Updated on 2021/12/28

写真a

 
ISHIHARA Takashi
 
Organization
Faculty of Environmental and Life Science Professor
Position
Professor
Profile
スーパーコンピュータを用いた計算科学の手法と数理科学の新しい手法を駆使して、「乱流現象の解明」を目的とした先端的な研究を実施しています。
External link

Degree

  • Doctor of Engineering ( Nagoya University )

Research Interests

  • CG

  • Spectral method

  • Direct Numerical Simulation

  • Parallel Numerical Computation

  • Fluid Mechanics

  • Computational Science of Turbulence

Research Areas

  • Informatics / Computational science

  • Natural Science / Applied mathematics and statistics

  • Natural Science / Basic mathematics

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Fluid engineering

Education

  • Nagoya University   工学研究科   応用物理学

    - 1994

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    Country: Japan

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Research History

  • Okayama University   Graduate School of Environmental and Life Science   Professor

    2017.8

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  • Nagoya University   Graduate School of Engineering   Associate Professor

    2007.4 - 2017.7

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Professional Memberships

Committee Memberships

  • 日本流体力学会   フェロー会員  

    2020.2   

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    Committee type:Academic society

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  • 日本流体力学会   理事  

    2020.2 - 2022.2   

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    Committee type:Academic society

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  • 日本流体力学会   代議員  

    2017.4 - 2019.3   

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    Committee type:Academic society

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  • 日本流体力学会   代議員  

    2014.4 - 2016.3   

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    Committee type:Academic society

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  • 日本流体力学会   代議員  

    2011.4 - 2013.3   

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    Committee type:Academic society

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Papers

  • Non-local dispersion and the reassessment of Richardson's t3-scaling law Reviewed

    G.E. Elsinga, T. Ishihara, J.C.R. Hunt

    Journal of Fluid Mechanics   932   A17-1 - A17-32   2022.2

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    Publishing type:Research paper (scientific journal)   Publisher:Cambridge University Press (CUP)  

    The Richardson-scaling law states that the mean square separation of a fluid particle pair grows according to <italic>t</italic>3 within the inertial range and at intermediate times. The theories predicting this scaling regime assume that the pair separation is within the inertial range and that the dispersion is local, which means that only eddies at the scale of the separation contribute. These assumptions ignore the structural organization of the turbulent flow into large-scale shear layers, where the intense small-scale motions are bounded by the large-scale energetic motions. Therefore, the large scales contribute to the velocity difference across the small-scale structures. It is shown that, indeed, the pair dispersion inside these layers is highly non-local and approaches Taylor dispersion in a way that is fundamentally different from the Richardson-scaling law. Also, the layer's contribution to the overall mean square separation remains significant as the Reynolds number increases. This calls into question the validity of the theoretical assumptions. Moreover, a literature survey reveals that, so far, <italic>t</italic>3 scaling is not observed for initial separations within the inertial range. We propose that the intermediate pair dispersion regime is a transition region that connects the initial Batchelor- with the final Taylor-dispersion regime. Such a simple interpretation is shown to be consistent with observations and is able to explain why <italic>t</italic>3 scaling is found only for one specific initial separation outside the inertial range. Moreover, the model incorporates the observed non-local contribution to the dispersion, because it requires only small-time-scale properties and large-scale properties.

    DOI: 10.1017/jfm.2021.989

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  • Statistics of local Reynolds number in box turbulence: ratio of inertial to viscous forces Reviewed

    Yukio Kaneda, Takashi Ishihara, Koji Morishita, Mitsuo Yokokawa, Atsuya Uno

    Journal of Fluid Mechanics   929   A1-1 - A1-19   2021.12

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    Publishing type:Research paper (scientific journal)   Publisher:Cambridge University Press (CUP)  

    In high-Reynolds-number turbulence the spatial distribution of velocity fluctuation at small scales is strongly non-uniform. In accordance with the non-uniformity, the distributions of the inertial and viscous forces are also non-uniform. According to direct numerical simulation (DNS) of forced turbulence of an incompressible fluid obeying the Navier–Stokes equation in a periodic box at the Taylor microscale Reynolds number <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline1.png" />
    <tex-math>$R_\lambda \approx 1100$</tex-math>
    </alternatives>
    </inline-formula>, the average <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline2.png" />
    <tex-math>$\langle R_{loc}\rangle$</tex-math>
    </alternatives>
    </inline-formula> over the space of the ‘local Reynolds number’ <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline3.png" />
    <tex-math>$R_ {loc}$</tex-math>
    </alternatives>
    </inline-formula>, which is defined as the ratio of inertial to viscous forces at each point in the flow, is much smaller than the conventional ‘Reynolds number’ given by <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline4.png" />
    <tex-math>$Re \equiv UL/\nu$</tex-math>
    </alternatives>
    </inline-formula>, where <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline5.png" />
    <tex-math>$U$</tex-math>
    </alternatives>
    </inline-formula> and <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline6.png" />
    <tex-math>$L$</tex-math>
    </alternatives>
    </inline-formula> are the characteristic velocity and length of the energy-containing eddies, and <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline7.png" />
    <tex-math>$\nu$</tex-math>
    </alternatives>
    </inline-formula> is the kinematic viscosity. While both conditional averages of the inertial and viscous forces for a given squared vorticity <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline8.png" />
    <tex-math>$\omega ^{2}$</tex-math>
    </alternatives>
    </inline-formula> increase with <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline9.png" />
    <tex-math>$\omega ^{2}$</tex-math>
    </alternatives>
    </inline-formula> at large <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline10.png" />
    <tex-math>$\omega ^{2}$</tex-math>
    </alternatives>
    </inline-formula>, the conditional average of <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline11.png" />
    <tex-math>$R_ {loc}$</tex-math>
    </alternatives>
    </inline-formula> is almost independent of <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline12.png" />
    <tex-math>$\omega ^{2}$</tex-math>
    </alternatives>
    </inline-formula>. A comparison of the DNS field with a random structureless velocity field suggests that the increase in the conditional average of <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline13.png" />
    <tex-math>$R_ {loc}$</tex-math>
    </alternatives>
    </inline-formula> with <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline14.png" />
    <tex-math>$\omega ^{2}$</tex-math>
    </alternatives>
    </inline-formula> at large <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline15.png" />
    <tex-math>$\omega ^{2}$</tex-math>
    </alternatives>
    </inline-formula> is suppressed by the Navier–Stokes dynamics. Something similar is also true for the conditional averages for a given local energy dissipation rate per unit mass. Certain features of intermittency effects such as that on the <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline16.png" />
    <tex-math>$Re$</tex-math>
    </alternatives>
    </inline-formula> dependence of <inline-formula>
    <alternatives>
    <inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0022112021008065_inline17.png" />
    <tex-math>$\langle R_{loc}\rangle$</tex-math>
    </alternatives>
    </inline-formula> are explained by a multi-fractal model by Dubrulle (<italic>J. Fluid Mech.</italic>, vol. 867, 2019, P1).

