2023/11/29 更新

写真a

ナガタ タカユキ
永田 貴之
NAGATA Takayuki
所属
大学院工学研究科 航空宇宙工学専攻 空力・推進 特任助教
職名
特任助教

研究キーワード 4

  1. 圧縮性低Reynolds数流れ

  2. 実験空気力学

  3. 数値流体力学

  4. 流体力学

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

経歴 4

  1. 東北大学   大学院工学研究科   特任助教

    2021年3月 - 現在

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    国名:日本国

  2. 東北大学   大学院工学研究科   学術研究員(博士研究員)

    2020年4月 - 2021年3月

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    国名:日本国

  3. 東北大学   大学院工学研究科・工学部 航空宇宙工学専攻 航空システム講座 実験空気力学分野   日本学術振興会特別研究員 (DC2)

    2018年4月 - 2020年3月

  4. 東北大学   学際高等研究教育院   博士研究教育院生

    2017年4月 - 2020年3月

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    国名:日本国

学歴 3

  1. 東北大学   大学院工学研究科   航空宇宙工学専攻

    2017年4月 - 2020年3月

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    国名: 日本国

  2. 東海大学   大学院工学研究科   航空宇宙工学専攻

    2015年4月 - 2017年3月

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    国名: 日本国

  3. 東海大学   工学部   航空宇宙学科 航空宇宙学専攻

    2011年4月 - 2015年3月

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    国名: 日本国

所属学協会 5

  1. 日本流体力学会

    2020年7月 - 現在

  2. 日本地球惑星科学連合

    2020年 - 現在

  3. 日本航空宇宙学会

    2015年 - 現在

  4. アメリカ航空宇宙学会

    2015年 - 現在

  5. 日本機械学会

    2014年 - 現在

受賞 4

  1. NASA Group Achievement Award

    2023年4月   National Aeronautics and Space Administration  

    STMD Early Career, ROAMX Team

  2. 第54回流体力学講演会/第40回航空宇宙シミュレーション技術シンポジウム 最優秀賞(流体力学部門)

    2022年11月   日本航空宇宙学会   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

  3. 工学研究科長賞

    2020年3月   東北大学  

  4. 第51回流体力学講演会/37回航空宇宙シミュレーション技術シンポジウム 優秀発表賞

    2019年9月   日本航空宇宙学会   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

 

論文 63

  1. 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

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    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: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

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

  2. 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

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    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

  3. Density field reconstruction from time-series schlieren images via extended phase-consistent dynamic mode decomposition 査読有り

    Shigeta, T; Nagata, T; Nonomura, T

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

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    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  

    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

  4. Efficient Sensor Node Selection for Observability Gramian Optimization 査読有り

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

    SENSORS   23 巻 ( 13 )   2023年7月

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    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

  5. Reservoir computing reduced-order model based on particle image velocimetry data of post-stall flow 査読有り

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

    AIP ADVANCES   13 巻 ( 6 )   2023年6月

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    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

  6. 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

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    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

  7. Randomized Group-Greedy Method for Large-Scale Sensor Selection Problems 査読有り

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

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

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    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: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

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  8. Experimental investigation of the supersonic cavity by spectral-POD of high-sampling rate pressure-sensitive paint data 査読有り

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

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

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    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

  9. 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

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    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

    その他リンク: https://academic.oup.com/gji/article-pdf/234/3/1786/50241650/ggad165.pdf

  10. The development of the novel simulation system that calculates the trajectories of 10000 stones in a short time

    Komeya, M; Nara, S; Young, HJ; Kamei, Y; Uchida, H; Nagata, T; Takahashi, S; Kimura, H; Fukuda, K; Matsuzaki, J; Makiyama, K

    EUROPEAN UROLOGY   83 巻   頁: S516 - S517   2023年2月

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  11. Sensor Selection with Cost Function using Nondominated-Solution-based Multi-objective Greedy Method

    Yuji Saito, Kumi Nakai, Takayuki Nagata, Keigo Yamada, Taku Nonomura, Kazuki Sakaki, Yoshio Nunome

    IEEE Sensors Journal     頁: 1 - 1   2023年

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:Institute of Electrical and Electronics Engineers (IEEE)  

    DOI: 10.1109/jsen.2023.3328005

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

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

    IEEE ACCESS   11 巻   頁: 67850 - 67864   2023年

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    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

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    Scopus

  13. 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

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    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

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  14. 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

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    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: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

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  15. 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 ) 頁: 095203 - 095203   2022年9月

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    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

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  16. 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

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    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: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

  17. 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

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    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  

    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

  18. 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

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    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

  19. 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

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    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: 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

  20. 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

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    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

  21. Optimizing Sparse Sensor Placement for Flow Field Estimation Using Time-Averaged Pressure-Sensitive Paint Data: Application to Ground Vehicle

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

    AIAA AVIATION 2022 Forum     2022年6月

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    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 AVIATION 2022 Forum  

    The present study proposes a method for estimating the wind direction against a simple automobile model (Ahmed model) and reconstructing surface pressure distribution on it by the sparse pressure sensors. The sparse pressure sensor placement was optimized by the three algorithms based on data-driven sparse sampling using the time-averaged surface pressure distributions as the training data. The surface pressure distributions were obtained by pressure-sensitive paint (PSP) measurements. The estimation models were constructed based on the training data, and then, the estimation accuracy of yaw angles and pressure distributions was compared and evaluated.

