 4 deg, generates an unusual shock wave movement, resulting in a unique lift loop for the variation in the angle of attack. The study also demonstrated a good prediction accuracy of the URANS with the SA model for the unsteady aerodynamics around the pitching airfoil with the shock and shock-induced boundary-layer separation.

    DOI: 10.2514/1.J062054

    Web of Science

    Scopus

    researchmap

  46. Spatiotemporal superresolution measurement based on POD and sparse regression applied to a supersonic jet measured by PIV and near-field microphone 査読有り

    Ozawa, Y; Nagata, T; Nonomura, T

    JOURNAL OF VISUALIZATION   25 巻 ( 6 ) 頁: 1169 - 1187   2022年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Visualization  

    The present study proposed the framework of the spatiotemporal superresolution measurement based on the sparse regression with dimensionality reduction using the proper orthogonal decomposition (POD). The non-time-resolved particle image velocimetry (PIV) and the time-resolved near-field acoustic measurements using microphones were simultaneously performed for a Mach 1.35 supersonic jet. POD is applied to PIV and microphone data matrices, and the sparse linear regression model of the reduced-order data is calculated using the least absolute shrinkage and selection operator regression. The effects of the hyperparameters of the superresolution measurement were quantitatively evaluated through randomized cross-validation. The superresolved velocity field indicated the smooth convection of the velocity fluctuations associated with the screech tone, while the convection of the large-scale structures at the downstream side was not observed. The proposed framework can reconstruct the unsteady fluctuation with multiple frequency phenomena, although the reconstruction is limited to the phenomena that are associated with the microphone output. Graphical Abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s12650-022-00855-6

    Web of Science

    Scopus

    researchmap

  47. Effect of particle arrangement and density on aerodynamic interference between twin particles interacting with a plane shock wave 査読有り

    Takahashi, S; Nagata, T; Mizuno, Y; Nonomura, T; Obayashi, S

    PHYSICS OF FLUIDS   34 巻 ( 11 ) 頁: 113301 - 113301   2022年11月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    Unsteady drag, unsteady lift, and movement of one or two moving particles caused by the passage of a planar shock wave are investigated using particle-resolved simulations of viscous flows. The particle motion analysis is carried out based on particle-resolved simulations for one or two particles under a shock Mach number of 1.22 and a particle Reynolds number of 49, and the particle migration and fluid forces are investigated. The unsteady drag, unsteady lift, and particle behavior are investigated for different densities and particle configurations. The time evolution of the unsteady drag and lift is changed by interference by the planar shock wave, Mach stem convergence, and the shock wave reflected from the other particle. These two particles become closer after the shock wave passes than in the initial state under most conditions. Two particles placed in an in-line arrangement approach each other very closely due to the passage of a shock wave. On the other hand, two particles placed in a side-by-side arrangement are only slightly closer to each other after the shock wave passes between them. The pressure waves resulting from Mach stem convergence of the upstream particle and the reflected shock waves from the downstream particle are the main factors responsible for the force in the direction that pushes the particles apart. The wide distance between the two particles attenuates these pressure waves, and the particles reduce their motion away from each other.

    DOI: 10.1063/5.0101365

    Web of Science

    Scopus

    researchmap

  48. Simultaneous measurement of pressure and temperature on the same surface by sensitive paints using the sensor selection method 査読有り

    Tiwari, N; Uchida, K; Inoba, R; Saito, Y; Asai, K; Nonomura, T

    EXPERIMENTS IN FLUIDS   63 巻 ( 11 )   2022年11月

     詳細を見る

    担当区分:最終著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    A novel measurement method is developed for a simultaneous measurement of pressure and temperature on an airfoil by sensitive paints. The proposed method requires two sets of measurements: in the first set, the temperature distribution is measured on the entire surface of the airfoil by temperature-sensitive paint (TSP). This temperature field is further utilized to evaluate sparse sensor locations based on the sensor selection methods. For the second set of measurements, TSP was sprayed on sparse points and pressure-sensitive paint (PSP) on the remaining airfoil surface. A full temperature field can be reconstructed using temperature data measured at those sparse locations. The temperature-induced error due to temperature sensitivity of PSP is corrected, and a time-averaged pressure field is compared with the pressure tap data. The proposed method is demonstrated on a flow over a NACA 0015 airfoil. Time-averaged and spanwise averaged pressure agrees very well with pressure sensor data measured simultaneously with PSP giving further confidence in our measurement. The present results also show that the Bayesian estimation and a corresponding sensor selection method overperform the linear least squares estimation and a corresponding sensor selection method, and the Bayesian estimation framework is recommended for the practical sparse sensor for temperature reconstruction.

    DOI: 10.1007/s00348-022-03501-x

    Web of Science

    Scopus

    researchmap

    その他リンク: https://link.springer.com/article/10.1007/s00348-022-03501-x/fulltext.html

  49. Demonstration and verification of exact DMD analysis applied to double-pulsed schlieren image of supersonic impinging jet 査読有り

    Ohmizu, K; Ozawa, Y; Nagata, T; Nonomura, T; Asai, K

    JOURNAL OF VISUALIZATION   25 巻 ( 5 ) 頁: 929 - 943   2022年10月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Visualization  

    The exact dynamic mode decomposition (DMD) was applied to the nonsequential image dataset obtained by the double-pulsed schlieren measurement of a supersonic impinging jet, and the effect of the dataset length on the obtained spatial modes and estimated frequencies of the aeroacoustic fields was investigated. The Mach number of the jet was 2.0, the Reynolds number based on the diameter of the nozzle exit was 1.0 × 10 6 and the distance between the nozzle exit and the flat plate was four times the nozzle diameter long. The DMD modes extract the characteristic pattern and its frequency that relate to the aeroacoustic fields. The estimated frequencies of DMD modes were compared with the acoustic spectra measured using microphones. The estimated frequency of the DMD mode that has the largest amplitude approximately coincides with that of the highest peak in the acoustic spectra regardless of the dataset length. However, the variation in the estimated frequencies of the high-order DMD modes increases when the dataset length is short. Although the estimated frequencies of the second and third DMD modes did not match the peak frequencies of the acoustic spectra, the estimation accuracy of the frequency of the modes can be improved by recalculating the frequency based on the wavelength of the corresponding spatial mode. The order of the amplitude of DMD modes did not agree with the order of the peak magnitude in the acoustic spectra, except for the first mode. This is because the schlieren method visualizes the density gradient resulting in emphasizing the high-frequency fluctuations. This mismatch was mitigated by correcting the acoustic spectrum considering the first derivative of the acoustic spectrum. Therefore, the verification of the estimation accuracy considering the data characteristics is important when the exact DMD analysis is applied to the noisy experimental data. Graphical abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s12650-022-00836-9

    Web of Science

    Scopus

    researchmap

  50. Optimal gate selection method for simultaneous lifetime-based measurement of PSP and TSP 査読有り

    Kasai, M; Nagata, T; Nonomura, T; Saito, Y; Asai, K

    MEASUREMENT SCIENCE AND TECHNOLOGY   33 巻 ( 9 )   2022年9月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Measurement Science and Technology  

    In this study, a new method that optimizes a measurement condition in a lifetime-based simultaneous measurement of a pressure-sensitive paint (PSP) and a temperature-sensitive paint (TSP) is proposed for the improvement of the accuracy of the pressure measurement. An optimal gate is selected based on a pressure measurement error when calculating the pressure and the temperature simultaneously from measurement values of a PSP and a TSP. A shot noise of a PSP, a temperature error, and a fluctuation in an emission intensity ratio due to blurring were considered error factors of the PSP measurement. The pressure measurement error propagated from each error source was considered as an evaluation index in an optimization of a measurement condition. We evaluated 17 types of TSP characteristics and selected an optimal TSP and a measurement condition for the PSP measurement. Further, the optimized measurement condition was evaluated in a PSP/TSP simultaneous measurement using a coupon-based test. The optimal measurement condition obtained based on the proposed method and an empirical selection method were compared by a PSP/TSP simultaneous measurement using a coupon-based test. A small-pressure measurement error, i.e. high pressure-measurement accuracy, was realized by the proposed method in the simultaneous lifetime-based method of a PSP and a TSP. In addition to the analyses above, the blurring effects were found to be minor and briefly summarized in appendices.

    DOI: 10.1088/1361-6501/ac769b

    Web of Science

    Scopus

    researchmap

  51. Practical Fast-Response Anodized-Aluminum Pressure-Sensitive Paint Using Chemical Adsorption Luminophore as Optical Unsteady Pressure Sensor 査読有り

    Oka, Y; Nagata, T; Kasai, M; Ozawa, Y; Asai, K; Nonomura, T

    SENSORS   22 巻 ( 17 )   2022年9月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors  

    We developed and evaluated an anodized-aluminum pressure-sensitive paint (AA-PSP) with new formulations of free-base porphyrin, (Formula presented.), as an optical unsteady pressure sensor. The luminophore (Formula presented.) has quite a short fluorescent lifetime (2.4 ns on the condition of the AA-PSP). The fluorescence spectroscopy result shows that the excitation wavelength of (Formula presented.) corresponds to violet-colored (425 nm) and green-colored (longer than 520 nm) lights. The pressure sensitivity is sufficiently high for the pressure sensor (0.33–0.51%/kPa) and the temperature sensitivity is very low (0.07–1.46%/K). The photodegradation of the AA-PSPs is not severe in both excitation light sources of the green LED and the Nd:YAG laser. The resonance tube experiment result shows the cut-off frequency of the AA-PSPs is over 9.0 kHz, and the results of the shock tube experiment show the 10 µs order time constant of the normal shock wave.

    DOI: 10.3390/s22176401

    Web of Science

    Scopus

    PubMed

    researchmap

  52. Visualization of Pressure and Skin-Friction Fields on Rotating Blade Under Low-Pressure Conditions 査読有り

    Nagata, T; Sato, H; Okochi, M; Matsuyama, T; Sugioka, Y; Kasai, M; Kusama, K; Numata, D; Nonomura, T; Asai, K

    AIAA JOURNAL   60 巻 ( 9 ) 頁: 5422 - 5435   2022年9月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    Distributions of the pressure and mass transfer coefficient on rotating blades under low-pressure (low-Reynoldsnumber) conditions were visualized, whereas the latter is closely related to the skin-friction distribution. Two types of optical measurement techniques, lifetime-based pressure-sensitive paint (PSP) measurements and sublimation visualization, were implemented for the experiment inside a low-pressure chamber. For the lifetime-based PSP measurement, different types of PSP were compared, and the one most suitable in low-pressure applications was selected. In addition, the gate time setting for the low-pressure condition was determined. For the sublimation method, naphthalene was selected as the sublimation surface based on previous studies. The rotating blade test model was a 0.3-m-diam rotor system with two rectangular blades with an aspect ratio of two. The experiments were carried out at a rotational speed of 2400 rpm and at an ambient pressure of 10 kPa. The three-fourth-span Reynolds number was 9000. The pitch angle of the blades was set to 0–20 deg. Both methods successfully illustrated clear images of the distribution of pressure and mass transfer coefficients on the upper surface of the blade, and the measurement in the low-pressure environment was successful.

    DOI: 10.2514/1.J061638

    Web of Science

    Scopus

    researchmap

  53. Sound source characteristics generated by shocklets in isotropic compressible turbulence 査読有り

    Terakado, D; Nonomura, T; Kawai, S; Aono, H; Sato, M; Oyama, A; Fujii, K

    PHYSICAL REVIEW FLUIDS   7 巻 ( 8 )   2022年8月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physical Review Fluids  

    This study analyzes the effects of shocklets on sound source characteristics using direct numerical simulations. The sound sources are obtained from the source terms of the Lighthill equation. The highest initial turbulent Mach number Mt0 is set to be 1.0, and the strong effects of shocklets on sound sources are investigated. Results show that the occurrence of shocklets in high turbulent Mach numbers Mt0≥0.7 affects the sound generation mechanism in addition to vortical motions which are well-known sound sources in low Mach number turbulent flows. The change in mechanism influences the relationship between the Reynolds stress and entropy terms. For low turbulent Mach number flows without shocklets, the Reynolds stress and entropy terms partially show the same signs around and on vortices. However, for high turbulent Mach numbers with shocklets, the terms exhibit opposite signs across shocklets. The behaviors of the Reynolds stress and entropy terms across shocklets are explained analytically by using a one-dimensional shock relation. The change in sound source characteristics keeps velocity dependence on total sound source strength almost unchanged independent of the turbulent Mach number, though each term's sound source strength (normalized by the total sound source strength) becomes larger for the higher turbulent Mach numbers Mt0≥0.9 than those for low turbulent Mach numbers Mt0≤0.4. Besides, the applicability of the present study to predict far-field acoustic wave characteristics is discussed. The source terms based on Lilley's decomposition show that the sound sources derived by shocklets have quadruple characteristics. Also, it is shown that the given knowledge in the present study, especially for the relation between the Reynolds stress and entropy terms across shocklets, can be used to improve the source modeling for a nonlinear acoustic analogy based on the Lighthill's acoustic analogy and Burgers' equation. In addition, the paper provides a possible explanation of the contributions of the shocklets for a mechanism of crackle noise that the generated acoustic waves by shocklets propagates to the acoustic field and show high-frequency spectral characteristics.

    DOI: 10.1103/PhysRevFluids.7.084605

    Web of Science

    Scopus

    researchmap

    その他リンク: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevFluids.7.084605/fulltext

  54. Enhancement of signal-to-noise ratio of schlieren visualization measurements in low-density wind tunnel tests using modal decomposition 査読有り

    Shigeta, T; Nagata, T; Nonomura, T; Asai, K

    JOURNAL OF VISUALIZATION   25 巻 ( 4 ) 頁: 697 - 712   2022年8月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Visualization  

    Abstract: Signal processing methods that remove noise due to atmospheric fluctuation and image sensors and extract fluid phenomena from schlieren images obtained in the low-density wind tunnel test were developed together with the highly sensitive schlieren measurement setup. Time-series schlieren images of the flow around a triangular airfoil were analyzed, and the effectiveness of noise reduction methods using the randomized singular value decomposition and band-pass filtering using the fast Fourier transform (FFT) and the inverse FFT were investigated. The proposed method succeeded in removing noise by taking advantage of the frequency difference between the noise and fluid phenomena, and the fluid phenomena around the airfoil were clearly visualized at a Reynolds number of 3000 and a Mach number of 0.15. Graphical abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s12650-022-00829-8

    Web of Science

    Scopus

    researchmap

  55. Slanted cylinder afterbody aerodynamics measured by 0.3-m magnetic suspension and balance system with six-degrees-of-freedom control 査読有り

    Tashiro, K; Yokota, S; Zigunov, F; Ozawa, Y; Asai, K; Nonomura, T

    EXPERIMENTS IN FLUIDS   63 巻 ( 8 )   2022年8月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    In this study, a cylinder with a slanted afterbody was magnetically levitated without support structures by means of a magnetic suspension and balance system (MSBS) with six-degrees-of-freedom (6-DOF) control. The levitation stability during the 6-DOF levitation was first confirmed and accurate to less than 8.9 μm and 18.6 mdeg at 15 m/s freestream. The results show that the model can be rigidly levitated with the 6-DOF control. Then, aerodynamic force on the levitated model was measured and its wake was visualized. Hystereses in aerodynamics and wake structure were observed around the critical Reynolds number between 3.3 × 10 4 and 3.6 × 10 4. Graphical abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-022-03470-1

    Web of Science

    Scopus

    researchmap

  56. Direct Numerical Simulation of Flow over a Triangular Airfoil Under Martian Conditions 査読有り

    Caros, L; Buxton, O; Shigeta, T; Nagata, T; Nonomura, T; Asai, K; Vincent, P

    AIAA JOURNAL   60 巻 ( 7 ) 頁: 3961 - 3972   2022年7月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    Martian conditions present various challenges when designing rotorcraft. Specifically, the thin atmosphere and low sound speed require Martian rotor blades to operate in a low-Reynolds-number (1000–10,000) compressible regime, for which conventional airfoils are not designed. Here, we use PyFR to undertake high-order direct numerical simulations (DNS) of flow over a triangular airfoil at a Mach number of 0.15 and Reynolds number of 3000. Initially, spanwise periodic DNS are undertaken. Extending the domain-span-to-chord ratio from 0.3 to 0.6 leads to better agreement with wind-tunnel data at higher angles of attack, when the flow is separated. This is because smaller domain spans artificially suppress three-dimensional breakdown of coherent structures above the suction surface of the airfoil. Subsequently, full-span DNS in a virtual wind tunnel are undertaken, including all wind-tunnel walls. These capture blockage and wall boundary-layer effects, leading to better agreement with wind-tunnel data for all angles of attack compared to spanwise periodic DNS. The results are important in terms of understanding discrepancies between previous spanwise periodic DNS and wind-tunnel data. They also demonstrate the utility of high-order DNS as a tool for accurately resolving flow over triangular airfoils under Martian conditions.

    DOI: 10.2514/1.J061454

    Web of Science

    Scopus

    researchmap

  57. Instability of separated shear layer around levitated freestream-aligned circular cylinder 査読有り

    Yokota, S; Asai, K; Nonomura, T

    PHYSICS OF FLUIDS   34 巻 ( 6 )   2022年6月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    In the present study, characteristics of a shear layer around a freestream-aligned circular cylinder and the relationship between the shear layer motion and the aerodynamic force were investigated under supportless condition. A 0.3-m magnetic suspension and balance system was employed, and experiments were conducted without a mechanical supporting device. Velocity fields were measured using particle image velocimetry with a sufficient temporal and spatial resolution, and high-frequency velocity fluctuations caused by small Kelvin-Helmholtz (KH) vortices were captured. The power spectral densities of velocity fluctuations represent phenomena such as KH vortex convection, vortex pairing, and convection of multiple vortices. Furthermore, fluctuations of the shear layer position were investigated. The results illustrate that the dominant frequency of the shear layer position is lower than the frequency of the velocity, and it shows good agreement with the characteristic frequency of lift force fluctuations. The present results together with the report in the previous study illustrate that the pressure fluctuations are considered to drive both fluctuations of the shear layer position and lateral aerodynamic force.

    DOI: 10.1063/5.0091044

    Web of Science

    Scopus

    researchmap

  58. Proposal and verification of optical flow reformulation based on variational method for skin-friction-stress field estimation from unsteady oil film distribution 査読有り

    Endo, K; Ambo, T; Saito, Y; Nonomura, T; Chen, L; Asai, K

    JOURNAL OF VISUALIZATION   25 巻 ( 2 ) 頁: 263 - 280   2022年4月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Visualization  

    Abstract: In this study, the optical flow method for the skin-friction-stress estimation from the unsteady oil film distribution was reformulated based on the variational method, and the validity of the proposed method was verified in comparison with the conventional method. The regularization is proposed to be added directly to the skin-friction-stress field in the proposed method while the regularization is added to the amount of oil movement in the conventional method. As a result, the smoothness of the skin-friction-stress field can be controlled by adjusting the regularization parameter in the proposed method whereas it was difficult in the conventional method. The performance of the proposed method was evaluated to be superior to the previous method through the numerical and experimental data. Graphic Abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s12650-021-00794-8

    Web of Science

    Scopus

    researchmap

  59. Low-Grid-Resolution-RANS-Based Data Assimilation of Time-Averaged Separated Flow Obtained by LES 査読有り

    Nakamura, M; Ozawa, Y; Nonomura, T

    INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS   36 巻 ( 2 ) 頁: 167 - 185   2022年2月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Computational Fluid Dynamics  

    The objective of this study is to obtain accurate flow field analysis results in a short computational time by using data assimilation, which increases the accuracy of Reynolds averaged Navier-Stokes (RANS) simulations with low grid resolution. The large-eddy simulation (LES) results are assimilated into RANS simulations. In those simulations, the turbulence-model parameters are optimised by an ensemble Kalman filter with a proposed method for adaptive hyperparameter optimisation. The target of calculations is the flow field around a square cylinder of the Reynolds number of approximately (Formula presented.). Only the surface pressure of the square cylinder is used as an observation variable. For this shape, the assimilated RANS flow field is similar to that given by the LES analysis, and the drag coefficient reproducibility is improved by (Formula presented.). The turbulence-model parameters are also used in the analyses of different cross-sectional shape and are found to improve the reproducibility of the flow field.

    DOI: 10.1080/10618562.2022.2085257

    Web of Science

    Scopus

    researchmap

  60. Time-resolved particle image velocimetry and pressure sensitive paint measurements of afterbody flow dynamics 査読有り

    Zigunov, F; Sellappan, P; Alvi, F; Ozawa, Y; Saito, Y; Nonomura, T; Asai, K

    PHYSICAL REVIEW FLUIDS   7 巻 ( 2 )   2022年2月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physical Review Fluids  

    In this study, the dynamical behavior of the vortex pair produced in the wake of a cylinder with a slanted afterbody, relevant to cargo aircraft applications, is examined experimentally through time-resolved particle image velocimetry (TR-PIV) and fast-response pressure sensitive paint (PSP). The vortex wandering phenomenon, characterstic of this wake, is measured with state of the art, time-resolved diagnostics at Reynolds numbers ranging from ReD=25000 to 750000 and a slant angle of φ=45°. Spectral proper orthogonal decomposition reveals a consistent and narrow normalized frequency band (0.56<StD<0.64) with significant energetic peaks in both surface pressure and near-field vortex velocity fields across all Reynolds numbers examined. Pressure sensitive paint measurements at free stream velocities ranging from 15 m/s (ReD=150000) to 75 m/s (ReD=750000) reveal a strong unsteady signature of the flow structures that are related to the vortex wandering at these normalized frequencies. These structures consist of traveling pressure waves at the surface that excite the helical mode of the vortex core. These pressure patterns could be detected at free-stream velocities as low as 15 m/s, where the pressure fluctuations are of the order of 20 Pa.

    DOI: 10.1103/PhysRevFluids.7.024701

    Web of Science

    Scopus

    researchmap

  61. Markerless Image Alignment Method for Pressure-Sensitive Paint Image 査読有り

    Suzuki, K; Inoue, T; Nagata, T; Kasai, M; Nonomura, T; Matsuda, Y

    SENSORS   22 巻 ( 2 )   2022年1月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors  

    We propose a markerless image alignment method for pressure-sensitive paint measurement data replacing the time-consuming conventional alignment method in which the black markers are placed on the model and are detected manually. In the proposed method, feature points are detected by a boundary detection method, in which the PSP boundary is detected using the Moore-Neighbor tracing algorithm. The performance of the proposed method is compared with the conventional method based on black markers, the difference of Gaussian (DoG) detector, and the Hessian corner detector. The results by the proposed method and the DoG detector are equivalent to each other. On the other hand, the performances of the image alignment using the black marker and the Hessian corner detector are slightly worse compared with the DoG and the proposed method. The computational cost of the proposed method is half of that of the DoG method. The proposed method is a promising for the image alignment in the PSP application in the viewpoint of the alignment precision and computational cost.

    DOI: 10.3390/s22020453

    Web of Science

    Scopus

    PubMed

    researchmap

  62. Single-pixel correlation applied to background-oriented schlieren measurement 査読有り

    Sugisaki, H; Lee, C; Ozawa, Y; Nakai, K; Saito, Y; Nonomura, T; Asai, K; Matsuda, Y

    EXPERIMENTS IN FLUIDS   63 巻 ( 1 )   2022年1月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: A high-spatial resolution measurement system by the background-oriented schlieren (BOS) method is proposed in this note. The single-pixel correlation method is applied for the image pairs obtained by the BOS method, and the displacement is calculated. The backgrounds are projected by a high-speed projector and changed at 900 Hz for calculation of the pixel-to-pixel correlation. This method is compared with the conventional method which utilizes the constant background and calculates the displacement by the conventional spatial correlation. The results show that the proposed system can obtain the displacement distribution in the single-pixel resolution which is eight times as high resolution as the conventional one. Graphical abstract: [Figure not available: see fulltext.].

    DOI: 10.1007/s00348-021-03373-7

    Web of Science

    Scopus

    researchmap

  63. Data-Driven Sensor Selection Method Based on Proximal Optimization for High-Dimensional Data With Correlated Measurement Noise 査読有り

    Nagata, T; Yamada, K; Nonomura, T; Nakai, K; Saito, Y; Ono, S

    IEEE TRANSACTIONS ON SIGNAL PROCESSING   70 巻   頁: 5251 - 5264   2022年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Transactions on Signal Processing  

    The present paper proposes a data-driven sensor selection method for a high-dimensional nondynamical system with strongly correlated measurement noise. The proposed method is based on proximal optimization and determines sensor locations by minimizing the trace of the inverse of the Fisher information matrix under a block-sparsity hard constraint. The proposed method can avoid the difficulty of sensor selection with strongly correlated measurement noise, in which the possible sensor locations must be known in advance for calculating the precision matrix for selecting sensor locations. The problem can be efficiently solved by the alternating direction method of multipliers, and the computational complexity of the proposed method is proportional to the number of potential sensor locations when it is used in combination with a low-rank expression of the measurement noise model. The advantage of the proposed method over existing sensor selection methods is demonstrated through experiments using artificial and real datasets.

    DOI: 10.1109/TSP.2022.3212150

    Web of Science

    Scopus

    researchmap

  64. Evaluation of Optimization Algorithms and Noise Robustness of Sparsity-Promoting Dynamic Mode Decomposition 査読有り

    Iwasaki, Y; Nonomura, T; Nakai, K; Nagata, T; Saito, Y; Asai, K

    IEEE ACCESS   10 巻   頁: 80748 - 80763   2022年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Access  

    In the present study, we organize the existing sparsity-promoting dynamic mode decomposition (DMDsp) in terms of noise robustness, propose faster optimization algorithm for DMDsp, and evaluate its characteristics. Two kinds of DMDsp, namely system-based DMDsp (sDMDsp) and observation-based DMDsp (oDMDsp), combined with three kinds of optimization algorithm, namely the fast iterative shrinkage thresholding algorithm (FISTA), the alternating direction method of multipliers (ADMM), and a greedy algorithm, are investigated. For both sDMDsp and oDMDsp, FISTA yields the shortest processing time. The processing time for sDMDsp with FISTA is shorter than that for oDMDsp with FISTA. The original data reconstruction errors for sDMDsp and oDMDsp are similar among the three optimization algorithms. The noise robustness for sDMDsp and oDMDsp is evaluated. sDMDsp and oDMDsp have similar robustness to observation noise, except for a system with large system and observation noise, for which oDMDsp outperforms sDMDsp.

    DOI: 10.1109/ACCESS.2022.3193157

    Web of Science

    Scopus

    researchmap

  65. Nondominated-Solution-Based Multi-Objective Greedy Sensor Selection for Optimal Design of Experiments 査読有り

    Nakai, K; Sasaki, Y; Nagata, T; Yamada, K; Saito, Y; Nonomura, T

    IEEE TRANSACTIONS ON SIGNAL PROCESSING   70 巻   頁: 5694 - 5707   2022年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Transactions on Signal Processing  

    In this study, a nondominated-solution-based multi-objective greedy method is proposed and applied to a sensor selection problem based on the multiple indices of the optimal design of experiments. The proposed method simultaneously considers multiple set functions and applies the idea of Pareto ranking for the selection of sets. Specifically, a new index is iteratively added to the nondominated solutions of sets, and the multi-objective functions are evaluated for new sets. The nondominated solutions are selected from the examined solutions, and the next sets are then considered. With this procedure, the multi-objective optimization of multiple set functions can be conducted with reasonable computational costs. This paper defines a new class of greedy algorithms which includes the proposed nondominated-solution-based multi-objective greedy algorithm and the group greedy algorithm, and the characteristics of those algorithms are theoretically discussed. Then, the proposed method is applied to the sensor selection problem and its performance is evaluated. The results of the test case show that the proposed method not only gives the Pareto-optimal front of the multi-objective optimization problem but also produces sets of sensors in terms of D-, A-, and E-optimality, that are superior to the sets selected by pure greedy methods that consider only a single objective function.

    DOI: 10.1109/TSP.2022.3224643

    Web of Science

    Scopus

    researchmap

  66. Greedy Sensor Selection for Weighted Linear Least Squares Estimation Under Correlated Noise 査読有り

    Yamada, K; Saito, Y; Nonomura, T; Asai, K

    IEEE ACCESS   10 巻   頁: 79356 - 79364   2022年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Access  

    Optimization of sensor selection has been studied to monitor complex and large-scale systems with data-driven linear reduced-order modeling. An algorithm for greedy sensor selection is presented under the assumption of correlated noise in the sensor signals. A noise model is given using truncated modes in reduced-order modeling, and sensor positions that are optimal for generalized least squares estimation are selected. The determinant of the covariance matrix of the estimation error is minimized by efficient one-rank computations in both underdetermined and overdetermined problems. The present study also reveals that the objective function with correlated noise is neither submodular nor supermodular. Several numerical experiments are conducted using randomly generated data and real-world data. The results show the effectiveness of the selection algorithm in terms of accuracy in the estimation of the states of large-dimensional measurement data.

    DOI: 10.1109/ACCESS.2022.3194250

    Web of Science

    Scopus

    researchmap

  67. Feasibility Study of Controlling Supersonic Boundary-layer Flows Using Jets Flapping at Several Tens of Kilohertz 査読有り

    Aoki, R; Fujimura, I; Handa, T; Lee, C; Ozawa, Y; Saito, Y; Nonomura, T; Asai, K

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   65 巻 ( 5 ) 頁: 221 - 229   2022年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    An experimental study is performed to investigate the feasibility of success in controlling supersonic boundary-layer flows using a device to discharge the jets flapping at several tens of kilohertz (kHz). In the experiments, a shadowgraph image velocimetry (SIV) technique is applied for measuring the velocities in a supersonic boundary-layer flow with a freestream Mach number of 2.05. Five operations in the device are tested (i.e., the operation of discharging no jet, non-flapping jets, and jets flapping at 15 kHz, 17 kHz, and 30 kHz). The experimental results reveal that the flapping jets work so as to effectively increase the boundary layer fullness in the near-wall region as compared to that of the non-flapping jets. In addition, the operation of discharging the jets flapping at 30 kHz displays the most remarkable increase in the boundary layer fullness among the five operations. These experimental results illustrate that the device to generate a high-frequency flapping jet can be a practicable actuator for controlling supersonic boundary-layer flows.

    DOI: 10.2322/tjsass.65.221

    Web of Science

    Scopus

    researchmap

  68. Schlieren Visualization and Motion Analysis of an Isolated and Clustered Particle(s) after Interacting with Planar Shock 査読有り

    Nagata, T; Nonomura, T; Ohtani, K; Asai, K

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   65 巻 ( 4 ) 頁: 185 - 194   2022年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    In the present study, the visualization of compressible flow around a particle/particles including wake vortices and drag estimation were conducted through shock-particle interaction experiments. An experimental method that can investigate flow over isolated and clustered particle(s) (with a minimum diameter of 0.3 mm) interacting with a planar shock was established. For flow visualization, the Mach number (M) and Reynolds number (Re) based on the relative velocity between the particle and the quantities behind the planar shock wave were 0.46 ¯ M ¯ 1.24 and 3500 ¯ Re ¯ 9800, respectively. The present measurement system succeeded in visualizing flow structures not only for shock waves, but also wake structures formed behind the particle(s) under subsonic and transonic conditions, and the Mach number effect was provided. The mean drag coefficient was estimated from the time-position data of the particle at 3100 ¯ Re ¯ 9800 and M = 0.46. The estimated drag coefficient was close to that of the value estimated by the drag model and previous experiments. The flowfield around clustered particles was visualized and its breakdown process was observed. The particle cluster dispersed due to aerodynamic interference. Particularly, the particles located on the upper side of the particle cluster moved upward against the gravitational force.

    DOI: 10.2322/tjsass.65.185

    Web of Science

    Scopus

    researchmap

  69. Comparison of three-dimensional density distribution of numerical and experimental analysis for twin jets 査読有り

    Lee, C; Ozawa, Y; Haga, T; Nonomura, T; Asai, K

    JOURNAL OF VISUALIZATION   24 巻 ( 6 ) 頁: 1173 - 1188   2021年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Visualization  

    Abstract: Three-dimensional density fields of the twin jets were numerically and experimentally investigated. The present study focused on the comparison of the density distribution for the twin jets. The results obtained by the computational fluid dynamics (CFD) and three-dimensional background-oriented schlieren (3D-BOS) indicate that the periodic density fluctuation appears in the potential core each nozzle, and the flow structure of the twin jets is quite similar. The distribution of the normalized density value at the nozzle centerline agrees well with CFD and 3D-BOS. The density value of the shear layer between the nozzles increases as the interaction of the twin jets occurs. The trend of increasing and decreasing the interference between the nozzles was almost the same as each other. On the other hand, the position where the interaction of the twin jets starts and the growth rate of interaction were different. This is probably due to the effect of the laminar-to-turbulent transition occurred in the results of CFD. This result indicates that the laminar-to-turbulent transition can be estimated from the velocity fields obtained by CFD and particle image velocimetry (PIV). Graphic Abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s12650-021-00765-z

    Web of Science

    Scopus

    researchmap

  70. Flow-Control Characteristics with Nanosecond-Pulse Plasma Actuator for Different Airfoil Shapes 査読有り

    Komuro, A; Kanno, S; Suzuki, K; Ando, A; Nonomura, T; Asai, K

    AIAA JOURNAL   59 巻 ( 12 ) 頁: 5301 - 5309   2021年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    The wind tunnel experiments of separation flow control by a nanosecond-pulse-driven dielectric-barrier-discharge plasma actuator (ns-DBDPA) for three airfoil shapes of NASA-Common-Research-Model (NASA-CRM), Gottingen387, and NACA0015 airfoils were conducted and the results were compared. Aerodynamic forces, surface pressures, and particle image velocimetry images were obtained in the experiments. The results of the aerodynamic force and surface pressure measurements showed that the characteristics of the flow separation control by ns-DBDPA are clearly different depending on the airfoil shape, and particularly the type of stall. NACA0015 exhibited leading-edge stall under the conditions investigated, and ns-DBDPA achieved flow control by producing vortices. NASA-CRM exhibited thin-airfoil stall, and ns-DBDPA increased the maximum lift of the lift curve even after the stall. On the other hand, Gottingen387, which exhibited trailing-edge stall, achieved almost no flow control at any actuator position, actuation frequency, or voltage amplitude. The flow control mechanisms for different types of airfoils are discussed based on the particle image velocimetry measurement results.

    DOI: 10.2514/1.J060486

    Web of Science

    Scopus

    researchmap

  71. Generalized estimation methods of turbulent fluctuation of high-speed flow with single-pixel resolution particle image velocimetry 査読有り

    Nonomura, T; Ibuki, T; Ozawa, Y; Asai, K; Oyama, A

    MEASUREMENT SCIENCE AND TECHNOLOGY   32 巻 ( 12 )   2021年12月

     詳細を見る

    担当区分:筆頭著者   掲載種別:研究論文(学術雑誌)   出版者・発行元:Measurement Science and Technology  

    The methods that measure the turbulence statistics distribution of high-speed flow with high spatial resolution using particle-image-velocimetry images are proposed, and their performances are verified. Two methods are proposed, and the problems caused by blurring the particle shape due to the high-speed movements are resolved. While the conventional method approximates the unique particle shapes with a circular distribution for image pairs, the first proposed method approximates the different particle shapes with an ellipse for first and second images of pairs and reduces the effects of the blur in the flow direction of the particles. Meanwhile, the second proposed method treats the general particle shapes such as the blur of temporally changing laser intensity and adopts the deconvolution analysis using a Fourier transform. Synthetic particle images were created and a supersonic jet test was performed, and the proposed methods were evaluated to be superior to the previous method for the estimation of turbulent fluctuation using those data.

    DOI: 10.1088/1361-6501/ac27e9

    Web of Science

    Scopus

    researchmap

  72. Fast greedy optimization of sensor selection in measurement with correlated noise 査読有り

    Yamada, K; Saito, Y; Nankai, K; Nonomura, T; Asai, K; Tsubakino, D

    MECHANICAL SYSTEMS AND SIGNAL PROCESSING   158 巻   2021年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Mechanical Systems and Signal Processing  

    A greedy algorithm is proposed for sparse-sensor selection in reduced-order sensing that contains correlated noise in measurement. The sensor selection is carried out by maximizing the determinant of the Fisher information matrix in a Bayesian estimation operator. The Bayesian estimation with a covariance matrix of the measurement noise and a prior probability distribution of estimating parameters, which are given by the modal decomposition of high dimensional data, robustly works even in the presence of the correlated noise. After computational efficiency of the algorithm is improved by a low-rank approximation of the noise covariance matrix, the proposed algorithms are applied to various problems. The proposed method yields more accurate reconstruction than the previously presented method with the determinant-based greedy algorithm, with reasonable increase in computational time.