    DOI: 10.1017/jfm.2021.806

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  • Effects of the Compressibility of Turbulence on the Dust Coagulation Process in Protoplanetary Disks Reviewed

    Yoshiki Sakurai, Takashi Ishihara, Hitomi Furuya, Masayuki Umemura, Kenji Shiraishi

    The Astrophysical Journal   911 ( 2 )   140 - 140   2021.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Astronomical Society  

    Planetesimals are believed to be formed by the coagulation of dust grains in the protoplanetary disk turbulence. However, the bouncing and fragmentation barriers have not been completely solved, particularly for silicate dust. To circumvent these barriers, the turbulent clustering of dust particles must be properly treated. According to the minimum-mass solar nebula (MMSN) model, the Mach number of the turbulence ranges from Mrms ; 0.01–0.32, and thus the turbulence is often regarded as essentially incompressible. However, it has not been quantitatively investigated whether the incompressible limit is adequate for protoplanetary disk simulations. We therefore compare in this study the motions of inertial particles in direct numerical simulations (DNSs) of the Navier–Stokes equation between weakly compressible turbulence and incompressible turbulence. In the DNSs of compressible turbulence, we use an external force to set the total dissipation and the dilatational-to-solenoidal dissipation ratio. The DNSs reveal that despite the small Mach number Mrms(≾ 0.3), the compressible turbulence field notably differs from the incompressible field in terms of the density fluctuations, pressure fluctuations, and shocklet generation, depending on the ratio of the dilatational forcing. However, we quantitatively confirmed that these effects on the particle collision statistics are weak and that the motion of inertial particles in weakly compressible turbulence is dominated by the solenoidal velocity components. Therefore we can conclude that the incompressible assumption is appropriate for an investigation of the dust coagulation process in protoplanetary disk turbulence, as assumed in the MMSN model.

    DOI: 10.3847/1538-4357/abe9ba

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    Other Link: https://iopscience.iop.org/article/10.3847/1538-4357/abe9ba/pdf

  • Thin Shear Layers in High-resolution Direct Numerical Simulations of Turbulence

    Takashi Ishihara, Koji Morishita, J. C.R. Hunt

    Notes on Numerical Fluid Mechanics and Multidisciplinary Design   147   517 - 526   2021

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    Publishing type:Part of collection (book)  

    Recent studies based on high-resolution direct numerical simulations (DNSs) of turbulence have shown that there are three different types of shear layers in homogeneous and inhomogeneous turbulent flows; at the outer edge (T/NT), in the interior (T/T) and within the buffer layer near the wall (T/W). All the layers play important roles in various turbulence phenomena in the fields of natural sciences and engineering applications. Data analyses showed that all the shear layers act as a barrier of the velocity fluctuations by blocking velocity fluctuations from the one side to the other side. It was suggested that the blocking mechanism of thin turbulent wall (T/W) layers can be used to control the turbulent wake of aerofoils. For high Reynolds number, flows over typical aerofoils at low angle of incidence in the thin turbulent boundary layers (TBLs) have a conditional structure with thin T/W layers which act as a barrier to eddies in the outer part of the TBL. Recent studies indicate that using disturbance—devices at the airfoil surface enhances the blocking effect of the TW barrier and leads—unexpectedly-to reduced shear fluctuations at the wall. This suggests that deeper understanding of the structures and properties of the T/W layers may provide ideas to consider the better strategies for aerofoils designs. In this paper, we review the recent studies on the three different types of shear layers, which are based on the high-resolution DNSs of homogeneous isotropic turbulence (HIT), turbulent boundary layer (TBL), and turbulent channel flow (TCF).

    DOI: 10.1007/978-3-030-55594-8_43

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  • Optimizations of DNS Codes for Turbulence on SX-Aurora TSUBASA

    Yujiro Takenaka, Mitsuo Yokokawa, Takashi Ishihara, Kazuhiko Komatsu, Hiroaki Kobayashi

    Sustained Simulation Performance 2019 and 2020   51 - 59   2021

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    Publishing type:Part of collection (book)   Publisher:Springer International Publishing  

    DOI: 10.1007/978-3-030-68049-7_4

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  • Drastic Changes of Turbulence in the Ignition Process of an n-Heptane/Air Mixture

    Takashi Ishihara, Ryousuke Kuno

    Lecture Notes in Mechanical Engineering   205 - 209   2021

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    Publishing type:Research paper (international conference proceedings)  

    Two-dimensional turbulent combustion with rapid temperature and pressure growth in the ignition process of a homogeneous n-heptane/air mixture is studied by high-resolution direct numerical simulations (DNSs) of the flow field of the mixture with up to 20482 grid points. The DNSs show that the turbulent flow mixes the temperature field so that it affects on the ignition delay. The DNSs show also that the rapid temperature and pressure growth due to the heat release at ignition makes drastic changes in the turbulent velocity field, especially in its compressible component, and causes pressure oscillations in some cases.

    DOI: 10.1007/978-981-33-4960-5_32

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  • Extreme dissipation and intermittency in turbulence at very high Reynolds numbers Reviewed

    Gerrit E. Elsinga, Takashi Ishihara, Julian C. R. Hunt

    Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences   476 ( 2243 )   20200591 - 20200591   2020.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Royal Society  

    Extreme dissipation events in turbulent flows are rare, but they can be orders of magnitude stronger than the mean dissipation rate. Despite its importance in many small-scale physical processes, there is presently no accurate theory or model for predicting the extrema as a function of the Reynolds number. Here, we introduce a new model for the dissipation probability density function (PDF) based on the concept of significant shear layers, which are thin regions of elevated local mean dissipation. At very high Reynolds numbers, these significant shear layers develop layered substructures. The flow domain is divided into the different layer regions and a background region, each with their own PDF of dissipation. The volume-weighted regional PDFs are combined to obtain the overall PDF, which is subsequently used to determine the dissipation variance and maximum. The model yields Reynolds number scalings for the dissipation maximum and variance, which are in agreement with the available data. Moreover, the power law scaling exponent is found to increase gradually with the Reynolds numbers, which is also consistent with the data. The increasing exponent is shown to have profound implications for turbulence at atmospheric and astrophysical Reynolds numbers. The present results strongly suggest that intermittent significant shear layer structures are key to understanding and quantifying the dissipation extremes, and, more generally, extreme velocity gradients.

    DOI: 10.1098/rspa.2020.0591

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    Other Link: https://royalsocietypublishing.org/doi/full-xml/10.1098/rspa.2020.0591

  • Second-order velocity structure functions in direct numerical simulations of turbulence with Rλ up to 2250 Reviewed

    Takashi Ishihara, Yukio Kaneda, Koji Morishita, Mitsuo Yokokawa, Atsuya Uno

    Physical Review Fluids   5 ( 10 )   104608-1 - 104608-15   2020.10

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    We report results of a series of high-resolution direct numerical simulations (DNSs) of forced incompressible isotropic turbulence with the number of grid points and the Taylor scale Reynolds number Rλ up to 122883 and ∼2250, respectively. The DNSs show that there exists a scaling range (approximately 100<r/η<400), at which the second-order two-point velocity structure functions S2(r) fit well with a simple power-law, S2(r)/(ϵr)2/3=C2(r/L0)ζ, where r is the distance between the two points, η is the Kolmogorov length scale, ϵ is the mean rate of energy dissipation per unit mass, and L0 is the integral length scale. The exponent ζ is constant independent from Rλ. However, the coefficient C2 is dependent of Rλ or the viscosity. This implies that the power-law scaling range of 100<r/η<400 for Rλ up to ∼2250 is not the so-called "inertial subrange"in the sense that the statistics in the range are independent from the viscosity, as assumed in various turbulence theories. This suggests that the constancy of the scaling exponent of a structure function within a certain range does not necessarily mean that the exponent is the scaling exponent in "the inertial subrange."