    DOI: 10.2514/6.2022-3606

    Scopus

  22. 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 ) 頁: 453   2022年1月

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    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  

    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

  23. 超音速噴流の3次元超解像計測に基づくフラッピングモードの詳細解析

    李 忠日, 小澤 雄太, 永田 貴之, 野々村 拓

    流体工学部門講演会講演論文集   2022 巻 ( 0 ) 頁: OS03-48   2022年

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    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/jsmefed.2022.os03-48

    CiNii Research

  24. 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

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    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: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

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

    Kasumi Ohmizu, Yuta Ozawa, Takayuki Nagata, Taku Nonomura, Keisuke Asai

    Journal of Visualization     2022年

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    掲載種別:研究論文(学術雑誌)  

    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

    Scopus

  26. DMD-based Superresolution Measurement of a Supersonic Jet using Dual Planar PIV and Acoustic Data

    Ozawa Y., Nishikori H., Nagata T., Nonomura T., Asai K., Colonius T.

    28th AIAA/CEAS Aeroacoustics Conference, 2022     2022年

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    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:28th AIAA/CEAS Aeroacoustics Conference, 2022  

    The present study proposes a framework of the superresolution measurement based on the dynamic mode decomposition (DMD) with the Kalman filter and Rauch–Tung–Striebel smoother. The dual-planar particle image velocimetry (PIV) systems were constructed to acquire the paired velocity fields of a Mach 1.1 supersonic jet. The acoustic measurement was simultaneously performed, and the velocity and acoustic data are used for the superresolution. Although the dual PIV system measures the basic characteristics of the velocity fields, all the DMD modes calculated by the exact DMD are decay modes due to the measurement noise. The superresolved velocity field shows smooth convection of the large-scale structures at the downstream side. Therefore, the proposed method is effective to reconstruct the entire flow fluctuation because the DMD modes express the linear dynamical system of the velocity fields.

    DOI: 10.2514/6.2022-3065

    Scopus

  27. 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

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    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

  28. Experimental Investigation of Supersonic Cavity Flow Using Fast-responding Free-based Porphyrin Anodized-Aluminum Pressure-Sensitive Paint

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

    28th AIAA/CEAS Aeroacoustics Conference, 2022     2022年

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    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:28th AIAA/CEAS Aeroacoustics Conference, 2022  

    In this study, 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 supersonic flow was obtained using anodized-aluminum pressure-sensitivity paint (AA-PSP). The freestream Mach number was M = 1.85 and the frequencies of the dominant cavity modal phenomena called a Rossiter mode were on the order of 10 kHz. Fast-responding AA-PSP using free-based porphyrin luminophore and a high-frequency-repetition pulse laser were applied, and instantaneous pressure fields were measured. 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 schlieren and dynamic pressure transducer measurements were employed and PSD obtained by the PSP measurement was validated. The frequency spectra and amplitudes of PSD obtained by the PSP measurement were in good agreement with those obtained by the schlieren and dynamic pressure transducer data. A dynamic mode decomposition analysis was also conducted for sequential data of PSP, and the frequency and the energy distribution at the peak frequency could be extracted.

    DOI: 10.2514/6.2022-2959

    Scopus

  29. Improvement of signal-to-noise ratio of schlieren visualization images in low-density wind tunnel tests using mode-selection based signal processing

    Shigeta T., Nagata T., Nonomura T., Asai K.

    AIAA AVIATION 2022 Forum     2022年

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    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 AVIATION 2022 Forum  

    The objective of this study is to develop digital signal processing methods that reduce noise caused by atmospheric fluctuation and image sensors and extract signal of fluid phenomena from data obtained by the highly sensitive schlieren measurement in the low-density wind tunnel. Time-series schlieren images of the flow around a triangular airfoil were used for analysis, and the effectiveness of noise reduction methods based on the randomized singular value decomposition (RSVD). In the proposed method, noise and signal of fluid phenomena were separated by frequency components using fast Fourier transform (FFT) and inverse FFT in advance, and the flow was visualized at Re= 3000 and M = 0.15, where the signal-to-noise ratio was particularly low.

    DOI: 10.2514/6.2022-4166

    Scopus

  30. 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

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    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

  31. Reservoir Computing Reduced-order Model based on PIV data of Flow Field

    Iwasaki Y., Nakai K., Nagata T., Nonomura T., Asai K., Inubushi M.

    AIAA AVIATION 2022 Forum     2022年

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    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 AVIATION 2022 Forum  

    This study proposes a reservoir computing reduced-order model (RCROM) of the post-stall flow around NACA0015 airfoil based on the time series velocity field, and the estimation accuracy of RCROM is evaluated compared to that of a linear reduced-order model (LROM). The data is experimentally obtained by the particle image velocimetry measurement with the chord Reynolds number of 6.4 × 104, and the angle of attack of 18 deg. The low-dimensional description of the velocity field can be obtained by decomposing the velocity field with a proper orthogonal decomposition (POD) technique and treating the dominant POD modes amplitude as temporal variables. The nonlinear function that estimates one step ahead of the POD modes amplitude is obtained by the reservoir computing. Similarly, the linear function is calculated by postulating the linear development of the POD modes amplitudes. The hyper parameters of RCROM are tuned by the Bayesian optimization. The results show that the estimation accuracy of RCROM is better than that of LROM under the condition that the number of target POD modes is one, three, and five.