    DOI: 10.1016/j.ymssp.2021.107619

    Web of Science

    Scopus

    arXiv

    researchmap

  73. Effect of burst ratio on flow separation control using a dielectric barrier discharge plasma actuator at Reynolds number 2.6 x 10<SUP>5</SUP> 査読有り

    Suzuki, K; Komuro, A; Nonomura, T; Asai, K; Ando, A

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   54 巻 ( 31 )   2021年8月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Physics D: Applied Physics  

    In this study, the effect of the burst ratio (BR) on flow separation control using an alternating-current dielectric barrier discharge plasma actuator (DBDPA) was investigated. The effects of BR on the lift force on the NACA0015 airfoil were quantitatively evaluated by force measurements, and those on the flow field were measured by particle image velocimetry (PIV) and Schlieren visualisation. The force measurements showed that the recovery of the lift force decreased as BR increased, indicating that the flow separation control effect of the DBDPA decreased as BR increased. The PIV measurements showed that the temporal variation in vorticity was smaller at BR = 80% than at BR = 20% and that the vorticity did not change periodically at BR = 100%. Schlieren visualisation showed that DBDPA-induced flow produced a density gradient near the DBDPA electrode; the gradient was periodically observed and was found to be proportional to BR. In contrast, the density gradient in the separated shear layer varied at the end of each burst waveform, and the degree of variation decreased as BR increased. In addition, the root mean square value of the Schlieren signal intensity in the separated shear layer decreased with increasing BR. This result suggests that not only the strength and frequency of the disturbance input of the DBDPA but also the switching timing of the disturbance input are important for producing vorticity and thereby ensuring flow control.

    DOI: 10.1088/1361-6463/ac00ee

    Web of Science

    Scopus

    researchmap

  74. Supersonic and Hypersonic Drag Coefficients for a Sphere 査読有り

    Loth, E; Daspit, JT; Jeong, M; Nagata, T; Nonomura, T

    AIAA JOURNAL   59 巻 ( 8 ) 頁: 3261 - 3274   2021年8月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    A comprehensive review of all relevant experimental data was completed, including recent data for the drag coefficient for a sphere in supersonic and hypersonic flows. The primary characterization parameter included the relative Mach, Knudsen, and Reynolds numbers based on the relative velocity, the sphere diameter, and other parameters. This review of data showed that the previously proposed nexus at a Reynolds number below 45 was not strictly met, and it instead included a weak transonic bump, which was identified numerically for the first time with the present simulations. New continuum-gas and rarefied-gas simulations were conducted and were combined with the expanded experimental dataset to improve the quantitative description of the drag coefficient in this region. The results indicated that a quasi nexus bridges the rarefaction regime and the compressible flow regimes. The comprehensive dataset was then used to develop new empirical models for the drag coefficient that showed improved robustness and accuracy as compared to previous models. These models are limited by the critical Reynolds number associated with boundary-layer transition on the sphere, which was found to increase substantially with the sphere Mach number.

    DOI: 10.2514/1.J060153

    Web of Science

    Scopus

    researchmap

  75. Data-Driven Sparse Sensor Selection Based on A-Optimal Design of Experiment With ADMM 査読有り

    Nagata, T; Nonomura, T; Nakai, K; Yamada, K; Saito, Y; Ono, S

    IEEE SENSORS JOURNAL   21 巻 ( 13 ) 頁: 15248 - 15257   2021年7月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Sensors Journal  

    The present study proposes a sensor selection method based on the proximal splitting algorithm and the A-optimal design of experiment using the alternating direction method of multipliers (ADMM) algorithm. The performance of the proposed method was evaluated with a random sensor problem and compared with previously proposed methods, such as the greedy and convex relaxation methods. The performance of the proposed method is better than the existing greedy and convex relaxation methods in terms of the A-optimality criterion. Although, the proposed method requires a longer computational time than the greedy method, it is quite shorter than that of convex relaxation method in large-scale problems. Then the proposed method was applied to the data-driven sparse-sensor-selection problem. The dataset adopted was the National Oceanic and Atmospheric Administration optimum interpolation sea surface temperature dataset. At a number of sensors larger than that of the latent variables, the proposed method showed similar and better performance compared with previously proposed methods in terms of the A-optimality criterion and reconstruction error.

    DOI: 10.1109/JSEN.2021.3073978

    Web of Science

    Scopus

    researchmap

  76. Data-driven approach for noise reduction in pressure-sensitive paint data based on modal expansion and time-series data at optimally placed points 査読有り

    Inoue, T; Matsuda, Y; Ikami, T; Nonomura, T; Egami, Y; Nagai, H

    PHYSICS OF FLUIDS   33 巻 ( 7 )   2021年7月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    We propose a noise reduction method for unsteady pressure-sensitive paint (PSP) data based on modal expansion, the coefficients of which are determined from time-series data at optimally placed points. In this study, the proper orthogonal decomposition (POD) mode calculated from the time-series PSP data is used as a modal basis. Based on the POD modes, the points that effectively represent the features of the pressure distribution are optimally placed by the sensor optimization technique. Then, the time-dependent coefficient vector of the POD modes is determined by minimizing the difference between the time-series pressure data and the reconstructed pressure at the optimal points. Here, the coefficient vector is assumed to be a sparse vector. The advantage of the proposed method is a self-contained method, while existing methods use other data, such as pressure tap data for the reduction of the noise. As a demonstration, we applied the proposed method to the PSP data measuring the Kármán vortex street behind a square cylinder. The reconstructed pressure data agreed very well with the pressures independently measured by pressure transducers. This modal-based approach will be applicable not only to PSP data but other types of experimental data.

    DOI: 10.1063/5.0049071

    Web of Science

    Scopus

    researchmap

  77. Analysis of transonic buffet on ONERA-M4 model with unsteady pressure-sensitive paint 査読有り

    Uchida, K; Sugioka, Y; Kasai, M; Saito, Y; Nonomura, T; Asai, K; Nakakita, K; Nishizaki, Y; Shibata, Y; Sonoda, S

    EXPERIMENTS IN FLUIDS   62 巻 ( 6 )   2021年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: The transonic buffet on an ONERA-M4 model was experimentally investigated using an unsteady pressure-sensitive paint (PSP) in the present study. Wind tunnel tests were conducted in a blowdown-type transonic wind tunnel at a Mach number of 0.84 and a chord Reynolds number of 2.0 × 10 6. The angle of attack was varied in between - 3. 0 ∘ and 4. 0 ∘. The left wing was painted with a polymer/ceramic PSP with low surface roughness, and the right wing was painted with a temperature-sensitive paint. The measured PSP data were processed to calculate time-series pressure coefficients, root-mean-squares pressure-coefficient fluctuations, power spectral density, coherence, and phase shift. The behavior of the unsteady pressure field was different from that observed for the NASA Common Research Model (CRM) in a previous study. The dominant frequency of the shock oscillation shifted from the low-Strouhal-number component (St< 0.05) to the bump Strouhal number (St= 0.11 for the center frequency) with increasing angle of attack. The separation processes with an increasing angle of attack were also found to be different for the two models. The separation starts from the mid-span region in the CRM, while the separation starts from the wingtip in the ONERA-M4 model. The characteristic pressure fluctuations known as “buffet cells” were not observed for the ONERA-M4 model. These differences are considered to be caused by the difference in model geometries, such as the wing twist and the airfoil cross-sectional profile. Graphical abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-021-03228-1

    Web of Science

    Scopus

    researchmap

  78. Flow characteristics around extremely low fineness-ratio circular cylinders 査読有り

    Kuwata, M; Abe, Y; Yokota, S; Nonomura, T; Sawada, H; Yakeno, A; Asai, K; Obayashi, S

    PHYSICAL REVIEW FLUIDS   6 巻 ( 5 )   2021年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Physical Review Fluids  

    The accurate measurement of flows and aerodynamic characteristics around a bluff body has been a challenging task due to the existence of interference between the wake and mechanical model supports in wind-tunnel experiments. The present study focuses on a freestream-aligned circular cylinder with an extremely low fineness ratio (the ratio of the axial length to diameter) ranging from 0.30 to 0.50, which has never been investigated without interference from a mechanical model support. We employed a magnetic suspension and balance system to eliminate interference from the model support and measured the drag and velocity fields in the diameter-based Reynolds number between 2.0×104 and 7.7×104. As the fineness ratio decreases below 1.50, the size of the recirculation bubble increases and the velocity distribution on the central axis inside the bubble gradually converges to that of the circular disk. Furthermore, large-eddy simulations were performed in the Reynolds number of 4.0×104, whose drag coefficient agrees well with experiments. Based on those results, it was found that the drag coefficient monotonically converges to that of the circular disk without local maximum. This study revealed that in the low-fineness-ratio regime (0.10-0.50), a critical geometry, at which the drag coefficient shows a local maximum, does not exist in the circular cylinder. Subsequently, unsteady flow analyses were performed, where two characteristic frequencies, i.e., St=0.05 and 0.155, were identified from power spectral densities of the drag coefficient and the pitching moment coefficient. The associated flow structures are then extracted by a phase-averaging procedure, where the phase-averaged flows with St=0.05 represent the recirculation bubble pumping while the phase-averaged flows with St=0.155 show nonaxisymmetric structures inside the recirculation bubble.

    DOI: 10.1103/PhysRevFluids.6.054704

    Web of Science

    Scopus

    researchmap

  79. Data-Driven Sparse Sampling for Reconstruction of Acoustic-Wave Characteristics Used in Aeroacoustic Beamforming 査読有り

    Kaneko, S; Ozawa, Y; Nakai, K; Saito, Y; Nonomura, T; Asai, K; Ura, H

    APPLIED SCIENCES-BASEL   11 巻 ( 9 ) 頁: 4216 - 4216   2021年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Applied Sciences (Switzerland)  

    In this study, the propagation time and attenuation rate distributions of each sound source grid point (200 × 200) to a microphone of an arbitrary position across the shear layer, which are required for beamforming, were reconstructed by the reduced-order model with sparse sampling for acceleration of the computation. First, the propagation time and attenuation rate distributions, including the refraction of sound by the shear layer were calculated over 100 patterns of combinations of the wind speed and the microphone position, as training data. The dominant modes and optimum sampling points were discovered from the training data. Subsequently, data-driven sparse sampling for reconstruction was applied and the propagation time and the attenuation rate from each grid point (200 × 200) to a microphone were quickly calculated for the given microphone position and wind speed. The error of the obtained calculation result is 1% or less, and the approximation by data-driven sparse sampling is concluded to be effective.

    DOI: 10.3390/app11094216

    Web of Science

    Scopus

    researchmap

  80. Frequency Response of Pressure-Sensitive Paints under Low-Pressure Conditions 査読有り

    Kasai, M; Sasaki, D; Nagata, T; Nonomura, T; Asai, K

    SENSORS   21 巻 ( 9 ) 頁: 3187 - 3187   2021年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors  

    The characteristics of fast-response pressure-sensitive paints (PSPs) in low-pressure conditions were evaluated. Three representative porous binders were investigated: polymer-ceramic PSP (PC-PSP), anodized-aluminum PSP (AA-PSP), and thin-layer chromatography PSP (TLC-PSP). For each PSP, two types of luminophores, Pt(II) meso-tetra (pentafluorophenyl) porphine (PtTFPP) and tris(bathophenanthroline) ruthenium dichloride (Ru(dpp)3 ), were used as sensor molecules. Pressure sensitivities, temperature sensitivities, and photodegradation rates were measured and evaluated using a pressure chamber. The effect of ambient pressure on the frequency response was investigated using an acoustic resonance tube. The diffusivity coefficients of PSPs were estimated from the measured frequency response and luminescent lifetime, and the governing factor of the frequency response under low-pressure conditions was identified. The results of static calibration show that PC-PSP/PtTFPP, AA-PSP/Ru(dpp)3, and TLC-PSP/PtTFPP have high pressure sensitivities that exceed 4%/kPa under low-pressure conditions and that temperature sensitivity and photodegradation rates become lower as the ambient pressure decreases. Dynamic calibration results show that the dynamic characteristics of PSPs with PtTFPP are dependent on the ambient pressure, whereas those of PSPs with Ru(dpp)3 are not influenced by the ambient pressure. This observation indicates that the governing factor in the frequency response under low-pressure conditions is the lifetime for PC-PSP and TLC-PSP, whereas the governing factor for AA-PSP is diffusion.

    DOI: 10.3390/s21093187

    Web of Science

    Scopus

    PubMed

    researchmap

  81. Effects of compressibility and Reynolds number on the aerodynamics of a simplified corrugated airfoil 査読有り

    Herrero, AG; Noguchi, A; Kusama, K; Shigeta, T; Nagata, T; Nonomura, T; Asai, K

    EXPERIMENTS IN FLUIDS   62 巻 ( 4 )   2021年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: This study aims to isolate and evaluate the influence of a corrugation on flow structures and aerodynamics under compressible low Reynolds number conditions, and to compare it to simpler but well-known model: the flat plate. The simplified corrugated model was made by a flat surface with only two corrugations on the leading edge. The models only differ for the corrugations on the leading edge. Force values were measured at a Reynolds number ranging from 10,000 to 25,000 and at a Mach number from 0.2 to 0.6. Pressure sensitive paint was used at the same flow conditions and the pressure distribution over the models was obtained. Schlieren visualization was also conducted and flow characteristics were observed. Detailed analysis showed that the corrugated model experiences strong depression on the leading edge caused by the separation of the boundary layer. Because of the presence of the corrugation, the shear layer transitions to turbulent rapidly and reattaches to the surface before reaching the summit of the first corrugation, separating again at its peak. Instabilities in the shear layer were dissipated thanks to the shape of the corrugation allowing pressure recovery and discouraging flow separation. The flow reattaches before reaching the trailing edge. The results showed that the transition of the boundary layer was accelerated as the Reynolds number increases on corrugated model, leading to a stronger negative pressure zone in the leading edge. Due to pressure recovery being less effective, lead to similar performances for the range of studied Reynolds numbers. The compressibility effects resulted in a delay on the transition of the instability of the shear layer, negatively affecting the intensity of the pressure gradients as well as pressure recovery. This contributed to the variation in the performance of the wing. As a result, the corrugated model has a better aerodynamic performance compared to the flat plate at low Reynolds numbers, but not for higher Mach numbers. Graphic abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-021-03164-0

    Web of Science

    Scopus

    researchmap

  82. Effect of Oxygen Mole Fraction on Static Properties of Pressure-Sensitive Paint 査読有り

    Okudera, T; Nagata, T; Kasai, M; Saito, Y; Nonomura, T; Asai, K

    SENSORS   21 巻 ( 4 ) 頁: 1 - 15   2021年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors (Switzerland)  

    The effects of the oxygen mole fraction on the static properties of pressure-sensitive paint (PSP) were investigated. Sample coupon tests using a calibration chamber were conducted for poly(hexafluoroisopropyl methacrylate)-based PSP (PHFIPM-PSP), polymer/ceramic PSP (PC-PSP), and anodized aluminum PSP (AA-PSP). The oxygen mole fraction was set to 0.1–100%, and the ambient pressure (Pref) was set to 0.5–140 kPa. Localized Stern–Volmer coefficient Blocal increased and then decreased with increasing oxygen mole fraction. Although Blocal depends on both ambient pressure and the oxygen mole fraction, its effect can be characterized as a function of the partial pressure of oxygen. For AA-PSP and PHFIPM-PSP, which are low-pressure-and relatively low-pressure-type PSPs, respectively, Blocal peaks at PO2 ref < 12 kPa. In contrast, for PC-PSP, which is an atmospheric-pressure-type PSP in the investigated range, Blocal does not have a peak. Blocal has a peak at a relatively high partial pressure of oxygen due to the oxygen permeability of the polymer used in the binder. The peak of SPR, which is the emission intensity change with respect to normalized pressure fluctuation, appears at a lower partial pressure of oxygen than that of Blocal. This is because the intensity of PSP becomes quite low at a high partial pressure of oxygen even if Blocal is high. Hence, the optimal oxygen mole fraction depends on the type of PSP and the ambient pressure range of the experiment. This optimal value can be found on the basis of the partial pressure of oxygen.

    DOI: 10.3390/s21041062

    Web of Science

    Scopus

    PubMed

    researchmap

  83. Investigation of Mach number effects on flow over a flat plate at Reynolds number of 1.0 x 10<SUP>4</SUP> by schlieren visualization 査読有り

    Kusama, K; Nagata, T; Anyoji, M; Nonomura, T; Asai, K

    FLUID DYNAMICS RESEARCH   53 巻 ( 1 ) 頁: 015513 - 015513   2021年2月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Fluid Dynamics Research  

    Flow over a flat plate with a 5% thickness ratio is investigated by schlieren visualization in compressible low-Reynolds-number conditions. The results show that flow separates at the leading-edge and laminar separation-bubble forms. The position of the maximum root mean square of the schlieren image which is related to the position of the vortex shedding moves downstream as a Mach number increases. Furthermore, the two-dimensional structure of generated vortices is maintained up to the trailing edge at the Mach number of 0.66. The frequency analysis of the time-series intensity value of the schlieren images also shows that the flow is stabilized with increasing the Mach number. The position of the end of the pressure plateau region matches the position where the root-mean-square value of the intensity image becomes a maximum due to vortex shedding.

    DOI: 10.1088/1873-7005/abe04c

    Web of Science

    Scopus

    researchmap

  84. Analysis of unsteady flow around an axial circular cylinder of critical geometry using combined synchronous measurement in magnetic suspension and balance system 査読有り

    Yokota, S; Ochiai, T; Ozawa, Y; Nonomura, T; Asai, K

    EXPERIMENTS IN FLUIDS   62 巻 ( 1 )   2021年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: The wake structure of a freestream-aligned circular cylinder and its aerodynamic characteristics were investigated using a magnetic suspension and balance system (MSBS), which can levitate a model to eliminate support interference. The objectives of the present study were to investigate the flow field around a freestream-aligned circular cylinder and to clarify its effect on the aerodynamic force and base pressure. Experiments were conducted using a 0.3-m MSBS for support-free wind tunnel tests. Six models with fineness ratios (length to diameter, L/D) of 1.0, 1.25, 1.5, 1.75, 2.0, and 2.25 were used. The freestream velocity was set to 10 and 20 m/s, which correspond to Reynolds numbers based on model diameters of 3.3 × 10 4 and 6.7 × 10 4, respectively. The velocity field, aerodynamic force, and base pressure were measured for each freestream-aligned circular cylinder. Two characteristic fluctuations with frequencies of St < 0.05 and St ≈ 0.13 were observed in a nonreattaching flow field. A low-frequency axisymmetric fluctuation related to the drag force and base pressure was observed in the axial direction. A high-frequency antisymmetric fluctuation related to the lift force was observed in the radial direction. These features are in good agreement with those of both recirculation-bubble pumping and vortex shedding observed in the wake of a disk reported in previous studies (Berger et al., J Fluids Struct 4(3):231–257, 1990; Yang et al., Phys Fluids 27(6):064101, 2015). Graphic abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-020-03101-7

    Web of Science

    Scopus

    researchmap

  85. Characteristic unsteady pressure field on a civil aircraft wing related to the onset of transonic buffet 査読有り

    Sugioka, Y; Nakakita, K; Koike, S; Nakajima, T; Nonomura, T; Asai, K

    EXPERIMENTS IN FLUIDS   62 巻 ( 1 )   2021年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: Unsteady pressure fields on a civil aircraft wing near the onset of transonic buffet have been investigated experimentally to identify flow unsteadiness that relates to the buffet onset determined by global criteria. An 80%-scale NASA Common Research Model was tested in the JAXA 2 m × 2 m Transonic Wind Tunnel at a Mach number of 0.85 and a chord Reynolds number of 2.27 × 106. The angle of attack was varied in small increments around the buffet onset angle determined by global criteria based on the lift curve and wing-root strain-gauge data. Unsteady pressure fields over the wing were measured using unsteady pressure-sensitive paint (PSP) with temperature-effect correction by temperature-sensitive paint (TSP). Characteristic pressure fluctuations, known as “buffet cells”, were observed under the off-design conditions at a bump Strouhal number of 0.2–0.5. The PSP results showed that the buffet cells arise at the mid-span wing at η ≈ 0.45, where a strong shock wave causes an initial boundary-layer separation. Phase shift distributions indicated that a pressure perturbation propagates from the inboard wing toward the outboard wing. The convection velocity and spanwise wavelength were approximately 0.5U∞ and 1.3cMAC, respectively. The angle of attack at which buffet cells first appear was found to be approximately equal to the buffet onset determined by the global criteria, indicating that the occurrence of the buffet cells is deeply related to the buffet onset for the present wing geometry. Graphic abstract: [Figure not available: see fulltext.].

    DOI: 10.1007/s00348-020-03118-y

    Web of Science

    Scopus

    researchmap

  86. Feasibility of skin-friction field measurements in a transonic wind tunnel using a global luminescent oil film 査読有り

    Costantini, M; Lee, T; Nonomura, T; Asai, K; Klein, C

    EXPERIMENTS IN FLUIDS   62 巻 ( 1 )   2021年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: The feasibility of skin-friction field measurements using the global luminescent oil-film skin-friction field estimation method was evaluated for a challenging case of a supercritical airfoil model under transonic wind-tunnel conditions (freestream Mach number of 0.72) at a high Reynolds number (10 million, based on the model chord length). The oil-film thickness and skin-friction coefficient distributions were estimated over the airfoil model upper surface for a range of angles of attack (from - 0. 4 ∘ to 2. 0 ∘), thus enabling the study of different boundary-layer stability situations with laminar–turbulent transition, including cases with shock-wave/boundary-layer interaction. Conventional pressure measurements on the surface and in the wake of the model as well as Schlieren flow visualizations were conducted to support the oil-film based investigations. In the laminar-flow regions, the oil-film thickness could be generally kept below the critical limit of roughness that would induce premature boundary-layer transition. The skin friction in this region could be estimated with a moderate confidence level, as confirmed for portions of the chord by the reasonable agreement with numerical data obtained via laminar boundary-layer computations. Moreover, the location of transition onset was evaluated from the skin-friction estimations with relatively low uncertainty, thus enabling the examination of the transition location evolution with varying angle of attack. The estimated locations of transition onset were shown to be in general agreement with reference transition locations measured via temperature-sensitive paint. On the other hand, the oil-film thickness in the turbulent-flow regions was larger than the height of the viscous sublayer, which led to an hydraulically rough surface with increased skin friction, as compared to the clean configuration. For this reason, quantitative skin-friction estimations were not feasible in the turbulent-flow regions. The global effects of the oil-film setup on the flow around the airfoil were evaluated from the estimations of the aerodynamic coefficients. In particular, it was shown that the presence of the specific base coat used for the application of the oil film already induced a significant increase in airfoil drag, as compared to the clean configuration, whereas a thin oil film led to negligible or small additional increases in drag. Based on the present observations, considerations for the further improvement of the global luminescent oil-film skin-friction field estimation method in transonic flow experiments at high Reynolds numbers are elucidated. Graphic abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-020-03109-z

    Web of Science

    Scopus

    researchmap

  87. Aeroacoustic Fields of Supersonic Twin Jets at the Ideally Expanded Condition 査読有り

    Ozawa, Y; Nonomura, T; Saito, Y; Asai, K

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   64 巻 ( 6 ) 頁: 312 - 324   2021年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    The aeroacoustic fields of twin jets and the equivalent single jet were experimentally investigated using particle image velocimetry (PIV), schlieren visualization, and acoustic measurement. The present study focuses on the aeroacoustic fields of the twin jets, and the effect of the interaction between each jet was investigated using various nozzle spacing. The PIV results indicated that strong interaction causes elliptical jet growth on a cross-stream plane and a decrease in the Reynolds stress of the inner shear layer on a plane containing both jet axes. The dynamic mode decomposition of the double-pulsed schlieren images extracted the interaction of each jet, which relates to the Mach wave generation. The noise of the twin jets was basically quieter than the noise of an equivalent single jet because of a shielding effect and a reduction in the Reynolds stress resulting in a decrease in the overall sound pressure level.

    DOI: 10.2322/tjsass.64.312

    Web of Science

    Scopus

    researchmap

  88. Data-Driven Determinant-Based Greedy Under/Oversampling Vector Sensor Placement 査読有り

    Saito, Y; Yamada, K; Kanda, N; Nakai, K; Nagata, T; Nonomura, T; Asai, K

    CMES-COMPUTER MODELING IN ENGINEERING & SCIENCES   129 巻 ( 1 ) 頁: 1 - 30   2021年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:CMES - Computer Modeling in Engineering and Sciences  

    A vector-measurement-sensor-selection problem in the undersampled and oversampled cases is considered by extending the previous novel approaches: a greedy method based on D-optimality and a noise-robust greedy method in this paper. Extensions of the vector-measurement-sensor selection of the greedy algorithms are proposed and applied to randomly generated systems and practical datasets of flowfields around the airfoil and global climates to reconstruct the full state given by the vector-sensor measurement.

    DOI: 10.32604/cmes.2021.016603

    Web of Science

    Scopus

    researchmap

  89. Effect of Objective Function on Data-Driven Greedy Sparse Sensor Optimization 査読有り

    Nakai, K; Yamada, K; Nagata, T; Saito, Y; Nonomura, T

    IEEE ACCESS   9 巻   頁: 46731 - 46743   2021年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Access  

    The problem of selecting an optimal set of sensors estimating a high-dimensional data is considered. Objective functions based on D-, A-, and E-optimality criteria of optimal design are adopted to greedy methods, that maximize the determinant, minimize the trace of the inverse, and maximize the minimum eigenvalue of the Fisher information matrix, respectively. First, the Fisher information matrix is derived depending on the numbers of latent state variables and sensors. Then, a unified formulation of the objective function based on A-optimality is introduced and proved to be submodular, which provides the lower bound on the performance of the greedy method. Next, greedy methods based on D-, A-, and E-optimality are applied to randomly generated systems and a practical dataset concerning the global climate; these correspond to an almost ideal and a practical case in terms of statistics, respectively. The D- and A-optimality-based greedy methods select better sensors. The E-optimality-based greedy method does not select better sensors in terms of the index of E-optimality in the oversample case, while the A-optimality-based greedy method unexpectedly does so in terms of the index of E-optimality. The poor performance of the E-optimality-based greedy method is due to the lack of submodularity in the E-optimality index and the better performance of the A-optimality-based greedy method is due to the relation between A- and E-optimality. Indices of D- and A-optimality seem to be important in the ideal case where the statistics for the system are well known, and therefore, the D- and A-optimality-based greedy methods are suitable for accurate reconstruction. On the other hand, the index of E-optimality seems to be critical in the more practical case where the statistics for the system are not well known, and therefore, the A-optimality-based greedy method performs best because of its superiority in terms of the index of E-optimality.

    DOI: 10.1109/ACCESS.2021.3067712

    Web of Science

    Scopus

    researchmap

  90. Determinant-Based Fast Greedy Sensor Selection Algorithm 査読有り

    Saito, Y; Nonomura, T; Yamada, K; Nakai, K; Nagata, T; Asai, K; Sasaki, Y; Tsubakino, D

    IEEE ACCESS   9 巻   頁: 68535 - 68551   2021年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Access  

    In this paper, the sparse sensor placement problem for least-squares estimation is considered, and the previous novel approach of the sparse sensor selection algorithm is extended. The maximization of the determinant of the matrix which appears in pseudo-inverse matrix operations is employed as an objective function of the problem in the present extended approach. The procedure for the maximization of the determinant of the corresponding matrix is proved to be mathematically the same as that of the previously proposed QR method when the number of sensors is less than that of state variables (undersampling). On the other hand, the authors have developed a new algorithm for when the number of sensors is greater than that of state variables (oversampling). Then, a unified formulation of the two algorithms is derived, and the lower bound of the objective function given by this algorithm is shown using the monotone submodularity of the objective function. The effectiveness of the proposed algorithm on the problem using real datasets is demonstrated by comparing with the results of other algorithms. The numerical results show that the proposed algorithm improves the estimation error by approximately 10% compared with the conventional methods in the oversampling case, where the estimation error is defined as the ratio of the difference between the reconstructed data and the full observation data to the full observation. For the NOAA-SST sensor problem, which has more than ten thousand sensor candidate points, the proposed algorithm selects the sensor positions in few seconds, which required several hours with the other algorithms in the oversampling case on a 3.40 GHz computer.

    DOI: 10.1109/ACCESS.2021.3076186

    Web of Science

    Scopus

    arXiv

    researchmap

  91. Feasibility Study on Real-time Observation of Flow Velocity Field using Sparse Processing Particle Image Velocimetry 査読有り

    Kanda, N; Nakai, K; Saito, Y; Nonomura, T; Asai, K

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   64 巻 ( 4 ) 頁: 242 - 245   2021年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    DOI: 10.2322/tjsass.64.242

    Web of Science

    Scopus

    researchmap

  92. Direct numerical simulation of subsonic, transonic and supersonic flow over an isolated sphere up to a Reynolds number of 1000 査読有り

    Nagata, T; Nonomura, T; Takahashi, S; Fukuda, K

    JOURNAL OF FLUID MECHANICS   904 巻   2020年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Fluid Mechanics  

    In the present study, compressible low-Reynolds-number flow past a stationary isolated sphere was investigated by direct numerical simulations of the Navier-Stokes equations using a body-fitted grid with high-order schemes. The Reynolds number based on free-stream quantities and the diameter of the sphere was set to be between 250 and 1000, and the free-stream Mach number was set to be between 0.3 and 2.0. As a result, it was clarified that the wake of the sphere is significantly stabilized as the Mach number increases, particularly at the Mach number greater than or equal to 0.95, but turbulent kinetic energy at the higher Mach numbers conditions is higher than that at the lower Mach numbers conditions of similar flow regimes. A rapid extension of the length of the recirculation region was observed under the transitional condition between the steady and unsteady flows. The drag coefficient increases as the Mach number increases mainly in the transonic regime and its increment is almost due to the increment in the pressure component. In addition, the increment in the drag coefficient is approximately a function of the Mach number and independent of the Reynolds number in the continuum regime. Moreover, the effect of the Mach and Reynolds numbers on the flow properties such as the drag coefficient and flow regime can approximately be characterized by the position of the separation point.

    DOI: 10.1017/jfm.2020.629

    Web of Science

    Scopus

    researchmap

  93. Effect of flux evaluation methods on the resolution and robustness of the two-step finite-difference weno scheme 査読有り

    Kamiya T., Asahara M., Nonomura T.

    Numerical Mathematics   13 巻 ( 4 ) 頁: 1068 - 1097   2020年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Numerical Mathematics  

    The resolution and the robustness of the weighted essentially non-oscillatory (WENO) scheme and two-step finite-difference WENO (TSFDWENO) schemes are compared by strictly using the same flux evaluation method and smoothness indicators. TSFDWENO schemes are defined to include a family of weighted compact nonlinear scheme (WCNS) and an alternativeWENO scheme. Comparison results indicate that WCNS has a higher resolution than the WENO scheme, while the WENO scheme is more robust than WCNS. Additionally, various flux evaluation methods are combined with TSFDWENO schemes, and they are evaluated. Then, the effects of the flux evaluation methods on the resolution and robustness of the scheme are investigated, and the results show that the robustness and the resolution can be significantly altered by changing the flux evaluation method. This study reveals the advantage of being able to use various flux evaluation methods in the TSFDWENO scheme as well as the fair comparison of the WENO schemes and WCNS. On the other hand, these effects are marginalized when changing the interpolation and differencing method. Such knowledge can be important when selecting schemes for actual simulation and developing guidelines for scheme improvement.

    DOI: 10.4208/NMTMA.OA-2019-0033

    Scopus

    researchmap

  94. Single-Pixel Particle Image Velocimetry for Characterization of Dielectric Barrier Discharge Plasma Actuators 査読有り

    Nonomura, T; Ozawa, Y; Ibuki, T; Nankai, K; Komuro, A; Nishida, H; Marios, K; Kubo, N; Kawabata, H

    AIAA JOURNAL   58 巻 ( 11 ) 頁: 4952 - 4957   2020年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    In a study, particle image pairs of the induced velocity emanating from the dielectric barrier discharge plasma actuator (DBDPA) are acquired for several amplitudes of applied voltage. The detailed averaged velocity distribution is estimated using the single-pixel ensemble correlation (SPC) method at a spatial resolution, which is higher for plasma actuator characterization than any other results using conventional spatial correlation (CSC) method. The averaged velocity distributions from the SPC and CSC methods are compared, and the effectiveness of the SPC method in characterizing the induced flow of plasma actuators is evaluated. In addition, the body-force distribution is estimated from the averaged velocity distribution obtained by the SPC method and compared with that of the CSC method.

    DOI: 10.2514/1.J059239

    Web of Science

    Scopus

    researchmap

  95. Experimental demonstration of low-voltage operated dielectric barrier discharge plasma actuators using SiC MOSFETs 査読有り

    Sato, S; Ozawa, Y; Komuro, A; Nonomura, T; Asai, K; Ohnishi, N

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   53 巻 ( 43 )   2020年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Physics D: Applied Physics  

    Successful operation of a multi-stage dielectric-barrier-discharge (DBD) plasma actuator is demonstrated by operating it on voltage one order of magnitude lower than that of a conventional single-stage DBD plasma actuator. An applied voltage waveform of direct current (DC) voltage combined with high-frequency repetitive pulses is generated by a simple power system consisting of a DC power supply and silicon carbide metal-oxide-semiconductor field-effect transistors. The time-averaged flow field obtained by particle image velocimetry indicates that a successively accelerated ionic wind is obtained by the eight-stage DBD plasma actuator. The velocity of the induced ionic wind increases with increasing DC voltage and repetitive pulse frequency. The maximum velocity of approximately 4.5 m s-1 is achieved when the DC voltage of 1500∼ V is applied with the switching frequency of 150∼ kHz, suggesting that the proposed multi-stage DBD plasma actuator induces the same level of ionic wind as a conventional high-voltage-operated single-stage DBD plasma actuator, even with a low voltage.

    DOI: 10.1088/1361-6463/aba0e1

    Web of Science

    Scopus

    researchmap

    その他リンク: https://iopscience.iop.org/article/10.1088/1361-6463/aba0e1/pdf

  96. Evaluating the applicability of a phase-averaged processing of skin-friction field measurement using an optical flow method 査読有り

    Lee, C; Lee, T; Nonomura, T; Asai, K

    JOURNAL OF VISUALIZATION   23 巻 ( 5 ) 頁: 773 - 782   2020年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Visualization  

    Abstract: The phase-averaged skin-friction analysis based on global luminescent oil film (GLOF) was conducted for periodically fluctuating unsteady phenomena at the frequency of approximately 150 Hz which is estimated based on Karman vortex shedding. An unsteady pressure transducer and a camera were synchronized, and the time-averaged and phase-averaged skin-friction fields were investigated. The time-series image pair data obtained by the camera were decomposed into eight intervals of a phase angle of π/ 4 with synchronizing the signal of the unsteady pressure. The phase-averaged result shows the periodical pattern corresponding to the vortices structure generated from the edge of the test model which was not resolved by the time-averaged result. The phase-averaged processing was successfully applied to the GLOF measurement, and the results showed the detail information of skin friction at each phase. Graphic abstract: [Figure not available: see fulltext.].

    DOI: 10.1007/s12650-020-00667-6

    Web of Science

    Scopus

    researchmap

  97. Unsteady skin-friction field estimation based on global luminescent oil-film image analysis 査読有り

    Lee, T; Lee, C; Nonomura, T; Asai, K

    JOURNAL OF VISUALIZATION   23 巻 ( 5 ) 頁: 763 - 772   2020年10月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Visualization  

    Abstract: A global luminescent oil-film (GLOF) image analysis method to estimate unsteady skin-friction fields in an unsteady flow field is proposed and demonstrated. A governing equation describing the dynamics of the oil film (the thin-oil-film equation) is employed for the unsteady oil-film images. The frequency response of the oil-film movement is analyzed, and a cutoff frequency is defined as a function of the oil-film thickness and the kinematic oil viscosity. The estimating skin-friction vector is defined along with a spatiotemporal weighted window and obtained by solving the overdetermined system of the thin-oil-film equation. The system can be solved by using the weighted linear least-squares method, and the time-resolved skin-friction field can be estimated. The time-resolved GLOF image analysis method is demonstrated on an experiment of a junction flow on a flat surface with a square cylinder. The GLOF images in the Kármán vortex shedding bounding the flat surface were acquired, and the time-resolved skin-friction fields were obtained. The results showed that fluctuation in the skin-friction vectors corresponds to the shedding frequency, and the vortices bounding the surface were extracted. The averaged skin-friction field is compared with the result of the previous study based on the time-independent model. The normalized skin friction from both methods showed good agreement, which indicates that the quantitative value will be obtained when a calibration process is involved in a future study. Graphic abstract: [Figure not available: see fulltext.].