    DOI: 10.1103/physrevfluids.5.104608

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevFluids.5.104608/fulltext

  • Thin shear layers in high Reynolds number turbulence - DNS results

    T. Ishihara, J. C.R. Hunt, Y. Kaneda

    ETC 2013 - 14th European Turbulence Conference   2020

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    Publishing type:Research paper (international conference proceedings)  

    Data analysis of high resolution DNS of isotropic turbulence with the Taylor micro-scale Reynolds number Rλ = 1131 on 40963 grid points shows that there are significant thin shear layers of thickness of the order of Taylor micro-scale, consisting of a cluster of strong vortex tubes with typical diameter of order 10η (η is the Kolmogorov length scale). There are big velocity jumps of the order of the rms of the fluctuation velocity across the layers. The locally averaged energy dissipation rate in the layers is much greater than the mean energy dissipation rate, and contributes disproportionately to the overall mean dissipation rate. Up scale and down scale energy transfer to small eddies is largest within and just outside these layers (where the most intense vortices and dissipation occur). The statistics (based on a systematic study) of the layers will be presented and their Reynolds number dependence will be discussed.

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  • Thin shear layers in high Reynolds number turbulence - A coherent-structure model

    J. C.R. Hunt, T. Ishihara, Y. Kaneda

    ETC 2013 - 14th European Turbulence Conference   2020

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    Publishing type:Research paper (international conference proceedings)  

    Direct numerical simulations of homogeneous isotropic turbulence at the Taylor microscale Reynolds number of order 103 show that the most energetic small scale motions and places with the most intense dissipation in the homogeneous isotropic turbulence are highly inhomogeneous and are located inside thin shear layers. We propose a local mechanism for how the most intense small scale and dissipative motions are produced in the vicinity of well separated thin shear layers. A model is developed based on a local rapid distortion analysis and the Townsend-Obukhov energy transfer hypothesis which is consistent with the data of the numerical simulation.

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  • Dynamic geometrical analysis of high-enstrophy structures in isotropic turbulence

    Yuji Hattori, Takashi Ishihara

    ETC 2013 - 14th European Turbulence Conference   2020

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    Publishing type:Research paper (international conference proceedings)  

    The time evolution of fine-scale tube-like vortical structures in isotropic turbulence is investigated by dynamic geometrical analysis. Our method successfully captures series of events like deformation, creation, extinction, merging and fission of the vortical structures. It is found that extinction and fission are more frequent than creation and merging, respectively.

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  • Estimation of turbulence-development by a multifractal theory

    Toshihico Arimitsu, Naoko Arimitsu, Kohei Takechi, Yukio Kaneda, Takashi Ishihara

    ETC 2013 - 14th European Turbulence Conference   2020

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    Publishing type:Research paper (international conference proceedings)  

    It is shown for the first time how the degree of development in turbulence, i.e., if it is fully developed or if not how much developed, can be estimated by the multifractal theory called multifractal probability density function theory (MPDFT) [1]. Precise and self-consistent analyses of 40963 DNS turbulence [2] by means of MPDFT reveal that the turbulence with Rλ = 675 is in the fully developed turbulent state, but that the one with Rλ = 1132 is not fully developed yet. The degree of turbulence-development of the latter is estimated.

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  • Performance of a Two-Path Aliasing Free Calculation of a Spectral DNS Code Reviewed

    Mitsuo Yokokawa, Koji Morishita, Takashi Ishihara, Atsuya Uno, Yukio Kaneda

    ICCS 2019. Lecture Notes in Computer Science   11539   587 - 595   2019.6

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    Publishing type:Research paper (international conference proceedings)  

    A direct numerical simulation (DNS) code was developed for solving incompressible homogeneous isotropic turbulence with high Reynolds numbers in a periodic box using the Fourier spectral method. The code was parallelized using the Message Passing Interface and OpenMP with two-directional domain decomposition and optimized on the K computer. High resolution DNSs with up to grid points were performed on the K computer using the code. Efficiencies of 3.84%, 3.14%, and 2.24% peak performance were obtained in double precision DNSs with grid points, respectively. In addition, a two-path alias-free procedure is proposed and clarified its effectiveness for some number of parallel processes.

    DOI: 10.1007/978-3-030-22747-0_44

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  • Length Scales in Turbulent Channel Flow Reviewed

    K Morishita, T Ishihara, Y Kaneda

    Journal of the Physical Society of Japan   88 ( 6 )   064401   2019.5

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    Language:English   Publishing type:Research paper (scientific journal)  

    The position- and direction-dependence of length scales in turbulent channel flow was studied using the data from a series of direct numerical simulations (DNSs) of turbulent channel flow with the wall Reynolds number and the number of grid points ranging up to 5120 and 2048 × 1536 × 2048, respectively. According to the DNSs, there is a region of y in which the mean flow profile fits well with the log-law (log-law region), where y is the distance from the wall. The Taylor microscale is anisotropic, but has a simple y-dependence (∝ y1=2) in this region. The two-point fluctuating-velocity correlation at ∣r∣ ∼ y is also anisotropic and approximately depends on r through r=‘ðyÞ, where r is the displacement vector between two points, ‘ðyÞ is a function of only y, and ‘ðyÞ is close to, but not exactly equal to y.

    DOI: 10.7566/JPSJ.88.064401

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  • Relationships between Small-scale Fluid Motions and Inertial Particle Clustering in Turbulence Reviewed

    Yoshiki Sakurai, Takashi Ishihara

    Journal of the Physical Society of Japan   87 ( 9 )   093401 - 0934014   2018.8

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    Authorship:Last author   Publishing type:Research paper (scientific journal)  

    To quantitatively study the relationships between small-scale fluid motions and inertial particle clustering in turbulence, we track inertial particles in a turbulent flow through a direct numerical simulation of the forced incompressible Navier–Stokes equations. Further, we investigate the particle distribution in the eigenframe of the rate-of-strain tensor of the turbulent velocity field. The unconditional averages of the particle densities in the eigenframe demonstrate that the particle distribution exhibits specific patterns. In addition, the conditional averages in high-vorticity regions show that a strong vortex anisotropically generates low- and high-number-density regions depending on particle inertia.

    DOI: 10.7566/JPSJ.87.093401

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  • Dust Coagulation Regulated by Turbulent Clustering in Protoplanetary Disks Reviewed

    Takashi Ishihara, Naoki Kobayashi, Kei Enohata, Masayuki Umemura, Kenji Shiraishi

    ASTROPHYSICAL JOURNAL   854 ( 2 )   81   2018.2

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    The coagulation of dust particles is a key process in planetesimal formation. However, the radial drift and bouncing barriers are not completely resolved, especially for silicate dust. Since the collision velocities of dust particles are regulated by turbulence in a protoplanetary disk, turbulent clustering should be properly treated. To that end, direct numerical simulations (DNSs) of the Navier-Stokes equations are requisite. In a series of papers, Pan & Padoan used a DNS with Reynolds number Re similar to 1000. Here, we perform DNSs with up to Re = 16,100, which allow us to track the motion of particles with Stokes numbers of 0.01 less than or similar to St less than or similar to 0.2 in the inertial range. Through the DNSs, we confirm that the rms relative velocity of particle pairs is smaller by more than a factor of two, compared to that by Ormel & Cuzzi. The distributions of the radial relative velocities are highly non-Gaussian. The results are almost consistent with those by Pan & Padoan or Pan et al. at low Re. Also, we find that the sticking rates for equal-sized particles are much higher than those for different-sized particles. Even in the strong-turbulence case with alpha-viscosity of 10(-2), the sticking rates are as high as greater than or similar to 50% and the bouncing probabilities are as low as similar to 10% for equal-sized particles of St less than or similar to 0.01. Thus, turbulent clustering plays a significant role in the growth of centimetersized compact aggregates (pebbles) and also enhances the solid abundance, which may lead to the streaming instability in a disk.