    DOI: 10.2514/6.2022-3242

    Scopus

  32. 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

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    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:一般社団法人 日本航空宇宙学会  

    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

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    CiNii Research

  33. Time-Resolved Three-Dimensional Velocity Fields of Supersonic Jet using PIV and Near-Field Acoustic Data based on POD

    Lee C., Nishikori H., Nagata T., Ozawa Y., Nonomura T., Asai K.

    28th AIAA/CEAS Aeroacoustics Conference, 2022     2022年

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    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:28th AIAA/CEAS Aeroacoustics Conference, 2022  

    The method for estimating time-resolved three-dimensional velocity field is developed to investigate the high spatial and temporal flow structures of the supersonic jet with the Mach number of 1.35. The supersonic jet were measured by non-time-resolved particle image velocimetry (PIV) measurement and time-resolved near-field acoustic measurement. The multi-time-delay modified linear stochastic estimation (MTD-mLSE) was applied into the reduced-order velocity data and the Fourier coefficient acoustic data which is decomposed by the complex Fourier expansion series. The four azimuhal modes were reconstructed from the developed method. The azimuthal mode 0 is the axisymmetric mode, the azimuthal mode 1 and 3 are helical mode and the azimuthal mode 2 is the helical and the lateral modes. The dominant azimuthal mode of the Mach number of 1.35 can be identified from time-resolved three-dimensional velocity fields which are the sum of the mean and the fluctuations components.

    DOI: 10.2514/6.2022-3024

    Scopus

  34. レイノルズ数 <i>O</i> (10<sup>3</sup>)における臨界形状近傍角柱周り流れに対するマッハ数・レイノルズ数 効果の検討

    木村 聡志, 永田 貴之, 笠井 美玖, 小澤 雄太, 野々村 拓

    流体工学部門講演会講演論文集   2022 巻 ( 0 ) 頁: OS03-04   2022年

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    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/jsmefed.2022.os03-04

    CiNii Research

  35. 生理学的三次元腎盂・腎杯モデルを用いた自然排石を促す運動の検証

    何 鎮陽, 垣内 祐哉, 亀井 結紀, 永田 貴之, 古目谷 暢, 福田 紘大, 高橋 俊, 木村 啓志

    日本機械学会関東支部総会講演会講演論文集   2022.28 巻 ( 0 ) 頁: 15F10   2022年

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    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/jsmekanto.2022.28.15f10

    CiNii Research

  36. 生理的三次元腎臓模型を用いた自然排石予測シミュレータの構築

    何 鎮陽, 垣内 祐哉, 亀井 結紀, 永田 貴之, 古目谷 暢, 福田 紘大, 高橋 俊, 木村 啓志

    年次大会   2022 巻 ( 0 ) 頁: J025-05   2022年

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    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.2022.j025-05

    CiNii Research

  37. 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

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    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

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  38. 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

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    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: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

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  39. Computational fluid dynamic modeling of renal stones in the renal calyx

    Komeya, M; Nara, S; Nagata, T; Takahashi, S; Uchida, H; Kimura, H; Fukuda, K; Matsuzaki, J; Yao, M

    EUROPEAN UROLOGY   79 巻   頁: S300 - S301   2021年6月

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  40. 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

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    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  

    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

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    PubMed

  41. 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

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    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

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    その他リンク: https://link.springer.com/article/10.1007/s00348-021-03164-0/fulltext.html

  42. 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

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    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: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

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    その他リンク: https://iopscience.iop.org/article/10.1088/1873-7005/abe04c/pdf

  43. 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

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    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

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    PubMed

  44. 生理学的3D腎杯モデルを用いた自然排石を促す運動の検証

    中里 遼太, ホー ジンヤン, 六反 陸, 亀井 結紀, 奈良 祥太朗, 永田 貴之, 古目谷 暢, 福田 紘大, 高橋 俊, 木村 啓志

    日本機械学会関東支部総会講演会講演論文集   2021.27 巻 ( 0 ) 頁: 10D14   2021年

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    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/jsmekanto.2021.27.10d14

    CiNii Research

  45. 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

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    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

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  46. Demonstration and Verification of Exact DMD Analysis Applying to Double-pulsed Schlieren Image of Supersonic Impinging Jet

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

    AIAA Aviation and Aeronautics Forum and Exposition, AIAA AVIATION Forum 2021     2021年

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    出版者・発行元:AIAA Aviation and Aeronautics Forum and Exposition, AIAA AVIATION Forum 2021  

    Applicability of exact dynamic mode decomposition (DMD) for the evaluation of the aeroacoustic field was investigated on the nonsequential data obtained by the double-pulsed schlieren measurement of the supersonic impinging jet. The Mach number of the jet was 2.0, the Reynolds number based on the diameter of the nozzle exit was 1.0×106, and the distance between the nozzle exit and the flat plate was 4 times the nozzle diameter. The effect of the length of a dataset on the obtained spatial modes and estimated frequencies of the acoustic field was provided. The estimated frequencies were compared with the result of microphone measurements. As a result, a non-time-resolved measurement system was demonstrated to be capable of clarifying physical phenomena and estimating the characteristic frequencies by applying DMD to paired images with a short time interval. In addition, the dataset length used affects the estimation accuracy, and its evaluation is important for discussion.