    DOI: 10.1007/s12650-020-00661-y

    Web of Science

    Scopus

    researchmap

  98. Optimum pressure range evaluation toward aerodynamic measurements using PSP in low-pressure conditions 査読有り

    Nagata, T; Kasai, M; Okudera, T; Sato, H; Nonomura, T; Asai, K

    MEASUREMENT SCIENCE AND TECHNOLOGY   31 巻 ( 8 )   2020年8月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Measurement Science and Technology  

    In the present study, new performance evaluation parameters for pressure-sensitive paint (PSP) were proposed, and the effects of ambient pressure on the characteristics of the PSP were evaluated. The proposed parameters allow us to determine the optimal pressure range on the basis of the following quantities: (1) the Stern-Volmer coefficient, (2) the normalized pressure sensitivity to intensity changes due to flow-induced pressure fluctuations, (3) the change in the intensity of PSP emissions in response to the given change in pressure, and (4) the signal-to-noise ratio of the change in the PSP emission intensity due to flow-induced pressure fluctuations. The characteristics of several types of PSP were evaluated using the proposed parameters. It was demonstrated that the proposed parameters enable a comparison of the effects of ambient pressure on the characteristics of PSP, and the optimal pressure range for aerodynamic measurements could be successfully identified for the different PSP.

    DOI: 10.1088/1361-6501/ab81bb

    Web of Science

    Scopus

    researchmap

  99. Data-Driven Vector-Measurement-Sensor Selection Based on Greedy Algorithm 査読有り

    Saito, Y; Nonomura, T; Nankai, K; Yamada, K; Asai, K; Sasaki, Y; Tsubakino, D

    IEEE SENSORS LETTERS   4 巻 ( 7 ) 頁: 1 - 4   2020年7月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEEE Sensors Letters  

    A vector-measurement-sensor problem for the least squares estimation is considered, by extending a previous novel approach in this letter. An extension of the vector-measurement-sensor selection of the greedy algorithm is proposed and is applied to particle-image-velocimetry data to reconstruct the full state based on the information given by sparse vector-measurement sensors.

    DOI: 10.1109/LSENS.2020.2999186

    Web of Science

    Scopus

    arXiv

    researchmap

  100. Dynamic surface heat transfer and re-attachment flow measurement using luminescent molecular sensors 査読有り

    Chen, L; Kawase, C; Nonomura, T; Asai, K

    INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER   155 巻   2020年7月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Heat and Mass Transfer  

    Luminescent molecular sensors, which can be used as Temperature Sensitive Paint (TSP) or Pressure Sensitive Paint (PSP) in respective temperature or pressure measurements, has been proved to be one promising surface quantity measurement technology in recent years. It is advantageous in the experiments with complicated surface and is able to give flow field information such as surface flux and wall shear-stress. The current study is focused on the dynamic heat transfer measurement of a backward-facing step model, using luminescent molecular sensors as temperature probe. The effects of flow separation and re-attachment after a back-step model were experimentally discussed in wind tunnel tests. The experimental system was consisted of a molecular sensor calibration system, a dynamic data recording system and a data processing system. It is found that the reattachment process will form a low temperature region, which then gives the clear temperature field of the flow. Dynamic temperature field data show a re-attachment position around x/h = 5.7, which agrees well with oil-flow measurements as well as previous experiments. The dynamic temperature fluctuation data is discussed with the vibrations of flow and transient heat transfer behaviors after the backward step, which then is used in the analysis of surface wall shear-stress variations. It is concluded that the current luminescent molecular sensor method is capable of quantitative measurement for surface heat transfer and fluid flows.

    DOI: 10.1016/j.ijheatmasstransfer.2020.119684

    Web of Science

    Scopus

    researchmap

  101. Experimental investigation on compressible flow over a circular cylinder at Reynolds number of between 1000 and 5000 査読有り

    Nagata, T; Noguchi, A; Kusama, K; Nonomura, T; Komuro, A; Ando, A; Asai, K

    JOURNAL OF FLUID MECHANICS   893 巻   2020年6月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Fluid Mechanics  

    In the present study, a compressible low-Reynolds-number flow over a circular cylinder was investigated using a low-density wind tunnel with time-resolved schlieren visualizations and pressure and force measurements. The Reynolds number based on freestream quantities and the diameter of a circular cylinder was set to be between 1000 and 5000, and the freestream Mach number between 0.1 and 0.5. As a result, we have clarified the effect of on the aerodynamic characteristics of flow over a circular cylinder at. The results of the schlieren visualization showed that the trend of effect on the flow field, that are the release location of the Kármán vortices, the Strouhal number of vortex shedding and the maximum width of the recirculation, is changed at approximately. In addition, the spanwise phase difference of the surface pressure fluctuation was captured by the measurement using pressure-sensitive paint at approximately of higher- cases. The observed spanwise phase difference is considered to relate to the spanwise phase difference of the vortex shedding due to the oblique instability wave on the separated shear layer caused by the compressibility effects. The Strouhal number of the vortex shedding is influenced by and , and those effects are nonlinear. However, the effects of and can approximately be characterized by the maximum width of the recirculation. In addition, the effect on the drag coefficient can be characterized by the maximum width of the recirculation region and the Prandtl-Glauert transformation.

    DOI: 10.1017/jfm.2020.221

    Web of Science

    Scopus

    researchmap

  102. Experimental analysis of transonic buffet on a 3D swept wing using fast-response pressure-sensitive paint (vol 59, 108, 2018) 査読有り

    Sugioka, Y; Koike, S; Nakakita, K; Numata, D; Nonomura, T; Asai, K

    EXPERIMENTS IN FLUIDS   61 巻 ( 6 )   2020年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    There are typographical errors in the original publication of this article.

    DOI: 10.1007/s00348-020-02980-0

    Web of Science

    Scopus

    researchmap

  103. Single-pixel resolution velocity/convection velocity field of a supersonic jet measured by particle/schlieren image velocimetry 査読有り

    Ozawa, Y; Ibuki, T; Nonomura, T; Suzuki, K; Komuro, A; Ando, A; Asai, K

    EXPERIMENTS IN FLUIDS   61 巻 ( 6 )   2020年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: A single-pixel ensemble correlation method was applied to the schlieren and shadowgraph image velocimetry (SIV) and a velocimetry method that can obtain the convection velocity distribution of high spatial resolution without an expensive pulsed laser system being achieved for a laboratory-scale supersonic jet flow. A cold axisymmetric supersonic jet was employed, and the basic characteristics of the convection velocity fields are measured by SIV as well as those of the velocity fields by the particle image velocimetry (PIV) in the single-pixel resolution. The Mach number of a supersonic jet was 2.0, and the Reynolds number based on the diameter of the nozzle exit was 1.0 × 106. A pulsed light-emitting-diode light source was used for SIV as a less expensive light source. The single-pixel ensemble correlation method applied to PIV clearly visualizes the potential core and the shear layer development with the high spatial resolution. The axial velocity of SIV at the jet centerline is approximately 0.7–0.8 times of that of PIV which seems to relate to the convection velocity. The velocity calculated from the shadowgraph images agrees well with the convection velocity estimated from the Mach wave emission angle. The comparison between the scale of the visualized turbulent structure and the length scale of large eddies implied that the quantitative discussion of the SIV measurement requires careful consideration of the scale of the visualized turbulent structure on the SIV image. Graphic abstract: [Figure not available: see fulltext.]

    DOI: 10.1007/s00348-020-02963-1

    Web of Science

    Scopus

    researchmap

  104. Characteristic Evaluation of Chameleon Luminophore Dispersed in Polymer 査読有り

    Kasai, M; Sugioka, Y; Yamamoto, M; Nagata, T; Nonomura, T; Asai, K; Hasegawa, Y

    SENSORS   20 巻 ( 9 ) 頁: 2623 - 2623   2020年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors (Switzerland)  

    A temperature-sensitive paint (TSP) using a chameleon luminophore [Tb0.99Eu0.01 (hfa)3 (dpbp)]n is proposed. The chameleon luminophore was dispersed in isobutyl methacrylate polymer in a toluene solvent to fix it on a sample coupon. Temperature and pressure sensitivities of the chameleon luminophore-based TSP were measured using a spectrofluorophotometer. The emission for each wavelength was confirmed to be dependent on the temperature and pressure. The temperature and pressure sensitivities of the TSP were 0.81–2.8%/K and 0.08–0.12%/kPa, respectively. Higher temperature sensitivity can be obtained using the ratio of emissions from the two lanthanide ions, TbIII and EuIII . The temperature sensitivity when using the ratio of the emission intensities at 616 nm derived from EuIII and at 545 nm derived from TbIII was 3.2%/K, which was the highest value in the present study. In addition, the pressure sensitivity for the case using the ratio of the emission intensities at 616 and 545 nm was 4.8 × 10−2%/kPa. Higher temperature sensitivity and lower pressure sensitivity than that with a single wavelength can be achieved using the ratio of the emission intensities at the two peak wavelengths derived from TbIII and EuIII .

    DOI: 10.3390/s20092623

    Web of Science

    Scopus

    PubMed

    researchmap

  105. Effect of the Reynolds number on the aeroacoustic fields of a transitional supersonic jet 査読有り

    Ozawa, Y; Nonomura, T; Oyama, A; Asai, K

    PHYSICS OF FLUIDS   32 巻 ( 4 )   2020年4月

     詳細を見る

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.5138195

    Web of Science

    researchmap

  106. Dynamic Stall Control around Practical Airfoil Using Nanosecond-Pulse-Driven Dielectric Barrier Discharge Plasma Actuators 査読有り 国際誌

    Iwasaki, Y; Nonomura, T; Nankai, K; Asai, K; Kanno, S; Suzuki, K; Komuro, A; Ando, A; Takashima, K; Kaneko, T; Yasuda, H; Hayama, K; Tsujiuchi, T; Nakajima, T; Nakakita, K

    ENERGIES   13 巻 ( 6 ) 頁: 1376-1 - 17   2020年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Energies  

    The flow control effects of a nanosecond-pulse-driven dielectric barrier discharge plasma actuator (ns-DBDPA) in dynamic stall flow were experimentally investigated. The ns-DBDPA was installed on the leading edge of an airfoil model designed in the form of a helicopter blade. The model was oscillated periodically around 25% of the chord length. Aerodynamic coefficients were calculated using the pressure distribution, which was obtained by the measurement of the unsteady pressure by sensors inside the model. The flow control effect and its sensitivity to pitching oscillation and ns-DBDPA control parameters are discussed using the aerodynamic coefficients. The freestream velocity, the mean of the angle of attack, and the reduced frequency were employed as the oscillation parameters. Moreover, the nondimensional frequency of the pulse voltage, the peak pulse voltage, and the type and position of the ns-DBDPA were adopted as the control parameters. The result shows that the ns-DBDPA can decrease the hysteresis of the aerodynamic coefficients and a flow control effect is obtained in all cases. The flow control effect can be maximized by adopting the low nondimensional frequency of the pulse voltage.

    DOI: 10.3390/en13061376

    Web of Science

    Scopus

    researchmap

  107. Experimental investigation of transonic and supersonic flow over a sphere for Reynolds numbers of 10<SUP>3</SUP>-10<SUP>5</SUP> by free-flight tests with schlieren visualization 査読有り

    Nagata, T; Noguchi, A; Nonomura, T; Ohtani, K; Asai, K

    SHOCK WAVES   30 巻 ( 2 ) 頁: 139 - 151   2020年3月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Shock Waves  

    In this study, free-flight tests of a sphere for Reynolds numbers between 3.9 × 103 and 3.8 × 105 and free-flight Mach numbers between 0.9 and 1.6 were conducted using a ballistic range, and compressible low-Reynolds-number flows over an isolated sphere were investigated with the schlieren technique. The flow visualization was carried out under low-pressure conditions with a small sphere (minimum diameter of 1.5 mm) to produce compressible low-Reynolds-number flow. Also, time-averaged images of the flow near the sphere were obtained and compared to previous numerical results for Reynolds numbers between 50 and 1000. The experimental results clarified the structure of shock waves, recirculation region, and wake structures at the Reynolds number of 103–105 under transonic and supersonic flows. As a result, the following characteristics were clarified: (1) the amplitude of the wake oscillation was attenuated as the free-flight Mach number increased; (2) use of singular value decomposition permitted extraction of the mode of the wake structure even when schlieren images were unclear due to severe condition, and different modes in the wake structure were identified; (3) the Reynolds number had little effect on the separation point, but the length of the recirculation region increased as the Reynolds number decreased; and (4) the wake diameter at the end of the recirculation region decreased as the Mach number increased.

    DOI: 10.1007/s00193-019-00924-0

    Web of Science

    Scopus

    researchmap

  108. Flow visualization and transient behavior analysis of luminescent mini-tufts after a backward-facing step 査読有り

    Chen, L; Suzuki, T; Nonomura, T; Asai, K

    FLOW MEASUREMENT AND INSTRUMENTATION   71 巻   2020年3月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Flow Measurement and Instrumentation  

    Luminescent mini-tufts method has been used for surface flow visualization for a long time. One major challenging point of this method is quantitative analysis of transient flows and the dynamic structures. This study is focused on the application of luminescent mini-tufts method in transient flows. A backward-facing step (BFS) is used in this analysis, which is one classic model that consists both flow separation and re-attachment processes. In this study, the instantaneous mini-tufts recognition, image averaging and tuft inclination angle/tuft angle estimation processes are introduced for the analysis of luminescent mini-tufts for the first time on backward-facing step flow (Rem = 2.0 × 105–7.9 × 105 and Reh = 1.3 × 104–5.3 × 104). Detailed transient features and characterization process for the backward-facing step model are explained in this study. The combination of optical-oil flow and hot-wire anemometry methods with luminescent mini-tufts are also shown useful to give comprehensive flow field information, including the surface flow behaviors, boundary layer, re-attachment position identification, etc. In addition, the decomposition of the luminescent mini-tufts visualization data is also conducted to give the power spectral density (PSD) and characteristic frequencies for the mini-tufts behaviors under transient fluctuating flow conditions.

    DOI: 10.1016/j.flowmeasinst.2019.101657

    Web of Science

    Scopus

    researchmap

  109. Separated Flow Control of Small Horizontal-Axis Wind Turbine Blades Using Dielectric Barrier Discharge Plasma Actuators 査読有り

    Aono, H; Fukumoto, H; Abe, Y; Sato, M; Nonomura, T; Fujii, K

    ENERGIES   13 巻 ( 5 )   2020年3月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Energies  

    The flow control over the blades of a small horizontal-axis wind turbine (HAWT) model using a dielectric barrier discharge plasma actuator (DBD-PA) was studied based on large-eddy simulations. The numerical simulations were performed with a high-resolution computational method, and the effects of the DBD-PA on the flow fields around the blades were modeled as a spatial body force distribution. The DBD-PA was installed at the leading edge of the blades, and its impacts on the flow fields and axial torque generation were discussed. The increase in the ratios of the computed, cycle-averaged axial torque reasonably agreed with that of the available experimental data. In addition, the computed results presented a maximum of 19% increase in the cycle-averaged axial torque generation by modulating the operating parameters of the DBD-PA because of the suppression of the leading edge separation when the blade’s effective angles of attack were relatively high. Thus, the suppression of the leading edge separation by flow control can lead to a delay in the breakdown of the tip vortex as a secondary effect.

    DOI: 10.3390/en13051218

    Web of Science

    Scopus

    researchmap

  110. Validation and uncertainty analysis of global luminescent oil-film skin-friction field measurement 査読有り

    Lee, T; Nonomura, T; Asai, K; Naughton, JW

    MEASUREMENT SCIENCE AND TECHNOLOGY   31 巻 ( 3 )   2020年3月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Measurement Science and Technology  

    Results from a skin-friction-field measurement method using global luminescent oil-film images, in which the oil film covers a large portion of the surface, were examined by comparing them with those obtained from conventional hot-wire measurements. The measurement processes including calibrations, oil-film image acquisition, and image processing are explained, and error sources are analyzed. The experimental results show that the skin frictions measured by both methods in a turbulent boundary layer on a flat surface agree when the oil-film thickness is less than the height of the viscous sublayer (corresponding to an oil-film thickness of less than five wall units). The uncertainty of the measurements is presented. When the measurement conditions were optimum (illumination, exposure time, frame rate, oil height, etc), the uncertainty was approximately 3%-4%.

    DOI: 10.1088/1361-6501/ab512a

    Web of Science

    Scopus

    researchmap

  111. Active flow control using plasma actuators in a reduced pressure environment 査読有り

    Komuro, A; Sato, K; Maruyama, Y; Takashima, K; Nonomura, T; Kaneko, T; Ando, A; Asai, K

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   53 巻 ( 7 )   2020年2月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Physics D: Applied Physics  

    This paper proposes a lightweight, energy-efficient airflow control device that uses plasma discharge to realize stratospheric flight. Wind-tunnel experiments were performed in a reduced-pressure environment, and it was noted that plasma can suppress the flow separation around an airfoil, thereby dynamically changing the performance of the airfoil. The results demonstrate that even if the electron mean free path, reduced electric field for the plasma, and the aerodynamic Reynolds number for the stratospheric flight are very different from those at ground level, the plasma is effective in an airflow control device. Moreover, the proposed device operates by simply adhering thin tapes on a ready-made airfoil or hull of the airship and applying voltage to them, which contrasts with the conventionally developed plasma propulsion system. The airflow control technique using plasma will be a key technology in extending human activity to the stratosphere or regions at higher altitudes.

    DOI: 10.1088/1361-6463/ab598b

    Web of Science

    Scopus

    researchmap

  112. Unified mechanisms for separation control around airfoil using plasma actuator with burst actuation over Reynolds number range of 10<SUP>3</SUP>-10<SUP>6</SUP> 査読有り

    Sato, M; Okada, K; Asada, K; Aono, H; Nonomura, T; Fujii, K

    PHYSICS OF FLUIDS   32 巻 ( 2 )   2020年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    We conduct large-eddy simulations of separated airfoil flows with control by a dielectric-barrier-discharge plasma actuator over a wide range of Reynolds numbers. The Reynolds numbers based on the chord length (Re) are set at Re = 5.0 × 103, 1.0 × 104, 6.3 × 104, 2.6 × 105, and 1.6 × 106. These Reynolds numbers cover most of the conditions used in the previous studies on separation control by a plasma actuator. The burst frequency nondimensionalized by the chord length and freestream velocity (F+) is used as the computational parameter, and the effective burst actuation and control mechanisms at each Reynolds number condition are investigated. With regard to cases without the control, the flows separate near the leading edge in the laminar state at the Reynolds number range of 103-105, and a substantial turbulent separation occurs at the Reynolds number of 1.6 × 106. Separation control with a high burst frequency [F+ ≃ O(10)] can cause early flow reattachment through the promotion of turbulent transition of a separation shear-layer for Re = 6.3 × 104 and 2.6 × 105. Flow reattachment is mainly caused by momentum entrainment into the boundary layer by fine-scale turbulent vortices. On the other hand, the large-scale spanwise vortices play an important role at F+ = 1 for Re = 1.0 × 104 and 1.6 × 106. In these cases, the dynamics of the spanwise vortices show similar behavior and the pairing of these vortices significantly contributes to the separation control by increasing the momentum entrainment. The optimum value of F+ changes with a Reynolds number. In contrast, when a nondimensional burst frequency based on the characteristics of the separation shear-layer (Fθs) is considered, a high lift-to-drag ratio is found at Fθs≃O(10-2) for all Reynolds numbers. This demonstrates that one of the effective burst frequencies is closely related to the scale of the separation shear-layer, especially for the spanwise vortex shed from the separation shear-layer.

    DOI: 10.1063/1.5136072

    Web of Science

    Scopus

    researchmap

  113. Aerodynamic characteristics of low-fineness-ratio freestream-aligned cylinders with magnetic suspension and balance system 査読有り

    Shinji K., Nagaike H., Nonomura T., Asai K., Okuizumi H., Konishi Y., Sawada H.

    AIAA Journal   58 巻 ( 8 ) 頁: 3711 - 3714   2020年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    A study investigates the aerodynamic characteristics of the circular cylinder without support interference by using an magnetic suspension and balance system (MSBS), along with the investigation of a finer fineness ratio region is required for construction of a complete database. To elucidate the relationship between the aerodynamic force acting on a freestream-aligned circular cylinder with a low fineness ratio and the resulting wake structure, it is necessary to measure the aerodynamic force and the base pressure, as well as consider the flowfield, when the fineness ratio is systematically varied below a value of 0.75, whereas the existing data of drag coefficients in this region were scattered. The objectives of this study are to determine whether there exists a fineness ratio between 0.50 and 0.75 that maximizes the drag coefficient and to show the characteristics of aerodynamic forces without support interference.

    DOI: 10.2514/1.J058925

    Scopus

    researchmap

  114. Aerodynamics of Owl-like Wing Model at Low Reynolds Numbers

    Aono, H; Kondo, K; Nonomura, T; Anyoji, M; Oyama, A; Fujii, K; Yamamoto, M

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   63 巻 ( 1 ) 頁: 8 - 17   2020年

     詳細を見る

  115. Aerodynamics of owl-like wing model at low reynolds numbers 査読有り

    Aono H., Kondo K., Nonomura T., Anyoji M., Oyama A., Fujii K., Yamamoto M.

    Transactions of the Japan Society for Aeronautical and Space Sciences   63 巻 ( 1 ) 頁: 8 - 17   2020年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    Aerodynamics of an owl-like wing model at low Reynolds numbers (Re = O(104-5)) are investigated using large-eddy simulations with high-resolution computational schemes. The airfoil shape of the owl-like wing model is constructed based on a cross-sectional geometry of the owl wing at 40% wingspan from the root. The chord-based Re ranges from 1.0 © 104 to 5.0 © 104 and the angle of attack (¡) varies from 0 to 14 deg. The time-averaged lift (Cl) and drag coefficients computed are in reasonable agreement with the results of force measurement. The results computed clarify a nonlinear change in the Cl curve slope, which is due to an increase in the suction peaks in conjunction with the change in type of separation, the formation of a laminar separation bubble (LSB), and pressure recovery on the pressure side. The generation of the LSB on the suction and/or pressure sides at the Re of 2.3 © 104 and 4.6 © 104 are seen, while reattachments are observed only on the pressure side at the Re of 1.0 © 104 due to the camber of the wing. Furthermore, the owl-like wing model demonstrates favorable aerodynamic performance in terms of a maximum lift-to-drag ratio in comparison with several airfoils at the Re range considered. This is due to the strong suction peaks and distribution of surface pressure on the pressure side. It is emphasized that the concave lower surface enhances the time-averaged aerodynamic performance at all of the ¡ even though the LSB is generated and fluctuation in lift history is induced at low ¡.

    DOI: 10.2322/tjsass.63.28

    Scopus

    researchmap

  116. Large eddy simulation of acoustic waves generated from a hot supersonic jet 査読有り

    Nonomura, T; Nakano, H; Ozawa, Y; Terakado, D; Yamamoto, M; Fujii, K; Oyama, A

    SHOCK WAVES   29 巻 ( 8 ) 頁: 1133 - 1154   2019年11月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Shock Waves  

    The effects of jet temperature on acoustic waves generated by a supersonic jet are investigated using large eddy simulation (LES) based on a high-fidelity computational code. The sixth-order compact scheme and the fourth-order Runge–Kutta scheme are employed for spatial derivatives and time integration, respectively. First, a verification and validation study is conducted using simulations of a cold supersonic jet with a jet Mach number of 2.0 and Reynolds number of 9.0 × 10 5, and the effects of grid resolution and disturbance strength are evaluated. The verification and validation study shows that 6.5 × 10 8 grid points are sufficient for qualitative discussion of acoustic wave generation phenomena and that the addition of disturbances is important for suppressing the acoustic waves caused by the turbulent transition at the nozzle exit, as seen in previous studies for a subsonic jet. Then, LESs of supersonic jets with a jet Mach number of 2.0 and Reynolds number of 9.0 × 10 5 are performed for three temperature cases where the ratios of chamber to atmospheric temperature are 1.0, 2.7, and 4.0. The present results illustrate that different jet temperatures do not change the shear layer thickness, but the shear layer develops more inside the jet as the jet temperature increases, resulting in a shorter potential core for the hot jet. With regard to the acoustic fields, as the jet temperature increases, stronger Mach waves are emitted from a wider source region at wider radiation angles. We observe multiple Mach waves with different angles in the hot jet cases.

    DOI: 10.1007/s00193-019-00895-2

    Web of Science

    Scopus

    researchmap

  117. Mechanisms for turbulent separation control using plasma actuator at Reynolds number of 1.6 x 10<SUP>6</SUP> 査読有り

    Sato, M; Asada, K; Nonomura, T; Aono, H; Yakeno, A; Fujii, K

    PHYSICS OF FLUIDS   31 巻 ( 9 )   2019年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    We have conducted large-eddy simulations of turbulent separated flows over a NACA0015 airfoil with control by a plasma actuator. The Reynolds number based on the chord length is 1 600 000, and the angle of attack is 20.1°. At this angle of attack, the flow around the airfoil is fully separated. The effects of the location and operating conditions of the plasma actuator on the separation control are investigated. The plasma actuator is set at the leading edge, the turbulent reattachment point, or near the turbulent separation point. The nondimensional burst frequency (F+) is set to 1, 4, or 100. These frequencies are determined based on the dominant frequencies of the turbulent separated flow field of the no control case. A continuous actuation case has also been conducted. The location of the actuator where it most effectively suppresses the separation is the one closest to the turbulent separation point. In the burst mode case, the nondimensional burst frequency of unity is most effective in terms of the increase in the lift. To clarify the effective control mechanism, five objectives for turbulent separation control are compared. The results show that it is difficult to suppress the turbulent separation using the same strategies as in laminar separation control. The effective mechanism for turbulent separation control by burst actuation is found to be inducing the pairing of large-scale vortices near the airfoil surface. This large-scale vortex pairing induces freestream momentum into the boundary layer, leading to separation suppression. In addition, three other control effects can be achieved by varying the operating settings of the plasma actuator. The drag is slightly improved by reducing the length of the laminar separation bubble through high-frequency actuation from the leading edge.

    DOI: 10.1063/1.5110451

    Web of Science

    Scopus

    researchmap

  118. Cross-spectral analysis of PSP images for estimation of surface pressure spectra corrupted by the shot noise 査読有り

    Ozawa, Y; Nonomura, T; Mercier, B; Castelain, T; Bailly, C; Asai, K

    EXPERIMENTS IN FLUIDS   60 巻 ( 8 )   2019年8月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: We proposed applying the cross-spectrum analysis to the unsteady pressure-sensitive paint (PSP) images to eliminate the electronic shot noise component from the pressure fluctuation spectrum. The data of surface pressure fluctuation behind a square cylinder which measured by means of the polymer/ceramic PSP with a frequency response of approximately 5 kHz which is sufficiently high for studying the Kármán vortex shedding was used for the validation of this analysis method. The cross spectrum is compared with the auto-spectrum of PSP images and that of the Kulite pressure transducer that corresponds to the reference signal. The cross spectrum can drastically reduce the electronic shot noise component in the pressure fluctuation spectrum. The second peak of vortex shedding which is not observed in the result of auto-spectrum can be observed thanks to the noise reduction. The convergence of calculation is faster as the size of the spatial area for calculating cross spectrum increases. Graphic abstract: [Figure not available: see fulltext.].

    DOI: 10.1007/s00348-019-2776-4

    Web of Science

    Scopus

    researchmap

  119. Unsteady pressure-sensitive-paint (PSP) measurement in low-speed flow: characteristic mode decomposition and noise floor analysis 査読有り

    Sugioka, Y; Hiura, K; Chen, L; Matsui, A; Morita, K; Nonomura, T; Asai, K

    EXPERIMENTS IN FLUIDS   60 巻 ( 7 )   2019年7月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: Pressure-sensitive-paint (PSP) measurement was conducted for unsteady phenomena at various frequencies up to the order of kHz in low-speed flow to evaluate measurement accuracy of PSP. Pressure fluctuations on the floor surface induced by the Karman vortex were measured by PSP and unsteady pressure transducer. The dominant frequency of the pressure fluctuations is varied from 0.15 to 1.7 kHz by changing the size of the square cylinder. While regions with large pressure fluctuations could be visualized by calculating root mean square of pressure fluctuations from PSP images, the values significantly differed from those measured by pressure transducer. By applying Fast Fourier Transform (FFT), the power spectral density (PSD) at peak frequencies could be obtained within an error of 20%. Singular-value decomposition (SVD) yields a remarkable improvement in signal-to-noise ratio. However, amplitude of pressure fluctuations is changed depending on the way how to select modes. Three mode-selection methods for SVD filtering/reconstruction analysis are proposed in this study which show good improvement compared with convection method and are proved capable of extracting characteristic behaviors of the flow phenomena even below the noise floor.

    DOI: 10.1007/s00348-019-2755-9

    Web of Science

    Scopus

    researchmap

  120. Influence of discharge energy on the lift and drag forces induced by a nanosecond-pulse-driven plasma actuator 査読有り

    Komuro, A; Takashima, K; Suzuki, K; Kanno, S; Nonomura, T; Kaneko, T; Ando, A; Asai, K

    PLASMA SOURCES SCIENCE & TECHNOLOGY   28 巻 ( 6 )   2019年6月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Plasma Sources Science and Technology  

    Wind tunnel experiments at a flow velocity of 40 m s-1 with a nanosecond-pulse-driven plasma actuator (ns-DBDPA) on an airfoil have been performed (i) to study discharge parameters inducing the ns-DBDPA flow control effect and (ii) to investigate discharge-mediating flow parameters representing the induced discharge-flow interactions. The lift and drag forces' measurements demonstrate that, in addition to the well-known frequency effect, the discharge energy per pulse can be the key discharge parameter representing the ns-DBDPA effect on the forces rather than the discharge power under various discharge energy per pulse raised up to 80 mJ m-1 and discharge frequencies ranged from 10 to 1600 Hz. In a single pulse operation free from the discharge frequency effect, Schlieren imaging and particle image velocimetry show that the dynamic of two heated zones generated by ns-DBDPA is identical to those of the induced two vortices. This discharge-flow interaction observed under the frequency-free condition implies that the key discharge mediating flow parameter can lie in the identical dynamics of the heated zones. This study suggests that the discharge-mediating flow parameters for the discharge-flow interaction leading to the flow control effect on the forces can be a statistical variation in the Schlieren image intensity or the angles of the heated zones' trajectories.

    DOI: 10.1088/1361-6595/ab1daf

    Web of Science

    Scopus

    researchmap

  121. Characterization of luminescent mini-tufts in quantitative flow visualization experiments: Surface flow analysis and modelization 査読有り

    Chen, L; Suzuki, T; Nonomura, T; Asai, K

    EXPERIMENTAL THERMAL AND FLUID SCIENCE   103 巻   頁: 406 - 417   2019年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Experimental Thermal and Fluid Science  

    As a widely used surface flow visualization method, luminescent mini-tuft has become one challenging topic with its practical advantages in quantitative flow measurement. The luminescent mini-tufts method is preferred with its reduced size and increased luminescence, which is suitable for surface visualization measurement. To provide a standard method/procedure in quantitative analysis for luminescent mini-tuft measurement, the current study established an experimental characterization platform of luminescent mini-tufts method and conducted flat-pate model for flow analysis. The experimental system is consisted of wind tunnel and model section, high-speed image data recording system, digital image processing as well as the control system. The digital imaging processing method for result analysis is also explained, which includes the dark current image extraction, averaging, mini-tufts recognition, and tuft inclination angle/tuft angle estimation process. In this study, the steady flow characterization and quantitative flow analysis is conducted on a flat plate model (Re = 1.6 × 105–6.6 × 105), which is combined with hot-wire anemometry to investigate the basic surface flow topology and boundary layer behaviors. The method is shown capable of capturing both the steady and transient behaviors of a surface flow. Luminescent mini-tufts physical model is also established and found good agreement with the experimental results in this study, which in turn support the mini-tufts characterization and selection in practical applications.

    DOI: 10.1016/j.expthermflusci.2019.02.002

    Web of Science

    Scopus

    researchmap

  122. Visualization of density variations produced by alternating-current dielectric-barrier-discharge plasma actuators using the background-oriented schlieren method 査読有り

    Komuro, A; Ogura, N; Ito, M; Nonomura, T; Asai, K; Ando, A

    PLASMA SOURCES SCIENCE & TECHNOLOGY   28 巻 ( 5 )   2019年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Plasma Sources Science and Technology  

    Gas density perturbations generated by an alternating-current dielectric-barrier-discharge plasma actuator (ac-DBDPA) are quantitatively visualised using the background-oriented schlieren (BOS) method. A method of setting the optimum boundary condition for solving the Poisson equation in the BOS method is studied, and an integration method for the boundary condition in the vicinity of the plasma where the density change is steep is proposed. The BOS method is applied in two cases with different voltage amplitudes, and the variation in the absolute value of the density is discussed with the discharge properties. The results show a decrease in density in the synthetic jet induced by the ac-DBDPA and a spatiotemporal variation indicating a step-wise gas-heating phenomenon due to plasma discharge.

    DOI: 10.1088/1361-6595/ab1465

    Web of Science

    Scopus

    researchmap

  123. Effect of Reynolds number on flow behavior and pressure drag of axisymmetric conical boattails at low speeds 査読有り

    Tran, TH; Ambo, T; Lee, T; Ozawa, Y; Chen, L; Nonomura, T; Asai, K

    EXPERIMENTS IN FLUIDS   60 巻 ( 3 )   2019年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Abstract: The effect of Reynolds number on flow behaviors and pressure drag around axisymmetric conical boattails was experimentally investigated at low-speed conditions. Four conical boattails with slant angles of 12°, 16°, 20°, and 22° were studied. The Reynolds number ranged from 4.34 × 10 4 to 8.89 × 10 4 based on the model diameter. The global-luminescent-oil-film skin-friction measurement was employed to analyze the surface skin-friction topology. Quantitative skin-friction values at the centerline were obtained in this study. The results show that a separation bubble can be formed on boattail surfaces at angles from 12° to 20°. However, at a boattail angle of 22°, flow is fully separated near the boattail shoulder. The integrated afterbody pressure drag indicated that, at angles of 12°, 16°, and 22°, the Reynolds number has very small effect on the afterbody drag, while, at 20° the drag coefficient decrease was relatively large with increasing Reynolds number. We believe that this study provided the first results for a boattail angle of 20° and we observed that the size of the separation bubble decreased as the Reynolds number increased. The effect of the separation bubble on the pressure distribution was also examined in detail. Graphical abstract: [Figure not available: see fulltext.].

    DOI: 10.1007/s00348-019-2680-y

    Web of Science

    Scopus

    researchmap

  124. Extended-Kalman-filter-based dynamic mode decomposition for simultaneous system identification and denoising 査読有り

    Nonomura, T; Shibata, H; Takaki, R

    PLOS ONE   14 巻 ( 2 )   2019年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PLoS ONE  

    A new dynamic mode decomposition (DMD) method is introduced for simultaneous system identification and denoising in conjunction with the adoption of an extended Kalman filter algorithm. The present paper explains the extended-Kalman-filter-based DMD (EKFDMD) algorithm which is an online algorithm for dataset for a small number of degree of freedom (DoF). It also illustrates that EKFDMD requires significant numerical resources for many-degree-of-freedom (many-DoF) problems and that the combination with truncated proper orthogonal decomposition (trPOD) helps us to apply the EKFDMD algorithm to many-DoF problems, though it prevents the algorithm from being fully online. The numerical experiments of a noisy dataset with a small number of DoFs illustrate that EKFDMD can estimate eigenvalues better than or as well as the existing algorithms, whereas EKFDMD can also denoise the original dataset online. In particular, EKFDMD performs better than existing algorithms for the case in which system noise is present. The EKFDMD with trPOD, which unfortunately is not fully online, can be successfully applied to many-DoF problems, including a fluid-problem example, and the results reveal the superior performance of system identification and denoising.