    DOI: 10.3847/1538-4357/aaa976

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  • The scaling of straining motions in homogeneous isotropic turbulence Reviewed

    GE Elsinga, T Ishihara, MV Goudar, CB da Silva, JCR Hunt

    Journal of Fluid Mechanics   829   31 - 64   2017.9

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    Language:English   Publishing type:Research paper (scientific journal)  

    The scaling of turbulent motions is investigated by considering the flow in the eigenframe of the local strain-rate tensor. The flow patterns in this frame of reference are evaluated using existing direct numerical simulations of homogeneous isotropic turbulence over a Reynolds number range from Reλ=34:6 up to 1131, and also with reference to data for inhomogeneous, anisotropic wall turbulence. The average flow in the eigenframe reveals a shear layer structure containing tube-like vortices and a dissipation sheet, whose dimensions scale with the Kolmogorov length scale. The vorticity stretching motions scale with the Taylor length scale, λT , while the flow outside the shear layer scales with the integral length scale, L. Furthermore, the spatial organization of the vortices and the dissipation sheet defines a characteristic small-scale structure. The overall size of this characteristic small-scale structure is 120in all directions based on the coherence length of the vorticity. This is considerably larger than the typical size of individual vortices, and reflects the importance of spatial organization at the small scales. Comparing the overall size of the characteristic small-scale structure with the largest flow scales and the vorticity stretching motions on the scale of 4λT shows that transitions in flow structure occur where Reλ∼45 and 250. Below these respective transitional Reynolds numbers, the small-scale motions and the vorticity stretching motions are progressively less well developed. Scale interactions are examined by decomposing the average shear layer into a local flow, which is induced by the shear layer vorticity, and a non-local flow, which represents the environment of the characteristic small-scale structure. The non-local strain is 4λT in width and height, which is consistent with observations in high Reynolds number flow of a 4λT wide instantaneous shear layer with many -scale vortical structures inside (Ishihara et al., Flow Turbul. Combust., vol. 91, 2013, pp. 895-929). In the average shear layer, vorticity aligns with the intermediate principal strain at small scales, while it aligns with the most stretching principal strain at larger scales, consistent with instantaneous turbulence. The length scale at which the alignment changes depends on the Reynolds number. When conditioning the flow in the eigenframe on extreme dissipation, the velocity is strongly affected over large distances. Moreover, the associated peak velocity remains Reynolds number dependent when normalized by the Kolmogorov velocity scale. It signifies that extreme dissipation is not simply a small-scale property, but is associated with large scales at the same time.

    DOI: 10.1017/jfm.2017.538

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  • Coherent structure extraction in turbulent channel flow using boundary adapted wavelets Reviewed

    Teluo Sakurai, Katsunori Yoshimatsu, Kai Schneider, Marie Farge, Koji Morishita, Takashi Ishihara

    JOURNAL OF TURBULENCE   18 ( 4 )   352 - 372   2017

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    We introduce boundary adaptedwavelets, which are orthogonal and have the same scale in the three spatial directions. The construction thus yields a multiresolution analysis. We analyse direct numerical simulation data of turbulent channel flow computed at a friction Reynolds number of 395, and investigate the role of coherent vorticity. Thresholding of the vorticity wavelet coefficients allows us to split the flow into two parts, coherent and incoherent flows. The coherent vorticity is reconstructed fromits few intensewavelet coefficients and the coherent velocity is reconstructed using Biot-Savart's law. The statistics of the coherent flow, i.e. energy and enstrophy spectra, are close to the statistics of the total flow, and moreover, the nonlinear energy budgets of the total flow are very well preserved. The remaining incoherent part, represented by the large majority of the weak wavelet coefficients, corresponds to a structureless, i.e. noise-like, background flow whose energy is equidistributed.

    DOI: 10.1080/14685248.2017.1284326

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  • Energy spectrum in high-resolution direct numerical simulations of turbulence Reviewed

    Takashi Ishihara, Koji Morishita, Mitsuo Yokokawa, Atsuya Uno, Yukio Kaneda

    PHYSICAL REVIEW FLUIDS   1 ( 8 )   082403   2016.12

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    A study is made about the energy spectrum E(k) of turbulence on the basis of highresolution direct numerical simulations (DNSs) of forced incompressible turbulence in a periodic box using a Fourier spectral method with the number of grid points and the Taylor scale Reynolds number R-lambda up to 12 288(3) and approximately 2300, respectively. The DNS data show that there is a wave-number range (approximately 5 x 10(-3) < k eta< 2 x 10(-2)) in which E(k) fits approximately well to Kolmogorov's k(-5/3) scaling, where eta is the Kolmogorov length scale. However, a close inspection shows that the exponent is a little smaller than -5/3, and E(k) in the range fits to E(k)/[<is an element of >(2/3)k(-5/3)] = c(kL)(m), where <is an element of > is the mean energy dissipation rate per unit mass; L is the integral length scale; and m approximate to -0.12. The coefficient c is independent of k, but has a R-lambda dependence, such as c = CR lambda zeta, where C approximate to 0.9 and zeta approximate to 0.14.

    DOI: 10.1103/PhysRevFluids.1.082403

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  • A new statistical tool to study the geometry of intense vorticity clusters in turbulence Reviewed

    Alberto Vela-Martin, Takashi Ishihara

    2ND MULTIFLOW SUMMER SCHOOL ON TURBULENCE   708 ( 708 )   012004   2016

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    Recent large-scale direct numerical simulations (DNS) of high-Reynolds number (high-Re) turbulence, suggest that strong micro-scale tube-like vortices form clusters in localized thin regions of space. However, to this date no thorough quantitative and statistical analysis of the geometry of such vortical clusters has been conducted. This study is intended to generate new statistical tools to study the shape and dynamics of these intense vorticity and strain regions. We first propose a new method for locating and analysing the geometrical properties of thresholded vortical clusters contained inside boxes of a given size. Second, we use this new tool to investigate the natural presence of intense shear layers and their relevance as geometrical features of high-Re homogeneous turbulence. This new method is applied to the DNS of homogeneous incompressible turbulence with up to 40963 grid points, showing that the geometry of high vorticity regions varies strongly depending on the threshold and on the size of the clusters. In particular for sizes in the inertial range of scales and high thresholds, approximately layer-like structures of vortices are extracted and visualized. Agreement of results with previous observations and known features of turbulence supports the validity of the proposed method to characterize the geometry of intense vorticity and strain regions in high-Re turbulence.

    DOI: 10.1088/1742-6596/708/1/012004

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  • Turbulence Near Interfaces-Modelling and Simulations Reviewed

    J. C. R. Hunt, T. Ishihara, D. Szubert, I. Asproulias, Y. Hoarau, M. Braza

    ADVANCES IN FLUID-STRUCTURE INTERACTION   133 ( 133 )   283 - 292   2016

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    DOI: 10.1007/978-3-319-27386-0_17

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  • 高レイノルズ数乱流中の渦の組織構造とその時間発展

    石原 卓, 宇野 篤也, 森下 浩二, YOKOKAWA MITSUO, 金田 行雄

    第29回数値流体力学シンポジウム講演論文集   2015   1 - 5   2015.12

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    High vorticity regions obtained by the large-scale direct numerical simulations with up to 122883 grid points, of forced incompressible turbulence in a periodic box are visualized using the method developed for handling such large-scale data. The visualization shows that in high Reynolds number turbulence, strong micro-scale vortices are dense in clusters of various sizes up to

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  • Analysis of conditional statistics obtained near the turbulent/non-turbulent interface of turbulent boundary layers Reviewed