    DOI: 10.2514/6.2021-2217

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  47. 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

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    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

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  48. 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

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    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

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    arXiv

  49. POD-based Spatio-temporal Superresolution Measurement on a Supersonic Jet using PIV and Near-field Acoustic Data

    Ozawa Y., Nagata T., Nishikori H., Nonomura T., Asai K.

    AIAA Aviation and Aeronautics Forum and Exposition, AIAA AVIATION Forum 2021     2021年

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    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 Aviation and Aeronautics Forum and Exposition, AIAA AVIATION Forum 2021  

    Supersonic jets of M=1.35 and 2.0 were measured by time-resolved near-field acoustic measurement and non-time-resolved particle image velocimetry (PIV). The multi-time-delay modified linear stochastic estimation (MTD-mLSE) was applied to the reduced-order acoustic and velocity field data based on the proper orthogonal decomposition (POD) coefficients. Time-resolved snapshots of the velocity field reconstructed by MTD-mLSE show the smooth convection of the velocity fluctuations. The fluctuations of the shock cell structure that seems to be the noise source of the screech tone were observed.

    DOI: 10.2514/6.2021-2106

    Scopus

  50. 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

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    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: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

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  51. A simple collision algorithm for arbitrarily shaped objects in particle-resolved flow simulation using an immersed boundary method 査読有り

    Nagata, T; Hosaka, M; Takahashi, S; Shimizu, K; Fukuda, K; Obayashi, S

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS   92 巻 ( 10 ) 頁: 1256 - 1273   2020年10月

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    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:International Journal for Numerical Methods in Fluids  

    In the present study, we proposed a simple collision algorithm, which can be handled arbitrarily shaped objects, for flow solvers using the immersed boundary method (IBM) based on the level set and ghost cell methods. The proposed algorithm can handle the collision of the arbitrarily shaped object with little additional computational costs for the collision calculation because collision detection and calculation are performed using the level set function and image point, which are incorporated into the original IBM solver. The proposed algorithm was implemented on the solid-liquid IBM flow solver and validated by simulations of the flow over an isolated cylinder and sphere. Also, grid and time step size sensitivity on the total energy conservation of objects were investigated in cylinder-cylinder, cylinder-red-blood-cells-shaped (RBC-shaped) objects, sphere-sphere, and sphere-flat plate interaction problems. Through validation, good agreement with previous studies, grid and time step size convergence, and sufficient total energy conservation were confirmed. As a demonstration, the drafting, kissing, and tumbling processes were computed, and it was confirmed that the present result by the proposed method is similar to the previous computations. In addition, particle-laden flow in a channel including obstacles with collision and adhesion phenomena and the interaction of cylinders and wavy-wall were computed. The results of these simulations reveal the capability of solving a flow containing arbitrarily shaped moving objects with collision phenomena by a simple proposed method.

    DOI: 10.1002/fld.4826

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  52. 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 ) 頁: 085303   2020年8月

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    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  

    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

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  53. 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

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    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: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

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  54. 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

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    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)  

    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

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    PubMed

  55. 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

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    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: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

  56. 下腎杯内流れと腎結石の挙動の数値シミュレーション

    内田 日出, 戸本 幸志郎, 永田 貴之, 高橋 俊, 福田 紘大, 木村 啓志, 古目谷 暢, 松崎 純一

    流体工学部門講演会講演論文集   2019 巻 ( 0 ) 頁: OS9-09   2019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/jsmefed.2019.os9-09

    CiNii Research

  57. Direct numerical simulation of supersonic flow over a counter-rotating vane-type vortex generator implemented on slip wall 査読有り

    Nagata T., Daspit T., Nonomura T., Loth E.

    ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019   1 巻   2019年

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    担当区分:筆頭著者   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:ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019  

    In this study, flow over a pair of vane-type vortex generator is investigated by solving the Navier–Stokes equation. A pair of the vane-type vortex generator implemented on a slip wall in laminar flow is considered so that the problem setting could be simple. The Reynolds number based on freestream quantities and the height of the vanes is set to be 500. The effect of the arrangement and geometry of vanes on the circulation coefficients, induced flow velocities, and aerodynamic force coefficients of VGs are investigated. In addition, a new non-dimensional circulation coefficient, normalized by freestream velocity and the height of the vortex core was introduced and its effectiveness is examined. This new parameter, Ct´, include the height of the vortex core, so that appears to be a better measure of VG effectiveness on momentum exchange. From the computational results, the wider arrangement can introduce the effective vortices with small drag. Also, the longer vanes can introduce strong and effective vortices with smaller drag coefficient.