    DOI: 10.1371/journal.pone.0209836

    Web of Science

    Scopus

    PubMed

    arXiv

    researchmap

  125. Development of the Magnetic Pulse Compression Circuit for DBD-PA (Dielectric Barrier Discharge Plasma Actuator) and the Application for Dynamic Stall Control 査読有り

    K. Suzuki, A. Komuro, S. Kanno, M. Koike, K. Nankai, K. Takashima, H. Yasuda, A. Ochi, K. Hayama, T. Tsujiuchi, K. Nakakita, K. Mitsuo, T. Nonomura, T. Kaneko, A. Ando, K. Asai

    Journal of the Institute of Electrostatics Japan   43 巻 ( 1 ) 頁: 43 - 48   2019年

     詳細を見る

  126. Effect of Boattail Angle on Pressure Distribution and Drag of Axisymmetric Afterbodies under Low-Speed Conditions 査読有り

    Tran, TH; Ambo, T; Chen, L; Nonomura, T; Asai, K

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   62 巻 ( 4 ) 頁: 219 - 226   2019年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    This study is focused on the effect of boattail angle on the pressure distribution and drag force of axisymmetric afterbodies under low-speed conditions. Experiments were conducted on three conical boattails with angles of 10°, 14° and 20°. The diameter-based Reynolds number is approximately 4.3 © 104 under the experimental conditions. Two types of flows, a fully-attached flow (¢ = 10°) and a flow with a separation bubble (¢ = 14°, 20°), were observed. The aerodynamic drag measurements were conducted using both a strut-supported model and a support-free (levitated) model. The results show that boattail model with the angle of 20° has a relatively large effect on the pressure distribution. The pressure drag resulting from pressure distribution on the vertical plane indicates that the model with a boattail angle of 14° has the lowest drag. A good trend in agreement between afterbody drag (measured using pressure taps) and total aerodynamic drag (measured using the levitated system) was obtained. The effect of strut support on pressure distribution at different polar angles is also explained in this study.

    DOI: 10.2322/tjsass.62.219

    Web of Science

    Scopus

    researchmap

  127. Effects of heaving and pitching motions on underside aerodynamics of a sedan vehicle 査読有り

    Maruyama, R; Shinji, K; Nonomura, T; Asai, K

    JOURNAL OF FLUID SCIENCE AND TECHNOLOGY   14 巻 ( 2 )   2019年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Fluid Science and Technology  

    Unsteady pressure distributions around a simplified sedan automobile model were investigated by conducting dynamic wind-tunnel testing using the newly developed forced oscillating apparatus, HEXA-X3, which can produce 6-degrees-of-freedom motion. The effects of heaving and pitching oscillation were investigated as the model simulated a vehicle running on a flat road at approximately 40 m/s and 1 Hz oscillation. The effects of the ground plate on unsteady pressure distributions over the model surfaces were measured while simulating heaving and pitching motion at Strouhal-number conditions similar to those for actual vehicles. The influence of the tubing on the frequency response of the pressure sensor was evaluated to be negligible by conducting a calibration experiment first. In the static case, the overall pressure distribution was consistent with that for a typical sedan, and the influence of the local relative flow velocity changes due to the contraction effect was observed in the underside of the model. In the forced oscillation tests, the effect of heaving and pitching motions on the flow around the underside was investigated. Effects of oscillation parameters, specifically amplitude and frequency, were investigated using the gain and phase-lag normalized by data from the steady model. Results of the test indicate that there is a characteristic distribution in pressure fluctuation, and the phenomena that become dominant in the flow around the underside vary according to location. The dynamic heaving motion was shown to change the pressure distribution, possibly due to changes in the effective angle of attack in addition to the static effect. The pitching test showed that a dynamic camber effect works in addition to those effects.

    DOI: 10.1299/jfst.2019jfst0012

    Web of Science

    Scopus

    researchmap

  128. Linear Reduced-order Model Based on PIV Data of Flow Field around Airfoil 査読有り

    Nankai, K; Ozawa, Y; Nonomura, T; Asai, K

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   62 巻 ( 4 ) 頁: 227 - 235   2019年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    In this study, a linear reduced-order model of flow fields around a NACA0015 is constructed based on time-resolved particle image velocimetry (PIV) data. The PIV data were obtained at the chord Reynolds number of 6.4 © 104, and angles of attack from 11° to 20°. Proper orthogonal decomposition (POD) analysis is employed for the PIV data and the degrees of freedom are reduced by truncating the POD modes. Next, a linear model of the POD modes is constructed using the least-squares method based on the POD-mode time histories. Although the estimated POD modes initially reproduce original data, they gradually attenuate and converge to zero. This behavior is also supported by the eigenvalue analysis results of the model’s coefficient matrices. In addition, the behavior of the low-order (more energetic) POD modes was reproduced better than that of the high-order (less energetic) POD modes. These results imply that the temporal fluctuation of large vortex structures has strong linearity and is not significantly affected by noise included in data. The former insight is also supported by the fact that the behaviors of POD modes were reproduced well in the case of high angle of attack.

    DOI: 10.2322/tjsass.62.227

    Web of Science

    Scopus

    researchmap

  129. Simple Estimation of Frequency Response of Two-layer Pressure-sensitive-paint Model 査読有り

    Nonomura, T; Asai, K

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   62 巻 ( 2 ) 頁: 112 - 115   2019年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    DOI: 10.2322/tjsass.62.112

    Web of Science

    Scopus

    researchmap

  130. Direct numerical simulation of flow past a transversely rotating sphere up to a Reynolds number of 300 in compressible flow 査読有り

    Nagata, T; Nonomura, T; Takahashi, S; Mizuno, Y; Fukuda, K

    JOURNAL OF FLUID MECHANICS   857 巻   頁: 878 - 906   2018年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Fluid Mechanics  

    In this study, direct numerical simulation of the flow around a rotating sphere at high Mach and low Reynolds numbers is conducted to investigate the effects of rotation rate and Mach number upon aerodynamic force coefficients and wake structures. The simulation is carried out by solving the three-dimensional compressible Navier-Stokes equations. A free-stream Reynolds number (based on the free-stream velocity, density and viscosity coefficient and the diameter of the sphere) is set to be between 100 and 300, the free-stream Mach number is set to be between 0.2 and 2.0, and the dimensionless rotation rate defined by the ratio of the free-stream and surface velocities above the equator is set between 0.0 and 1.0. Thus, we have clarified the following points: (1) as free-stream Mach number increased, the increment of the lift coefficient due to rotation was reduced; (2) under subsonic conditions, the drag coefficient increased with increase of the rotation rate, whereas under supersonic conditions, the increment of the drag coefficient was reduced with increasing Mach number; and (3) the mode of the wake structure becomes low-Reynolds-number-like as the Mach number is increased.

    DOI: 10.1017/jfm.2018.756

    Web of Science

    Scopus

    researchmap

  131. Dominant parameters for maximum velocity induced by body-force models for plasma actuators 査読有り

    Kawai, S; Bouwhuis, T; Abe, Y; Yakeno, A; Nonomura, T; Aono, H; Oyama, A; Hoeijmakers, HWM; Fujii, K

    THEORETICAL AND COMPUTATIONAL FLUID DYNAMICS   32 巻 ( 6 ) 頁: 805 - 820   2018年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Theoretical and Computational Fluid Dynamics  

    This study investigates the relationship between body-force fields and maximum velocity induced in quiescent air for development of a simple body-force model of a plasma actuator. Numerical simulations are conducted with the body force near a wall. The spatial distribution and temporal variation of the body force are a Gaussian distribution and steady actuation, respectively. The dimensional analysis is performed to derive a reference velocity and Reynolds number based on the body-force distribution. It is found that the derived Reynolds number correlates well with the nondimensional maximum velocity induced in quiescent conditions when the center of the Gaussian distribution is fixed at the wall. Additionally, two flow regimes are identified in terms of the Reynolds number. Considering the variation of the center of gravity of force fields, another Reynolds number is defined by introducing a new reference length. The nondimensional maximum velocity is found to be scaled with the latter Reynolds number, i.e., the maximum induced velocity in quiescent conditions is determined from three key parameters of the force field: the total induced momentum per unit time, the height of the center of gravity, and the standard deviation from it. This scaling turns out to be applicable to existing body-force models of the plasma actuator, despite the force distributions different from the Gaussian distribution. Comparisons of velocity profiles with experimental data validate the results and show that the flow induced by a plasma actuator can be simulated with simple force distributions by adjustment of the key body-force parameters.

    DOI: 10.1007/s00162-018-0478-9

    Web of Science

    Scopus

    researchmap

  132. Effect of boattail angles on the flow pattern on an axisymmetric afterbody surface at low speed 査読有り

    Tran, TH; Ambo, T; Lee, T; Chen, L; Nonomura, T; Asai, K

    EXPERIMENTAL THERMAL AND FLUID SCIENCE   99 巻   頁: 324 - 335   2018年12月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experimental Thermal and Fluid Science  

    The surface flow pattern over a conical boattail on an axisymmetric body was investigated experimentally under low-speed and turbulent-boundary-layer conditions. Seven conical boattails with the same length but different angles from 10° to 22° were tested at a Reynolds number around 4.3 × 104, based on the model diameter. The study used the global luminescent oil-film (GLOF) skin friction measurement technique. The skin friction fields were measured and the corresponding flow topologies were extracted from the GLOF measurements. The effect of oil-film thickness on the separation position was also evaluated. Experimental results showed three different flow types on the boattail surface: (1) flow without separation, (2) flow with a separation bubble, and (3) fully separated flow. The critical angles for the transitions are discussed and compared with classic results for similar boattail models. The separation bubble generated at moderate boattail angles was observed for what we believe to be the first time under low-speed conditions, and the flow topology was clearly shown by the GLOF results. The azimuthally-averaged skin friction projected on the centerline showed different trends inside and behind the reattachment position when the boattail angle increased.

    DOI: 10.1016/j.expthermflusci.2018.07.034

    Web of Science

    Scopus

    researchmap

  133. Unsteady shear layer flow under excited local body-force for flow-separation control in downstream of a two-dimensional hump 査読有り

    Yakeno, A; Abe, Y; Kawai, S; Nonomura, T; Fujii, K

    INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW   74 巻   頁: 15 - 27   2018年12月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Heat and Fluid Flow  

    We present a detailed numerical investigation of unsteady shear layer dynamics in downstream under an excited local body force, based on the assumption that a plasma actuator is positioned near the top of a two-dimensional hump for flow-separation control. A local body force works in temporal burst mode, which is homogeneous in the spanwise direction. In our previous report (Yakeno et al., 2015), the most effective frequency to cause early reattachment is fh=0.2, which corresponds to what Hasan (1992) and many other past studies referred to as the step mode. A periodic excitation generates two-dimensional roll vortices and other three-dimensional turbulence between downstream rolls, such as rib structures. These vortex characteristics significantly depend on the excitation frequency. In the study, we discuss these multi-scale turbulence motion separately by considering decomposition of temporal phase-locked periodic statistics of the excitation frequency and non-periodic turbulence fluctuation. At first, we found that non-periodic turbulence kinetic energy due to three-dimensional rib structure increases the most at the optimal frequency fh=0.2, although that frequency corresponds to the time scale that a hump-height vortex grows. It seems that non-periodic turbulence energy growth near separation point correlates with the control performance more than two-dimensional roll vortex increase. We operated linear hydrodynamic stability analysis on a free shear layer and confirmed that periodic phase fluctuation at high frequency grew on the Kelvin-Helmholtz instability. At low-frequency, periodic turbulence fluctuation is not reproduced with the exponential assumption, while its magnitude is large. From those results, we consider that the time and spanwise-averaged non-periodic turbulence energy becomes strong near the separation point the most at fh=0.2 because a hump-height vortex occurs the most times at this frequency, which is associated with a generation of the rib structure around it. Temporal-periodic momentum balance based on the decomposition is also investigated. A difference of terms contribution at high and low frequencies to the term of a pressure gradient in the wall-normal direction is discussed. Finally, we investigated how excitation position affects a total drag around a hump and found that, in some cases, two recirculation regions separately emerge in the downstream of the hump, and thus the control performance is degraded. At fh=0.2, one recirculation occurs regardless of the excitation position, while the most effective position is near the inflection point of the mean velocity of the uncontrolled flow near the wall.

    DOI: 10.1016/j.ijheatfluidflow.2018.08.008

    Web of Science

    Scopus

    researchmap

  134. Evaluation of the Characteristics and Coating Film Structure of Polymer/Ceramic Pressure-Sensitive Paint 査読有り

    Sugioka, Y; Arakida, K; Kasai, M; Nonomura, T; Asai, K; Egami, Y; Nakakita, K

    SENSORS   18 巻 ( 11 ) 頁: E4041   2018年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Sensors (Switzerland)  

    Polymer/ceramic pressure-sensitive paint (PC-PSP), which incorporates a high percentage of particles in the binder layer, is proposed in order to improve the characteristics of PSP. The procedure for embedding particles into the binder layer was modified. In the conventional procedure, dye is adsorbed onto a polymer/ceramic coating film (denoted herein as a dye-adsorbed (D-adsorbed) PSP). In the new procedure, the mixture of a dye and particles is adsorbed onto a polymer coating film (denoted herein as the particle/dye-adsorbed (PD-adsorbed) PSP). The effect of particle mass content on PSP characteristics was investigated. In addition, the effect of solvent on PSP characteristics and film structure were evaluated for the PD-adsorbed PSP. As a result, the difference in the PSP characteristics between the two types of PSP was clarified. Although surface roughness and time response increase with increased mass content of particles for both D-and PD-adsorbed PSPs, the critical pigment volume concentration (CPVC) for the PD-adsorbed PSP is smaller than that of the D-adsorbed PSP (88 wt% and 93 wt%, respectively). The PD-adsorbed PSP has a higher frequency response comparing with the D-adsorbed PSP while maintaining the same surface roughness. Observation by scanning electron microscope showed that the CPVC of the PC-PSP is governed primarily by surface structure. The coating film structure can be roughly classified into two states depending on the particle mass content. One is a state in which the coating film consisted of two layers: a lower particle-rich layer and an upper polymer-rich layer. This type of structure was observed in the PD-adsorbed PSP as well as in the D-adsorbed PSP. In the other state, polymer and particles are homogeneously distributed in the film, and pores are formed. This difference in the coating structure results in a change in the time response.

    DOI: 10.3390/s18114041

    Web of Science

    Scopus

    PubMed

    researchmap

    その他リンク: http://orcid.org/0000-0001-7739-7104

  135. Dynamic mode decomposition using a Kalman filter for parameter estimation 査読有り

    Nonomura, T; Shibata, H; Takaki, R

    AIP ADVANCES   8 巻 ( 10 ) 頁: 105106   2018年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIP Advances  

    A novel dynamic mode decomposition (DMD) method based on a Kalman filter is proposed. This paper explains the fast algorithm of the proposed Kalman filter DMD (KFDMD) in combination with truncated proper orthogonal decomposition for many-degree-of-freedom problems. Numerical experiments reveal that KFDMD can estimate eigenmodes more precisely compared with standard DMD or total least-squares DMD (tlsDMD) methods for the severe noise condition if the nature of the observation noise is known, though tlsDMD works better than KFDMD in the low and medium noise level. Moreover, KFDMD can track the eigenmodes precisely even when the system matrix varies with time similar to online DMD, and this extension is naturally conducted owing to the characteristics of the Kalman filter. In summary, the KFDMD is a promising tool with strong antinoise characteristics for analyzing sequential datasets.

    DOI: 10.1063/1.5031816

    Web of Science

    Scopus

    arXiv

    researchmap

  136. Gas-heating phenomenon in a nanosecond pulse discharge in atmospheric-pressure air and its application for high-speed flow control 査読有り

    Komuro, A; Takashima, K; Suzuki, K; Kanno, S; Nonomura, T; Kaneko, T; Ando, A; Asai, K

    PLASMA SOURCES SCIENCE & TECHNOLOGY   27 巻 ( 10 )   2018年10月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Plasma Sources Science and Technology  

    The interaction between the gas-heating phenomenon in a pulsed discharge in atmospheric-pressure air and the separated shear layer in the flow around the airfoil is discussed. The first half of the paper details the development of the modeling for gas heating in a pulsed discharge in atmospheric-pressure air and reviews recent research results. Particular attention is paid to the processes of fast and slow gas heating. In the latter half of the paper, the experimental results of the high-speed Schlieren visualization are presented and the interaction between the nanosecond-pulse-driven dielectric-barrier-discharge plasma actuator (ns-DBDPA) actuation and the density field is discussed, based on the periodic and time-averaged components of the Schlieren signal intensity. The time-averaged intensity of the contrast of the Schlieren signal that originates in the separated shear layer changes according to the normalized actuation frequency of ns-DBDPA, F +. As F + increases from 0.1 to 2, the periodic component of the Schlieren signal intensity increases, resulting in a decrease in the time-averaged contrast of the Schlieren signal. When F + > 2, the heated air caused by ns-DBDPA actuation is accumulated along the separated shear layer, resulting in an increase in the time-averaged contrast of the Schlieren signal.

    DOI: 10.1088/1361-6595/aae23c

    Web of Science

    Scopus

    researchmap

  137. Multiple control modes of nanosecond-pulse-driven plasma-actuator evaluated by forces, static pressure, and PIV measurements 査読有り

    Komuro, A; Takashima, K; Tanaka, N; Konno, K; Nonomura, T; Kaneko, T; Ando, A; Asai, K

    EXPERIMENTS IN FLUIDS   59 巻 ( 8 )   2018年8月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    The control authority of a nanosecond-pulse-driven dielectric-barrier discharge plasma actuator (ns-DBDPA) was evaluated via wind tunnel experiments with the simultaneous measurement of lift and drag forces, pressure on the airfoil surface, and particle image velocimetry (PIV) measurements. In these experiments, a Reynolds number of Re = 2.6 × 105 was applied with a freestream velocity of 40 m/s under atmospheric pressure. The force measurements revealed multiple peaks of lift force recovery and drag force modulation depending on the angle of attack, α, and non-dimensional frequency, F+. At the positive post-stall α close to stall α of approximately 16°, F+ values around 2.0 were effective for lift recovery and drag reduction. When the deep-stall angle α is larger than 20° (either positive or negative), relatively low F+ values around 0.25 were effective for lift recovery. When actuating at a deep-stall angle corresponding to F+ = 0.25, the surface pressure measurements showed that a near flat pressure distribution is formed on the suction side, and the PIV measurement showed that this near flat distribution is caused by the increase in backflow velocity near the surface of the airfoil. This backflow enhancement near the suction side surface leads to the reduction in pressure in separated flow, resulting in significant increases in the lift and drag coefficients. Thus, this simultaneous measurement of force, pressure, and PIV is capable of evaluating the multiple control modes underlying lift and drag control by ns-DBDPA. Graphical abstract: [Figure not available: see fulltext.].

    DOI: 10.1007/s00348-018-2584-2

    Web of Science

    Scopus

    researchmap

  138. A review of Backward-Facing Step (BFS) flow mechanisms, heat transfer and control 査読有り

    Chen, L; Asai, K; Nonomura, T; Xi, GN; Liu, TS

    THERMAL SCIENCE AND ENGINEERING PROGRESS   6 巻   頁: 194 - 216   2018年6月

     詳細を見る

    出版者・発行元:Thermal Science and Engineering Progress  

    Backward-Facing Step (BFS) flow is one representative model for separation flows, which can be widely seen in aerodynamic flows (airfoil, spoiler, high attack angle process), engine flows, condensers, vehicles (cars, boat), heat transfer systems, and even the flow around buildings, etc. The flow separation after a simple stage will introduce separation bubble formation, evolution and re-attachment process, which is dependent on the BFS geometric design, the inlet and outlet conditions, turbulent intensity, as well as heat transfer conditions. In the past decades, it has been widely studied by various theoretical, experimental and numerical methods. Considering the importance of BFS flow in both theoretical and engineering aspects, this paper is focused on a review study of BFS flows from fundamental understandings to various experimental and numerical developments in a historical viewpoint. Basic models and the parameter-based after-step flow laws are summarized and categorized in this study. It is shown that the step size (duct expansion ratio) will define the basic re-circulation and re-attachment process, while the coupled effects of inflow parameters and the perturbation designs also help shape the flow behaviors after BFS. The review is also extended with model generalizations and the implications on system design, especially the heat transfer effects and the representative control designs are discussed in detail. Future trends and prospects in BFS studies are also included in this study.

    DOI: 10.1016/j.tsep.2018.04.004

    Web of Science

    Scopus

    researchmap

  139. Experimental analysis of transonic buffet on a 3D swept wing using fast-response pressure-sensitive paint 査読有り

    Sugioka, Y; Koike, S; Nakakita, K; Numata, D; Nonomura, T; Asai, K

    EXPERIMENTS IN FLUIDS   59 巻 ( 6 )   2018年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    Transonic buffeting phenomena on a three-dimensional swept wing were experimentally analyzed using a fast-response pressure-sensitive paint (PSP). The experiment was conducted using an 80%-scaled NASA Common Research Model in the Japan Aerospace Exploration Agency (JAXA) 2 m × 2 m Transonic Wind Tunnel at a Mach number of 0.85 and a chord Reynolds number of 1.54 × 106. The angle of attack was varied between 2.82° and 6.52°. The calculation of root-mean-square (RMS) pressure fluctuations and spectral analysis were performed on measured unsteady PSP images to analyze the phenomena under off-design buffet conditions. We found that two types of shock behavior exist. The first is a shock oscillation characterized by the presence of “buffet cells” formed at a bump Strouhal number St of 0.3–0.5, which is observed under all off-design conditions. This phenomenon arises at the mid-span wing and is propagated spanwise from inboard to outboard. The other is a large spatial amplitude shock oscillation characterized by low-frequency broadband components at St < 0.1, which appears at higher angles of attack (α ≥ 6.0°) and behaves more like two-dimensional buffet. The transition between these two shock behaviors correlates well with the rapid increase of the wing-root strain fluctuation RMS.

    DOI: 10.1007/s00348-018-2565-5

    Web of Science

    Scopus

    researchmap

  140. Linear least-squares method for global luminescent oil film skin friction field analysis 査読有り

    Lee, T; Nonomura, T; Asai, K; Liu, TS

    REVIEW OF SCIENTIFIC INSTRUMENTS   89 巻 ( 6 )   2018年6月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Review of Scientific Instruments  

    A data analysis method based on the linear least-squares (LLS) method was developed for the extraction of high-resolution skin friction fields from global luminescent oil film (GLOF) visualization images of a surface in an aerodynamic flow. In this method, the oil film thickness distribution and its spatiotemporal development are measured by detecting the luminescence intensity of the thin oil film. From the resulting set of GLOF images, the thin oil film equation is solved to obtain an ensemble-averaged (steady) skin friction field as an inverse problem. In this paper, the formulation of a discrete linear system of equations for the LLS method is described, and an error analysis is given to identify the main error sources and the relevant parameters. Simulations were conducted to evaluate the accuracy of the LLS method and the effects of the image patterns, image noise, and sample numbers on the results in comparison with the previous snapshot-solution-averaging (SSA) method. An experimental case is shown to enable the comparison of the results obtained using conventional oil flow visualization and those obtained using both the LLS and SSA methods. The overall results show that the LLS method is more reliable than the SSA method and the LLS method can yield a more detailed skin friction topology in an objective way.

    DOI: 10.1063/1.5001388

    Web of Science

    Scopus

    PubMed

    researchmap

  141. Direct numerical simulation of flow around a heated/cooled isolated sphere up to a Reynolds number of 300 under subsonic to supersonic conditions 査読有り

    Nagata, T; Nonomura, T; Takahashi, S; Mizuno, Y; Fukuda, K

    INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER   120 巻   頁: 284 - 299   2018年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Heat and Mass Transfer  

    In this study, an analysis of the flow properties around an isolated sphere under isothermal conditions for flows with high Mach numbers and low Reynolds numbers is conducted via direct numerical simulation (DNS) of the three-dimensional compressible Navier–Stokes equations. The calculations are performed with a boundary-fitted coordinate system. The Reynolds number based on the diameter of the sphere and the freestream quantities is varied from 100 to 300, the freestream Mach number is varied between 0.3 and 2.0, and the temperature ratio between the sphere surface and the freestream is varied between 0.5 and 2.0. We focus on the effects of the Mach number and the temperature ratio on the flow properties. The results show the following characteristics: (1) unsteady vortex shedding from the sphere is promoted (suppressed) when the temperature ratio is less (greater) than unity; (2) the drag coefficient increases with the temperature ratio, but previous drag relations give poor prediction on effect of the temperature ratio on the drag coefficient in the continuum regime; (3) Nusselt number relations proposed in previous studies can be applied if the temperature ratio is close to unity under subsonic conditions; (4) the changes in several flow properties can be characterized by a separation point in the range investigated.

    DOI: 10.1016/j.ijheatmasstransfer.2017.12.042

    Web of Science

    Scopus

    researchmap

  142. Effect of fineness ratios of 0.75-2.0 on aerodynamic drag of freestream-aligned circular cylinders measured using a magnetic suspension and balance system 査読有り

    Nonomura, T; Sato, K; Fukata, K; Nagaike, H; Okuizumi, H; Konishi, Y; Asai, K; Sawada, H

    EXPERIMENTS IN FLUIDS   59 巻 ( 5 )   2018年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    © 2018, Springer-Verlag GmbH Germany, part of Springer Nature. The drag coefficients of freestream-aligned circular cylinders of fineness ratios of 0.75–2.0 were investigated with a magnetic suspension and balance system (MSBS). The objective was to find the critical geometry, that is, the fineness ratio at which the drag coefficient becomes the local maximum within this ratio range. The experiments were conducted using the 1-m MSBS at the low turbulence wind tunnel at the Institute of Fluid Science, Tohoku University. The drag and base pressure coefficients of various cylinders were measured. The freestream velocity was varied to produce flows with Reynolds numbers ranging from 0.6 × 10 5 to 1.0 × 10 5 . The drag coefficient monotonically decreases as the fineness ratio increases and no critical geometry or local maximum of the drag coefficient is found in the range we investigated. The base pressure coefficient decreases as the fineness ratio increases. The temporal fluctuations of the base pressure of the models with fineness ratios of 0.75, 1.0, and 1.2 are approximately twice as large as that of the model with a ratio of 2.0. The relationship between the fineness ratio and the drag coefficient is similar to that between the fineness ratio and the base pressure coefficient, similar to the findings of previous studies of two-dimensional bodies.

    DOI: 10.1007/s00348-018-2531-2

    Web of Science

    Scopus

    researchmap

  143. Stable, non-dissipative, and conservative flux-reconstruction schemes in split forms 査読有り

    Abe, Y; Morinaka, I; Haga, T; Nonomura, T; Shibata, H; Miyaji, K

    JOURNAL OF COMPUTATIONAL PHYSICS   353 巻   頁: 193 - 227   2018年1月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    A stable, non-dissipative, and conservative flux-reconstruction (FR) scheme is constructed and demonstrated for the compressible Euler and Navier–Stokes equations. A proposed FR framework adopts a split form (also known as the skew-symmetric form) for convective terms. Sufficient conditions to satisfy both the primary conservation (PC) and kinetic energy preservation (KEP) properties are rigorously derived by polynomial-based analysis for a general FR framework. It is found that the split form needs to be expressed in the PC split form or KEP split form to satisfy each property in discrete sense. The PC split form is retrieved from existing general forms (Kennedy and Gruber [33]); in contrast, we have newly introduced the KEP split form as a comprehensive form constituting a KEP scheme in the FR framework. Furthermore, Gauss–Lobatto (GL) solution points and g2 correction function are required to satisfy the KEP property while any correction functions are available for the PC property. The split-form FR framework to satisfy the KEP property, eventually, is similar to the split-form DGSEM–GL method proposed by Gassner [23], but which, in this study, is derived solely by polynomial-based analysis without explicitly using the diagonal-norm SBP property. Based on a series of numerical tests (e.g., Sod shock tube), both the PC and KEP properties have been verified. We have also demonstrated that using a non-dissipative KEP flux, a sixteenth-order (p15) simulation of the viscous Taylor–Green vortex (Re=1,600) is stable and its results are free of unphysical oscillations on relatively coarse mesh (total number of degrees of freedom (DoFs) is 1283).

    DOI: 10.1016/j.jcp.2017.10.007

    Web of Science

    Scopus

    researchmap

  144. Effect of Mach Number on Airfoil Characteristics at Reynolds Number of 3,000 査読有り

    Morizawa, S; Nonomura, T; Oyama, A; Fujii, K; Obayashi, S

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   61 巻 ( 6 ) 頁: 258 - 267   2018年

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    The effects of Mach number at Re = 3,000 for different airfoils (NACA0012, NACA0002, NACA4412, NACA4402) with thickness and camber geometries are investigated for the propeller blade design of a Mars airplane. The present study shows that thin and cambered airfoils have larger variations in Cl than symmetric airfoils. As for thin airfoils, Cl at higher ¡ has rapid increases when the M¨ is low. This is because the flow separation occurs at the leading edge, and the flow is reattached on the airfoil surface. However, the rapid increase in Cl disappear as M¨ increases because the flow reattachment does not occurs. As for cambered airfoils, the decrease in Cl becomes larger than that on the symmetric airfoils when M¨ is higher. This is because Cp near the leading edge on the lower surface is smaller than that on the upper surface and the high-speed region on the lower side of the leading edge is enlarged as M¨ increases. Then, the Mcr at Re = 3,000 tends to be larger than that predicted by linear theory.

    DOI: 10.2322/tjsass.61.258

    Web of Science

    Scopus

    researchmap

  145. Identification of Acoustic Wave Propagation Pattern of a Supersonic Jet Using Frequency-Domain POD 査読有り

    Ozawa, Y; Nonomura, T; Anyoji, M; Mamori, H; Fukushima, N; Oyama, A; Fujii, K; Yamamoto, M

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   61 巻 ( 6 ) 頁: 281 - 284   2018年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Transactions of the Japan Society for Aeronautical and Space Sciences  

    DOI: 10.2322/tjsass.61.281

    Web of Science

    Scopus

    researchmap

  146. Compressibility effects on flat-plates with serrated leading-edges at a low Reynolds number 査読有り

    Mangeol, É; Ishiwaki, D; Wallisky, N; Asai, K; Nonomura, T

    EXPERIMENTS IN FLUIDS   58 巻 ( 11 )   2017年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Experiments in Fluids  

    This study evaluates the influence of a serrated leading edge on flat-plate aerodynamics at low-Reynolds-number and subsonic high-Mach-number conditions. Forces are measured for a Mach number ranging from 0.2 to 0.64 at a Reynolds number of (12,000 ± 1000). Pressure distributions are obtained under the same conditions using pressure sensitive paint (PSP) measurement. Three models are tested: a flat plate without serrations used as the baseline case and two flat plates with serrated leading edges of different wavelength-to-amplitude ratios. Results show that the aerodynamic performance of flat plates with serrations is slightly changed from the baseline case. The plate with short-wavelength serrations underperforms in terms of the lift-to-drag ratio under all the conditions compared to the baseline case while the plate with large-wavelength serrations slightly outperforms it at around the stall angle. The Mach number has little effect on the attached flow while the lift increases with the Mach number under deep stall conditions. Serrations maintain the lift even under high angle of attack conditions when Mach number varies. The two-dimensional pressure distributions and the analyses of local chordwise pressure coefficient distributions at different spanwise locations and of periodicity of spanwise pressure coefficients allow categorisation of the complex flow structures into three types. These configurations feature different types of low pressure regions downstream of troughs. The periodicity of the pattern depends not only on the angle of attack but also on the Mach number.

    DOI: 10.1007/s00348-017-2443-6

    Web of Science

    Scopus

    researchmap

  147. Plasma-Actuator Burst-Mode Frequency Effects on Leading-Edge Flow-Separation Control at Reynolds Number 2.6 x 10<SUP>5</SUP> 査読有り

    Aono, H; Kawai, S; Nonomura, T; Sato, M; Fujii, K; Okada, K

    AIAA JOURNAL   55 巻 ( 11 ) 頁: 3789 - 3806   2017年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:AIAA Journal  

    Copyright © 2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. This paper investigates the control of leading-edge flow separation over an airfoil using a dielectric-barrier discharge plasma actuator. A chord-based Reynolds number and an angle of attack are 2.6 × 10 5 and 18.8 deg, respectively. The flow around the stalled airfoil is computed by using large-eddy simulations. The body-force distribution-based plasma actuator model is adopted and set near the leading edge of the airfoil. Effects of a nondimensional burst frequency with a constant duty cycle onthe performance of flow control are studied. It isfound that, for the cases of the nondimensional burst frequencies 5, 10, 25, and 50, lift-to-drag ratios increase in comparison with that in the cases of the burst frequencies 1 and 100 and without the control. Controlled flow separates near the 30% chord from the leading edge due to adverse pressure gradient associated with the angleofattack. Mechanisms of suppression of the leading-edge flow separation in those cases are discussed.

    DOI: 10.2514/1.J055727

    Web of Science

    Scopus

    researchmap

  148. Characteristic finite-difference WENO scheme for multicomponent compressible fluid analysis: Overestimated quasi-conservative formulation maintaining equilibriums of velocity, pressure, and temperature 査読有り

    Nonomura, T; Fujii, K

    JOURNAL OF COMPUTATIONAL PHYSICS   340 巻   頁: 358 - 388   2017年7月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    The characteristic-interpolation-based finite-difference weighted essentially non-oscillatory (WENO) scheme, which maintains the equilibriums of velocity, pressure, and temperature, is implemented to simulate compressible multicomponent flow fields. We propose the overestimated quasi-conservative form of the characteristic-interpolation-based finite-difference WENO scheme. The proposed WENO scheme is written in the split form that has the consistent and dissipation parts of the numerical flux. The dissipation part of the numerical flux is in the conservative form to maintain the conservation of conservative variables. The scheme implemented in this study can maintain the equilibriums of velocity, pressure, and temperature in various one- and two-dimensional problems. The results of the present studies provide new insights into the vector form of numerical dissipation.

    DOI: 10.1016/j.jcp.2017.02.054

    Web of Science

    Scopus

    researchmap

  149. Schlieren visualization of flow-field modification over an airfoil by near-surface gas-density perturbations generated by a nanosecond-pulse-driven plasma actuator 査読有り

    Komuro, A; Takashima, K; Konno, K; Tanaka, N; Nonomura, T; Kaneko, T; Ando, A; Asai, K

    JOURNAL OF PHYSICS D-APPLIED PHYSICS   50 巻 ( 21 ) 頁: 215202   2017年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Physics D: Applied Physics  

    Gas-density perturbations near an airfoil surface generated by a nanosecond dielectric-barrier-discharge plasma actuator (ns-DBDPA) are visualized using a high-speed Schlieren imaging method. Wind-tunnel experiments are conducted for a wind speed of 20 m s-1 with an NACA0015 airfoil whose chord length is 100 mm. The results show that the ns-DBDPA first generates a pressure wave and then stochastic perturbations of the gas density near the leading edge of the airfoil. Two structures with different characteristics are observed in the stochastic perturbations. One structure propagates along the boundary between the shear layer and the main flow at a speed close to that of the main flow. The other propagates more slowly on the surface of the airfoil and causes mixing between the main and shear flows. It is observed that these two heated structures interact with each other, resulting in a recovery in the negative pressure coefficient at the leading edge of the airfoil.