    Takashi Ishihara, Hiroki Ogasawara, Julian C. R. Hunt

    JOURNAL OF FLUIDS AND STRUCTURES   53   50 - 57   2015.2

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    Direct numerical simulations of turbulent boundary layers (TBL) along a flat plate are used to study the properties of turbulent/non-turbulent (T/NT) interface of the TBL. The values of the momentum-thickness-based Reynolds numbers, Re-theta, used for this study, are 500-2200. Analysis of the conditional statistics near the interface of the TBL shows that there are a small peak in the spanwise voracity, and an associated small jump in streamwise velocity. It is shown that the interfacial layer has an inertia-viscous double structure which consists of a turbulent sublayer with a thickness of the order of the Taylor micro-scale and its outer boundary with a thickness of the order of the Kolmogorov length scale. The velocity jump near the TINT interface of the TBL is of the order of the rms value of velocity fluctuations near the interface. Conditional cross correlations of the streamwise or the wall-normal velocity fluctuations change sharply across the interface, which are consistent with the blocking mechanism of the interface. 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license

    DOI: 10.1016/j.jfluidstructs.2014.10.008

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  • Accurate Parallel Algorithm for Tracking Inertial Particles in Large-Scale Direct Numerical Simulations of Turbulence

    Takashi Ishihara, Kei Enohata, Koji Morishita, Mitsuo Yokokawa, Katsuya Ishii

    PARALLEL COMPUTING TECHNOLOGIES (PACT 2015)   9251   522 - 527   2015

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    Statistics on the motion of small heavy (inertial) particles in turbulent flows with a high Reynolds number are physically fundamental to understanding realistic turbulent diffusion phenomena. An accurate parallel algorithm for tracking particles in large-scale direct numerical simulations (DNSs) of turbulence in a periodic box has been developed to extract accurate statistics on the motion of inertial particles. The tracking accuracy of the particle motion is known to primarily depend on the spatial resolution of the DNS for the turbulence and the accuracy of the interpolation scheme used to calculate the fluid velocity at the particle position. In this study, a DNS code based on the Fourier spectral method and two-dimensional domain decomposition method was developed and optimised for the K computer. An interpolation scheme based on cubic splines is implemented by solving tridiagonal matrix problems in parallel.

    DOI: 10.1007/978-3-319-21909-7_51

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  • External and Internal interfacial turbulent shear layers

    Julian Hunt, Takashi Ishihara, Jerke Eisma, Wim Paul Breugen, Jerry Westerweel, Marianna Braza

    Proceedings - 15th European Turbulence Conference, ETC 2015   2015

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    Simulation, PIV data, and local models show characteristics and conditional statistics of turbulence either side and within interfacial layers [I] depending on the mean profile and the presence of resistive/porous walls. Key words; turbulence, interface structure, conditional statistics, numerical models

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  • ノルマルヘプタン予混合自己着火過程に対する温度非一様性及び乱流の影響の直接数値計算による解析 Reviewed

    石原 卓, 伊藤 貴政, 三木 貴史, 芳松 克則, 寺地 淳

    日本機械学会論文集   80 ( 820 )   1-9   2014.12

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    DOI: 10.1299/transjsme.2014tep0

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  • Thin Shear Layer Structures in High Reynolds Number Turbulence Tomographic Experiments and a Local Distortion Model

    Julian C. R. Hunt, Takashi Ishihara, Nicholas A. Worth, Yukio Kaneda

    FLOW TURBULENCE AND COMBUSTION   92 ( 3 )   607 - 649   2014.3

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    Three-dimensional tomographic time dependent PIV measurements of high Reynolds number (Re) laboratory turbulence are presented which show the existence of long-lived, highly sheared thin layer eddy structures with thickness of the order of the Taylor microscale and internal fluctuations. Highly sheared layer structures are also observed in direct numerical simulations of homogeneous turbulence at higher values of Re (Ishihara et al., Annu Rev Fluid Mech 41:165-180, 2009). But in the latter simulation, where the fluctuations are more intense, the layer thickness is greater. A rapid distortion model describes the structure and spectra for the velocity fluctuations outside and within 'significant' layers; their spectra are similar to the Kolmogorov (C R Acad Sci URSS 30:299-303, 1941) and Obukhov (Dokl Akad Nauk SSSR 32:22-24, 1941) statistical model (KO) for the whole flow. As larger-scale eddy motions are blocked by the shear layers, they distort smaller-scale eddies leading to local zones of down-scale and up-scale transfer of energy. Thence the energy spectrum for high wave number k is . The exponent p depends on the forms of the large eddies. The non-linear interactions between the distorted inhomogeneous eddies produce a steady local structure, which implies that 2p = 5/3 and a flux of energy into the thin-layers balancing the intense dissipation, which is much greater than the mean . Thence as in KO. Within the thin layers the inward flux energises extended vortices whose thickness and spacing are comparable with the viscous microscale. Although peak values of vorticity and velocity of these vortices greatly exceed those based on the KO scaling, the form of the viscous range spectrum is consistent with their model.

    DOI: 10.1007/s10494-013-9518-0

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  • Thin Shear Layers in High Reynolds Number Turbulence-DNS Results Reviewed

    Takashi Ishihara, Yukio Kaneda, Julian C. R. Hunt

    FLOW TURBULENCE AND COMBUSTION   91 ( 4 )   895 - 929   2013.12

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    Using direct numerical simulation of turbulence in a periodic box driven by homogeneous forcing, with a maximum of 4096(3) grid points and Taylor micro-scale Reynolds numbers R (lambda) up to 1131, it is shown that there is a transition in the forms of the significant, high vorticity, intermittent structures, from isolated vortices when R (lambda) is less than 10(2) to complex thin-shear layers when R (lambda) exceeds about 10(3). Both the distance between the layers and their widths are comparable with the integral length scale. The thickness of each of the layers is of the order of the Taylor micro-scale lambda. Across the layers the velocity 'jumps' are of the order of the rms velocity u (o) of the whole flow. Within the significant layers, elongated vortical eddies are generated, with microscale thickness a"" (v) similar to 10 eta a parts per thousand(a)aEuro parts per thousand lambda, with associated peak values of vorticity as large as 35 omega (rms) and with velocity jumps as large as 3.4u (o) , where eta is the Kolmogorov micro scale and omega (rms) the rms vorticity. The dominant vortical eddies in the layers, which are approximately parallel to the vorticity averaged over the layers, are separated by distances of order a"" (v) . The close packing leads to high average energy dissipation inside the layer, as large as ten times the mean rate of energy dissipation over the whole flow. The interfaces of the layers act partly as a barrier to the fluctuations outside the layer. However, there is a net energy flux into the small scale eddies within the thin layers from the larger scale motions outside the layer.

    DOI: 10.1007/s10494-013-9499-z

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  • 3D DNS analysis of interaction between turbulence and chemical reaction in an auto-ignition process under homogeneous n-heptane mixture Reviewed

    Atsushi Teraji, Hironari Ikuta, Takashi Miki, Takashi Ishihara

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B   79 ( 799 )   431 - 438   2013

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    The role of turbulence in the combustion systems of flame propagation and diffusion combustion is to mix burned region with unburned region to promote combustion. Meanwhile homogeneous charged compression ignition (HCCI) is a combustion system which goes through the chemical reaction in overall field. It makes no rigid distinction between unburned region and burned region, and differs from the systems of flame propagation and diffusion combustion. Therefore, the role of turbulence in HCCI differs from other combustion systems. Three-dimensional direct numerical simulation (DNS) of auto-ignition process of n-heptane/air mixture was performed to analyze the interaction between chemical reaction and turbulence. In conclusions, the progress of chemical reaction delays under the area where rotation dominants in comparion with the area where distortion dominants under higher temperature region. Turbulence makes complicated structure of heat release which includes sheet and coherent structures. ©2013 The Japan Society of Mechanical Engineers.