    DOI: 10.1115/AJKFluids2019-5312

    Scopus

  58. Flow visualization and drag measurement of a circular cylinder in compressible flow at reynolds number between 1000 and 5000 査読有り

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

    ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019   1 巻   2019年

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    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:ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019  

    In this study, a compressible low-Reynolds number flow over a circular cylinder was investigated by schlieren visualization and the force measurement. A Reynolds number based on freestream quantities and a diameter of a cylinder is set to be 1000 = Re = 5000 and a Mach number is set to be 0.1 = M = 0.5 by using the low-pressure wind tunnel. From the schlieren visualization, frequency of the vortex shedding was obtained by performing frequency analysis on the time series schlieren images. Near wake structure by the circular cylinder is measured by time-averaged schlieren image. Even though M is less than 0.5, the structure of the flow fields changes depending on M. The effect of M on the scale of wake structure depends on Re. Under the condition at Re of 1000-3000, the scale becomes large as M increases more than 0.2. On the other hand, under the condition that Re is 4000-5000, it becomes small as M increase 0.3 or more St is revealed to be decrease for Re of 2000-3000 with increasing M, and St increases at Re of 4000-5000. From the force measurement, drag coefficient (Cd) and pressure distribution on a circular cylinder (Cp) obtained. The effect of M on Cd does not depend on Re, and Cd also increases as M increases. The effect of Re on Cd is also observed that Cd increases as Re increases and this trend doesn’t depend on M. The Cp decrease with Re increase. The M effect on Cp is that the range of Cp is enlarged with M increase.

    DOI: 10.1115/AJKFluids2019-5164

    Scopus

  59. 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

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    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: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

  60. 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

    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: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

  61. Numerical Simulation on Solid–liquid Multiphase Flow including Complex-shaped Objects with Collision and Adhesion Effects using Immersed Boundary Method 査読有り 国際誌

    International Journal of Computational Methods and Experimental Measurements   6 巻 ( 1 ) 頁: 162 - 175   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)  

    DOI: 10.2495/CMEM-V6-N1-162-175

    Scopus

  62. 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

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

    Physics of Fluids   28 巻 ( 5 ) 頁: 056101 - 056101   2016年5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:{AIP} Publishing  

    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

    Scopus

  63. A Simple Immersed Boundary Method for Compressible Flow Simulation around a Stationary and Moving Sphere 査読有り 国際誌

    Yusuke Mizuno, Shun Takahashi, Taku Nonomura, Takayuki Nagata, Kota Fukuda

    Mathematical Problems in Engineering   2015 巻   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:HINDAWI PUBLISHING CORP  

    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

▼全件表示

MISC 23

  1. 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

  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. 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

  4. 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

  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. 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

  7. 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

  8. 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

  9. 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

  10. 固気液混相流解析による工業製品の設計開発

    高橋俊, 大林茂, 永田貴之, 水野祐介, 川本裕樹  

    東北大学流体科学研究所共同利用・共同研究拠点流体科学国際研究教育拠点活動報告書2019 巻   2021年

     詳細を見る

  11. 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

  12. 数値流体解析と離散要素法を用いて腎杯・腎盂内での微小結石の挙動を可視化するシミュレーションシステムの開発

    古目谷暢, 古目谷暢, 奈良祥太朗, ホー ジンヤン, 亀井結紀, 永田貴之, 高橋俊, 福田紘大, 木村啓志, 松崎純一, 矢尾正祐  

    日本泌尿器科学会総会(Web)109th 巻   2021年

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  13. 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

  14. 新規結石形成リスク分類法および予防法の実現に向けた腎杯・腎盂内における結石流動シミュレーションシステムの開発

    古目谷 暢, 内田 日出, 戸本 幸志郎, 永田 貴之, 高橋 俊, 福田 紘大, 木村 啓志, 矢尾 正祐, 松崎 純一  

    日本泌尿器科学会総会108回 巻   頁: 908 - 908   2020年12月

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    記述言語:日本語   出版者・発行元:(一社)日本泌尿器科学会総会事務局  

    J-GLOBAL

  15. 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

  16. 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

  17. 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

  18. 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

  19. 埋め込み境界法を用いた衝突・付着を伴う数値シミュレーション

    保坂 衛, 永田 貴之, 高橋 俊, 福田 紘大  

    計算力学講演会講演論文集2016 巻 ( 0 ) 頁: 4_176   2016年

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    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/jsmecmd.2016.29.4_176

    J-GLOBAL

  20. 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

  21. 高マッハ数・低レイノルズ数・断熱条件下での球周り流れ解析

    永田貴之, 野々村拓, 福田紘大, 高橋俊  

    数値流体力学シンポジウム講演論文集(CD-ROM)28th 巻   頁: ROMBUNNO.B06-3   2014年

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

  22. 高性能グライダーの製作に向けて

    永田貴之, 石原昂典, 相馬大祐  

    日本物理学会誌66 巻   頁: 142   2011年3月

     詳細を見る

    記述言語:日本語  

    J-GLOBAL

  23. 26pJPS-6 高性能グライダーの製作に向けて(ポスター発表,日本物理学会第7回Jr.セッション)