    DOI: 10.1088/1361-6463/aa6a80

    Web of Science

    Scopus

    researchmap

  150. Application of central differencing and low-dissipation weights in a weighted compact nonlinear scheme 査読有り

    Kamiya, T; Asahara, M; Nonomura, T

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   84 巻 ( 3 ) 頁: 152 - 180   2017年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal for Numerical Methods in Fluids  

    This paper proposes WCNS-CU-Z, a weighted compact nonlinear scheme, that incorporates adapted central difference and low-dissipative weights together with concepts of the adaptive central-upwind sixth-order weighted essentially non-oscillatory scheme (WENO-CU) and WENO-Z schemes. The newly developed WCNS-CU-Z is a high-resolution scheme, because interpolation of this scheme employs a central stencil constructed by upwind and downwind stencils. The smoothness indicator of the downwind stencil is calculated using the entire central stencil, and the downwind stencil is stopped around the discontinuity for stability. Moreover, interpolation of the sixth-order WCNS-CU-Z exhibits sufficient accuracy in the smooth region through use of low-dissipative weights. The sixth-order WCNS-CU-Zs are implemented with a robust linear difference formulation (R-WCNS-CU6-Z), and the resolution and robustness of this scheme were evaluated. These evaluations showed that R-WCNS-CU6-Z is capable of achieving a higher resolution than the seventh-order classical robust weighted compact nonlinear scheme and can provide a crisp result in terms of discontinuity. Among the schemes tested, R-WCNS-CU6-Z has been shown to be robust, and variable interpolation type R-WCNS-CU6-Z (R-WCNS-CU6-Z-V) provides a stable computation by modifying the first-order interpolation when negative density or negative pressure arises after nonlinear interpolation. © 2016 The Authors. International Journal for Numerical Methods in Fluids published by John Wiley & Sons Ltd.

    DOI: 10.1002/fld.4343

    Web of Science

    Scopus

    researchmap

  151. Burst-Mode Frequency Effects of Dielectric Barrier Discharge Plasma Actuator for Separation Control 査読有り

    Sekimoto, S; Nonomura, T; Fujii, K

    AIAA JOURNAL   55 巻 ( 4 ) 頁: 1385 - 1392   2017年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    The various separation control mechanisms of burst-mode actuation with a dielectric barrier discharge plasma actuator were experimentally investigated in this study. The control of the separated flow around aNACA0015 airfoil at a Reynolds number of 6.3 × 104 was investigated using a plasma actuator mounted at a distance from the leading edge of 5% of the chord length. A parametric study on the nondimensionalized burst frequency was conducted at three poststall angles of attack and various input voltages using time-Averaged pressure measurements and timeresolved particle imaging velocimetry (PIV) results. The measurement results of the trailing edge pressure, which was selected as the index of separation control, indicate that the optimal burst frequency varies with the angle of attack. Several flow fields are discussed in detail in this paper, and two flow control mechanisms were observed: The use of a large-scale vortex and the promotion of turbulent transition. With regard to the first mechanism, the phase-locked PIV results indicate that a vortex structure, the size of which increases with decreasing burst frequency in the experimental range, is shed from the shear layer for each burst actuation. With regard to the second mechanism, timeaveraged pressure and PIV measurements reveal that a burst frequency of F+ = 6-10 is able to promote turbulent transition. Among these two mechanisms, at higher angles of attack, the use of a large-scale vortex structure provides better separation control, whereas near the stall angle, the promotion of the turbulent transition provides better separation control.

    DOI: 10.2514/1.J054678

    Web of Science

    Scopus

    researchmap

  152. Large-Eddy Simulation of NACA 0015 Airfoil Flow at Reynolds Number of 1.6x10<SUP>6</SUP> 査読有り

    Sato, M; Asada, K; Nonomura, T; Kawai, S; Fujii, K

    AIAA JOURNAL   55 巻 ( 2 ) 頁: 673 - 679   2017年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    DOI: 10.2514/1.J054963

    Web of Science

    Scopus

    researchmap

  153. Spanwise modulation effects of local body force on downstream turbulence growth around two-dimensional hump 査読有り

    Yakeno, A; Abe, Y; Kawai, S; Nonomura, T; Fujii, K

    INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW   63 巻   頁: 108 - 118   2017年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Heat and Fluid Flow  

    Flow characteristics under flow-separation control by the spanwise-modulated body force of a plasma actuator around a two-dimensional hump are numerically investigated. When the Reynolds number is set to Reh=16000, the incoming flow contains much disturbance and a near-wall streak structure appears around the hump. The local body force induces stable streamwise velocity to form a streak-like profile artificially. Under the forcing, turbulence fluctuations increase downstream, with resulting in early flow reattachment. These changes alter the momentum balance around the hump. Particularly, the wall-normal pressure gradient and velocity fluctuation terms in the momentum equation are modified. This somewhat suggests a relation between increases in wall-normal gradient terms and the flow reattachment profile under the control. In addition, the turbulence growth depends on the spanwise modulation wavelength of the forcing. The most effective wavelength among those tested here is λz=0.08, normalized by the hump height, which is λz+=150 in local viscous wall units. This viscous scale corresponds to that of a streak structure appearing around a two-dimensional hump.

    DOI: 10.1016/j.ijheatfluidflow.2016.11.012

    Web of Science

    Scopus

    researchmap

  154. A Comparative Study on Evaluation Methods of Fluid Forces on Cartesian Grids 査読有り

    Nonomura, T; Onishi, J

    MATHEMATICAL PROBLEMS IN ENGINEERING   2017 巻   2017年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Mathematical Problems in Engineering  

    We investigate the accuracy and the computational efficiency of the numerical schemes for evaluating fluid forces in Cartesian grid systems. A comparison is made between two different types of schemes, namely, polygon-based methods and mesh-based methods, which differ in the discretization of the surface of the object. The present assessment is intended to investigate the effects of the Reynolds number, the object motion, and the complexity of the object surface. The results show that the mesh-based methods work as well as the polygon-based methods, even if the object surface is discretized in a staircase manner. In addition, the results also show that the accuracy of the mesh-based methods is strongly dependent on the evaluation of shear stresses, and thus they must be evaluated by using a reliable method, such as the ghost-cell or ghost-fluid method.

    DOI: 10.1155/2017/8314615

    Web of Science

    Scopus

    researchmap

  155. Assessment of WENO-extended two-fluid modelling in compressible multiphase flows 査読有り

    Kitamura, K; Nonomura, T

    INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS   31 巻 ( 3 ) 頁: 188 - 194   2017年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Computational Fluid Dynamics  

    The two-fluid modelling based on an advection-upwind-splitting-method (AUSM)-family numerical flux function, AUSM+-up, following the work by Chang and Liou [Journal of Computational Physics 2007;225: 840–873], has been successfully extended to the fifth order by weighted-essentially-non-oscillatory (WENO) schemes. Then its performance is surveyed in several numerical tests. The results showed a desired performance in one-dimensional benchmark test problems: Without relying upon an anti-diffusion device, the higher-order two-fluid method captures the phase interface within a fewer grid points than the conventional second-order method, as well as a rarefaction wave and a very weak shock. At a high pressure ratio (e.g. 1,000), the interpolated variables appeared to affect the performance: the conservative-variable-based characteristic-wise WENO interpolation showed less sharper but more robust representations of the shocks and expansions than the primitive-variable-based counterpart did. In two-dimensional shock/droplet test case, however, only the primitive-variable-based WENO with a huge void fraction realised a stable computation.

    DOI: 10.1080/10618562.2017.1311410

    Web of Science

    Scopus

    researchmap

  156. Comparative studies of numerical methods for evaluating aerodynamic characteristics of two-dimensional airfoil at low Reynolds numbers 査読有り

    Lee, D; Nonomura, T; Oyama, A; Fujii, K

    INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS   31 巻 ( 1 ) 頁: 57 - 67   2017年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Computational Fluid Dynamics  

    This study investigates the predictability of the aerodynamic performance of some numerical methods at low Reynolds numbers and their dependency on the geometric shape of airfoil. We conducted three-dimensional large-eddy simulations (3-D LES), two-dimensional laminar simulations (2-D Lam), and Reynolds-averaged Navier–Stokes simulations with Baldwin–Lomax (2-D RANS(BL)) and Spalart–Allmaras (2-D RANS(SA)) turbulence models. Although there is little discrepancy between the 3-D LES, 2-D Lam, and 2-D RANS(SA) results in terms of the lift and drag characteristics, significant differences are observed in the predictability of the separation and reattachment points. The predicted lift, separation, and reattachment points of the 2-D Lam are qualitatively similar to those of the 3-D LES, except for high angles of attack at which a massive separation occurs. The 2-D RANS(SA) shows good predictability of the lift and separation points, but it does not estimate reattachment points accurately. The 2-D RANS(BL) fails to predict the precise separation points, which results in a poor lift predictability. These characteristics appear regardless of the airfoil geometry shapes. The results suggest that a 2-D Lam without any turbulence models can be used to estimate qualitative airfoil aerodynamic characteristics at the low Reynolds numbers.

    DOI: 10.1080/10618562.2016.1274398

    Web of Science

    Scopus

    researchmap

  157. Control of dynamic flowfield around a pitching NACA63<inf>3</inf>−618 airfoil by a DBD plasma actuator

    Fukumoto H., Aono H., Watanabe T., Tanaka M., Matsuda H., Osako T., Nonomura T., Oyama A., Fujii K.

    International Journal of Heat and Fluid Flow   62 巻   頁: 10 - 23   2016年12月

     詳細を見る

    出版者・発行元:International Journal of Heat and Fluid Flow  

    High-fidelity computations of the flow control around a pitching NACA633−618 airfoil by a plasma actuator are conducted. The effectiveness of the plasma actuator and the effects of its installation position are investigated. The plasma actuator is installed at x/c=0%, 10%, and 60% from the leading edge of the airfoil. The installation position of 60% is chosen based on the investigation of the uncontrolled flowfield; the case with this position successfully enhanced the aerodynamic performances of the airfoil. The results show the importance of a priori investigation of the separation and the reattachment points for an uncontrolled flowfield. In addition, the results illustrate that a properly installed and actuated plasma actuator is capable of controlling the dynamic flowfields and improving the aerodynamic performances of an airfoil.

    DOI: 10.1016/j.ijheatfluidflow.2016.10.012

    Scopus

  158. Computational Analysis of Compressible Gas-Particle-Multuphase Turbulent Mixing Layer in Euler-Euler Formulation 査読有り

    D.Terakado, Y.Nagata, T.Nonomura, Y.Nagata, K.Fujii, M.Yamamoto

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   14 巻 ( 30 ) 頁: Po_2_25 - Po_2_31   2016年12月

     詳細を見る

    記述言語:英語  

    researchmap

  159. Control of dynamic flowfield around a pitching NACA63<sub>3</sub>-618 airfoil by a DBD plasma actuator

    Fukumoto, H; Aono, H; Watanabe, T; Tanaka, M; Matsuda, H; Osako, T; Nonomura, T; Oyama, A; Fujii, K

    INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW   62 巻   頁: 10 - 23   2016年12月

  160. Conservative high-order flux-reconstruction schemes on moving and deforming grids 査読有り

    Abe, Y; Haga, T; Nonomura, T; Fujii, K

    COMPUTERS & FLUIDS   139 巻   頁: 2 - 16   2016年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Computers and Fluids  

    An appropriate procedure to construct symmetric conservative metrics is presented for the high-order conservative flux-reconstruction scheme on three-dimensionally moving and deforming grids. The present framework enables direct discretization of the strong conservation form of governing equations without any errors in the freestream preservation and global conservation properties. We demonstrate that a straightforward implementation of the symmetric conservative metrics often fails to construct metric polynomials having the same order as a solution polynomial, which severely degrades the numerical accuracy. On the other hand, the symmetric conservative metrics constructed using an appropriate procedure can preserve the freestream solution regardless of the order of shape functions. Moreover, a convecting vortex is more accurately computed on deforming grids. The global conservation property is also demonstrated numerically for the convecting vortex on deforming grids.

    DOI: 10.1016/j.compfluid.2016.03.024

    Web of Science

    Scopus

    researchmap

  161. Multi-Objective Aeroacoustic Design Exploration of Launch-Pad Flame Deflector Using Large-Eddy Simulation 査読有り

    Tatsukawa, T; Nonomura, T; Oyama, A; Fujii, K

    JOURNAL OF SPACECRAFT AND ROCKETS   53 巻 ( 4 ) 頁: 751 - 758   2016年7月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Spacecraft and Rockets  

    This study explores possible designofan aeroacoustic flame deflector forarocket launch pad. The design objectives are 1) minimization of the overall sound pressure level near the payload fairing, 2) minimization of the time-averaged maximum pressure on the flame-deflector surface, and 3) minimization of the shape difference from a flat plate inclined at 45 deg. The acoustic wave characteristics associated with deflector shapes are identified by large-eddy simulations. To overcome difficulties of required computational time, the following are adopted: 1) a high-order scheme that reduces the computational cost of large-eddy simulations, 2) amulti-objective evolutionary algorithm for efficient parallelization, and 3) large-scale parallelization on the Japanese supercomputer "K". Total computational time for optimization is approximately 350 h with 6500 processors of the K computer. The analysis of nondominated (Pareto-optimal) solutions reveals a tradeoff relation and correlation among the objective functions. In the result, there appears a well-balanced solution that significantly reduces the overall sound pressure level. The shape difference is relatively minor, with a small bump located somewhat upstream of the impinging region. The result suggests that the local angle of the inclined deflector near the impinging region plays an important role for the reduction of overall sound pressure level near the rocket fairing.

    DOI: 10.2514/1.A33420

    Web of Science

    Scopus

    researchmap

  162. Low-cost and ultimately-downsized X-band deep-space telecommunication system for PROCYON mission 査読有り

    Kobayashi Y., Ito T., Mita M., Takeuchi H., Funase R., Tomiki A., Kobayashi D., Nonomura T., Fukushima Y., Kawakatsu Y.

    IEEE Aerospace Conference Proceedings   2016-June 巻   2016年6月

     詳細を見る

    掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:IEEE Aerospace Conference Proceedings  

    PROCYON is a first full-scale, 50-kg-class probe featuring most of the key technologies for deep-space exploration. It was developed by the University of Tokyo and ISAS/JAXA and launched with Hayabusa 2 on 3 Dec 2014. PROCYON has a newly developed X-band telecommunication system fully compatible with the frequency range, up- and down-link turn-around ratio, modulation scheme, and DDOR tones following CCSDS-recommended standards, and it can establish X-band coherent two-way communication and ranging links with deep-space stations as larger deep-space probes have done. The total mass of the onboard telecommunication system is 7.3 kg excluding its RF coaxial harness, and total power consumption during two-way communication, 15 W of RF output power at SSPA, is 54.3 W. After launch, PROCYON's telecommunication system has been successfully working according to the system design. These achievements will provide core technologies for next-generation deep-space exploration by ultra-small probes.

    DOI: 10.1109/AERO.2016.7500745

    Scopus

    researchmap

  163. Investigation on subsonic to supersonic flow around a sphere at low Reynolds number of between 50 and 300 by direct numerical simulation 査読有り

    Nagata, T; Nonomura, T; Takahashi, S; Mizuno, Y; Fukuda, K

    PHYSICS OF FLUIDS   28 巻 ( 5 ) 頁: 056101   2016年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    In this study, analysis of flow properties around a sphere and its aerodynamic coefficients in the high-Mach-and-low-Reynolds-numbers conditions is carried out by direct numerical simulations solving the three-dimensional compressible NavierStokes equations. The calculation is performed on a boundary-fitted coordinate system with a high-order scheme of sufficient accuracy. The analysis is conducted by assuming a rigid sphere with a Reynolds number of between 50 and 300, based on the diameter of the sphere and the freestream velocity and a freestream Mach number of between 0.3 and 2.0, together with the adiabatic wall boundary condition. The calculation shows the following yields: (1) unsteady fluctuation of hydrodynamic forces become smaller as the Mach number increases under the same Reynolds number condition, (2) the drag coefficient increases with the Mach number due to an increase in the pressure drag by the shock wave, and (3) an accurate prediction of the drag coefficient in the supersonic regime using traditional models might be difficult.

    DOI: 10.1063/1.4947244

    Web of Science

    Scopus

    researchmap

  164. Numerical study of plasma dynamics and electrohydrodynamic effect in DBD plasma actuator 査読有り

    Nishida H., Nonomura T., Abe T.

    International Journal of Plasma Environmental Science and Technology   10 巻 ( 1 ) 頁: 70 - 75   2016年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Plasma Environmental Science and Technology  

    Discharge plasma evolution of DBD plasma actuator was numerically simulated to analyze the electrohydrodynamic (EHD) force field which is the source of the wall-surface jet generation of DBD plasma actuator. The simulation was conducted in the three-dimensional space, and three-dimensionality of the discharge and EHD force field was discussed in detail. As a result, many micro-discharges repetitively appear in the three-dimensional simulation. Although many of them appears at random position on the electrode edge, some of them appear at the same position. These discharge characteristics are in good agreement with observations in experiments. The EHD force field is also spanwise non-uniform corresponding to the plasma structure. To analyze the effects of the three-dimensional non-uniformity on the fluid, three-dimensional CFD simulation of the induced wall-surface jet was also conducted using the EHD force field obtained in the plasma simulation. The result indicated that not only transverse but also longitudinal vortex structures are generated, and the transverse vortex breaks into many small vortices with downstream advection.

    Scopus

    researchmap

  165. Plate-Angle Effects on Acoustic Waves from Supersonic Jets Impinging on Inclined Plates 査読有り

    Nonomura, T; Honda, H; Nagata, Y; Yamamoto, M; Morizawa, S; Obayashi, S; Fujii, K

    AIAA JOURNAL   54 巻 ( 3 ) 頁: 816 - 827   2016年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    The effects of plate angle on acoustic waves from a supersonic jet impinging on an inclined flat plate at angles of 30, 45, and 60 deg are numerically investigated. Three-dimensional compressible Navier-Stokes equations are solved using the modified weighted compact nonlinear scheme. Similar to previous studies, the acoustic fields indicate that there are at least three types of acoustic waves in all of the cases considered herein: 1) Mach waves generated from the shear layer of the main jet, 2) acoustic waves generated from the impingement region, and 3) Mach waves generated from the shear layer of the supersonic flow downstreamof the jet impingement. Acoustic waves (2) are generated from two different acoustic sources: 1) the interaction between the plate shock wave and the shear layer, and 2) the interaction between the bubble-induced shock waves and the shear layer. The frequency characteristics of acoustic waves are related to the thickness of the shear layer in the impingement region. The results of the present study indicate the source location and the characteristics of acoustic waves (2) for various flat-plate angles.

    DOI: 10.2514/1.J054152

    Web of Science

    Scopus

    researchmap

  166. 反応性多成分流体に適用したRobust Weighted Compact Nonlinear Schemeによるデトネーションの数値解析 査読有り

    朝原 誠, 神谷 朋宏, 飯田 遼平, 坪井 伸幸, 野々村 拓, 林 光一, Makoto ASAHARA, Tomohiro KAMIYA, Ryohei IIDA, Nobuyuki TSUBOI, Taku NONOMURA, A. Koichi HAYASHI, 青山学院大学理工学部, 青山学院大学大学院理工学研究科, 青山学院大学大学院理工学研究科, 九州工業大学大学院工学研究院, 宇宙航空研究開発機構宇宙科学研究所, 青山学院大学理工学部, Department of Mechanical Engineering Aoyama, Gakuin University, Department of Mechanical Engineering Aoyama, Gakuin University, Department of Mechanical Engineering Aoyama, Gakuin University, Department of Mechanical, Control Engineering Kyushu, Institute of Technology, Institute of Space, Astronautical Science Japan Aerospace Exploration Agency, Department of Mechanical Engineering Aoyama, Gakuin University

    ながれ : 日本流体力学会誌   35 巻 ( 1 ) 頁: 33 - 44   2016年2月

     詳細を見る

    記述言語:日本語  

    超音速燃焼であるデトネーションの数値解析では,デトネーション波面を構成する衝撃波を厳密に解く必要がある.しかし,デトネーションの数値解析に使用される離散化手法には,数値散逸の大きい古い手法が多く,数値流体力学分野で発展が目覚ましい高次精度解析手法の導入例は少ない.そこで,9化学種の質量保存式を含む多成分流体の基礎方程式に,高次精度解析手法の一つであるrobust weighted compact nonlinear scheme(RWCNS)を実装し,研究例の多いH_2-Airデトネーションの数値解析を行った.その結果,従来の手法よりもデトネーション波面構造を詳細に捉えることができた.本稿では,反応性多成分流体にRWCNSを実装するための方法と得られたデトネーション波面構造について報告する.In order to simulate detonation which is a supersonic combustion, it is necessary to exactly solve a shock wave which is a part of detonation front. However, most of discretization methods used in earlier studies of detonation have strong numerical dissipation at discontinuity, and high order schemes developed in the field of computational fluid dynamics are hardly used. We calculate detonations by implementation of robust weighted compact nonlinear scheme (RWCNS). The present results using RWCNS show the detailed detonation wave structure. In this paper, we propose an efficient implementation of RWCNS to reactive multi-component fluid, and present the detonation wave structure.

    J-GLOBAL

    researchmap

  167. Numerical Study on Spanwise Nonuniformity in Body-Force Field of Dielectric-Barrier-Discharge Plasma Actuator 査読有り

    Nishida, H; Nonomura, T; Abe, T

    AIAA JOURNAL   54 巻 ( 2 ) 頁: 659 - 669   2016年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    The discharge plasma evolution of a dielectric barrier discharge plasma actuator is numerically simulated in the three-dimensional space. The spanwise nonuniformity in the body force field is analyzed, and the validity of the twodimensional analysis is discussed. A sinusoidal voltage at the electrode is simulated, and the simulation successfully reproduces the characteristics of microdischarge as reported by previous experimental studies. The body force field obtained in the simulation is nonuniform in the spanwise direction, and a strong spanwise force is generated, even from the time-averaged viewpoint. The spanwise-averaged body force field is compared with the two-dimensional simulation result. Although the qualitative characteristics of the body force field in the two-dimensional simulation are the same as in the three-dimensional simulation, the two-dimensional simulation underestimates the chordwise extension of the force field and the force amplitude due to the weaker electric field concentration in the twodimensional plasma structure. It can be expected that the two-dimensional simulation is useful for preliminary study on the dielectric barrier discharge plasma actuator. However, the three-dimensional simulation is indispensable to reproduce the spatial structure of the dielectric barrier discharge plasma, and understanding the interplay between plasma structure and actuator performance is an important aspect of plasma actuator research.

    DOI: 10.2514/1.J054315

    Web of Science

    Scopus

    researchmap

  168. Control of dynamic flowfield around a pitching NACA63<inf>3</inf>−618 airfoil by a DBD plasma actuator 査読有り

    Hiroaki Fukumoto, Hikaru Aono, Takeshi Watanabe, Motofumi Tanaka, Hisashi Matsuda, Toshiki Osako, Taku Nonomura, Akira Oyama, Kozo Fujii

    International Journal of Heat and Fluid Flow   62 巻   頁: 10 - 23   2016年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    © 2016 Elsevier Inc. High-fidelity computations of the flow control around a pitching NACA63 3 −618 airfoil by a plasma actuator are conducted. The effectiveness of the plasma actuator and the effects of its installation position are investigated. The plasma actuator is installed at x/c=0%, 10%, and 60% from the leading edge of the airfoil. The installation position of 60% is chosen based on the investigation of the uncontrolled flowfield; the case with this position successfully enhanced the aerodynamic performances of the airfoil. The results show the importance of a priori investigation of the separation and the reattachment points for an uncontrolled flowfield. In addition, the results illustrate that a properly installed and actuated plasma actuator is capable of controlling the dynamic flowfields and improving the aerodynamic performances of an airfoil.

    DOI: 10.2514/6.2016-4239

    Web of Science

    Scopus

    researchmap

  169. Development of a Cooling System for GAPS using Oscillating Heat Pipe 査読有り

    FUKE Hideyuki, MIYAZAKI Yoshiro, MORI Junichi, NAGAI Hiroki, NONOMURA Taku, OGAWA Hiroyuki, OKAZAKI Shun, OKUBO Takuma, OZAKI Shinji, SATO Daisuke, SHIMIZU Kensei, ABE Takumi, TAKAHASHI Katsumasa, TAKAHASHI Shun, YAMADA Noboru, YOSHIDA Takanori, DAIMARU Takuro, INOUE Takayoshi, KAWACHI Akiko, KAWAI Hiroki, MASUYAMA Yosuke, MATSUMIYA Hiroaki, MATSUMOTO Daishi

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN   14 巻 ( 30 ) 頁: Pi_17 - Pi_26   2016年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:一般社団法人 日本航空宇宙学会  

    <p>A cooling system using oscillating heat pipe (OHP) has been developed for a balloon-borne astrophysics project GAPS (General Anti-Particle Spectrometer). Taking advantages of OHP, such as high conductivity, low-power, and suitability for spread heat source, OHP is planned to be used to cool the GAPS core detectors. OHP is a novel technique and it has never been utilized in practical use neither for a spacecraft nor for a balloon-craft, regardless of its many advantages. In these several years, we have investigated OHP's suitability for GAPS step by step. At first, we have succeeded in developing a scaleddown OHP model with a three-dimensional routing, which can operate in a wide temperature range around between 230 K and 300 K. We also succeeded in the first OHP flight demonstration with a prototype GAPS balloon experiment. Subsequently, we developed actual-sized OHP models with various routings. Numerical simulation models have been developed in parallel to further optimize the OHP design by understanding the OHP performance both macroscopically and microscopically. The design of the OHP check valve has been improved as well. This paper discusses the latest status of the GAPS-OHP development.</p>

    DOI: 10.2322/tastj.14.Pi_17

    researchmap

  170. Multiobjective Design Exploration of Propeller Airfoils at Low-Reynolds and High-Mach Numbers Conditions towards the Mars Airplane, 査読有り

    S. Morizawa, T. Nonomura, A.Oyama, S. Obayashi, K. Fujii

    Transaction of the Japan Society for Aeronautical Sciences, Aerospace Technology Japan, Aerospace Technology   14 巻 ( ists30 ) 頁: Pk_47 - Pk_53   2016年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2322/tastj.14.Pk_47

    researchmap

  171. Generation of acoustic disturbances in supersonic laminar cavity flows

    Li W., Nonomura T., Fujii K.

    International Journal of Acoustics and Vibrations   20 巻 ( 4 ) 頁: 135 - 142   2015年12月

     詳細を見る

    出版者・発行元:International Journal of Acoustics and Vibrations  

    The generation of acoustic disturbances in supersonic laminar cavity flows is investigated by large-eddy simulations of supersonic laminar flow (M = 1:2, 2:0, and 3:0) past a rectangular cavity with a length-to-depth ratio of 2. Results suggest that well-originated large-scale vortical structures with strong spanwise coherence are present in the shear layer. Compressibility effects have significant impacts on the shear-layer development and the fluctuation properties. The dominant mechanism for the acoustic radiation in supersonic laminar cavity flows is shown to be associated with the successive passage of large-scale vortices over the cavity trailing edge. It is found that Mach waves radiated from the cavity shear layer may have significant contributions for the noiseradiation in terms of enhancing the strength of the feedback compression waves.

    Scopus

  172. Plate-Angle Effects on Acoustic Waves from Supersonic Jets Impinging on Inclined Plates 査読有り

    T.Nonomura, H.Honda, Y.Nagata, M.Yamamoto, S.Morizawa, S.Obayashi, K.Fujii

    AIAA JOURNAL   53 巻 ( 12 ) 頁: 1 - 21   2015年12月

     詳細を見る

    記述言語:英語  

    researchmap

  173. Mechanisms for laminar separated-flow control using dielectric-barrier-discharge plasma actuator at low Reynolds number 査読有り

    Sato, M; Nonomura, T; Okada, K; Asada, K; Aono, H; Yakeno, A; Abe, Y; Fujii, K

    PHYSICS OF FLUIDS   27 巻 ( 11 ) 頁: 117101   2015年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    Large-eddy simulations have been conducted to investigate the mechanisms of separated-flow control using a dielectric barrier discharge plasma actuator at a low Reynolds number. In the present study, the mechanisms are classified according to the means of momentum injection to the boundary layer. The separated flow around the NACA 0015 airfoil at a Reynolds number of 63 000 is used as the base flow for separation control. Both normal and burst mode actuations are adopted in separation control. The burst frequency non-dimensionalized by the freestream velocity and the chord length (F+) is varied from 0.25 to 25, and we discuss the control mechanism through the comparison of the aerodynamic performance and controlled flow-fields in each normal and burst case. Lift and drag coefficients are significantly improved for the cases of F+ = 1, 5, and 15 due to flow reattachment associated with a laminarseparation bubble. Frequency and linear stability analyses indicate that the F+ = 5 and 15 cases effectively excite the natural unstable frequency at the separated shear layer, which is caused by the Kelvin-Helmholtz instability. This excitation results in earlier flow reattachment due to earlier turbulent transition. Furthermore, the Reynolds stress decomposition is conducted in order to identify the means of momentum entrainment resulted from large-scale spanwise vortical structure or small-scale turbulent vortices. For the cases with flow reattachment, the large-scale spanwise vortices, which shed from the separated shear layer through plasma actuation, significantly increase the periodic component of the Reynolds stress near the leading edge. These large-scale vortices collapse to small-scale turbulent vortices, and the turbulent component of the Reynolds stress increases around the large-scale vortices. In these cases, although the combination of momentum entrainment by both Reynolds stress components results in flow reattachment, the dominant component is identified as the turbulent component. This indicates that one of the effective control mechanisms for laminar separation is momentum entrainment by turbulent vortices through turbulent transition.

    DOI: 10.1063/1.4935357

    Web of Science

    Scopus

    researchmap

  174. Separation control based on turbulence transition around a two-dimensional hump at different Reynolds numbers 査読有り

    Yakeno, A; Kawai, S; Nonomura, T; Fujii, K

    INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW   55 巻   頁: 52 - 64   2015年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Heat and Fluid Flow  

    Separation and reattachment around a two-dimensional hump controlled by a two-dimensional periodic excitations induced by a dielectric barrier discharge plasma actuator are investigated at Reynolds numbers of 4000 and 16, 000 based on the freestream velocity and the hump height. A two-dimensional excitation is adopted in the present study for promoting two-dimensional instability in the shear layer and a resulting laminar-turbulent transition. Note that the most effective frequency for reattachment is fh(=f*u∞*/h*)=0.20 among the presently considered cases at both Reynolds numbers, which is close to the reference value previously reported for the flow around a backward-facing step (Hasan, 1992).This frequency is the highest among the frequencies that provide sufficient time for the vortex scale to become the hump height. In addition, the momentum balance around the hump is examined by decomposing the averaged momentum equations. The velocity fluctuation terms are found to be considerable in size: they increase around the separation position under periodic excitation control. These terms are balanced with other terms: the gradient of the velocity fluctuation in the streamwise direction is comparable to the sum of convection terms of the time-averaged velocity and that in the wall-normal direction is comparable to the pressure gradient in the wall-normal direction. The control performance for reattachment is correlated with these velocity fluctuation effects. There is a possibility that the excitation control enforces reattachment by increasing turbulence fluctuation and modifying the momentum transfer balance.

    DOI: 10.1016/j.ijheatfluidflow.2015.07.014

    Web of Science

    Scopus

    researchmap

  175. Generation of Acoustic Disturbances in Supersonic Laminar Cavity Flows

    Li, WP; Nonomura, T; Fujii, K

    INTERNATIONAL JOURNAL OF ACOUSTICS AND VIBRATION   20 巻 ( 3 ) 頁: 135 - 142   2015年9月

     詳細を見る

  176. Multifactorial Effects of Operating Conditions of Dielectric-Barrier-Discharge Plasma Actuator on Laminar-Separated-Flow Control 査読有り

    Sato, M; Aono, H; Yakeno, A; Nonomura, T; Fujii, K; Okada, K; Asada, K

    AIAA JOURNAL   53 巻 ( 9 ) 頁: 2544 - 2559   2015年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    A substantial number of large-eddy simulations are conducted on separated flow controlled by a dielectric barrier discharge plasma actuator at a Reynolds number of 63,000. In the present paper, the separated flow over a NACA 0015 airfoil at an angle of attack of 12 deg, which is just poststall, is used as the base flow for separation control. The effects of the location and operating conditions of the plasma actuator on the separation control are investigated by a parametric study. The control effect is evaluated based on the improvement of not only the lift coefficient but also the drag coefficient over an airfoil. The most effective location of the plasma actuator for both lift and drag improvement is precisely confirmed to be upstream of the natural separation point. Even a low burst ratio is found to be sufficient to obtain the same improvements as the cases with a high burst ratio. The effective nondimensional burst frequency F<sup>+</sup> is observed at 4 ≤ F<sup>+</sup> ≤ 6 for the improvement in the lift coefficient and at 6 ≤ F<sup>+</sup> ≤ 20 for that in the drag coefficient. The lift/drag ratio shows a clear peak at 6 ≤ F<sup>+</sup> ≤ 10. To clarify the mechanism of the laminar-separation control, the effect of a turbulent transition is investigated. There is a clear relationship between the separation control effect and the turbulent transition at the shear layer. An earlier and smoother transition case shows greater improvements in the lift and drag coefficients. Flow analyses show that the cases with early and smooth turbulent transition can attach the separated flow further upstream, resulting in a higher suction peak of the pressure coefficient. In addition, another mechanism of the separation control is observed in which the lift coefficient is improved, not by the reattachment through the turbulent transition but by the large-scale vortex shedding induced by the actuation. It is possible to separate these two dominant mechanisms based on the effect of the turbulent transition on the separation control.

    DOI: 10.2514/1.J053700

    Web of Science

    Scopus

    researchmap

  177. Generation of acoustic disturbances in supersonic laminar cavity flows 査読有り

    Li W., Nonomura T., Fujii K.

    International Journal of Acoustics and Vibrations   20 巻 ( 3 ) 頁: 135 - 142   2015年9月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Acoustics and Vibrations  

    The generation of acoustic disturbances in supersonic laminar cavity flows is investigated by large-eddy simulations of supersonic laminar flow (M = 1:2, 2:0, and 3:0) past a rectangular cavity with a length-To-depth ratio of 2. Results suggest that well-originated large-scale vortical structures with strong spanwise coherence are present in the shear layer. Compressibility effects have significant impacts on the shear-layer development and the fluctuation properties. The dominant mechanism for the acoustic radiation in supersonic laminar cavity flows is shown to be associated with the successive passage of large-scale vortices over the cavity trailing edge. It is found that Mach waves radiated from the cavity shear layer may have significant contributions for the noiseradiation in terms of enhancing the strength of the feedback compression waves.

    DOI: 10.20855/ijav.2015.20.3377

    Scopus

    researchmap

  178. LES of transient flows controlled by DBD plasma actuator over a stalled airfoil 査読有り

    Asada, K; Nonomura, T; Aono, H; Sato, M; Okada, K; Fujii, K

    INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS   29 巻 ( 3-5 ) 頁: 215 - 229   2015年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Computational Fluid Dynamics  

    Large-eddy simulations (LES) are employed to understand the flow field over a NACA 0015 airfoil controlled by a dielectric barrier discharge (DBD) plasma actuator. The Suzen body force model is utilised to introduce the effect of the DBD plasma actuator. The Reynolds number is fixed at 63,000. Transient processes arising due to non-dimensional excitation frequencies of one and six are discussed. The time required to establish flow authority is between four and six characteristic times, independent of the excitation frequency. If the separation is suppressed, the initial flow conditions do not affect the quasi-steady state, and the lift coefficient of the higher frequency case converges very quickly. The transient states can be categorised into following three stages: (1) the lift and drag decreasing stage, (2) the lift recovery stage, and (3) the lift and drag converging stage. The development of vortices and their influence on control is delineated. The simulations show that in the initial transient state, separation of flow suppression is closely related to the development spanwise vortices while during the later, quasi-steady state, three-dimensional vortices become more important.

    DOI: 10.1080/10618562.2015.1032271

    Web of Science

    Scopus

    researchmap

  179. Mechanisms of surface pressure distribution within a laminar separation bubble at different Reynolds numbers 査読有り

    Lee, D; Kawai, S; Nonomura, T; Anyoji, M; Aono, H; Oyama, A; Asai, K; Fujii, K

    PHYSICS OF FLUIDS   27 巻 ( 2 ) 頁: 1.4913500   2015年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    Mechanisms behind the pressure distribution and skin friction within a laminar separation bubble (LSB) are investigated by large-eddy simulations around a 5% thickness blunt flat plate at the chord length based Reynolds number 5.0 × 103, 6.1 × 103, 1.1 × 104, and 2.0 × 104. The characteristics inside the LSB change with the Reynolds number; a steady laminar separation bubble (LSB_S) at the Reynolds number 5.0 × 103 and 6.1 × 103, and a steady-fluctuating laminar separation bubble (LSB_SF) at the Reynolds number 1.1 × 104, and 2.0 × 104. Different characteristics of pressure and skin friction distributions are observed by increasing the Reynolds number, such that a gradual monotonous pressure recovery in the LSB_S and a plateau pressure distribution followed by a rapid pressure recovery region in the LSB_SF. The reasons behind the different characteristics of pressure distributions at different Reynolds numbers are discussed by deriving the Reynolds averaged pressure gradient equation. It is confirmed that the viscous stress distributions near the surface play an important role in determining the formation of different pressure distributions. Depending on the Reynolds numbers, the viscous stress distributions near the surface are affected by the development of a separated laminar shear layer or the Reynolds shear stress. In addition, we show that the same analyses can be applied to the flows around a NACA0012 airfoil.

