Faculty Profiles - YOSHIMATSU Katsunori

Papers - YOSHIMATSU Katsunori

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Coherent vorticity and current density simulation of three-dimensional magnetohydrodynamic turbulence using orthogonal wavelets Reviewed

K. Yoshimatsu, N. Okamoto, Y. Kawahara, K. Schneider and M. Farge

Geophysical and Astrophysical Fluid Dynamics Vol. 107 ( 1-2 ) page： 73-92 2013.3

Coherent Vorticity and Current Density Simulation of Magnetohydrodynamic Turbulence Reviewed

page： 184-189 2012.9

Examination of the four-fifths law for longitudinal third-order moments in incompressible magnetohydrodynamic turbulence in a periodic box Reviewed

Katsunori Yoshimatsu

Physical Review E Vol. 85 ( 6 ) page： 066313 2012.6

Intermittency of quasi-static magnetohydrodynamic turbulence: A wavelet viewpoint

N Okamoto, K Yoshimatsu, K Schneider and M Farge

Journal of Physics: Conference Series Vol. 318 page： 072035 2011.12

Intermittency and geometrical statistics of three-dimensional homogeneous magnetohydrodynamic turbulence: A wavelet viewpoint Reviewed

Katsunori Yoshimatsu, Kai Schneider, Naoya Okamoto, Yasuhiro Kawahara, and Marie Farge

PHYSICS OF PLASMAS Vol. 18 ( 9 ) page： 092304 2011.9

Coherent Vorticity Simulation of Three-Dimensional Forced Homogeneous Isotropic Turbulence Reviewed

Naoya Okamoto, Katsunori Yoshimatsu, Kai Schneider, Marie Farge, and Yukio Kaneda

Multiscale Modeling & Simulation Vol. 9 ( 3 ) page： 1144-1161 2011.9

Columnar eddy formation in freely decaying homogeneous rotating turbulence Reviewed

K. Yoshimatsu, M. Midorikawa and Y. Kaneda

Journal of Fluid Mechanics Vol. 677 page： 154-178 2011.6

DIRECTIONAL AND SCALE-DEPENDENT STATISTICS OF QUASI-STATIC MAGNETOHYDRODYNAMIC TURBULENCE Reviewed

Naoya Okamoto, Katsunori Yoshimatsu, Kai Schneider and Marie Farge

ESAIM: Proceedings Vol. 32 page： 95-102 2011

Coherent Vorticity and Current Extraction in Three-Dimensional Homogeneous Magnetohydrodynamic Turbulence: Comparison Between Wavelet and Fourier Filtering

Naoya Okamoto, Katsunori Yoshimatsu, Yuji Kondo, Kai Schneider and Marie Farge

Procs. of V European Conference on ComputationalFluid Dynamics ECCOMAS CFD 2010, J. C. F. Pereira, A. Sequeira and J. M. C. Pereira (Eds) page： 01379_1-12 2010.6

Coherent Vortex Extraction from Three-Dimesional Homogeneous Isotropic Turbulence: Comparison of Wavelet and Fourier Nonlinear Filtering Methods Reviewed

K. Yoshimatsu, N. Okamoto, M. Farge and K. Schneider

Thehoretical and Applied Mechanics Japan Vol. 58 page： 227-233 2010.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Two nonlinear filtering methods for extracting coherent structures from direct numerical simulation data of isotropic turbulence are compared. One is based on the orthonormal wavelet decomposition, called coherent vortex extraction (CVE) method, and the other is based on the Fourier decomposition, called Fourier nonlinear filtering (FNF) method. We examine contributions of structures extracted by applying these methods to turbulent flows. Coherent structures extracted by using the CVE method, reconstructed from only 3.6 % of the degrees of freedom, preserve the vortex tubes as well as statistical quantities of turbulence. In contrast, the structures extracted by using the FNF method, represented by 7.3 % of the degrees of freedom, only well preserve low-order statistical quantities, e.g., energy, enstrophy and the energy spectrum in the inertial range, but smooth out the vortex tubes.

*Wavelet-based coherent vorticity sheet and current sheet extraction from three-dimensional homogeneous magnetohydrodynamic turbulence Reviewed

Katsunori Yoshimatsu, Yuji Kondo, Kai Schneider, Naoya Okamoto, Hiroyuki Hagiwara, and Marie Farge

Physics of Plasmas Vol. 16 ( 8 ) page： 082306-1 - 082306-11 2009.8

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

A method for extracting coherent vorticity sheets and current sheets out of three-dimensional homogeneous magnetohydrodynamic (MHD) turbulence is proposed, which is based on the orthogonal wavelet decomposition of the vorticity and current density fields. Thresholding the
wavelet coefficients allows both fields to be split into coherent and incoherent parts. The fields to be analyzed are obtained by direct numerical simulation (DNS) of forced incompressible MHD turbulence without mean magnetic field, using a classical Fourier spectral method at a resolution of
512^3. Coherent vorticity sheets and current sheets are extracted from the DNS data at a given time instant. It is found that the coherent vorticity and current density preserve both the vorticity sheets and the current sheets present in the total fields while retaining only a few percent of the degrees of freedom. The incoherent vorticity and current density are shown to be structureless and of mainly dissipative nature. The spectral distributions of kinetic and magnetic energies of the coherent fields
only differ in the dissipative range, while the corresponding incoherent fields exhibit near-equipartition of energy. The probability distribution functions of total and coherent fields for both vorticity and current density coincide almost perfectly, while the incoherent fields have
strongly reduced variances. Studying the energy flux confirms that the nonlinear dynamics is fully captured by the coherent fields only.