    永田 貴之, 石原 昂典, 相馬 大祐  

    日本物理學會誌66 巻 ( 3 ) 頁: 142 - 142   2011年3月

     詳細を見る

    記述言語:日本語   出版者・発行元:一般社団法人日本物理学会  

    CiNii Books

▼全件表示

講演・口頭発表等 26

  1. 遷音速域における自由飛行カプセルの後流解析

    桐谷英樹, 永田貴之, 永井大樹, 大谷清伸, 小川俊広

    衝撃波シンポジウム講演論文集(CD-ROM)  2019年 

     詳細を見る

    開催年月日: 2019年

    記述言語:日本語  

  2. 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)  2019年 

     詳細を見る

    開催年月日: 2019年

    記述言語:日本語  

  3. 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)  2019年 

     詳細を見る

    開催年月日: 2019年

    記述言語:日本語  

  4. Schlieren visualization of transonic and supersonic flow over a sphere at reynolds number between 10<sup>3</sup>and 10<sup>5</sup>through free-flight tests

    Takayuki Nagata, Akito Noguchi, Taku Nonomura, Toshihiro Ogawa, Kiyonobu Ohtani, Kesuke Asai

    AIAA Scitech 2019 Forum  2019年 

     詳細を見る

    開催年月日: 2019年

    © 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. In this study, free-flight tests of a sphere at a Reynolds number between 5.7 × 103and 3.1 × 105under transonic to supersonic condition is conducted using ballistic range and investigate the flow over a sphere under compressible low-Reynolds number conditions. The flow visualization is carried out by schlieren technique. A free-flight Reynolds number is between 5.7 × 103and 3.1 × 105and a free-flight Mach number is between 0.9 and 1.6. To realize the compressible low-Reynolds number flow, the flow visualization is carried out under low-pressure conditions with a small sphere (minimum diameter is 2.0 mm). in addition, the time-averaged images around a sphere are obtained and compared with previous numerical results for the Reynolds number between 50 and 1000. From the experimental results, the near field and far field flow structure at the Reynolds number of between 5.7 × 103and 3.1 × 105under supersonic conditions are visualized. As a result, following characteristics are clarified: 1) the perturbation amplitude of wake vortex is attenuated as a free-flight Mach number increases, 2) mode of wake structure is changed by changing the free-flight Mach number, 3) there is no Reynolds number dependences on the separation point, but a length of the recirculation region is influenced by the Reynolds number.

  5. 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)  2018年 

     詳細を見る

    開催年月日: 2018年

    記述言語:日本語  

  6. 126 シュリーレン法による圧縮性低レイノルズ数流れの可視化

    野口 暁人, 石脇 大地, 佐藤 郷之助, 永田 貴之, 小室 淳史, 野々村 拓, 安藤 晃, 浅井 圭介

    東北支部総会・講演会 講演論文集  2018年  一般社団法人 日本機械学会

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    開催年月日: 2018年

    記述言語:日本語  

  7. Direct numerical simulation of flow past a sphere at a reynolds number between 500 and 1000 in compressible flows

    Takayuki Nagata, Taku Nonomura, Shun Takahashi, Shun Takahashi

    AIAA Aerospace Sciences Meeting, 2018  2018年 

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    開催年月日: 2018年

    © 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. 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.

  8. 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)  2018年 

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    開催年月日: 2018年

    記述言語:日本語  

  9. 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)  2018年 

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    開催年月日: 2018年

    記述言語:日本語  

  10. 埋め込み境界法を用いた腎臓結石の流動解析

    清水健, 保坂衛, 加藤祐樹, 永田貴之, 高橋俊, 福田紘大, 古目谷暢, 木村啓志, 松崎純一

    バイオエンジニアリング講演会講演論文集(CD-ROM)  2017年12月13日 

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    開催年月日: 2017年12月

    記述言語:日本語  

  11. 埋め込み境界法によるステント形状の改良に向けた血流の付着を伴う流体解析

    保坂衛, 永田貴之, 高橋俊, 福田紘大, 後藤信哉

    バイオエンジニアリング講演会講演論文集(CD-ROM)  2017年12月13日 

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    開催年月日: 2017年12月

    記述言語:日本語  

  12. 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)  2017年 

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    開催年月日: 2017年

    記述言語:日本語  

  13. 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年9月10日  一般社団法人 日本機械学会

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    開催年月日: 2016年9月

    記述言語:日本語  

  14. Direct numerical simulation of shock waves passed by multiple particles using immersed boundary method

    Yusuke Mizuno, Shun Takahashi, Taku Nonomura, Takayuki Nagata, Kota Fukuda

    54th AIAA Aerospace Sciences Meeting  2016年 

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    開催年月日: 2016年

    © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All Rights Reserved. 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.

  15. Analysis of the temperature ratio effects on the flow properties of the low reynolds and high mach number flow around a sphere

    Takayuki Nagata, Taku Nonomura, Shun Takahashi, Yusuke Mizuno, Kota Fukuda

    54th AIAA Aerospace Sciences Meeting  2016年 

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    開催年月日: 2016年

    © 2016, American Institute of Aeronautics and Astronautics Inc, AIAA. All Rights Reserved. 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.