    DOI: 10.1063/1.4913500

    Web of Science

    Scopus

    researchmap

  180. A new technique for freestream preservation of finite-difference WENO on curvilinear grid 査読有り

    Nonomura, T; Terakado, D; Abe, Y; Fujii, K

    COMPUTERS & FLUIDS   107 巻   頁: 242 - 255   2015年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Computers and Fluids  

    A new technique for a finite-difference weighted essentially nonoscillatory scheme (WENO) on curvilinear grids to preserve freestream is introduced. This technique first divides the standard finite-difference WENO into two parts: (1) a consistent central difference part and (2) a numerical dissipation part. For the consistent central difference part, the conservative metric technique is directly adopted. For the numerical dissipation part, it is proposed that the metric term should be frozen for constructing the upwinding flux. This treatment only affects the numerical dissipation part, and the order of accuracy is maintained. With this technique, the freestream is perfectly preserved, and the flow fields are better resolved on wavy and random grids.

    DOI: 10.1016/j.compfluid.2014.09.025

    Web of Science

    Scopus

    researchmap

  181. On the freestream preservation of high-order conservative flux-reconstruction schemes 査読有り

    Abe, Y; Haga, T; Nonomura, T; Fujii, K

    JOURNAL OF COMPUTATIONAL PHYSICS   281 巻   頁: 28 - 54   2015年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    The appropriate procedure for constructing the symmetric conservative metric is presented with which both the freestream preservation and global conservation properties are satisfied in the high-order conservative flux-reconstruction scheme on a three-dimensional stationary-curvilinear grid. A freestream preservation test is conducted, and the symmetric conservative metric constructed by the appropriate procedure preserves the freestream regardless of the order of shape functions, while other metrics cannot always preserve the freestream. Also a convecting vortex is computed on three-dimensional wavy grids, and the formal order of accuracy is achieved when the symmetric conservative metric is appropriately constructed, while it is not when they are inappropriately constructed. In addition, although the sufficient condition for the freestream preservation with the nonconservative (cross product form) metric was reported in the previous study to be that the order of solution polynomial has to be greater than or equal to the twice of the order of a shape function, a special case is newly found in the present study: when the Radau polynomial is used for the correction function, the freestream is preserved even if the solution order is lower than the known condition. Using the properties of Legendre polynomials, the mechanism for this special case is analytically explained, considering the cancellation of aliasing errors.

    DOI: 10.1016/j.jcp.2014.10.011

    Web of Science

    Scopus

    researchmap

  182. Comparison of Numerical Methods Evaluating Airfoil Aerodynamic Characteristics at Low Reynolds Number 査読有り

    Lee, D; Nonomura, T; Oyama, A; Fujii, K

    JOURNAL OF AIRCRAFT   52 巻 ( 1 ) 頁: 296 - 306   2015年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Aircraft  

    The flowfields around the NACA0012 airfoil at Reynolds numbers 1 × 104 , 3 × 104 , and 5 × 104 are studied, and the predictability of aerodynamic characteristics derived from various numerical methods is examined. Twodimensional laminar simulation, two-dimensional Reynolds-averaged Navier-Stokes simulation using the Baldwin-Lomax turbulence model, and three-dimensional implicit large-eddy simulation are employed in this study. The twodimensional laminar and three-dimensional implicit large-eddy simulations accurately predict the separation point, and capture the characteristics of a separation bubble for each Reynolds number and each angle of attack. Nonlinearity in the lift curve is also captured in the results of the two-dimensional laminar and three-dimensional implicit large-eddy simulations. The two-dimensional Reynolds-averaged Navier-Stokes simulation using the Baldwin-Lomax turbulence model predicts the separation point nearer the trailing edge than does the twodimensional laminar and three-dimensional implicit large-eddy simulations, and the separation bubble is not captured for any Reynolds number and angle of attack by this method. Nonlinearity of the lift curve does not appear in the results of the two-dimensional Reynolds-averaged Navier-Stokes simulation using the Baldwin-Lomax turbulence model. The two-dimensional laminar simulation can predict airfoil aerodynamic characteristics qualitatively, and it can be used as an appropriate numerical method at lower Reynolds numbers. The three-dimensional-implicit-large-eddy-simulation technique can be employed when more accurate qualitative characteristics are needed.

    DOI: 10.2514/1.C032721

    Web of Science

    Scopus

    researchmap

  183. A Simple Immersed Boundary Method for Compressible Flow Simulation around a Stationary and Moving Sphere 査読有り

    Mizuno, Y; Takahashi, S; Nonomura, T; Nagata, T; Fukuda, K

    MATHEMATICAL PROBLEMS IN ENGINEERING   2015 巻   頁: 438086   2015年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Mathematical Problems in Engineering  

    This study is devoted to investigating a flow around a stationary or moving sphere by using direct numerical simulation with immersed boundary method (IBM) for the three-dimensional compressible Navier-Stokes equations. A hybrid scheme developed to solve both shocks and turbulent flows is employed to solve the flow around a sphere in the equally spaced Cartesian mesh. Drag coefficients of the spheres are compared with reliable values obtained from highly accurate boundary-fitted coordinate (BFC) flow solver to clarify the applicability of the present method. As a result, good agreement was obtained between the present results and those from the BFC flow solver. Moreover, the effectiveness of the hybrid scheme was demonstrated to capture the wake structure of a sphere. Both advantages and disadvantages of the simple IBM were investigated in detail.

    DOI: 10.1155/2015/438086

    Web of Science

    Scopus

    researchmap

  184. Implementation of a Robust Weighted Compact Nonlinear Scheme for Modeling of Hydrogen/Air Detonation 査読有り

    Iida, R; Asahara, M; Hayashi, AK; Tsuboi, N; Nonomura, T

    COMBUSTION SCIENCE AND TECHNOLOGY   186 巻 ( 10-11 ) 頁: 1736 - 1757   2014年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:Combustion Science and Technology  

    In order to simulate detonation, a high-order shock-capturing scheme that models chemical reactions is implemented, and its resolution is examined by testing it on several numerical problems. A robust weighted compact nonlinear scheme (RWCNS) is adopted to take advantage of its robustness and ability to handle different flux types. This study shows the high resolution of the RWCNS compared with the conventional scheme. The results show that the RWCNS predicts the detailed vortex structure behind the detonation wavefront. ©

    DOI: 10.1080/00102202.2014.935646

    Web of Science

    Scopus

    researchmap

  185. Computational and Experimental Analysis of a High-Performance Airfoil Under Low-Reynolds-Number Flow Condition 査読有り

    Anyoji, M; Nonomura, T; Aono, H; Oyama, A; Fujii, K; Nagai, H; Asai, K

    JOURNAL OF AIRCRAFT   51 巻 ( 6 ) 頁: 1864 - 1872   2014年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Aircraft  

    A high-performance Ishii airfoil was analyzed using both a wind-tunnel and large-eddy simulations at a low- Reynolds-number condition (Re = 23,000). The design guidelines for an airfoil shape with a high lift-to-drag ratio under the aforementioned condition are described by analyses of flowfields and aerodynamic characteristics of the Ishii airfoil. Compared with conventional airfoils, such as the NACA 0012 and NACA 0002, the shape characteristic effects of the Ishii airfoil on its flowfield and aerodynamic characteristics are discussed. The shape on the suction side of the Ishii airfoil can cause delays in the flow separation at low angle of attacks. The separated flow reattaches, and a separation bubble forms even when trailing-edge separation changes to leading-edge separation. The separation bubble contributes to an increase in lift coefficient. In addition, the Ishii airfoil can gain a high positive pressure on the pressure side as compared with the other two symmetric airfoils due to the camber near the trailing edge.Onthe other hand, the pressure drag of the Ishii airfoil, which is a dominant factor of total drag, is considerably smaller than those of the other two airfoils. It was found that the shape on the suction side as well as that on the pressure side (such as the leading-edge roundness and the camber) are very significant in the low-Reynolds-number airfoil with a high lift-todrag ratio.

    DOI: 10.2514/1.C032553

    Web of Science

    Scopus

    researchmap

  186. Simple and robust HLLC extensions of two-fluid AUSM for multiphase flow computations 査読有り

    Kitamura, K; Nonomura, T

    COMPUTERS & FLUIDS   100 巻   頁: 321 - 335   2014年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Computers and Fluids  

    A two-fluid AUSM+-up numerical flux function with the exact (Godunov) Riemann solver for the stratified flow model concept by Chang et al. (2007) has been extended for simple and robust computations of compressible multiphase flows. The present method replaces the Godunov part with the HLLC approximate Riemann solver with no-iteration procedure in a very simple manner: This two-fluid HLLC has been inspired by the work by Hu et al. (2009), but used in a totally different way. Numerical tests demonstrate that the present two-fluid AUSM+-up is, if only velocity and pressure in the middle zone are computed by HLLC, as robust as the original, Godunov-combined AUSM+-up, despite being free from iterations and convergence criteria. © 2014 Elsevier Ltd.

    DOI: 10.1016/j.compfluid.2014.05.019

    Web of Science

    Scopus

    researchmap

  187. Numerical Study of Vortex Flow Control on High-Angle-of-Attack Slender Body 査読有り

    M. Satoh, H. Nishida, T. Nonomura

    Transactions of JSASS, Aerospace Technology Japan   12 巻 ( ists29 ) 頁: Pe_43 - Pe_49   2014年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2322/tastj.12.Pe_43

    researchmap

  188. Planetary Atmosphere Wind Tunnel Tests on Aerodynamic Characteristics of a Mars Airplane Scale Model 査読有り

    Masayuki Anyoji, Masato Okamoto, Hidenori Hidaka, Taku Nonomura, Akira Oyama, Kozo Fujii

    Transactions of the Japan Society for Aeronautical and Space Sciences   12 巻 ( ists29 ) 頁: 7 - 12   2014年5月

     詳細を見る

    掲載種別:研究論文(学術雑誌)  

    DOI: 10.2322/tastj.12.Pk_7

    researchmap

  189. Three-dimensional simulations of discharge plasma evolution on a dielectric barrier discharge plasma actuator 査読有り

    Nishida, H; Nonomura, T; Abe, T

    JOURNAL OF APPLIED PHYSICS   115 巻 ( 13 ) 頁: 133301   2014年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Physics  

    To develop simulation techniques for reconstructing microdischarges in a dielectric barrier discharge (DBD) plasma actuator and analyze spanwise non-uniformity in a body force field, three-dimensional discharge plasma simulations of a DBD plasma actuator were conducted assuming step-like positive and negative applied voltages. Our study showed that to break the spanwise uniformity, some disturbances were required in the computational conditions to reconstruct the three-dimensional microdischarges, and the attachment of some minute bumps (several tens of micrometers in size) on the electrode edge allowed for the successful reconstruction of glow-type microdischarges and streamer-type filamentary discharges in the negative and positive applied voltage cases, respectively. The tentative body force field has strong spanwise non-uniformity corresponding to the plasma structure, and in addition, a spanwise directional body force also exists, especially in the streamer discharge. However, the spanwise averaged body force has the same spatial-distribution and time-evolution characteristics obtained with the two-dimensional simulation. © 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4870384

    Web of Science

    Scopus

    researchmap

  190. Geometric interpretations and spatial symmetry property of metrics in the conservative form for high-order finite-difference schemes on moving and deforming grids 査読有り

    Abe, Y; Nonomura, T; Iizuka, N; Fujii, K

    JOURNAL OF COMPUTATIONAL PHYSICS   260 巻   頁: 163 - 203   2014年3月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    The role of a geometric conservation law (GCL) on a finite-difference scheme is revisited for conservation laws, and the conservative forms of coordinate-transformation metrics are introduced in general dimensions. The sufficient condition of a linear high-order finite-difference scheme is arranged in detail, for which the discretized conservative coordinate-transformation metrics and Jacobian satisfy the GCL identities on three-dimensional moving and deforming grids. Subsequently, the geometric interpretation of the metrics and Jacobian discretized by a linear high-order finite-difference scheme is discussed, and only the symmetric conservative forms of the discretized metrics and Jacobian are shown to have the appropriate geometric structures. The symmetric and asymmetric conservative forms of the metrics and Jacobian are examined by the computation of an inviscid compressible fluid on highly-skewed stationary and deforming grids using sixth-order compact and fourth-order explicit central-difference schemes, respectively. The resolution of the isentropic vortex and the robustness of the computation are improved by employing symmetric conservative forms on the coordinate-transformation metrics and Jacobian that have an appropriate geometry background. An integrated conservation of conservative quantities is also attained on the deforming grid when symmetric conservative forms are adopted to the time metrics and Jacobian. © 2013 Elsevier Inc.

    DOI: 10.1016/j.jcp.2013.12.019

    Web of Science

    Scopus

    researchmap

  191. A simple interface sharpening technique with a hyperbolic tangent function applied to compressible two-fluid modeling 査読有り

    Nonomura, T; Kitamura, K; Fujii, K

    JOURNAL OF COMPUTATIONAL PHYSICS   258 巻   頁: 95 - 117   2014年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    A simple interface sharpening technique based on hyperbolic tangent interpolation, which was proposed in the previous study [F. Xiao, Y. Honma, K. Kono, A simple algebraic interface capturing scheme using hyperbolic tangent function, Int. J. Numer. Methods Fluids 48 (2005) 1023-1040], is applied to the compressible two-fluid modeling. The implementation of this scheme is very simple: the interpolation of the volume fraction in the monotonicity-upwind-scheme-for-conservation-law (MUSCL) solver is just replaced by the hyperbolic tangent interpolation, while the MUSCL interpolations for other variables are maintained. This technique is limited for the region near the interface to prevent the spurious oscillations of a minor phase. The one-dimensional and two-dimensional problems are solved, and the results are compared with those of the original MUSCL solver. The results show that the interface is significantly sharpened with this technique, and its sharpness is well controlled by one parameter. In addition, the robustness of the scheme does not change with sharpening the interface in the range we investigated. © 2013 Elsevier Inc.

    DOI: 10.1016/j.jcp.2013.10.021

    Web of Science

    Scopus

    researchmap

  192. A Numerical Scheme Based on an Immersed Boundary Method for Compressible Turbulent Flows with Shocks: Application to Two-Dimensional Flows around Cylinders 査読有り

    Takahashi, S; Nonomura, T; Fukuda, K

    JOURNAL OF APPLIED MATHEMATICS   2014 巻   頁: 252478   2014年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Mathematics  

    A computational code adopting immersed boundary methods for compressible gas-particle multiphase turbulent flows is developed and validated through two-dimensional numerical experiments. The turbulent flow region is modeled by a second-order pseudo skew-symmetric form with minimum dissipation, while the monotone upstream-centered scheme for conservation laws (MUSCL) scheme is employed in the shock region. The present scheme is applied to the flow around a two-dimensional cylinder under various freestream Mach numbers. Compared with the original MUSCL scheme, the minimum dissipation enabled by the pseudo skew-symmetric form significantly improves the resolution of the vortex generated in the wake while retaining the shock capturing ability. In addition, the resulting aerodynamic force is significantly improved. Also, the present scheme is successfully applied to moving two-cylinder problems. © 2014 Shun Takahashi et al.

    DOI: 10.1155/2014/252478

    Web of Science

    Scopus

    researchmap

  193. Analysis of Owl-like Airfoil Aerodynamics at Low Reynolds Number Flow 査読有り

    Katsutoshi Kondo, Hikaru Aono, Taku Nonomura, Masayuki Anyoji, Akira Oyama, Tianshu Liu, Kozo Fujii, Makoto Yamamoto

    The Japan Society of Aeronautical and Space Sciences, Aerospace Technology Japan   12 巻 ( 29 ) 頁: 35 - 40   2014年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    Aerodynamic characteristics and flow fields around an owl-like airfoil at a chord Reynolds number of 23,000 are investigated using two-dimensional laminar flow computations. Computed results demonstrate that the deeply concaved lower surface of the owl-like airfoil contributes to lift augmenting, and both a round leading edge and a flat upper surface lead to lift enhancement and drag reduction due to the suction peak and the presence of the thin laminar separation bubble near the leading edge. Subsequently, the owl-like airfoil has higher lift-to-drag ratio than the high lift-to-drag Ishii airfoil at low Reynolds number. However, when the minimum drag is presented, the Ishii airfoil gains lift coefficient of zero while lift coefficient of the owl-like airfoil does not becomes zero. Furthermore, a feature of unsteady flow structures around the owl-like airfoil at the maximum lift-to-drag ratio condition is highlighted.

    DOI: 10.2322/tastj.12.Tk_35

    researchmap

  194. Computational Prediction of Acoustic Waves from a Subscale Rocket Motor 査読有り

    T. Nonomura, S. Morizawa, S. Obayashi, K. Fujii

    Transaction of The Japan Society for Aeronautical Sciences, Aerospace Technology   12 巻 ( ists29 ) 頁: Pe_11 - Pe_17   2014年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2322/tastj.12.Pe_11

    researchmap

  195. Multi-objective Optimization of Airfoil for Mars Exploration Aircraft Using Genetic Algorithm 査読有り

    Gaku Sasaki, Tomoaki Tatsukawa, Taku Nonomura, Akira Oyama, Takaaki Matsumoto, Kouichi Yonemoto

    Transaction of The Japan Society for Aeronautical Sciences, Aerospace Technology Japan   12 巻 ( 29 ) 頁: 59 - 64   2014年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    The aim of this study is to find the optimal airfoil for Mars exploration aircraft, which requires high-lift-to-drag ratio. However, existing airfoils for flying in the Earth's atmosphere do not have a high enough lift-to-drag ratio in Mars flight condition. The airfoil studied here was designed using a Genetic Algorithm (GA) and evaluated using two-dimensional Computational Fluid Dynamics (CFD) without turbulence model (laminar). The objectives in this optimization include the maximization of lift and minimization of drag coefficients at only angle of attack of 6 °. The Reynolds number is 2.3 × 10<sup>4 </sup>under the aircraft cruising condition. B-spline curves that connect neighboring control points express the upper and lower surfaces of the airfoil. The results show that some typical types of airfoils excel in aerodynamic performance. Most optimal airfoils have a large upper surface curvature or a strong curvature at the center of the lower surface. The former feature generates a separation bubble that leads to a high negative pressure, and the latter character makes a high positive pressure. Both phenomena generate lift force, and yield higher lift coefficient and high lift-to-drag ratio. Furthermore, most airfoils on the Pareto front have a thickness less than 10 % of the chord length, which is suitable for the wing structure design of the Mars aircraft.

    DOI: 10.2322/tastj.12.Pk_59

    researchmap

  196. Thermal Condition of ASTRO-H under Air-cooled Environment before Launch

    NONOMURA Taku, SAWADA Makoto, TAKEI Yoh, IWATA Naoko, SHIBANO Yasuko, IRIKADO Tomoko, SHIMIZU Taro, TAKAKI Ryoji, OGAWA Hiroyuki, MITSUDA Kazuhisa

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN   12 巻 ( 29 ) 頁: To_4_1 - To_4_10   2014年

     詳細を見る

    記述言語:英語   出版者・発行元:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    The thermal condition of ASTRO-H under air-cooled environment before launch is investigated with a thermal testing and a computational analysis. The thermal testing shows that the temperatures of devices are confirmed to be within the operating range if the additional fans are used. Moreover, the results of the thermal testing are compared with those of computational results. The computational results of temperature of the devices around the dewar with the additional fans are in good agreement with those of the thermal testing. The good agreement in the condition with the additional fans is because the forced convection, which is a dominant effect, is well captured in the computational analysis. Meanwhile, the computational results of temperature on the side panels are in very good agreement with thermal testing despite the difference in the flow outside satellite by air conditioner: computational analysis models the air flow from the air-conditioner while thermal testing does not. This is because the air-flow is very slow (0.1[m/s] at the side panel locations) and forced convection effects are very small.

    DOI: 10.2322/tastj.12.To_4_1

    researchmap

  197. “Computational Analysis of Aerodynamic Performance of Mars Airplane 査読有り

    Naoya Fujioka, Taku Nonomura, Akira Oyama, Makoto Yamamoto, Kozo Fujii

    The Japan Society of Aeronautical and Space Sciences, Aerospace Technology Japan   12 巻 ( 29 ) 頁: 1 - 5   2014年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    Flow field and aerodynamic performance of the Mars airplane with a complete aircraft configuration are analyzed by RANS simulations. At the Reynolds number of 3.3x10<sup>4</sup>, a flow field is solved by an unstructured three-dimensional compressible CFD solver (LS-FLOW). Here, the Mars airplane is assumed to have the Ishii airfoil as the main wing shape. The Ishii airfoil is known as its good performance at the low Reynolds number condition. An objective of the present study is to clarify flow structures around a complete aircraft, for optimization of design of the Mars airplane. The results show that the features of the aerodynamic coefficients correspond to those of experimental results and the contribution of the main wing is significant on the aerodynamic characteristics of the entire airplane.

    DOI: 10.2322/tastj.12.Tk_1

    researchmap

  198. Analysis of Acoustic-fields Generated by a Supersonic Jet Impinging on Flat and Curved Inclined Plates 査読有り

    Y.Nagata, T. Nonomura, K.Fujii, M.Yamamoto

    International Journal of Aerospace and Lightweight Structures   3 巻 ( 3 )   2013年11月

     詳細を見る

    記述言語:英語  

    researchmap

  199. Robust explicit formulation of weighted compact nonlinear scheme 査読有り

    Nonomura, T; Fujii, K

    COMPUTERS & FLUIDS   85 巻   頁: 8 - 18   2013年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Computers and Fluids  

    This study presents a new weighted compact nonlinear scheme (WCNS). In the WCNS procedure, the linear difference scheme is modified to use the flux on the computational nodes together with that on the midpoints. This modification makes the scheme more robust, but at the same time, more dissipative. We conduct the truncation error analysis and discuss the reasons why this modification makes the scheme robust and dissipative. The standard shock problems are solved with both original and modified WCNS, and the results show that the discontinuity thickness of the modified WCNS increases, and over/undershoots at the discontinuities are suppressed better in WCNS. In addition, the stiff shock tube problems, which cannot be solved by the original WCNS because of negative pressure, can be solved using the modified WCNS without a blow-up of computation. A series of numerical tests show the robustness of the modified WCNS. © 2012 Elsevier Ltd.

    DOI: 10.1016/j.compfluid.2012.09.001

    Web of Science

    Scopus

    researchmap

  200. Mach-Number Effects on Vortex Breakdown in Subsonic Flows over Delta Wings 査読有り

    Nonomura, T; Fukumoto, H; Ishikawa, Y; Fujii, K

    AIAA JOURNAL   51 巻 ( 9 ) 頁: 2281 - 2286   2013年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    The article examines the Mach-number effects on vortex breakdown in subsonic flows over delta wings. The governing equations are three-dimensional compressible Navier-Stokes equations. The length and velocity are non-dimensionalized by the chord length and sound speed of the free stream condition, respectively. The computational code used here is based on the well validated Navier-Stokes code with recent modifications to realize more efficient implicit time-integration schemes and a high-order accurate evaluation of space derivatives. The wing-surface contours show pressure distribution is observed for the cases with a Mach number greater than 0.5. Here, the mode is distinguished by the instantaneous shape of the iso-surface of the second invariant of the velocity-gradient tensor. First, the results of the implicit large-eddy simulation and Reynolds averaged Navier-Stokes hybrid simulation using the Baldwin-Lomax turbulence model with a Mach number of 0.065 were validated with the experimental study.

    DOI: 10.2514/1.J052321

    Web of Science

    Scopus

    researchmap

  201. Mechanism of controlling supersonic cavity oscillations using upstream mass injection 査読有り

    Li, WP; Nonomura, T; Fujii, K

    PHYSICS OF FLUIDS   25 巻 ( 8 ) 頁: 086101   2013年8月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    The mechanism of controlling supersonic cavity oscillations using upstream mass injection is investigated by implicit large-eddy simulations of a turbulent flow (M∞ = 2.0, ReD = 105) past a rectangular cavity with a length-to-depth ratio of 2. The mass injection is simulated by specifying a vertical velocity profile of a jet ejecting steadily through a slot placed at the upstream of the cavity leading edge. The results show that the steady upstream mass injection produces significant attenuation of the cavity oscillations, and two primary mechanisms are demonstrated to be directly responsible for the noise suppression: lifting up of the cavity shear layer, and damping of the shear-layer instability. It is found that the case of low mass flow injection investigated is more effective in stabilizing the cavity shear layer than the high mass flow injection. A transition stage might exist between two well-developed oscillating modes, but "mode-switching" is not observed. © 2013 AIP Publishing LLC.

    DOI: 10.1063/1.4816650

    Web of Science

    Scopus

    researchmap

  202. On the feedback mechanism in supersonic cavity flows 査読有り

    Li, WP; Nonomura, T; Fujii, K

    PHYSICS OF FLUIDS   25 巻 ( 5 ) 頁: 056101   2013年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Fluids  

    Self-sustained oscillations in supersonic cavity flows are investigated by implicit large-eddy simulations of a supersonic flow (M∞ = 2.0, ReD = 105) past a three-dimensional rectangular cavity with length-to-depth ratio of 2. Both turbulent and laminar inflows are considered, and a variation of boundary-layer thickness in the turbulent inflow case is conducted. An additional simulation of turbulent free shear layer is also performed to illustrate the relationship between shedding vortices and acoustic excitations. Feedback mechanism is identified as the dominant mechanism driving the self-sustained oscillations in supersonic open cavity flows, regardless of the upstream turbulent state and the boundary-layer thickness. The generation of discrete vortices in the cavity shear layer is shown to be highly associated with acoustic excitations rather than natural instabilities of the cavity shear layer. Simulation results support that the primary noise source arises from the successive passage of large-scale vortices over the cavity trailing edge. The effects of upstream boundary layer on the shear-layer characteristics and acoustic fields will also be discussed. © 2013 AIP Publishing LLC.

    DOI: 10.1063/1.4804386

    Web of Science

    Scopus

    researchmap

  203. Study on application of DBD plasma actuator for side force control of high-angle-of-attack slender body

    Nishida H., Nonomura T., Inaba R., Sato M., Nonaka S.

    Advances in the Astronautical Sciences   146 巻   頁: 565 - 579   2013年4月

     詳細を見る

    出版者・発行元:Advances in the Astronautical Sciences  

    We have analyzed the asymmetric separation flow over a slender body at high angle of attack by numerical simulations aiming a control of the asymmetric vortices using a dielectric barrier discharge (DBD) plasma actuator. The Reynolds Averaged Navier Stokes/Large-Eddy Simulation hybrid method (RANS/LES) was adopted with the high-order compact spatial difference scheme. First, for investigating the characteristics of the asymmetric separation flow, the simulation of the flow field over the slender body was conducted for various angle of attack and bump height. Note that the bump is added near the body apex to simulate the symmetry-breaking imperfection. When the angle of attack or the bump becomes higher, the asymmetricity of vorticities becomes stronger. The side force has nonlinearity with the angle of attack or the bump height. Next, numerical simulations of the flow control using a plasma actuator were conducted. The side force coefficient can be continuously controlled in response to output power of the actuator within about ±1.0 on an average by the actuator's actuation at the aft body. However, the flow control effect is totally difference between starboard-side actuator's actuation and port-side actuator actuation. In addition, it is strongly influenced by the angle of attack.

    Scopus

  204. A new multiobjective genetic programming for extraction of design information from non-dominated solutions

    Tatsukawa T., Nonomura T., Oyama A., Fujii K.

    Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)   7811 LNCS 巻   頁: 528 - 542   2013年4月

     詳細を見る

    出版者・発行元:Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)  

    We propose a new type of multi-objective genetic programming (MOGP) for multi-objective design exploration (MODE). The characteristic of the new MOGP is the simultaneous symbolic regression to multiple objective functions using correlation coefficients. This methodology is applied to non-dominated solutions of the multi-objective design optimization problem to extract information between objective functions and design parameters. The result of MOGP is symbolic equations that are highly correlated to each objective function through a single GP run. These equations are also highly correlated to several objective functions. The results indicate that the proposed MOGP is capable of finding new design parameters more closely related to the objective functions than the original design parameters. The proposed MOGP is applied to the test problem and the practical design problem to evaluate the capability. © 2013 Springer-Verlag.

    DOI: 10.1007/978-3-642-37140-0_40

    Scopus

  205. Computational Analysis of Vortex Structures Induced by a Synthetic Jet to Control Separated Flows 査読有り

    K. Okada, T. Nonomura, K.Fujii, K. Miyaji

    International Journal of Flow Control   4 巻 ( 1+2 ) 頁: 45 - 46   2013年1月

     詳細を見る

    記述言語:英語  

    researchmap

  206. Conservative metric evaluation for high-order finite difference schemes with the GCL identities on moving and deforming grids 査読有り

    Abe, Y; Iizuka, N; Nonomura, T; Fujii, K

    JOURNAL OF COMPUTATIONAL PHYSICS   232 巻 ( 1 ) 頁: 14 - 21   2013年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    DOI: 10.1016/j.jcp.2012.08.031

    Web of Science

    Scopus

    researchmap

  207. Feedback Mechanism in Supersonic Laminar Cavity Flows 査読有り

    Li, WP; Nonomura, T; Oyama, A; Fujii, K

    AIAA JOURNAL   51 巻 ( 1 ) 頁: 253 - 257   2013年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    The mechanism driving the self-sustained oscillations in supersonic laminar cavity flows is studied to be a feedback-loop mechanism between the discrete vortices and acoustic disturbances. Implicit large eddy simulations (ILESs) are conducted. One typical feedback cycle is visualized with phase-averaged flowfields. The feedback compression waves are radiated from the region near the cavity trailing lip. Their generation is related to the passage of large-scale vortices over the trailing edge. In phase of acoustic excitation near the cavity leading edge, the incoming boundary layer rolls up into two well-originated vortices with highly two-dimensional characteristics and strong spanwise coherence. Vortex pairing seems to occur between these two discrete vortices. Phase averaging is shown to be a superior approach for the analysis of cavity oscillations.

    DOI: 10.2514/1.J051422

    Web of Science

    Scopus

    researchmap

  208. Large-Eddy Simulation of Low-Reynolds-Number Flow Over Thick and Thin NACA Airfoils 査読有り

    Kojima, R; Nonomura, T; Oyama, A; Fuji, K

    JOURNAL OF AIRCRAFT   50 巻 ( 1 ) 頁: 187 - 196   2013年1月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Aircraft  

    In this study, the flowfields around NACA0012 and NACA0002 airfoils at Reynolds number of 23,000 and the aerodynamic characteristics of these flowfields were analyzed using implicit large-eddy simulation and laminar-flow simulation. Around this Reynolds number, the flow over an airfoil separates, transits, and reattaches, resulting in the generation of a laminar separation bubble at the angle of attack in a certain degree range. Over an NACA0012 airfoil, the separation point moves toward its leading edge with an increasing angle of attack, and the separated flow may transit to create a short bubble. On the other hand, over an NACA0002 airfoil, the separation point is kept at its leading edge, and the separated flow may transit to create a long bubble. Moreover, nonlinearity appears in the lift curve of the NACA0012 airfoil, but not in that of NACA0002, despite the existence of a laminar separation bubble. Copyright © 2012 by Ryoji Kojima, Taku Nonomura, Akira Oyama, and Kozo Fujii.

    DOI: 10.2514/1.C031849

    Web of Science

    Scopus

    researchmap

  209. Aerodynamic Design Exploration for Reusable Launch Vehicle Using Genetic Algorithm with Navier-Stokes Solver 査読有り

    Tomoaki Tatsukawa, Taku Nonomura, Akira Oyama, Kozo Fujii

    Transactions of the Japan Society for Aeronautical and Space Sciences, Aerospace Technology Japan   6182 巻 ( 28 ) 頁: 57 - 63   2013年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    In this study, aerodynamic design exploration for reusable launch vehicle (RLV) is conducted using genetic algorithm with Navier-Stokes solver to understand the aerodynamic characteristics for various body configurations and find design information such as tradeoff information among objectives. The multi-objective aerodynamic design optimization for minimizing zero-lift drag at supersonic condition, maximizing maximum lift-to-drag ratio (<i>L/D</i>) at subsonic condition, maximizing maximum <i>L/D</i> at supersonic condition, and maximizing volume of shape is conducted for bi-conical shape RLV based on computational fluid dynamics (CFD). The total number of evaluation in multi-objective optimization is 400, and it is necessary for evaluating one body configuration to conduct 8 CFD runs. In total, 3200 CFD runs are conducted. The analysis of Pareto-optimal solutions shows that there are various trade-off relations among objectives clearly, and the analysis of flow fields shows that the shape for the minimum drag configuration is almost the same as that of the shape for the maximum <i>L/D</i> configuration at supersonic condition. The shape for the maximum <i>L/D</i> at subsonic condition obtains additional lift at the kink compared with the minimum drag configuration. It leads to enhancement of <i>L/D</i>.

    DOI: 10.2322/tastj.10.Pe_55

    researchmap

  210. Scalar tuning of a fluid solver using compact scheme for a supercomputer with a distributed memory architecture 査読有り

    Aono H., Nonomura T., Iizuka N., Ohsako T., Inari T., Hashimoto Y., Takaki R., Fujii K.

    CFD Letters   5 巻 ( 4 ) 頁: 143 - 152   2013年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CFD Letters  

    The scalar tuning of a compressible fluid solver for a supercomputer with a distributed memory architecture is conducted. We use the K computer which is one of the peta-scale supercomputers recently developed in Japan. A computational code "LANS3D" and its high-order compact differencing option are tuned. The original version of the code achieves approximately 4.5% of full performance of CPU for the simple test case. Scalar tuning based on combining do-loops works well, and the tuned code attains about 10% of full performance for the same case. The reasons are the improvement in the use of the cache, the suppression of the data transfer, and the efficient use of the data that once transferred to the cache from the memory that results in hiding the low speed of data transfer. The tuned code becomes twice faster than the original one in the wall-clock time and enables us to perform over-160-case parametric study about airfoil flow computation by large-eddy simulations with high-order accurate and high resolution numerical scheme. © 2013 All rights reserved. ISSR Journals.

    Scopus

    researchmap

  211. Study on application of DBD plasma actuator for side force control of high-angle-of-attack slender body 査読有り

    Nishida, H, Nonomura, T, Inaba, R, Sato, M, Nonaka, S

    Adv Astronaut Sci   146 巻   頁: 565 - 579   2013年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    Web of Science

    Scopus

    researchmap

    その他リンク: http://orcid.org/0000-0001-7739-7104

  212. STUDY ON APPLICATION OF DBD PLASMA ACTUATOR FOR SIDE FORCE CONTROL OF HIGH-ANGLE-OF-ATTACK SLENDER BODY

    Nishida, H; Nonomura, T; Inaba, R; Sato, M; Nonaka, S

    SPACE FOR OUR FUTURE   146 巻   頁: 565 - 579   2013年

     詳細を見る

  213. Numerical Investigation of Asymmetric Separation Vortices over Slender Body by RANS/LES Hybrid Simulation 査読有り

    R. Inaba, H. Nishida, T. Nonomura, K. Asada, K. Fujii

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES   10 巻 ( 28 ) 頁: 89 - 96   2012年8月

     詳細を見る

    記述言語:英語   出版者・発行元:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    We analyze the asymmetric vortices in the flow over a slender body at high angle of attack by numerical simulations aiming a proportional control of the side forces generated by vortices with a device such as dielectric barrier discharge (DBD) plasma actuator. With regard to the computational method, Reynolds averaged Navier Stokes/large-eddy simulation hybrid method is adopted with high-order compact spatial difference scheme. The grid convergence analysis is firstly conducted and the results show that the computational grid adopted in this study is fine enough for qualitative discussion. The total number of the grid point is 411 million points. Then, the effects of bump height on flow fields and aerodynamic characteristics are discussed. Note that bump is added near the body apex to simulate the symmetry-breaking imperfection. As a higher bump is adopted, stronger asymmetry is observed in the flow fields. On the other hand, side-force has nonlinearity with the bump height.