Wavelet解析による一様等方性電磁流体乱流の秩序構造抽出

近藤祐史、芳松克則、岡本直也、萩原裕之

応用力学研究所研究集会報告 20ME-S6乱流現象及び多自由度系の動力学, 構造と統計法則 page： 16－21 2009.3

*Intermittency and scale-dependent statistics in fully developed turbulence Reviewed

K. Yoshimatsu, N. Okamoto, K. Schneider, Y. Kaneda and M. Farge

Physical Review E Vol. 79 ( 2 ) page： 026303-1 - 026303-5 2009.2

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

Fully developed homogeneous isotropic turbulent fields, computed by direct numerical simulation, are
compared to divergence-free random fields having the same energy spectrum and either the same helicity
spectrum as that of the turbulent data, or vanishing helicity. We show that the scale-dependent velocity flatness
quantifies the spatial variability of the energy spectrum. The flatness exhibits a substantial increase at small
scales for the turbulent field, but remains constant for the random fields. A diagnostic, the scale-dependent
helicity, is proposed to quantify the geometrical statistics of the flow, which shows that only the turbulent flow
is intermittent. Finally, statistical scale-dependent analyses of both Eulerian and Lagrangian accelerations
confirm the inherently different dynamics of turbulent and random flows.

Intermittency in high resolution direct numerical simulation of turbulence in a periodic box: a wavelet viewpoint Reviewed

K. Yoshimatsu, N. Okamoto, K. Schneider, Y. Kaneda and M. Farge

Advances in Turbulence XII, Proceedings of the 12th EUROMECHEuropean Turbulence Conference,September 7-10, 2009, Marburg, Germany, Springer page： 945 2009

Coherent vortex simulation: application to 3D homogeneous isotropic turbulence Reviewed

N. Okamoto, K. Yoshimatsu, K. Schneider, M. Farge and Y. Kaneda

Advances in Turbulence XII, Proceedings of the 12th EUROMECHEuropean Turbulence Conference, September 7–10, 2009, Marburg, Germany, Springer page： 759-762 2009

Wavelet-based statistics of energy transfer in high resolution direct numerical simulation of three-dimensional homogeneous isotropic turbulence Reviewed

K. Yoshimatsu and N. Okamoto

Journal of Turbulence Vol. 9 page： No45, pp.1-25 2008.12

Energy transfer in high Reynolds number three-dimensional homogeneous isotropic turbulence: A wavelet viewpoint Reviewed

N. Okamoto and K. Yoshimatsu

Proceedings of International Symposium onFrontiers of Computational Science 2008, Kaneda, Sasai, Tachibana (Eds), CD-ROM page： 173-180 2008.11

Wavelet-Based Statistics of Energy Transfer in High Reynolds Number Three-Dimensional Homogeneous Isotropic Turbulence Reviewed

N. Okamoto and K. Yoshimatsu

IUTAM Symposium on Computational Physics and New Perspectives in Turbulence page： 155-160 2008.11

Authorship：Lead author Language：English

We examine small-scale statistics of energy transfer from a scale within grid
scales to subgrid scales localized in space and scale in high Reynolds number
fully developed turbulence. An orthonormal wavelet decomposition method
is applied to data of three-dimensional incompressible homogeneous isotropic
turbulence with Taylor microscale Reynolds number 471. We find that the
energy transfer and the kinetic energy localized in space and scale have strong
correlation in the inertial subrange though they are almost uncorrelated in the
dissipation range. The correlation is enhanced by the positive values for the
transfer, while it is reduced by the negative values for the transfer.

高レイノルズ数一様等方性乱流における秩序渦：ウェーブレットの視点から

岡本直也,芳松克則, Kai Schneider, M. Farge, 金田行雄

数理解析研究所考究録 1608 「オイラー方程式250年：連続体力学におけるオイラーの遺産」 Vol. 1608 page： 151-158 2008.7

Coherent vortices formation in homogeneous rotating turbulence: asymmetry between cyclonic and anticyclonic vortices Reviewed

K. Yoshimatsu, M. Midorikawa and Y. Kaneda

Proceedings of International Symposium onFrontiers of Computational Science 2008, Kaneda, Sasai, Tachibana (Eds), CD-ROM page： pp.83-90 2008

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Papers - YOSHIMATSU Katsunori