  16. Analysis on flow around a sphere at high Mach number, low reynolds number and adiabatic condition for high accuracy analysis of gas particle flows

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

    COUPLED PROBLEMS 2015 - Proceedings of the 6th International Conference on Coupled Problems in Science and Engineering  2015年4月 

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    開催年月日: 2015年4月

    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.

  17. 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)  2015年 

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    開催年月日: 2015年

    記述言語:日本語  

  18. 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  2015年  一般社団法人 日本機械学会

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    開催年月日: 2015年

    記述言語:日本語  

    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.

  19. 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  2015年  一般社団法人 日本機械学会

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    開催年月日: 2015年

    記述言語:日本語  

    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.

  20. Coupled simulation of shock waves in gas-particle mixtures introducing motion equations

    Yusuke Mizuno, Shun Takahashi, Taku Nonomura, Takayuki Nagata, Kota Fukuda

    COUPLED PROBLEMS 2015 - Proceedings of the 6th International Conference on Coupled Problems in Science and Engineering  2015年 

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    開催年月日: 2015年

    記述言語:英語  

    In this work, direct numerical analyses for flow around particles passing a shock wave was carried out to predict effects of small particles in rocket plumes. A flow solver based on three-dimensional compressible Navier-Stokes equations is developed for the purpose of high accurate prediction of the acoustic field around rocket plumes. This flow solver is capable of analysing a flow around moving multiple particles and motion equations was introduced. The flow field and the drag coefficient after the shock wave passage were validated by comparing with the drag models at shock Mach number 1.2-2.8. The result was in good agreement with the drag models. In the flow around multiple particles, the interference between particles was confirmed.

  21. 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)  2015年 

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    開催年月日: 2015年

    記述言語:日本語  

  22. 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)  2015年 

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    開催年月日: 2015年

    記述言語:日本語  

  23. 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)  2015年 

     詳細を見る

    開催年月日: 2015年

    記述言語:日本語  

  24. 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)  2015年 

     詳細を見る

    開催年月日: 2015年

    記述言語:日本語  

  25. 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)  2015年 

     詳細を見る

    開催年月日: 2015年

    記述言語:日本語  

  26. 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)  2015年 

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    開催年月日: 2015年

    記述言語:日本語  

▼全件表示

科研費 4

  1. 高速固気混相流における壁面近傍での粒子挙動の現象理解と高精度予測に向けたモデル化

    研究課題/研究課題番号:23K13249  2023年4月 - 2026年3月

    日本学術振興会  科学研究費助成事業  若手研究

    永田 貴之

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    担当区分:研究代表者 

    配分額:4680000円 ( 直接経費:3600000円 、 間接経費:1080000円 )

    圧縮性混相流の高忠実度シミュレーションに向け,圧縮性流中の微粒子と物体壁面の干渉現象の理解とモデル化を行う.壁面近傍に固定された粒子周り圧縮性流れの直接数値計算を行い,主流条件および粒子の回転や速度勾配,壁面からの距離を変化させ,空力係数や流れ場に対する影響を精緻に調べ,粒子周り流れの基礎的知見を体系的に明らかにする.その知見を元にモデルを構築し,楔形状周りの超音速固気混相流を例に,構築したモデルの検証と現象の再現に重要な効果を同定する.これにより,圧縮性混相流の壁面近傍流れにおける粒子の影響の理解や評価,流体機械の性能向上や寿命予測の高精度化を狙う.

  2. 高忠実度な圧縮性混相流シミュレーションに向けた粒子間干渉効果の解明とモデル化

    研究課題/研究課題番号:21K14071  2021年4月 - 2023年3月

    日本学術振興会  科学研究費助成事業 若手研究  若手研究

    永田 貴之

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    担当区分:研究代表者 

    配分額:4550000円 ( 直接経費:3500000円 、 間接経費:1050000円 )