    DOI: 10.2322/tastj.10.Pe_89

    researchmap

  214. Numerical (error) issues on compressible multicomponent flows using a high-order differencing scheme: Weighted compact nonlinear scheme 査読有り

    Nonomura, T; Morizawa, S; Terashima, H; Obayashi, S; Fujii, K

    JOURNAL OF COMPUTATIONAL PHYSICS   231 巻 ( 8 ) 頁: 3181 - 3210   2012年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    A weighted compact nonlinear scheme (WCNS) is applied to numerical simulations of compressible multicomponent flows, and four different implementations (fully or quasi-conservative forms and conservative or primitive variables interpolations) are examined in order to investigate numerical oscillation generated in each implementation. The results show that the different types of numerical oscillation in pressure field are generated when fully conservative form or interpolation of conservative variables is selected, while quasi-conservative form generally has poor mass conservation property. The WCNS implementation with quasi-conservative form and interpolation of primitive variables can suppress these oscillations similar to previous finite volume WENO scheme, despite the present scheme is finite difference formulation and computationally cheaper for multi-dimensional problems. Series of analysis conducted in this study show that the numerical oscillation due to fully conservative form is generated only in initial flow fields, while the numerical oscillation due to interpolation of conservative variables exists during the computations, which leads to significant spurious numerical oscillations near interfaces of different component of fluids. The error due to fully conservative form can be greatly reduced by smoothing interface, while the numerical oscillation due to interpolation of conservative variables cannot be significantly reduced. The primitive variable interpolation is, therefore, considered to be better choice for compressible multicomponent flows in the framework of WCNS. Meanwhile better choice of fully or quasi-conservative form depends on a situation because the error due to fully conservative form can be suppressed by smoothed interface and because quasi-conservative form eliminates all the numerical oscillation but has poor mass conservation. © 2012 Elsevier Inc.

    DOI: 10.1016/j.jcp.2011.12.035

    Web of Science

    Scopus

    researchmap

  215. A numerical study of the effects of aerofoil shape on low reynolds number aerodynamics

    Aono H., Nonomura T., Anyoji M., Oyama A., Fujii K.

    Civil-Comp Proceedings   100 巻   2012年

     詳細を見る

    出版者・発行元:Civil-Comp Proceedings  

    A numerical study of the effects of airfoil shape on low Reynolds number aerodynamics is presented. The large-eddy simulations are performed with 6 <sup>th</sup>-order compact finite difference scheme and 10<sup>th</sup>-order low pass filter, and 2<sup>nd</sup>-order backward implicit time integration with inner iterations. Systematic numerical excesses show the feasibility of the current simulations to predict flow fields around fixed-wing configurations involving a laminar separation and laminar-to-turbulence transition at low Reynolds number. At the Reynolds number of 2.3×10<sup>4</sup>, two types of thin and asymmetric airfoils as a target airfoil shape of micro-size air vehicle are considered. The results show that the airfoil cross section affects the formation of a laminar separation bubble and the transition to turbulence in the three-dimensional flow around the wings at low angle of attack and hence significant influence on the aerodynamic performance. © Civil-Comp Press, 2012.

    Scopus

  216. An Effective Three-Dimensional Layout of Actuation Body Force for Separation Control 査読有り

    Kaneda, I; Sekimoto, S; Nonomura, T; Asada, K; Oyama, A; Fujii, K

    INTERNATIONAL JOURNAL OF AEROSPACE ENGINEERING   2012 巻   頁: 786960   2012年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Aerospace Engineering  

    We conducted large eddy simulations of the control of separated flow over an airfoil using body forces and discuss the role of a three-dimensional vortex structure in separation control. Two types of cases are examined: (1) the body force is distributed in a spanwise uniform layout and (2) the body force is distributed in a spanwise intermittent layout, with three-dimensional vortices being expected to be generated in the latter cases. The flow fields in the latter cases have a shorter separation bubble than those in the former cases although the total momentum of the body force in the latter cases is the same as or half of the former cases. In the flow fields of the latter type, the three-dimensional vortices, which are not observed in the former cases, are generated by the body force downstream of the body force distributed. Thus, three-dimensional vortices are considered to be effective in controlling the separated flow. Copyright © 2012 Ittetsu Kaneda et al.

    DOI: 10.1155/2012/786960

    Web of Science

    Scopus

    researchmap

  217. Preliminary Experimental Study on Aerodynamic Characteristics Control of Slender Body Using DBD Plasma Actuator 査読有り

    NISHIDA Hiroyuki, MIZUKI Sakae, MIYAZAKI Isao, NONAKA Satoshi, NONOMURA Taku, INATANI Yoshifumi

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN   10 巻 ( 28 ) 頁: Pe_97 - Pe_103   2012年

     詳細を見る

    記述言語:英語   出版者・発行元:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    Asymmetric separation vortices over a slender body at a high angle of attack exert a strong side force on the body and lead to the loss of attitude stability. We investigated the active control of the separation flow over a slender body and addressed the proportional control of the side force and the pitching moment. A flow control experiment was conducted in a wind tunnel using a cone-cylinder test body and a Dielectric Barrier Discharge (DBD) plasma actuator as a flow control device. The free-stream velocity was 9 m/s and the Reynolds number was approximately 42000. The side force coefficient was proportionally controlled within approximately ±1.0 using the actuator at the aft body, and the static stability angle of attack was controlled from 25 to 40 degrees and 65 to 85 degrees by controlling the pitching moment when the center of gravity was at the 55% position from the body apex. We estimated that a higher actuator output power is required for the effective control of the aerodynamics in a real flight. In addition, we confirmed that the actuator burst operation mode could reduce the required output power.

    DOI: 10.2322/tastj.10.Pe_97

    researchmap

  218. Overexpansion Effects on Characteristics of Mach Waves from a Supersonic Cold Jet 査読有り

    Nonomura, T; Fujii, K

    AIAA JOURNAL   49 巻 ( 10 ) 頁: 2282 - 2294   2011年10月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    For predicting acoustic waves emitted from a rocket plume, the overexpansion effects on Mach 3.0 supersonic jet acoustics are investigated using an implicit large eddy simulation.AMach 2.0 supersonic free jet is computed for code validation, and the results show qualitatively good agreement with the experiments. Then, computations of three different jets (design Mach numbers 3.0, 3.5, and 4.0 with fully expanded jet Mach number 3.0) are conducted, and nondimensionalizations based on design parameters and fully expanded parameters are discussed. Acoustic far-field spectra show that nondimensionalization based on fully expanded parameters works well for the high-Mach-number overexpanded jets, as it does for the low-Mach-number underexpanded jets that were investigated in previous studies. This nondimensionalization improves the accuracy of prediction of the acoustic waves emitted from rocket plumes because one parameter, the design Mach number, can be neglected for acoustic far fields. In addition, actual overexpansion effects after nondimensionalization are discussed. A comparison of the near flowfields and acoustic fields shows that Mach wave sources move upstream because of the existence of Mach disks, which enhances shearlayer mixing. Meanwhile, the overexpanded jet, which possesses only a shock cell without Mach disks, exhibits the same Mach wave generation characteristics as an ideally expanded jet. © 2011 by Taku Nonomura andKozo Fujii. Published by the American Institute of Aeronautics and Astronautics, Inc.

    DOI: 10.2514/1.J051054

    Web of Science

    Scopus

    researchmap

  219. Aeroacoustic waves generated from a supersonic jet impinging on an inclined flat plate 査読有り

    Nonomura, T; Goto, Y; Fujii, K

    INTERNATIONAL JOURNAL OF AEROACOUSTICS   10 巻 ( 4 ) 頁: 401 - 425   2011年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal of Aeroacoustics  

    This paper presents a computational study of the flow and flow-induced acoustic fields of a supersonic jet impinging on an inclined flat plate. For the numerical simulations, we solved three-dimensional compressible Navier-Stokes equations with a modified weighted compact nonlinear scheme. We analyzed the simulation results mainly from the viewpoint of the acoustic emission and propagation mechanism, and we investigated the acoustic field characteristics such as directivity, their spectra, and acoustic wave source positions. The acoustic fields indicate that there are at least three types of acoustic waves in all the cases considered in the study: (i) Mach waves generated from the shear layer of the main jet, (ii) acoustic waves generated from the impingement region, and (iii) Mach waves generated from the shear layer of the supersonic flow downstream of the jet impingement. The indication of the second type of wave (ii) is important because the commonly used empirical method for the estimation of the acoustic waves from a rocket plume does not consider such acoustic waves. We also discussed the effects of nozzle-plate distance and temperature on the second type of acoustic waves (ii).

    DOI: 10.1260/1475-472X.10.4.401

    Web of Science

    Scopus

    researchmap

  220. Toward accurate simulation and analysis of strong acoustic wave phenomena-A review from the experience of our study on rocket problems 査読有り

    Fujii, K; Nonomura, T; Tsutsumi, S

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   64 巻 ( 10-12 ) 頁: 1412 - 1432   2010年12月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:International Journal for Numerical Methods in Fluids  

    This paper gives an overview of the numerical simulations for the analysis of strong nonlinear acoustic waves during rocket development, with the emphasis on recent ones carried out using large-scale supercomputers. After the discussion on the difficulties encountered in such simulations, a computational study of blast wave propagation conducted for estimating the safety distance of a rocket is presented. The study was conducted about 20 years ago and the result showed the advantages of the moving grid method as well as the importance of grid resolution studies. A recent study on rocket plume acoustics is then presented. The result shows that the generation and propagation of Mach waves from the plume shear layers are key features to be captured. Direct simulations of such flows have now become feasible owing to the developments in computers and numerical schemes. Then, problems that still remain unsolved are discussed. Our study so far has been limited to simulations using structured grids of high spatial resolution although direct simulations of strongly nonlinear acoustic waves are becoming feasible. More studies have to be carried out for developing highly accurate schemes for unstructured grid systems for the applications to flow configurations over complex geometries. With such improvements, computational fluid dynamics (CFD) would become a still better effective tool for the analysis and estimation of nonlinear acoustic phenomena, especially in aerospace applications. © 2010 John Wiley & Sons, Ltd.

    DOI: 10.1002/fld.2446

    Web of Science

    Scopus

    researchmap

  221. Data mining of Pareto-optimal transonic airfoil shapes using proper orthogonal decomposition

    Oyama A., Nonomura T., Fujii K.

    Journal of Aircraft   47 巻 ( 5 ) 頁: 1756 - 1762   2010年9月

     詳細を見る

    出版者・発行元:Journal of Aircraft  

    A new approach to extract useful design information from the shape data of Pareto-optimal solutions of an optimization problem is proposed and applied to the optimization of airfoil shapes for good aerodynamic performance at transonic speed. The proposed approach decomposes shape data into principal modes and corresponding base vectors, using proper orthogonal decomposition. The advantageofthe proposed approachisthat the knowledge one can obtain does not depend onhow the shape is parameterized for design optimization. Analysis of the airfoil shapes obtained as the Pareto-optimal solutions for aerodynamic performance at transonic speeds shows that the optimized airfoils can be categorized into three families (low-drag designs, high-lift-to-drag designs, and high-lift designs), where the lift is increased by changing the camber near the trailing edge among the low-drag designs, while the lift is increased by moving the lower surface upward among the high-lift designs. Copyright © 2010 bythe American Institute of Aeronautics and Astronautics, Inc.

    DOI: 10.2514/1.C000264

    Scopus

  222. Data Mining of Pareto-Optimal Transonic Airfoil Shapes Using Proper Orthogonal Decomposition

    Oyama, A; Nonomura, T; Fujii, K

    JOURNAL OF AIRCRAFT   47 巻 ( 5 ) 頁: 1756 - 1762   2010年9月

     詳細を見る

  223. Computational Analysis of Mach Number Effects on the Edgetone Phenomenon 査読有り

    Nonomura, T; Muranaka, H; Fujii, K

    AIAA JOURNAL   48 巻 ( 6 ) 頁: 1248 - 1251   2010年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AIAA Journal  

    A study was conducted to investigate the computational analysis of Mach number effects on the Edgetone phenomenon. It was demonstrated that the feedback loop of the edgetone was verified by investigating the effect of Mach number. It was observed that the Strouhal number Sr of the peak frequency of the same mode decreased with increasing jet Mach number when the feedback-loop equation in non-dimensional form was correct. It was easy to change the jet Mach number in computational studies, while keeping the Reynolds number fixed. The computational approach was more appropriate to verify the feedback-loop mechanism. The edgetone phenomena of a two-dimensional laminar jet and a triangle wedge were also computed in the study at Mach numbers ranging from 0.087 to 0.435 at three fixed Reynolds numbers, such as 208, 416, and 624.

    DOI: 10.2514/1.44849

    Web of Science

    Scopus

    researchmap

  224. Freestream and vortex preservation properties of high-order WENO and WCNS on curvilinear grids 査読有り

    Nonomura, T; Iizuka, N; Fujii, K

    COMPUTERS & FLUIDS   39 巻 ( 2 ) 頁: 197 - 214   2010年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Computers and Fluids  

    Freestream and vortex preservation properties of a weighted essentially nonoscillatory scheme (WENO) and a weighted compact nonlinear scheme (WCNS) on curvilinear grids are investigated. While the numerical technique used for the compact difference scheme can be applied to WCNS, applying it to WENO is difficult. This difference is caused by difference in the formulation of numerical fluxes. WENO computed in the generalized coordinate system does not work well for either freestream or vortex preservation, whereas WENO computed in the Cartesian coordinate system works well for both freestream and vortex preservation, but its resolution is lower than that of WCNS. In addition, WENO in the Cartesian coordinate system costs three times as much as WENO or WCNS in the generalized coordinate system. Therefore, WENO in the Cartesian coordinate system is not suitable for solving Euler equations on a curvilinear grid. On the other hand, WCNS computed in the generalized coordinate system works well for freestream and vortex preservation when used with the numerical technique proposed for the compact difference scheme. The results show that WCNS with this numerical technique can be used for an arbitrary grid system. In this paper, the excellent freestream and vortex preservation properties of WCNS when used with the numerical technique, compared with those of WENO, are shown for the first time. © 2009 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.compfluid.2009.08.005

    Web of Science

    Scopus

    researchmap

  225. Effects of difference scheme type in high-order weighted compact nonlinear schemes 査読有り

    Nonomura, T; Fujii, K

    JOURNAL OF COMPUTATIONAL PHYSICS   228 巻 ( 10 ) 頁: 3533 - 3539   2009年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    DOI: 10.1016/j.jcp.2009.02.018

    Web of Science

    Scopus

    researchmap

  226. ADI-SGS scheme on ideal magnetohydrodynamics 査読有り

    Nishida, H; Nonomura, T

    JOURNAL OF COMPUTATIONAL PHYSICS   228 巻 ( 9 ) 頁: 3182 - 3188   2009年5月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Computational Physics  

    DOI: 10.1016/j.jcp.2009.01.032

    Web of Science

    Scopus

    researchmap

▼全件表示

MISC 176

  1. 広範なレイノルズ数におけるプラズマアクチュエータを用いた翼周り剥離制御の統一的なメカニズム : 論文賞受賞記念解説—Unified Mechanisms for Separation Control around Airfoil using Plasma Actuator with Burst Actuation over Reynolds Number Range of 10³-10⁶

    佐藤 允, 岡田 浩一, 浅田 健吾, 青野 光, 野々村 拓, 藤井 孝藏  

    ながれ : 日本流体力学会誌 = Nagare : journal of Japan Society of Fluid Mechanics41 巻 ( 3 ) 頁: 151 - 155   2022年6月

     詳細を見る

    記述言語:日本語  

    CiNii Books

    researchmap

  2. 可観測性グラミアン最適化に基づく凸緩和法・勾配貪欲法を用いたセンサ位置選択

    山田圭吾, 永田貴之, 中井公美, 野々村拓, 浅井圭介, 佐々木康雄, 椿野大輔  

    計測自動制御学会制御部門マルチシンポジウム(CD-ROM)9th 巻   2022年

     詳細を見る

  3. 垂直衝撃波の可視化計測によるフリーベースポリフィリンを用いた陽極酸化アルミ被膜型感圧塗料の特性評価と超音速キャビティ流れ場計測への適用

    岡慶典, 永田貴之, 小澤雄太, 野々村拓, 浅井圭介  

    衝撃波シンポジウム講演論文集(CD-ROM)2021 巻   2022年

     詳細を見る

  4. 圧縮性低レイノルズ数流れにおける平板状の層流剥離泡および乱流遷移に対するマッハ数効果の数値的研究

    永田貴之, 野々村拓  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)54th-40th 巻   2022年

     詳細を見る

  5. 直接数値シミュレーションによる二粒子間の流体力学的干渉に対するマッハ数効果および粒子の相対位置効果の解析

    永田貴之, 高橋俊, 水野祐介, 野々村拓  

    衝撃波シンポジウム講演論文集(CD-ROM)2021 巻   2022年

     詳細を見る

  6. 翼周り流れの時系列速度場に基づくリザーバーコンピューティング低次元モデルの構築

    岩崎有登, 中井公美, 永田貴之, 野々村拓, 浅井圭介, 犬伏正信  

    人工知能学会全国大会(Web)36th 巻   2022年

     詳細を見る

  7. 超音速噴流のPIV計測と近傍音響計測によるスクリーチ騒音発生機構の時空間超解像計測

    錦織広樹, 小澤雄太, 永田貴之, 野々村拓, 浅井圭介  

    可視化情報シンポジウム(CD-ROM)49th (Web) 巻   2021年

     詳細を見る

  8. スペクトル行列解析を用いた低SNR地震動検出手法の時間遅延座標による拡張

    永田貴之, 椋平祐輔, 野々村拓  

    統計関連学会連合大会講演報告集2021 巻   2021年

     詳細を見る

  9. 寿命法感圧・感温塗料計測における最適ゲート選定法

    笠井美玖, 永田貴之, 野々村拓, 齋藤勇士, 浅井圭介  

    可視化情報シンポジウム(CD-ROM)49th (Web) 巻   2021年

     詳細を見る

  10. 信号処理を用いた低密度風洞試験におけるシュリーレン可視化計測の高信号雑音比化

    重田剛志, 永田貴之, 野々村拓, 浅井圭介  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)53rd-39th 巻   2021年

     詳細を見る

  11. 並列に固定された2粒子間の流体力学的干渉に対する圧縮性効果の評価

    永田貴之, 高橋俊, 水野裕介, 野々村拓  

    数値流体力学シンポジウム講演論文集(CD-ROM)35th 巻   2021年

     詳細を見る

  12. 自動車模型周りの時間平均感圧塗料データを用いた風向予測のためのスパースセンサ位置最適化

    井野塲遼馬, 内田和樹, 小澤雄太, 永田貴之, 齋藤勇士, 野々村拓, 浅井圭介  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)53rd-39th 巻   2021年

     詳細を見る

  13. 衝撃波負荷により移動する2球体に生じる非定常抵抗低減効果

    高橋俊, 永田貴之, 水野裕介, 野々村拓, 大林茂  

    数値流体力学シンポジウム講演論文集(CD-ROM)35th 巻   2021年

     詳細を見る

  14. データ駆動型スパースセンシングのためのセンサ位置最適化

    齋藤 勇士, 野々村 拓, 浅井 圭介  

    計測と制御59 巻 ( 8 ) 頁: 559 - 564   2020年8月

     詳細を見る

    記述言語:日本語  

    DOI: 10.11499/sicejl.59.559

    researchmap

  15. 高速流体力学に関する学術研究

    佐藤英一, 大山聖, 福本浩章, 河合成孝, 関本諭志, 寺門大毅, 小澤雄太, 下村怜, 野々村拓, 谷口翔太, 中神貴裕, DWIANTO Bimo, 斎藤巧真, 二村成彦, 角田有紀人  

    宇宙航空研究開発機構特別資料 JAXA-SP-(Web) ( 20-002 )   2020年

     詳細を見る

  16. 酸素濃度が感圧塗料の特性に与える影響の評価

    奥寺智弘, 永田貴之, 笠井美玖, 齋藤勇士, 野々村拓, 浅井圭介  

    可視化情報シンポジウム(CD-ROM)48th 巻   2020年

     詳細を見る

  17. ポスト京重点課題8-D「航空機の設計・運用革新を実現するコア技術の研究開発」

    稲富裕光, 高木亮治, 野々村拓, 堤誠司, 福島裕馬, 河合宗司, 三吉郁夫, 関本諭志, 柴田寿一, 小泉拓, 久谷雄一, 稲荷智英, 平嶋良太, 玉置義治, 唐津卓哉  

    宇宙航空研究開発機構特別資料 JAXA-SP-(Web) ( 20-002 )   2020年

     詳細を見る

  18. 寿命法によるローターブレード表面の感圧・感温塗料計測

    笠井美玖, 小澤雄太, 齋藤勇士, 野々村拓, 浅井圭介  

    可視化情報シンポジウム(CD-ROM)48th 巻   2020年

     詳細を見る

  19. プラズマアクチュエータ研究会 ~5年間の活動と今後の展望~ 招待有り

    瀬川 武彦, 深潟 康二, 松野 隆, 野々村 拓, 大西 直文  

    日本機械学会流体工学部門ニューズレター「流れ」2019 巻 ( 2 ) 頁: 3   2019年2月

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(その他)  

    researchmap

  20. 高速流体力学に関する学術研究

    佐藤英一, 大山聖, 福本浩章, 渡邉誉良, 河合成孝, 関本諭志, 田村駿, 寺門大毅, 下村怜, 野々村拓, 石川達将, 江光希, 谷口翔太, 中神貴裕  

    宇宙航空研究開発機構特別資料 JAXA-SP-(Web) ( 19-002 )   2019年

     詳細を見る

  21. 高速流体力学に関する学術研究

    佐藤英一, 大山聖, 李東輝, 福本浩章, 原田拓弥, 中野宏章, 渡邉誉良, 井上翔太, 青木理紗子, 河合成孝, 関本諭志, 田村駿, スラナートスリカンス, 寺門大毅, 小澤雄太, 下村怜, 野々村拓  

    宇宙航空研究開発機構特別資料 JAXA-SP-(Web) ( 18-007 )   2019年

     詳細を見る

  22. 遷音速バフェットオンセット付近における旅客機翼上の非定常圧力場

    杉岡洋介, 中北和之, 小池俊輔, 中島努, 野々村拓, 浅井圭介  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)51st-37th 巻   2019年

     詳細を見る

  23. Reynolds数300‐1000の遷音速微小粒子周りの流れ場と抵抗係数に対するMach数・Reynolds数効果の考察

    永田貴之, 野々村拓, 高橋俊, 福田紘大  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)51st-37th 巻   頁: ROMBUNNO.1E08   2019年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  24. ポスト京重点課題8-D「航空機の設計・運用革新を実現するコア技術の研究開発」

    稲富裕光, 高木亮治, 野々村拓, 堤誠司, 福島裕馬, 河合宗司, 川口優樹, 三吉郁夫, 関本諭志, 柴田寿一, 小泉拓, 久谷雄一, 稲荷智英, 平嶋良太  

    宇宙航空研究開発機構特別資料 JAXA-SP-(Web) ( 18-007 )   2019年

     詳細を見る

  25. 感圧塗料による鉄道車両台車部の圧力変動分布の計測

    松居亮稔, 本多武史, 笠井美玖, 杉岡洋介, 野々村拓, 浅井圭介  

    可視化情報シンポジウム(CD-ROM)47th 巻   2019年

     詳細を見る

  26. 感圧塗料による鉄道車両の台車部の圧力変動分布の計測

    松居亮稔, 本多武史, 笠井美玖, 杉岡洋介, 野々村拓, 浅井圭介  

    日本機械学会流体工学部門講演会講演論文集(CD-ROM)97th 巻   2019年

     詳細を見る

  27. ポスト京重点課題8-D「航空機の設計・運用革新を実現するコア技術の研究開発」

    稲富裕光, 高木亮治, 野々村拓, 堤誠司, 福島裕馬, 河合宗司, 三吉郁夫, 関本諭志, 小泉拓, 稲荷智英, 平嶋良太, 玉置義治, 唐津卓哉  

    宇宙航空研究開発機構特別資料 JAXA-SP-(Web) ( 19-002 )   2019年

     詳細を見る

  28. 自由落下する小球と垂直衝撃波の干渉のシュリーレン可視化および球の抵抗係数の推定

    永田貴之, 野々村拓, 大谷清伸, 浅井圭介  

    衝撃波シンポジウム講演論文集(CD-ROM)2018 巻   頁: ROMBUNNO.1A1‐3   2019年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  29. 拡張カルマンフィルタに基づく動的モード分解

    野々村 拓, 柴田 寿一, 高木 亮治  

    年会講演会講演集49 巻   2018年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本航空宇宙学会  

    researchmap

  30. 高レイノルズ数風洞試験へのPSP計測にむけて

    野々村拓, 杉岡洋介, 浅井圭介  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)50th-36th 巻   2018年

     詳細を見る

  31. Direct numerical simulation of flow past a sphere at a reynolds number between 500 and 1000 in compressible flows 査読有り

    Nagata T., Nonomura T., Takahashi S.  

    AIAA Aerospace Sciences Meeting, 2018 ( 210059 )   2018年

     詳細を見る

    出版者・発行元:AIAA Aerospace Sciences Meeting, 2018  

    In this study, flow over an isolated sphere for a Reynolds number (Re) between 500 and 1000 and a Mach number (M) between 0.8 and 2.0 is investigated via direct numerical simulation (DNS) of three-dimensional compressible Navier–Stokes equations. We focused on the Mach and Reynolds numbers effect on the flow geometry, the flow regime, and the drag coefficient. The results show the following characteristics: 1) for previous studies, the flow field is axisymmetric for Re ≤ 300 and 1.2 ≤ M, but asymmetry and unsteadiness appears at Re = 750 and 1000, respectively, 2) the drag coefficient by DNS indicate different trends to the previous drag models.

    DOI: 10.2514/6.2018-0381

    Scopus

    researchmap

  32. シュリーレン法による圧縮性低レイノルズ数環境下における円柱周り流れの可視化

    野口暁人, 永田貴之, 石脇大地, 佐藤響之助, 小室淳史, 野々村拓, 安藤晃, 浅井圭介  

    可視化情報シンポジウム(CD-ROM)46th 巻   頁: ROMBUNNO.114 - 52   2018年

     詳細を見る

    記述言語:日本語   出版者・発行元:一般社団法人 日本機械学会  

    DOI: 10.1299/jsmeth.2018.53.51

    J-GLOBAL

    researchmap

  33. 実験用ジェット機上の衝撃波位置の感圧塗料による可視化

    杉岡洋介, 佐藤仁美, 中北和之, 中島努, 野々村拓, 浅井圭介  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)50th-36th 巻   2018年

     詳細を見る

  34. 埋め込み境界法を用いた圧縮性・非圧縮性固気混相流解析の並列性能比較

    水野裕介, 高橋俊, 野々村拓, 永田貴之, 福田紘大, 大林茂  

    数値流体力学シンポジウム講演論文集(CD-ROM)32nd 巻   頁: ROMBUNNO.C12‐3   2018年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  35. 分割型移流項を用いた高次精度流束再構築法の実用計算における安定性について

    渡邉誉良, 阿部圭晃, 芳賀臣紀, 高木亮治, 大山聖, 野々村拓, 宮路幸二  

    数値流体力学シンポジウム講演論文集(CD-ROM)32nd 巻   頁: ROMBUNNO.C10‐5   2018年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  36. ポリマー中に分散させたカメレオン発光体の特性評価

    笠井美玖, 杉岡洋介, 野々村拓, 浅井圭介, 山本昌紀, 長谷川靖哉  

    可視化情報シンポジウム(CD-ROM)46th 巻   2018年

     詳細を見る

  37. バリスティックレンジによるレイノルズ数10<sup>4</sup>オーダーの遷・超音速球周り流れのシュリーレン可視化

    永田貴之, 野口暁人, 小川俊広, 野々村拓, 大谷清伸, 浅井圭介  

    衝撃波シンポジウム講演論文集(CD-ROM)2017 巻   頁: ROMBUNNO.3C3‐2   2018年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  38. 直接数値解析データベースを用いた粒子Reynolds数50‐1000の圧縮性流れにおける微小粒子の空力係数および後流渦の解析

    永田貴之, 野々村拓, 吉田真優, 高橋俊, 福田紘大  

    数値流体力学シンポジウム講演論文集(CD-ROM)32nd 巻   頁: ROMBUNNO.A09‐1   2018年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  39. 航空機開発の高速化に向けた非定常空力計測技術の研究開発

    中北和之, 小池俊輔, 加藤裕之, 齊藤健一, 杉岡洋介, 野々村拓, 浅井圭介, 中島努, 岩本紘樹  

    飛行機シンポジウム講演集(CD-ROM)56th 巻   2018年

     詳細を見る

  40. 粒子/色素吸着型ポリマーセラミック感圧塗料の特性評価

    杉岡洋介, 荒木田一登, 笠井美玖, 野々村拓, 浅井圭介, 江上泰広, 中北和之  

    可視化情報シンポジウム(CD-ROM)46th 巻   2018年

     詳細を見る

  41. LW‐ACMにおける物体壁面境界の取り扱い方法に関する比較検討

    大西順也, 阿部圭晃, 野々村拓, 青野光  

    日本機械学会計算力学講演会論文集(CD-ROM)30th 巻   頁: ROMBUNNO.319   2017年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  42. ボルテックスジェネレータ型プラズマアクチュエータを用いたNACA4418周り流れの剥離制御メカニズム

    佐藤允, 佐藤允, 野々村拓, 青野光  

    日本機械学会年次大会講演論文集(CD-ROM)2017 巻   頁: ROMBUNNO.S0530303   2017年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  43. 次元削減されたデータに対する動的モード分解

    柴田 寿一, 野々村 拓  

    年会講演会講演集48 巻   頁: 4p   2017年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本航空宇宙学会  

    CiNii Books

    researchmap

  44. 火星飛行機の高高度飛行試験(MABE-1)の概要

    大山 聖, 永井 大樹, 得竹 浩, 藤田 昂志, 安養寺 正之, 豊田 裕之, 宮澤 優, 米本 浩一, 岡本 正人, 野々村 拓, 元田 敏和, 竹内 伸介, 鎌田 幸男, 大槻 真嗣, 浅井 圭介, 藤井 孝藏  

    年会講演会講演集48 巻   頁: 8p   2017年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本航空宇宙学会  

    CiNii Books

    researchmap

  45. 高度飛行試験による火星飛行機の空力データの取得

    大山聖, 永井大樹, 得竹浩, 藤田昂志, 安養寺正之, 豊田裕之, 宮澤優, 米本浩一, 岡本正人, 野々村拓, 元田敏和, 竹内伸介, 鎌田幸男, 大槻真嗣, 浅井圭介, 藤井孝藏  

    宇宙航空研究開発機構研究開発報告: 大気球研究報告JAXA-RR-16-00870 巻   頁: 69 - 80   2017年

  46. イリジウム錯体を用いた吸着型感圧コーティングの基礎特性評価

    菅原康司, 杉岡洋介, 野口暁人, 野々村拓, 浅井圭介, 沼田大樹  

    可視化情報学会誌37 巻 ( Suppl.1(CD-ROM) )   2017年

     詳細を見る

  47. レイノルズ数3×10<sup>6</sup>における大型風車ブレードの翼素周り流れに関するWall‐resolved LES

    佐藤允, 佐藤允, 浅田健吾, 野々村拓, 青野光  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)49th-35th 巻   頁: ROMBUNNO.1E03   2017年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  48. 寿命法による遷音速強制振動翼の感圧塗料計測

    杉岡洋介, 中北和之, 齋藤健一, 野々村拓, 浅井圭介  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)49th-35th 巻   2017年

     詳細を見る

  49. 圧縮性球周り流れのDNS(500≦Re≦1000)

    永田貴之, 野々村拓, 高橋俊, 水野裕介, 福田紘大  

    数値流体力学シンポジウム講演論文集(CD-ROM)31st 巻   頁: ROMBUNNO.A05‐3   2017年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  50. 低速流れの様々な周波数の非定常現象に対する感圧塗料の精度評価

    樋浦広大, 杉岡洋介, 野々村拓, 浅井圭介  

    可視化情報学会誌37 巻 ( Suppl.1(CD-ROM) )   2017年

     詳細を見る

  51. ブロック境界条件を応用したマルチブロックLES解析コードの開発と検証—The development of the large-eddy simulation analysis solver based on the block interface condition and its verification

    青野, 光, 野々村, 拓, Aono, Hikaru, Nonomura, Taku  

    宇宙航空研究開発機構特別資料: 第48回流体力学講演会/第34回航空宇宙数値シミュレーション技術シンポジウム論文集 = JAXA Special Publication: Proceedings of the 48th Fluid Dynamics Conference / the 34th Aerospace Numerical Simulation SymposiumJAXA-SP-16-007 巻   頁: 63 - 67   2016年12月

     詳細を見る

    記述言語:日本語   出版者・発行元:宇宙航空研究開発機構(JAXA)  

    第48回流体力学講演会/第34回航空宇宙数値シミュレーション技術シンポジウム (2016年7月6日-8日. 金沢歌劇座), 金沢市, 石川
    48th Fluid Dynamics Conference /the 34th Aerospace Numerical Simulation Symposium (July 6-8, 2016. The Kanazawa Theatre), Kanazawa, Ishikawa, Japan
    A large-eddy simulation analysis solver using the multi-block grid with several block interface conditions is developed. The governing equations are the three-dimensional compressible Navier-Stokes equations in the generalized curvilinear coordinates. We adopt a sixth-order compact finite difference scheme for the convective and viscous terms and a fourth-order Runge-Kutta method for time integration. We introduce a block interface condition (BIC) that is newly developed and constructed based on the analogy between the finite volume scheme and the finite difference scheme. The BIC is compared with a characteristic based interface condition (CIC). We consider a single vortex convection crossing the boundary interface between the uniform Cartesian grid and the uniform Cartesian grid with considerable tilt as a test problem. Effects of strength of the vortex on the pressure distribution of the moving vortex are studied. A comparison of the pressure distribution of the vortex at the boundary interface presents that in the case of strong vortex the results of BIC are comparable to those of the CIC while in the case of weak vortex numerical oscillations are observed when the vortex crosses the interface. Furthermore, results obtained using the CIC and the BIC are considerably improved with increasing grid resolution in normal to the block interface.
    形態: カラー図版あり
    Physical characteristics: Original contains color illustrations
    資料番号: AA1630031005
    レポート番号: JAXA-SP-16-007

    CiNii Books

    researchmap

  52. 高速流体力学に関する学術研究

    野々村拓, 青野光, 寺門大毅, 阿部圭晃, SLAIMAN Taufik, 李東輝, 福本浩章, NUCERA Fortunate, 浅野兼人, 森平光一, 松原暁良, 森中一誠, 加藤大祐, 小澤雄太, 原田拓弥, 中野宏章, DANIELE Sirigatti  

    宇宙航空研究開発機構特別資料 JAXA-SP-(Web) ( 16-003 ) 頁: 115‐116 (WEB ONLY)   2016年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  53. LW‐ACMのマクロ変数での計算機への実装とそのアルゴリズム理解(第一報)

    大西順也, 阿部圭晃, 野々村拓, 青野光  

    日本機械学会計算力学講演会論文集(CD-ROM)29th 巻   頁: ROMBUNNO.312   2016年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  54. 混合型移流項に基づく超高次精度流束再構築法の安定化とその検証計算

    阿部圭晃, 森中一誠, 芳賀臣紀, 野々村拓, 宮路幸二  

    日本機械学会計算力学講演会論文集(CD-ROM)29th 巻   頁: ROMBUNNO.180   2016年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  55. DBDプラズマアクチュエータによるNACA0012ピッチング翼周り流れの制御

    福本浩章, 青野光, 田中元史, 松田寿, 大迫俊樹, 野々村拓, 大山聖, 藤井孝藏  

    日本機械学会年次大会講演論文集(CD-ROM)2016 巻   頁: ROMBUNNO.S0530104   2016年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  56. 直接数値解析による複数粒子と渦の相互作用の把握

    水野 裕介, 高橋 俊, 野々村 拓, 永田 貴之, 福田 紘大  

    年次大会2016 巻 ( 0 ) 頁: ROMBUNNO.S0550104   2016年9月

     詳細を見る

    記述言語:日本語   出版者・発行元:一般社団法人 日本機械学会  

    DOI: 10.1299/jsmemecj.2016.S0550104

    J-GLOBAL

    researchmap

  57. 剥離泡を伴う翼型流れの表面圧力欠損データの簡便な補間方法

    野々村 拓  

    年会講演会講演集47 巻   頁: 8p   2016年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本航空宇宙学会  

    CiNii Books

    researchmap

  58. DNSによる高Mach数・低Reynolds数の球周りの流れ場に対するMach数や温度比の影響把握

    永田貴之, 野々村拓, 高橋俊, 水野裕介, 福田紘大  

    宇宙航空研究開発機構特別資料 JAXA-SP- ( 15-013 ) 頁: 85‐90   2016年3月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  59. 南極周回気球による宇宙線反粒子探索計画GAPS

    福家 英之, 井上 剛良, 加藤 千尋, 河内 明子, 小池 貴久, 宗像 一起, 永井 大樹, 野々村 拓, 小川 博之, 岡崎 峻, 崎本 一博, 清水 雄輝, 高橋 俊, 山田 昇, 吉田 篤正, 吉田 哲也, Boggs S., Craig W. W., Doetinchem P. v., Fabris R., Hailey C. J., Ong R., Perez K., Fuke Hideyuki, Inoue Takayoshi, Kato Chihiro, Kawachi Akiko, Koike T, Munakata Kazuoki, Nagai Daiki, Nonomura Taku, Ogawa Hiroyuki, Okazaki Shun, Sakimoto Kazuhiro, Shimizu Yuki, Takahashi Shun, Yamada Noboru, Yoshida Atsumasa, Yoshida Tetsuya, Boggs S., Craig W. W., Doetinchem P. v., Fabris R., Hailey C. J., Ong R., Perez K.  