    DOI: 10.1299/kikaib.79.431

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  • Small-scale statistics in direct numerical simulation of turbulent channel flow at high-Reynolds number Reviewed

    Koji Morishita, Takashi Ishihara, Yukio Kaneda

    13TH EUROPEAN TURBULENCE CONFERENCE (ETC13): WALL-BOUNDED FLOWS AND CONTROL OF TURBULENCE   318 ( SECTION 2 )   022016   2011

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    Small-scale statistics in turbulent channel flow are studied by high resolution direct numerical simulations with the friction Reynolds number up to Re-tau = 2560. The second order velocity statistics in the inertial subrange of the log-low region are found to be not far from those predicted by Kolmogorov's universal equilibrium theory, although the agreement is not perfect. The shear parameter S* decreases with the distance y(+) from the wall and S* less than or similar to 0.1 in y(+) &gt; 400 for large Re-tau, where S* is the ratio of the Kolmogorov time scale to the mean shear time scale. For larger Re-tau, the y(+)-dependence of S* is closer to a simple theoretical estimate in the log-low region.

    DOI: 10.1088/1742-6596/318/2/022016

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  • Conditional analysis near strong shear layers in DNS of isotropic turbulence at high Reynolds number Reviewed

    Takashi Ishihara, Julian C. R. Hunt, Yukio Kaneda

    13TH EUROPEAN TURBULENCE CONFERENCE (ETC13): STATISTICAL ASPECTS, MODELLING AND SIMULATIONS OF TURBULENCE   318 ( SECTION 4 )   042004   2011

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    Data analysis of high resolution DNS of isotropic turbulence with the Taylor scale Reynolds number R-lambda = 1131 shows that there are thin shear layers consisting of a cluster of strong vortex tubes with typical diameter of order 10 eta, where eta is the Kolmogorov length scale. The widths of the layers are of the order of the Taylor micro length scale. According to the analysis of one of the layers, coarse grained vorticity in the layer are aligned approximately in the plane of the layer so that there is a net mean shear across the layer with a mean velocity jump of the order of the root-mean-square of the fluctuating velocity, and energy dissipation averaged over the layer is larger than ten times the average over the whole flow. The mean and the standard deviation of the energy transfer T(x, k) from scales larger than 1/k to scales smaller than 1/k at position x are largest within the layers (where the most intense vortices and dissipation occur), but are also large just outside the layers (where viscous stresses are weak), by comparison with the average values of T over the whole region. The DNS data are consistent with exterior fluctuation being damped/filtered at the interface of the layer and then selectively amplified within the layer.

    DOI: 10.1088/1742-6596/318/4/042004

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  • Numerical analysis of intermediate species diffusion effect on low temperature oxidation in a homogeneous n-heptane mixture Reviewed

    Atsushi Teraji, Masashi Nishida, Takahiro Morikawa, Takashi Ishihara, Yukio Kaneda

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B   77 ( 779 )   1592 - 1600   2011

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    Two-dimensional direct numerical simulation (DNS) was applied to auto-ignition of n-heptane/air mixture. The diffusion of intermediate species was studied in terms of the influence on the ignition delay. The chemical reaction process. The simplified reaction mechanism was used in this study. Likewise, the influence of turbulence was investigated by comparing the results of 0 dimensional simulation and two-dimensional direct simulation of non-turbulence condition. In conclusions, the ignition delay was strongly affected by the different diffusion speeds of intermediate species. It was shown that the outflow of OH radical having larger diffusion coefficient decreases the reaction rate at the high temperature point. On the contrary, the reaction rate was enhanced by the influx of OH radical at the low temperature point. © 2011 The Japan Society of Mechanical Engineers. © 2012 The Japan Society of Mechanical Engineers.

    DOI: 10.1299/kikaib.77.1592

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  • Study of High-Reynolds Number Isotropic Turbulence by Direct Numerical Simulation Reviewed

    Takashi Ishihara, Toshiyuki Gotoh, Yukio Kaneda

    ANNUAL REVIEW OF FLUID MECHANICS   41   165 - 180   2009

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    We review studies of the statistics of isotropic turbulence in an incompressible fluid at high Reynolds numbers using direct numerical simulation (DNS) from the viewpoint of fundamental physics. The Reynolds number achieved by the largest DNS, with 4096(3) grid points, is comparable with the largest Reynolds number in laboratory experiments. The high-quality DNS data in the inertial subrange and the dissipative range enable the examination of detailed statistics at small scales, such as the normalized energy-dissipation rate, energy and energy-flux spectra, the intermittency of the velocity gradients and increments, scaling exponents, and flow-field structure. We emphasize basic questions of turbulence, universality in the sense of Kolmogorov's theory, and the dependence of the statistics on the Reynolds number and scale.

    DOI: 10.1146/annurev.fluid.010908.165203

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  • Examination of Kolmogorov's 4/5 law by high-resolution direct numerical simulation data of turbulence Reviewed

    Yukio Kaneda, Junya Yoshino, Takashi Ishihara

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   77 ( 6 )   064401   2008.6

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    Kolmogorov's 4/5 law is examined quantitatively by using the data of direct numerical simulations of incompressible turbulence in a periodic box with the number of grid points and the Taylor micro-scale Reynolds number 2048(3) and R-gimel approximate to 732, respectively. The examination is based on a generalization of the Karman-Howarth-Kolmogorov (KHK) equation for isotropic turbulence to anitropic turbulence. An emphasis is put on the influence of the finite Reynolds number, length-scale and the weak but finite anisotropy. The analysis of the DNS data gives a quantitative idea on the role of the viscous and forcing terms in the KHK equation. It also suggests that the anisotropy has substantial influence on the 4/5 law for a wide scale-range.

    DOI: 10.1143/JPSJ.77.064401

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  • Small-scale statistics in high-resolution direct numerical simulation of turbulence: Reynolds number dependence of one-point velocity gradient statistics Reviewed

    T. Ishihara, Y. Kaneda, M. Yokokawa, K. Itakura, A. Uno

    JOURNAL OF FLUID MECHANICS   592   335 - 366   2007.12

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    One-point statistics of velocity gradients and Eulerian and Lagrangian accelerations are studied by analysing the data from high-resolution direct numerical simulations (DNS) of turbulence in a periodic box, with up to 4096 3 grid points. The DNS consist of two series of runs; one is with k(max)eta similar to 1 (Series 1) and the other is with k(max)eta similar to 2 (Series 2), where k(max) is the maximum wavenumber and eta the Kolmogorov length scale. The maximum Taylor-microscale Reynolds number R-lambda in Series 1 is about 1130, and it is about 675 in Series 2. Particular attention is paid to the possible Reynolds number (Re) dependence of the statistics. The visualization of the intense vorticity regions shows that the turbulence field at high Re consists of clusters of small intense vorticity regions, and their structure is to be distinguished from those of small eddies. The possible dependence on Re of the probability distribution functions of velocity gradients is analysed through the dependence on R-lambda of the skewness and flatness factors (S and F). The DNS data suggest that the R-lambda dependence of S and F of the longitudinal velocity gradients fit well with a simple power law: S similar to -0.32R(lambda)(0.11) and F similar to 1.14(lambda)(0.34), in fairly good agreement with previous experimental data. They also suggest that all the fourth-order moments of velocity gradients scale with R-lambda similarly to each other at R-lambda &gt; 100, in contrast to R-lambda &lt; 100. Regarding the statistics of time derivatives, the sccond-order time derivatives of turbulent velocities are more intermittent than the first-order ones for both the Eulerian and Lagrangian velocities, and the Lagrangian time derivatives of turbulent velocities are more intermittent than the Eulerian time derivatives, as would be expected. The flatness factor of the Lagrangian acceleration is as large as 90 at R-lambda approximate to 430. The flatness factors of the Eulerian and Lagrangian accelerations increase with R-lambda approximately proportional to R-lambda(alpha E) and R-lambda(alpha L), respectively, where alpha(E) approximate to 0.5 and alpha(L) approximate to 1.0, while those of the second-order time derivatives of the Eulerian and Lagrangian velocities increases approximately proportional to R-lambda(beta E) and R-lambda(beta L), respectively, where beta(E) approximate to 1.5 and beta(L) approximate to 3.0.