    圧縮性混相流の高忠実度シミュレーションと現象理解に向けて,圧縮性低レイノルズ数流れ における粒子間の流体力学的干渉効果の解明とモデル化に挑む.三次元圧縮性Navier-Stokes方程式の直接数値計算および衝撃波管を用いた平面衝撃波と粒子クラスターの干渉実験により,圧縮性低レイノルズ数流れでの粒子間の流体力学的干渉効果を解明し,粒子間の流体力学的干渉により生じる流体力や応力分布の変化をモデル化する.粒子間干渉の効果を含めた精緻なモデル化により,圧縮性混相流の高忠実度シミュレーションとそれを用いた現象理解や流体機械の性能向上に向けた基盤を構築する.
    数値計算による研究に関しては,主流に対して並列,直列,斜めに配置された2粒子周り流れの直接数値計算を行った.レイノルズ数は150,マッハ数は0.3から1.2でNavier-Stokes方程式の直接数値計算を行った.今年度前半は計算格子などの準備を行い,テスト計算を行った.後半は本計算を実施し,粒子間の流体力学的干渉に対するマッハ数効果の影響を調べ,その結果を2件の国内学会で発表した.数値計算の結果より,粒子間の流体力学的干渉により再循環領域や衝撃波の構造が大きく変化し,特に,斜め配置の場合は下流側粒子の片面が上流側粒子の影響を強く受けるために流れ場の非対称性が強いことを明らかにした.粒子の位置関係の効果に関しては,位置関係に応じて流体力学的干渉による見かけ上の力で粒子が接近するか離れるかが変化する.また,低マッハ数条件では干渉による影響は小さいが高マッハ数条件ではその影響が強い.特に,並列配置の場合はマッハ数0.95ではマッハ数0.3の場合と比較して見かけ上の引力が3倍となり,流れ方向に粒子が集まりやすいことを明らかにした.また,当初予定にはなかったが,埋め込み境界法を用いて2粒子と垂直衝撃波の干渉現象の計算を行い,衝撃波の通過に対する粒子の非定常応答における粒子間干渉の影響を共同研究で調べ,1件の国内学会発表を共著者として行った.
    実験による研究に関しては,新規に導入した高輝度白色光源を用いて低圧環境下でシュリーレン可視化を行い,これまで利用してきた光源と比較して大幅に感度を向上できることを確認した.また,これまでの研究で用いてきた光学系による実験結果を筆頭著者として英文学術雑誌に投稿し,受理済みである.
    モデル化については,以前から共同で行っていた粒子抵抗モデルの改良を完了させ,共著者として国際学術雑誌に投稿し,掲載済みである.
    当初,令和3年度は数値計算と衝撃波管を用いた実験により粒子間干渉の現象解明を行う予定であったが,数値振動や複数物体の取り扱いの部分で問題が生じ,数値計算の実施までに想定より時間がかかった.また,粒子間距離の影響を比較的小さい距離で調べたため,高解像度の計算格子が必要となり当初の想定よりも計算資源と計算時間が必要となった.実験については,新規に導入した高輝度白色光源を用いた低圧環境におけるシュリーレン可視化のテストにとどまり,粒子間の流体力学的干渉を調べる本格的な実験については着手できなかった.
    最終年度となる令和4年度は,令和3年度までに行ってきた直接数値計算による研究を継続する.粒子間距離や角度についてケース数を増やし,モデル化に必要なデータを収集する.一連の計算で得られた結果を解析し,粒子間の流体力学的干渉に関する基礎的な知見として学術雑誌に投稿する.
    実験に関しては,衝撃波管を用いた粒子クラスターと垂直衝撃波の干渉実験により,圧縮性流れにおける粒子クラスターの振る舞いを調べることで,粒子間の流体力学的干渉について実験的に調べる.特に,数値計算での実施が難しい粒子間距離が小さい場合を対象とする予定である.
    干渉の影響のモデル化に関しては,粒子間に働く見かけ上の引力・斥力とマッハ数や粒子間距離,角度の関係を適切な関数でモデル化する.

  3. 球周り流れの数値的・実験的研究に基づく圧縮性混相流モデルの構築と微粒子の影響解明

    研究課題/研究課題番号:18J11205  2018年4月 - 2020年3月

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    永田 貴之, 永田 貴之

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:1900000円 ( 直接経費:1900000円 )

    去年度と同様に圧縮性Navier-Stokes方程式の直接数値解析と弾道飛行試験及び球-衝撃波干渉試験により球周りの圧縮性低Reynolds数流れの特性を調べた.
    直接数値解析による研究では球周りの一様剪断流の計算を行い,球に働く揚力や抵抗係数など基礎的なパラメタと流体物理の解明を行った.流れの速度勾配による揚力は本研究で対象としたRe=100-300の非圧縮性流れでは高速側から低速側へ働く負の揚力が発生し,Reynolds数の低下に伴い揚力係数の絶対値が小さくなることが知られているが,圧縮性流れでは非圧縮性流れと比較して大きな負の揚力が発生し,Reynolds数の低下に伴い絶対値が増加すること示した.また,圧縮性流れでの負の速度勾配による揚力は非圧縮性流れと全く異なるメカニズムで発生することを明らかにした.
    弾道飛行試験では去年度までの弾道飛行試験と数値計算の結果から再循環領域長さに変曲点があると思われたReynolds数1000程度の超音速流れの可視化を目指し,シュリーレン光学系の感度と撮影倍率の増強を行った.しかし,雰囲気の密度ムラの問題などから去年度よりも低Reynolds数の条件では流体現象の議論ができる可視化画像を取得できなかった.
    球-衝撃波干渉実験では去年度構築した実験系で単体球での可視化・抵抗係数計測を本格的に行った.また,複数球周り流れの可視化も行い,粒子クラスタにおける流体力学的相互作用を検討した.抵抗係数に関しては過去に行われた弾道飛行試験で得られた抵抗係数や抵抗モデルによる予測値よりも高い値を取ることを再度確認した.複数球周り流れの可視化ではクラスタ球と垂直衝撃波の干渉の様子を高速撮影し,流体力学的相互作用によりクラスタ球が崩壊する様子を捉えた.これにより,圧縮性低Reynolds数流れにおいて粒子同士が接近すると斥力が働く可能性を示唆した.

  4. 超音速混相流モデリングに向けた高Mach数・低Reynolds数の球周り流れの現象解明

    2017年4月 - 2020年3月

    東北大学 学際高等研究教育院  博士研究教育院生 研究費 

    永田貴之

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    担当区分:研究代表者  資金種別:競争的資金