    第16回宇宙科学シンポジウム 講演集 = Proceedings of the 16th Space Science Symposium   2016年1月

     詳細を見る

    記述言語:日本語   出版者・発行元:宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)  

    第16回宇宙科学シンポジウム (2016年1月6日-7日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県著者人数: 23名資料番号: SA6000046257レポート番号: S5-009

    researchmap

  60. 埋め込み境界法を用いた不等間隔直交格子による球周りの高解像度解析

    浜潟勇輝, 水野裕介, 高橋俊, 野々村拓, 福田紘大  

    日本機械学会計算力学講演会論文集(CD-ROM)29th 巻   2016年

     詳細を見る

  61. Analysis of the temperature ratio effects on the flow properties of the low reynolds and high mach number flow around a sphere 査読有り

    Nagata T., Nonomura T., Takahashi S., Mizuno Y., Fukuda K.  

    54th AIAA Aerospace Sciences Meeting0 巻   2016年

     詳細を見る

    出版者・発行元:54th AIAA Aerospace Sciences Meeting  

    In this study, direct numerical simulation of the flow around a sphere at the high Mach number and the low Reynolds number condition is carried out in order to investigate the flow properties. The three-dimensional compressible Navier-Stokes equations are solved on boundary fitted coordinate system. It is confirmed to have sufficient accuracy from the results of the previous study. Analyses are performed at the Reynolds number of between 50 and 300, the freestream Mach number of between 0.3 and 2.0, and the temperature ratio of the sphere surface and freestream of between 0.5 and 2.0. As the results, we clarified the following points: 1) the freestream Reynolds number and the temperature ratio influence the flow properties, 2) the effect of the temperature ratio can be summarized by the effective Reynolds number that is a newly proposed parameter.

    DOI: 10.2514/6.2016-1251

    Scopus

    researchmap

  62. Direct numerical simulation of shock waves passed by multiple particles using immersed boundary method 査読有り

    Mizuno Y., Takahashi S., Nonomura T., Nagata T., Fukuda K.  

    54th AIAA Aerospace Sciences Meeting   2016年

     詳細を見る

    出版者・発行元:54th AIAA Aerospace Sciences Meeting  

    A flow containing multiple particles and the shock wave is investigated by the direct numerical simulation with immersed boundary method. The shock Mach number and the Reynolds numbers of particle behind the shock wave are set to be 1.5 to 2.0 and 300 to 600, respectively. The comparison of the present results with one-dimensional simulation results, shows good agreement. From the results, we clarified characteristic flow structure at different shock Mach and Reynolds number. The turbulence kinetic energy was enhanced from the vortex structure in the wake of particles for the high Reynolds number case. The drag coefficient from the present simulation and the previous prediction models shows almost the same values at Mach number 1.5. At Mach number 2.0, however, discrepancy is obtained for the drag coefficient between the present flow simulation and the previous prediction models.

    Scopus

    researchmap

  63. フェーズロックPIVによる可視化を用いたDBDプラズマアクチュエータの駆動バースト比に関する実験研究

    関本諭志, 田中直樹, 田中直樹, 野々村拓, 西田浩之, 藤井孝藏  

    可視化情報学会誌36 巻 ( Suppl.1(CD-ROM) )   2016年

     詳細を見る

  64. プラズマアクチュエータを用いた流体制御における層流剥離泡の詳細構造の実験的観察

    宮川雄磨, 関本諭志, 野々村拓, 大山聖, 藤井孝藏, 伊藤慎一郎  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)48th-34th 巻   2016年

     詳細を見る

  65. ブロック境界条件を応用したマルチブロックLES解析コードの開発と検証

    青野光, 野々村拓  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)48th-34th 巻   頁: ROMBUNNO.1A08   2016年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  66. 流束再構築法の保存/非保存型メトリックの保存特性と精度に関する考察

    宮路幸二, 阿部圭晃, 芳賀臣紀, 野々村拓  

    数値流体力学シンポジウム講演論文集(CD-ROM)30th 巻   頁: ROMBUNNO.B03‐3   2016年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  67. 火星飛行機の高高度飛行試験結果の速報

    大山聖, 永井大樹, 得竹浩, 藤田昂志, 安養寺正之, 豊田裕之, 宮澤優, 米本浩一, 岡本正人, 野々村拓, 元田敏和, 竹内伸介, 鎌田幸男, 大槻真嗣, 浅井圭介, 藤井孝藏  

    飛行機シンポジウム講演集(CD-ROM)54th 巻   頁: ROMBUNNO.3J13   2016年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  68. 流体制御を利用した輸送システム・流体機器設計概念の革新を目指して : 「京」利用による流れ現象理解と制御パラメータの発見

    藤井 孝蔵, 野々村 拓, 青野 光  

    計算工学20 巻 ( 4 ) 頁: 3328 - 3331   2015年12月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本計算工学会  

    CiNii Books

    researchmap

  69. 0615 DBDプラズマアクチュエータによる低レイノルズ数・高性能翼型の剥離制御

    松原 暁良, 関本 愉志, Sulaiman Taufik, 野々村 拓, 大山 聖, 藤井 孝臧, 西田 浩之  

    流体工学部門講演会講演論文集2015 巻   頁: "0615 - 1"-"0615-2"   2015年11月

     詳細を見る

    記述言語:日本語   掲載種別:研究発表ペーパー・要旨(全国大会,その他学術会議)   出版者・発行元:一般社団法人日本機械学会  

    In this study, AC DBD plasma actuator is applied to control the flow around NACA0015 and Ishii airfoils in a low Reynolds number condition (Re = 63,000). Here, the Ishii airfoil is a high performance airfoil at the low Reynolds number condition. The DBD plasma actuator is located at x/c = 5% and is actuated in burst mode with the nondimensional burst frequency F+ from 0.1 to 20. Maximum control authority is achieved with Vpp = 6kV and F+higher than 6 for both airfoils. Results show that different effect of separation control between NACA0015 airfoil and Ishii airfoil.

    CiNii Books

    researchmap

  70. 0806 高マッハ数域での乱流混合層における音源のマッハ数及び密度比依存性

    寺門 大毅, 野々村 拓, 大山 聖, 藤井 孝藏  

    流体工学部門講演会講演論文集2015 巻   頁: "0806 - 1"-"0806-4"   2015年11月

     詳細を見る

    記述言語:日本語   掲載種別:研究発表ペーパー・要旨(全国大会,その他学術会議)   出版者・発行元:一般社団法人日本機械学会  

    The convective Mach number and density ratio dependences of sound sources and flow structures in a compressible mixing layer are investigated by direct numerical simulations. Characteristics of sound sources are analyzed using the source terms of Lighthill equation. As the Mach number increases sound source strength decreases, because vortex motion is weakened by compressibility. For density ratio dependence, the emission angle of Mach waves becomes shallower and vortices show sparse structures as density ratio increases. In addition, larger vortex structures appear at lower density side for higher density case.

    CiNii Books

    researchmap

  71. 0802 直接数値解析による複数粒子と衝撃波の相互作用の把握

    水野 裕介, 高橋 俊, 野々村 拓, 永田 貴之, 福田 紘大  

    流体工学部門講演会講演論文集2015 巻   頁: "0802 - 1"-"0802-4"   2015年11月

     詳細を見る

    記述言語:日本語   掲載種別:研究発表ペーパー・要旨(全国大会,その他学術会議)   出版者・発行元:一般社団法人日本機械学会  

    In this study, a direct numerical simulation is carried out for the flow that the particle passes a shock wave to investigate interference between the particles and shock wave. The flow simulation based on three-dimensional compressible Navier-Stokes equations is conducted by Cartesian mesh method with immersed boundary method to deal with multiple moving boundaries by Euler-Euler approach. This flow solver is developed for the purpose of accurate prediction of the acoustic field around a rocket launch site. The objective of this study is to investigate a flow containing shock waves and moving multiple particles. The shock Mach numbers are 1.2, 1.5, 2.0, and 2.5. When multiple particles pass the shock wave, characteristic vortex structure is formed in the wake. The vortex structure may be a key factor of the interference.

    CiNii Books

    researchmap

  72. 0801 超音速ジェットのせん断層速度分布とそこから発生する音響波の実験的研究

    小澤 雄太, 野々村 拓, 藤井 孝藏, 山本 誠, 守 裕也  

    流体工学部門講演会講演論文集2015 巻   頁: "0801 - 1"-"0801-3"   2015年11月

     詳細を見る

    記述言語:日本語   掲載種別:研究発表ペーパー・要旨(全国大会,その他学術会議)   出版者・発行元:一般社団法人日本機械学会  

    The effects of nozzle geometry on the acoustic waves from Mach 1.9 supersonic jet are experimentally investigated. PIV and microphone measurements are conducted to analyze the relationship between flows and acoustic waves. In this study, three different nozzles of conical nozzle, convergent-divergent nozzle (C-D) nozzle, and tab C-D nozzle in which tab is attached in nozzle inlet to generate disturbance are considered. Three noise sources are identified. Conical nozzle case shows screech and broad band shock noise spectra because of the existence of strong shock train in flow. For the other two cases (C-D nozzle and tab nozzle), there are not clear shock associated noise spectra due to nearly ideally expanded condition by the nozzle geometries so that turbulent mixing noise should be dominant. Tab nozzle case shows higher frequency acoustic spectra than that of C-D case. This is because inflow become turbulent flow from the very beginning by the existence of tab so that smaller scale turbulence is generated.

    CiNii Books

    researchmap

  73. 0704 DNSに基づく低Reynolds数流れにおける球の後流の渦構造に対するMach数や温度比の影響把握

    永田 貴之, 野々村 拓, 高橋 俊, 水野 裕介, 福田 紘大  

    流体工学部門講演会講演論文集2015 巻   頁: "0704 - 1"-"0704-5"   2015年11月

     詳細を見る

    記述言語:日本語   掲載種別:研究発表ペーパー・要旨(全国大会,その他学術会議)   出版者・発行元:一般社団法人日本機械学会  

    In this study, DNS of flow around a stationary sphere under the isothermal conditions with the high Mach numbers and low Reynolds numbers flow were conducted by solving three-dimensional compressible Navier-Stokes equations for investigation of the influence of the Mach number and temperature ratio on the vortex structures. From calculation result, we clarified the following facts that the Mach number and temperature ratio effect on the wake of the sphere: (1 the vortex shedding is decreases in the case of high Mach number or high temperature ratio, (2 the sphere releases strong vortex in the case of high Mach number or low temperature ratio and (3 turbulent kinetic energy at the wake of the sphere increases in the case of high Mach number or low temperature ratio.

    CiNii Books

    researchmap

  74. 南極周回気球による宇宙線反粒子探索計画GAPS の現状報告

    福家 英之, 野々村 拓, 小川 博之, 岡崎 峻, 崎本 一博, 吉田 哲也, 浅尾 義士, 高橋 克征, 山田 昇, 大丸 拓郎, 永井 大樹, 郷田 晃央, 井上 剛良, 橋本 岳, 蓑島 温志, 和田 拓也, 吉田 篤正, 井上 拓哉, 磯貝 亮, 河内 明子, 木俣 響, 高橋 俊, 加藤 千尋, 宗像 一起, 小池 貴久, 清水 雄輝, Hailey C.J., 荒牧 嗣夫, Gahbauer F., Madden N., 森 嘉野, Boggs S., Hoberman J., Craig W.W., Doetinchem P.v., Fabris R., Ziock K.P., Mognet S.A.I., Ong R., Zweerink J., Perez K., Fuke Hideyuki, Nonomura Taku, Ogawa Hiroyuki, Okazaki Shun, Sakimoto Kazuhiro, Yoshida Tetsuya, Takahashi Katsumasa, Yamada Noboru, Daimaru Takuro, Nagai Hiroki, Inoue Takayoshi, Hashimoto Takeshi, Wada Takuya, Yoshida Atsumasa, Kawachi Akiko, Takahashi Shun, Kato C., Munakata Kazuoki, Koike Takahisa, Shimizu Yuki, Hailey C.J., Aramaki Tsuguo, Gahbauer F., Madden N., Mori Kaya, Boggs S., Hoberman J., Craig W.W., Doetinchem P.v., Fabris R., Ziock K.P., Mognet S.A.I., Ong R., Zweerink J., Perez K.  

    大気球シンポジウム: 平成27年度 = Balloon Symposium: 2015   2015年11月

     詳細を見る

    記述言語:日本語   出版者・発行元:宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)  

    大気球シンポジウム 平成27年度(2015年11月5-6日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)), 相模原市, 神奈川県著者人数: 39名資料番号: SA6000044045レポート番号: isas15-sbs-045

    researchmap

  75. 火星探査飛行機の高高度飛行試験計画(その4)

    大山 聖, 永井 大樹, 得竹 浩, 竹内 伸介, 豊田 裕之, 宮澤 優, 大槻 真嗣, 元田 敏和, 岡本 正人, 安養寺 正之, 野々村 拓, 鎌田 幸男, 藤田 昂志, 米本 浩一, 浅井 圭介, 藤井 孝藏, 火星探査航空機ワーキンググループ, Oyama Akira, Nagai Hiroki, Tokutake Hiroshi, Takeuchi Shinsuke, Toyota Hiroyuki, Miyazawa Yu, Otsuki Masatsugu, Motoda Toshikazu, Okamoto Masato, Anyoji Masayuki, Nonomura Taku, Kamata Yukio, Fujita Koji, Yonemoto Koichi, Asai Keisuke, Fujii Kozo  

    大気球シンポジウム: 平成27年度 = Balloon Symposium: 2015   2015年11月

     詳細を見る

    記述言語:日本語   出版者・発行元:宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)  

    大気球シンポジウム 平成27年度(2015年11月5-6日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)), 相模原市, 神奈川県著者人数: 16名ほか資料番号: SA6000044002レポート番号: isas15-sbs-002

    researchmap

  76. 高次精度流束再構築法における自乗量保存型スキームの安定性

    森中一誠, 阿部圭晃, 野々村拓, 芳賀臣紀, 宮路幸二  

    日本機械学会計算力学講演会論文集(CD-ROM)28th 巻 ( 28 ) 頁: ROMBUNNO.304 - 1"-"304-2"   2015年10月

     詳細を見る

    記述言語:日本語   出版者・発行元:一般社団法人日本機械学会  

    高精度流束再構築法(FR法)の数値安定性を向上させることを目指し、1次元オイラー方程式における自乗量保存型スキームの定式化と数値実験に取り組んだ。計算結果より、移流項に擬混合型を用いることで安定性が向上することを確認した。また、FR法における解定義点や修正関数の選び方が安定性に影響を及ぼすことを確認した。

    CiNii Books

    J-GLOBAL

    researchmap

  77. 小特集:「プラズマアクチュエータの動向:1. はじめに」

    野々村 拓, 瀬川 武彦, 深潟 康二, 松野 隆, 清水 一男, 白石 裕之  

    プラズマ・核融合学会誌91 巻 ( 10 ) 頁: 648 - 650   2015年10月

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:プラズマ・核融合学会  

    本小特集では,ここ10年でマイクロ流体制御デバイスとして注目を集め,活発的に研究が行われているプラズマアクチュエータに関する成果を紹介する.本章では背景,歴史,原理,国内外の動向,本小特集の内容を示す.背景として,従来型の制御デバイスと比較した際の利点を紹介し,着目されてきた理由を示す.歴史に関してはキーとなる論文を紹介し,プラズマアクチュエータの研究の流れを示す.原理に関してはプラズマアクチュエータの構成を示し,そのメカニズムも短く説明する.最後に,国内外での最新の研究動向に触れながら2-5章で議論される,1)推力・駆動力基本特性,2)基礎流れへの適用,3)計測法,4)産業応用に関する研究の現状を簡単に紹介し,以降の章での詳細な解説に繋げる.

    CiNii Books

    researchmap

    その他リンク: http://dl.ndl.go.jp/info:ndljp/pid/10459677

  78. 小特集:「プラズマアクチュエータの動向:6. まとめ」

    野々村 拓, 瀬川 武彦, 深潟 康二, 松野 隆, 清水 一男, 白石 裕之  

    プラズマ・核融合学会誌91 巻 ( 10 ) 頁: 671 - 673   2015年10月

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

    researchmap

  79. S0530305 低レイノルズ数領域における高性能翼と剥離制御された単純翼の空力性能の比較

    浅野 兼人, 佐藤 允, 野々村 拓, 大山 聖, 藤井 孝藏  

    年次大会 : Mechanical Engineering Congress, Japan2015 巻   頁: "S0530305 - 1"-"S0530305-5"   2015年9月

     詳細を見る

    記述言語:日本語   出版者・発行元:一般社団法人日本機械学会  

    Large-eddy simulations of the separated flow over an NACA0015 airfoil controlled by the DBD plasma actuator are conducted and the flow fields and the aerodynamic performances are compared with the Ishii airfoil, one of the high performance airfoil at the low Reynolds number. The DBD plasma actuator is set at the 5% chord length from the leading edge of NACA0015 airfoil and operated in burst mode at the Reynolds number Re=63,000. In both cruise and post stall angle of attack, Ishii airfoil show higher aerodynamic performance than NACA0015 airfoil when DBD plasma actuator is OFF. However, when the DBD plasma actuator is activated, NACA0015 show higher aerodynamic performance.

    CiNii Books

    researchmap

  80. 複数のプラズマアクチュエータを用いた翼周り剥離制御のLES

    佐藤允, 加藤宏基, 青野光, 青野光, 焼野藍子, 野々村拓, 藤井孝藏  

    日本機械学会年次大会講演論文集(CD-ROM)2015 巻   頁: ROMBUNNO.S0530306   2015年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  81. 遷移する超音速ジェットの乱れとそこから発生する音響波の特性

    野々村 拓, 藤井 孝藏  

    年会講演会講演集46 巻   頁: 8p   2015年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本航空宇宙学会  

    researchmap

  82. Analysis on flow around a sphere at high Mach number, low reynolds number and adiabatic condition for high accuracy analysis of gas particle flows 査読有り

    Nagata T., Nonomura T., Takahashi S., Mizuno Y., Fukuda K.  

    COUPLED PROBLEMS 2015 - Proceedings of the 6th International Conference on Coupled Problems in Science and Engineering   頁: 760 - 771   2015年4月

     詳細を見る

    出版者・発行元:COUPLED PROBLEMS 2015 - Proceedings of the 6th International Conference on Coupled Problems in Science and Engineering  

    This study analyses gas particle flow around a sphere under an adiabatic condition at high Mach number and low Reynolds number by direct numerical simulation of the three- dimensional compressible Navier-Stokes equation to investigate flow properties. The calculation was performed on a boundary-fitted coordinate system with a high-order scheme of sufficient accuracy. Analysis is conducted by assuming a rigid sphere with a Reynolds number based on the diameter of the sphere, and the free-stream velocity set between 50 and 300 and a free-stream Mach number set between 0.3 and 2.0. The effect of the Mach number on the flow properties and drag coefficient are discussed. The calculation shows the following results: 1) unsteady fluctuation of the hydrodynamic force becomes smaller as the Mach number increases, 2) the drag coefficient increases along with the Mach number due to an increase in the pressure drag by the shock-wave, and 3) an accurate prediction of the drag coefficient in the supersonic regime using traditional models might be difficult.

    Scopus

    researchmap

  83. 二次元ハンプ剥離後流渦への周期的制御振動周波数の影響

    焼野藍子, 河合宗司, 野々村拓, 藤井孝藏  

    ながれ34 巻 ( 2 ) 頁: 97 - 102   2015年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本流体力学会  

    CiNii Books

    researchmap

    その他リンク: https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=377578

  84. 二次元ハンプ周り圧力勾配影響下での壁近傍準秩序構造の予測と制御 (乱流研究のフロンティア)

    焼野 藍子, 河合 宗司, 野々村 拓, 藤井 孝藏  

    数理解析研究所講究録1944 巻   頁: 46 - 57   2015年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:京都大学  

    CiNii Books

    researchmap

    その他リンク: http://hdl.handle.net/2433/223838

  85. 浸漬境界法による衝撃波と多重粒子を含有する流れの数値解析

    MIZUNO Yusuke, TAKAHASHI Shun, NONOMURA Taku, NAGATA Takayuki, FUKUDA Kota  

    Proceedings. International Conference on Flow Dynamics (CD-ROM)12th 巻   2015年

     詳細を見る

  86. 高Mach数・低Reynolds数・等温条件下における衝撃波を含む球周りの直接数値解析(Re=300)

    永田貴之, 野々村拓, 高橋俊, 水野裕介, 福田紘大  

    衝撃波シンポジウム講演論文集(CD-ROM)2014 巻   頁: ROMBUNNO.2A2-1   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  87. 高マッハ数・低レイノルズ数・等温条件下における回転する球周り流れの直接数値解析

    永田貴之, 野々村拓, 高橋俊, 水野祐介, 福田紘大  

    数値流体力学シンポジウム講演論文集(CD-ROM)29th 巻   頁: ROMBUNNO.E09‐5   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  88. DBDプラズマアクチュエータによる低レイノルズ数・高性能翼型の剥離制御

    松原暁良, 関本愉志, SULAIMAN Taufik, 野々村拓, 大山聖, 藤井孝臧, 西田浩之  

    日本機械学会流体工学部門講演会講演論文集(CD-ROM)93rd 巻   2015年

     詳細を見る

  89. Sharp Interface法による圧縮性二相流解析の高精度化に向けた研究

    井上拓哉, 高橋俊, 野々村拓, 福家英之  

    数値流体力学シンポジウム講演論文集(CD-ROM)29th 巻   2015年

     詳細を見る

  90. Ghost Fluid法を用いた圧縮性流れの熱流体解析

    高橋俊, 井上拓哉, 野々村拓, 福家英之  

    混相流シンポジウム講演論文集(CD-ROM)2015 巻   2015年

     詳細を見る

  91. DNSに基づく低Reynolds数流れにおける球の後流の渦構造に対するMach数や温度比の影響把握

    永田貴之, 野々村拓, 高橋俊, 水野裕介, 福田紘大  

    日本機械学会流体工学部門講演会講演論文集(CD-ROM)93rd 巻   頁: ROMBUNNO.0704   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  92. DNSによる高Mach数・低Reynolds数の球周りの流れ場に対するMach数や温度比の影響把握

    永田貴之, 野々村拓, 高橋俊, 水野裕介, 福田紘大  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)47th-33rd 巻   頁: ROMBUNNO.1D11   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  93. DBDプラズマアクチュエータのバースト駆動における剥離制御メカニズムの実験研究

    関本諭志, 関本諭志, 野々村拓, 藤井孝藏  

    日本機械学会年次大会講演論文集(CD-ROM)2015 巻   2015年

     詳細を見る

  94. ナノパルスプラズマアクチュエータが発生する衝撃波によるM0.3翼周り剥離流れの制御

    関本諭志, SULAIMAN Taufik, 松原暁良, 田中直樹, 野々村拓, 藤井孝藏, 西田浩之  

    衝撃波シンポジウム講演論文集(CD-ROM)2014 巻   2015年

     詳細を見る

  95. 大規模渦構造を伴う翼周り流れ場のLESの解析におけるスパン方向計算領域の影響について

    福本浩章, 青野光, 田中元史, 松田寿, 大迫俊樹, 野々村拓, 大山聖, 藤井孝藏  

    数値流体力学シンポジウム講演論文集(CD-ROM)29th 巻   頁: ROMBUNNO.D07‐1   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  96. 埋め込み境界法を用いた複数粒子が衝撃波を通過する流れ場の直接数値解析

    水野裕介, 高橋俊, 野々村拓, 永田貴之, 福田紘大  

    流体力学講演会/航空宇宙数値シミュレーション技術シンポジウム講演集(CD-ROM)47th-33rd 巻   頁: ROMBUNNO.1A05   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  97. 固気混相衝撃波流れ解析に向けた衝撃波を通過する粒子周りの流れ場の数値解析

    水野裕介, 高橋俊, 野々村拓, 永田貴之, 福田紘大  

    衝撃波シンポジウム講演論文集(CD-ROM)2014 巻   頁: ROMBUNNO.2A1-2   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  98. 熱伝達を考慮した埋め込み境界法を用いた球まわり流れの直接数値解析

    水野裕介, 高橋俊, 野々村拓, 永田貴之, 福田紘大  

    数値流体力学シンポジウム講演論文集(CD-ROM)29th 巻   頁: ROMBUNNO.B01‐1   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  99. 移流項に擬混合型を用いた高次精度流束再構築法における保存量保存性

    森中一誠, 阿部圭晃, 芳賀臣紀, 野々村拓, 宮路幸二  

    数値流体力学シンポジウム講演論文集(CD-ROM)29th 巻   頁: ROMBUNNO.B06‐2   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  100. 直接数値解析による複数粒子と衝撃波の相互作用の把握

    水野裕介, 高橋俊, 野々村拓, 永田貴之, 福田紘大  

    日本機械学会流体工学部門講演会講演論文集(CD-ROM)93rd 巻   頁: ROMBUNNO.0802   2015年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  101. 高次精度保存型FR法での一様流保持におけるエイリアシング誤差の除去

    阿部圭晃, 野々村拓, 芳賀臣紀, 藤井孝藏  

    日本機械学会計算力学講演会論文集(CD-ROM)27th 巻   頁: ROMBUNNO.2804   2014年11月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  102. 低レイノルズ数領域の翼型空力性能評価のための数値計算法の比較

    李 東輝, 野々村 拓, 大山 聖  

    宇宙科学技術連合講演会講演集58 巻   頁: 1 - 5   2014年11月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本航空宇宙学会  

    researchmap

  103. 南極周回気球による宇宙線反粒子探索計画 GAPS

    福家 英之, 野々村 拓, 小川 博之, 岡崎 峻, 田中 結, 吉田 哲也, 安部 拓洋, 井上 剛良, 松宮 宏明, 依田 悠太郎, 大丸 拓郎, 永井 大樹, 河内 明子, 増山 陽介, 清水 憲政, 高橋 俊, 小池 貴久, 宮崎 芳郎, 佐藤 大輔, 高橋 克征, 山田 昇, 吉田 貴則, 荒牧 嗣夫, Gahbauer F., Hailey C. J., Madden N., 森 嘉野, Perez K., Boggs S., Hoberman J., Fuke Hideyuki, Nonomura Taku, Ogawa Hiroyuki, Okazaki Shun, Tanaka Yui, Yoshida Tetsuya, Abe Takumi, Inoue Takayoshi, Matsumiya Hiroaki, Yoda Yutaro, Daimaru Takuro, Nagai Hiroki, Kawachi Akiko, Masuyama Yousuke, Shimizu Kensei, Takahashi Shun, Koike Takahisa, Miyazaki Yoshio, Sato Daisuke, Takahashi Katsumasa, Yamada Noboru, Yoshida Takanori, Aramaki Tsuguo, Gahbauer F., Hailey C. J., Madden N., Mori Kaya, Perez K., Boggs S., Hoberman J.  

    大気球シンポジウム: 平成26年度 = Balloon Symposium: 2014   2014年11月

     詳細を見る

    記述言語:日本語   出版者・発行元:宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)  

    大気球シンポジウム 平成26年度(2014年11月6-7日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)), 相模原市, 神奈川県著者人数: 37名資料番号: SA6000021002レポート番号: isas14-sbs-002

    researchmap

  104. 火星探査飛行機の高々度飛行試験の進捗報告

    大山 聖, 永井 大樹, 得竹 浩, 竹内 伸介, 豊田 裕之, 宮澤 優, 大槻 真嗣, 元田 敏和, 岡本 正人, 安養寺 正之, 野々村 拓, 鎌田 幸男, 藤田 昴志, 平栗 弘貴, 佐々木 岳, 米本 浩一, 浅井 圭介, 藤井 孝藏, 火星探査航空機ワーキンググループ, Oyama Akira, Nagai Hiroki, Tokutake Hiroshi, Takeuchi Shinsuke, Toyota Hiroyuki, Miyazawa Yu, Otsuki Masatsugu, Motoda Toshikazu, Okamoto Masato, Anyoji Masayuki, Nonomura Taku, Kamata Yukio, Fujita Koji, Hiraguri Hirotaka, Sasaki Gaku, Yonemoto Koichi, Asai Keisuke, Fujii Kozo  

    大気球シンポジウム: 平成26年度 = Balloon Symposium: 2014   2014年11月

     詳細を見る

    記述言語:日本語   出版者・発行元:宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)  

    大気球シンポジウム 平成26年度(2014年11月6-7日. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS)), 相模原市, 神奈川県著者人数: 18名資料番号: SA6000021006レポート番号: isas14-sbs-006

    researchmap

  105. 1401 一様等方性圧縮性乱流における音源項の統計的性質

    寺門 大毅, 野々村 拓, 佐藤 允, 青野 光, 河合 宗司, 藤井 孝藏  

    流体工学部門講演会講演論文集2014 巻   頁: "1401 - 1"-"1401-4"   2014年10月

     詳細を見る

    記述言語:日本語   掲載種別:研究発表ペーパー・要旨(全国大会,その他学術会議)   出版者・発行元:一般社団法人日本機械学会  

    The characteristics of sound sources are analyzed by Lighthill equation based on the direct numerical simulations of compressible isotropic turbulence to investigate the physical mechanisms of the noise from fine scale turbulence and their interactions with shocklets. We study mainly on the compressibility effects on the sound source terms in Lighthill equation by comparing various turbulent Mach numbers (M_<t0> = 0.1 to M_<t0> = 1.0), where the sound source terms are decomposed into the Reynolds stress, entropy, and viscous term. We show that the Reynolds stress term is the most contributer to the overall sound sources for all Mach number cases, on the other hand, the sound level of viscosity term is very small. Also the characteristics of sound sources are changed due to the generation of shocklets for high Mach number cases. For low Mach number flows, the Reynolds stress term and entropy term has positive correlation so that the overall sound level is intensified. However, for high Mach number flows, the overall sound level is weakened because the negative correlation between the Reynolds stress term and entropy term becomes stronger and they partially cancels out each other.

    CiNii Books

    researchmap

  106. 1405 超音速固気混相流の高解像度数値解析

    長田 裕樹, 野々村 拓, 朝原 誠, 藤井 孝藏, 山本 誠  

    流体工学部門講演会講演論文集2014 巻   頁: "1405 - 1"-"1405-3"   2014年10月

     詳細を見る

    記述言語:日本語   掲載種別:研究発表ペーパー・要旨(全国大会,その他学術会議)   出版者・発行元:一般社団法人日本機械学会  

    In this presentation, first, the high-order upwind finite difference scheme is considered for the gas-particle multi-phase shock containing flows. We used an alternative weighted essentially non oscillation scheme (AWENO) which is the numerical flux formulation of a kind of weighted compact nonlinear scheme and the use of a positive preserving limiter proposed recently which can be used with numerical flux formulation. AN AWENO scheme with a positivity preserving limiter for the density of solid particles are implemented to the gas-particle multiphase flow solver. With an AWENO scheme, we conducted 2-dimensional numerical test problem. As a result, higher resolution is obtained without blowing up of the computation by using an AWENO scheme.

    CiNii Books

    researchmap

  107. S0550303 DBDプラズマアクチュエータによる低レイノルズ数2次元翼周り動的剥離制御の数値解析([S055-03]プラズマアクチュエータ(3),流体工学部門)

    加藤 宏基, 阿部 圭晃, 青野 光, 野々村 拓, 藤井 孝藏  

    年次大会 : Mechanical Engineering Congress, Japan2014 巻   頁: "S0550303 - 1"-"S0550303-5"   2014年9月

     詳細を見る

    記述言語:日本語   出版者・発行元:一般社団法人日本機械学会  

    This paper investigates effective and robust feedback control of dynamic separation around the NACA0015 airfoil using a dielectric barrier discharge plasma actuator. A chord-based Reynolds number is 23,000, and an angle of attack varies from 7 to 15 degrees. The feedback control is based on the pressure coefficient on the airfoil surface (i.e., 0.4-chord location). Although the aerodynamic performance using the feedback control is comparable with that using the continuous mode, the input energy of the feedback control is significantly (approximately by 50%) reduced from that of the continuous mode.

    CiNii Books

    researchmap

  108. 高レイノルズ数におけるDBDプラズマアクチュエータを用いた翼周り乱流剥離制御のLES

    佐藤允, 浅田健吾, 野々村拓, 青野光, 焼野藍子, 藤井孝藏  

    日本機械学会年次大会講演論文集(CD-ROM)2014 巻   頁: ROMBUNNO.S0550204   2014年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  109. 2メーター直径3枚ブレード回転機器模型まわり剥離流れへのプラズマ気流制御効果に関する数値解析

    青野光, 阿部圭晃, 岡田浩一, 岡田浩一, 佐藤允, 焼野藍子, 野々村拓, 藤井孝藏  

    日本機械学会年次大会講演論文集(CD-ROM)2014 巻   頁: ROMBUNNO.S0550404   2014年9月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap

  110. 革新的流体制御技術の研究開発「京」大規模計算によるマイクロデバイス流体制御 (特集 スーパーコンピュータ「京」を利用した流体工学研究の新展開と機械工学関連の先端的産業応用事例)

    藤井 孝藏, 野々村 拓, 青野 光  

    ターボ機械42 巻 ( 5 ) 頁: 297 - 304   2014年5月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本工業出版  

    CiNii Books

    researchmap

  111. 革新的流体制御技術の研究開発「「京」大規模計算によるマイクロデバイス

    藤井孝藏, 野々村拓, 青野光, 佐藤允, 焼野藍子  

    ターボ機械   頁: 1 - 4   2014年5月

     詳細を見る

  112. 空力音響多目的設計探査(ロケット射点形状設計への適用)

    大山聖, 立川智章, 野々村拓, 藤井孝藏  

    ターボ機械   頁: 1 - 4   2014年5月

     詳細を見る

  113. 乱流遷移する超音速ジェットからの音響波の定量予測

    野々村 拓, 藤井 孝藏  

    年会講演会講演集45 巻   頁: 9p   2014年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本航空宇宙学会  

    researchmap

  114. 大迎角細長物体におけるDBDプラズマアクチュエータを用いた横力制御方法の数値的研究

    西田 浩之, 佐藤 雅幸, 野々村 拓  

    年会講演会講演集45 巻   頁: 1 - 8   2014年4月

     詳細を見る

    記述言語:日本語   出版者・発行元:日本航空宇宙学会  

    researchmap

  115. 複数粒子が高マッハ数・低レイノルズ数で移動する流れ解析コードの構築と評価

    水野裕介, 高橋俊, 野々村拓, 福田紘大  

    数値流体力学シンポジウム講演論文集(CD-ROM)28th 巻   2014年

     詳細を見る

  116. 陰解法の時間刻みと収束率が圧縮性非定常流体解析の精度・効率に与える影響

    青野光, 岡田浩一, 野々村拓, 河合宗司, 藤井孝藏  

    数値流体力学シンポジウム講演論文集(CD-ROM)28th 巻   頁: ROMBUNNO.C08-2   2014年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

    researchmap