    DOI: 10.1017/S0022112007008531

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  • Similarity scaling of pressure fluctuation in turbulence

    Yoshiyuki Tsuji, Takashi Ishihara

    Physical Review E - Statistical, Nonlinear, and Soft Matter Physics   68 ( 2 2 )   2003.8

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    The static pressure fluctuation in a fully developed turbulence was measured. The aim was to determine how the spectral form varies depending on the Reynolds number. In particular, the spectral exponent and constant Kp were studied from the standpoint of Kolmogorov scaling. Probability density functions were computed and compared with DNS in order to ascertain the qualitative accuracy.

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Books

  • 理工系の数理 ベクトル解析

    山本, 有作, 石原, 卓( Role: Joint author)

    裳華房  2020.11  ( ISBN:9784785315894

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    Total pages:viii, 172p   Language:Japanese Book type:Textbook, survey, introduction

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  • 理工学のための数値計算法[第3版]

    水島 二郎, 柳瀬 眞一郎, 石原 卓( Role: Joint author)

    数理工学社  2019.11 

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    Total pages:252   Language:Japanese Book type:Textbook, survey, introduction

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  • 乱流の計算科学 - 乱流解明のツールとしての大規模数値シミュレーション

    金田行雄, 石井克哉, 石原 卓, 岩本 薫, 吉田 恭, 芳松克則, 半場藤弘( Role: Joint author)

    共立出版  2012.7 

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    Responsible for pages:63-121   Language:Japanese

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  • Direct Numerical Simulations of Navier-Stokes Equation in Astrophysics : The Growth of Dust Grains in Protoplanetary Disk Turbulence Invited

    Masayuki Umemura, Takashi Ishihara

    39 ( 2 )   101 - 107   2020.6

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  • Large-scale Direct Numerical Simulations of Homogeneous Isotropic Turbulence Invited

    38 ( 2 )   74 - 78   2019.6

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)  

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  • Turbulence Near Interfaces-Modelling and Simulations

    J. C. R. Hunt, T. Ishihara, D. Szubert, I. Asproulias, Y. Hoarau, M. Braza

    ADVANCES IN FLUID-STRUCTURE INTERACTION   133   283 - 292   2016

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    Language:English   Publishing type:Rapid communication, short report, research note, etc. (scientific journal)   Publisher:SPRINGER-VERLAG BERLIN  

    DOI: 10.1007/978-3-319-27386-0_17

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  • 高レイノルズ数乱流中の渦の組織構造とその時間発展 Invited Reviewed

    ISHIHARA TAKASHI, UNO ATSUYA, MORISHITA KOJI, YOKOKAWA MITSUO, KANEDA YUKIO

    ながれ   35   109 - 113   2016

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:日本流体力学会  

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  • Coherent vorticity in turbulent channel flow: a wavelet viewpoint

    Katsunori Yoshimatsu, Teluo Sakurai, Kai Schneider, Marie Farge, Koji Morishita, Takashi Ishihara

    Proceedings of Ninth International Symposium on Turbulence and Shear Flow Phenomena   2   -   2015.7

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  • 自然や人工系の流体シミュレーション Invited

    石原 卓

    パリティ   30 ( 6 )   34-36   2015.6

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  • 18pCW-10 Energy spectrum in high-resolution direct numerical simulations of turbulence

    Ishihara T., Morishita K., Yokokawa M., Uno A., Kaneda Y.

    Meeting Abstracts of the Physical Society of Japan   70 ( 0 )   2807 - 2807   2015

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    Language:Japanese   Publisher:The Physical Society of Japan  

    DOI: 10.11316/jpsgaiyo.70.2.0_2807

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  • 一様等方性乱流の直接数値シミュレーションコードの京コンピュータ向け最適化

    森下浩二, 横川 三津夫, 宇野 篤也, 石原 卓, 金田 行雄

    研究報告ハイパフォーマンスコンピューティング(HPC)   147 ( 17 )   1-5   2014.12

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  • 一様等方性乱流の直接数値シミュレーションコードの京コンピュータ向け最適化

    森下 浩二, 横川 三津夫, 宇野 篤也, 石原 卓, 金田 行雄

    情報処理学会研究報告. 計算機アーキテクチャ研究会報告   2014 ( 17 )   1 - 5   2014.12

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    現在日本最速のスーパーコンピュータである 「京」 を用いて,一様等方性乱流の超大規模直接数値シミュレーション (DNS) を実現するために,地球シミュレータ向けに開発された,フーリエ・スペクトル法に基づく一様等方性乱流の DNS コードの 「京」 への移植,及び最適化を行った.移植の際には,従来の 1 次元分割によるデータ分散手法から,より効率的な All-to-all 通信が可能であると考えられる 2 次元分割による手法へと変更を行った.その結果,「京」 の 192×128 ノードを用いて最大格子点数 122883 の超大規模 DNS の実現に成功した.これはプロダクトランとしては世界最大の一様等方性乱流の DNS である.ピーク性能比として,格子点数 61443,81923,122883 の DNS でそれぞれ 3.84%,3.14%,2.24% の実効性能が得られた.また,コードの更なる高効率化のために,乱流 DNS 特有のアルゴリズムに対する最適化を試み,その性能評価を行った.

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  • 一様等方性乱流の直接数値シミュレーションコードの京コンピュータ向け最適化

    森下 浩二, 横川 三津夫, 宇野 篤也, 石原 卓, 金田 行雄

    情報処理学会研究報告. [ハイパフォーマンスコンピューティング]   2014 ( 17 )   1 - 5   2014.12

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    現在日本最速のスーパーコンピュータである 「京」 を用いて,一様等方性乱流の超大規模直接数値シミュレーション (DNS) を実現するために,地球シミュレータ向けに開発された,フーリエ・スペクトル法に基づく一様等方性乱流の DNS コードの 「京」 への移植,及び最適化を行った.移植の際には,従来の 1 次元分割によるデータ分散手法から,より効率的な All-to-all 通信が可能であると考えられる 2 次元分割による手法へと変更を行った.その結果,「京」 の 192×128 ノードを用いて最大格子点数 122883 の超大規模 DNS の実現に成功した.これはプロダクトランとしては世界最大の一様等方性乱流の DNS である.ピーク性能比として,格子点数 61443,81923,122883 の DNS でそれぞれ 3.84%,3.14%,2.24% の実効性能が得られた.また,コードの更なる高効率化のために,乱流 DNS 特有のアルゴリズムに対する最適化を試み,その性能評価を行った.

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  • 高レイノルズ数乱流中の強い渦の組織構造 (偏微分方程式の背後にある確率過程と解の族が示す統計力学的な現象の解析)

    石原 卓

    数理解析研究所講究録   1919   35 - 37   2014.9

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    Other Link: http://hdl.handle.net/2433/223374

  • 高レイノルズ数乱流中の強い渦の組織構造

    石原 卓

    偏微分方程式の背後にある確立過程と解の族が示す統計力学的な現象の解析 Stochastic Processes and Statistical Phenomena behind RDFs RIMS共同研究報告集   ( 1919 )   35-37   2014

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  • Dynamic Geometrical Analysis of High-Vorticity Regions in Isotropic Turbulence

    Hattori Yuji, Ishihara Takashi

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   228 - 228   2013.8

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  • Small scale universality and spectral characteristics in turbulent flows Reviewed

    Yukio Kaneda, Koji Morishita, Takashi Ishihara

    Proceedings of TSFP-8 (2013) Poitiers   1   1-6   2013.8

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    A review is given on studies of statistics at small scales in turbulent flows from a view point of universality. It is assumed in the view that the statistics at sufficiently small scales in the absence of mean flow are at a certain kind of local equilibrium state, and the influence of the mean flow may be regarded as a perturbation added to the equilibrium state. This idea has been examined by comparison of spectral characteristics derived by the idea with those in turbulent boundary layers, mixing layers and direct numerical simulations (DNS) of homogeneous turbulent shear flow. The applicability of this idea to turbulent channel flows is discussed in the light of the data of the log-law region in DNS of turbulent channel flows with the friction Reynolds number Ret up to 5120.

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  • Direct Numerical Simulations of Fundamental Turbulent Flows with the World's Largest Number of Grid-points and Application to Modeling of Engineering Turbulent Flows

    Annual report of the Earth Simulator Center   149 - 154   2013.4

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  • Conditional analysis of statistics obtained near the turbulent-nonturbulent interface of turbulent boundary layers

    T. Ishihara, H. Ogasawara

    Proceedings of ERCOFTAC SYMPOSIUM on Unsteady Separation in Fluid-Structure Interaction   399-403   2013

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  • Study of two elements constituting turbulence by a multifractal theory for probability density functions - Through the analyses of 4096(3) DNS

    T. Arimitsu, N. Arimitsu, K. Takechi, Y. Kaneda, T. Ishihara

    IC-MSQUARE 2012: INTERNATIONAL CONFERENCE ON MATHEMATICAL MODELLING IN PHYSICAL SCIENCES   410 ( 1 )   012083   2013

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    The probability density functions (PDFs) of energy dissipation rates created from the whole of the DNS region of the size 4096(3) (named whl-PDFs) for various sizes of coarse graining areas are analyzed by multifractal PDF theory (MPDFT). Furthermore, other PDFs named max-PDF and mm-PDF for various sizes of coarse graining areas, created respectively from the partial DNS regions of the size 512(3) with maximum and minimum enstrophy, are also analyzed by making use of the whl-PDF. It is shown that there is a whl-PDF with an appropriate size of coarse graining area, whose slope of the tail part can adjust the slope of the tail-part of a max-PDF. On the other hand, there is a whl-PDF whose center part can adjust quite accurately the center part of a min-PDF. Note that the partial DNS region with maximum (minimum) enstrophy is the region of maximally dense (rare) vortexes, and therefore contributes mainly to the tail (center) part of the whl-PDF. It is found that these adjustments are systematic with respect to the sizes of coarse graining areas.

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  • Volume Penalization法による翼果まわりの流れの数値解析

    澤村陽一, 石原 卓

    生物流体力学及び関連する問題の研究Study of bio-fluid mechanics and related problems RIMS 共同研究報告集   1808   101-120   2012.9

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  • 4D visualization of isotropic turbulence and dynamics of high-enstrophy structures Reviewed

    Yuji Hattori, Takashi Ishihara

    USB Proceedings of JSST 2012 International Conference on Simulation Technology   - ( - )   170-174   2012.9

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  • Interactive visualizations of the large-scale data generated by the DNS of isotropic turbulence on 40963 grid points Reviewed

    Takashi Ishihara, Kensaku Mori

    USB Proceedings of JSST 2012 International Conference on Simulation Technology   - ( - )   175-177   2012.9

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  • Improvement of Reality of CG Motion Pictures by Hydrodynamic Effects: Effects of Turbulence Reviewed

    Takashi Ishihara, Yuji Hattori

    Ninth International Conference on Flow Dynamics   - ( - )   -   2012.9

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  • 19aAA-11 Analysis of 4096^3DNS turbulence by Multifractal PDF theory

    Takechi K., Arimitsu N., Arimitsu T., Kaneda Y., Ishihra T.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   240 - 240   2012.8

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  • Velocity-Dependent Actomyosin ATPase Cycle Revealed by In Vitro Motility Assay with Kinetic Analysis Reviewed

    Masaaki K. Sato, Takashi Ishihara, Hiroto Tanaka, Akihiko Ishijima, Yuichi Inoue

    BIOPHYSICAL JOURNAL   103 ( 4 )   711 - 718   2012.8

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    The actomyosin interaction plays a key role in a number of cellular functions. Single-molecule measurement techniques have been developed to study the mechanism of the actomyosin contractile system. However, the behavior of isolated single molecules does not always reflect that of molecules in a complex system such as a muscle fiber. Here, we developed a simple method for studying the kinetic parameters of the actomyosin interaction using small numbers of molecules. This approach does not require the specialized equipment needed for single-molecule measurements, and permits us to observe behavior that is more similar to that of a complex system. Using an in vitro motility assay, we examined the duration of continuous sliding of actin filaments on a sparsely distributed heavy meromyosin-coated surface. To estimate the association rate constant of the actomyosin motile system, we compared the distribution of experimentally obtained duration times with a computationally simulated distribution. We found that the association rate constant depends on the sliding velocity of the actin filaments. This technique may be used to reveal new aspects of the kinetics of various motor proteins in complex systems.

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  • OS3-7 Numerical Analysis of Effect of Intermediate Species Diffusion on Low Temperature Oxidation Process in a Homogeneous n-Heptane Mixture(OS3 Application of chemical kinetics to combustion modeling,Organized Session Papers)

    Teraji Atsushi, Ishihara Takashi, Kaneda Yukio

    The ... international symposium on diagnostics and modeling of combustion in internal combustion engines   2012 ( 8 )   152 - 157   2012.7

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    A two-dimensional direct numerical simulation (DNS) was applied to investigate the autoignition process of an n-heptane/air mixture. The diffusion of intermediate species was studied in terms of the influence on the ignition delay period and the chemical reaction process. A simplified reaction mechanism was used in this study. The influence of turbulence was investigated by comparing the results of a zero-dimensional simulation and two-dimensional direct simulation of a non-turbulence condition. It was found that the ignition delay period was strongly affected by the different diffusion rates of intermediate species. It was shown that the outflow of OH radicals having a larger diffusion coefficient reduces the reaction rate at the high temperature point. In contrast, the reaction rate was enhanced by the influx of OH radicals at the low temperature point.

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  • 大規模直接数値シミュレーションによる周期境界乱流中のエネルギー散逸率とエネルギースペクトル

    金田行雄, 石原 卓, 横川三津夫, 板倉憲一, 宇野篤也

    ながれ   31   241-244   2012

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  • Numerical Analysis of Effect of Intermediate Species Diffusion on Low Temperature Oxidation Process in a Homogeneous n-Heptane Mixture Reviewed

    Atsushi Teraji, Takashi Ishihara, Yukio Kaneda

    Proc. COMODIA 2012   - ( - )   152-157 - 157   2012

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    A two-dimensional direct numerical simulation (DNS) was applied to investigate the autoignition process of an n-heptane/air mixture. The diffusion of intermediate species was studied in terms of the influence on the ignition delay period and the chemical reaction process. A simplified reaction mechanism was used in this study. The influence of turbulence was investigated by comparing the results of a zero-dimensional simulation and two-dimensional direct simulation of a non-turbulence condition. It was found that the ignition delay period was strongly affected by the different diffusion rates of intermediate species. It was shown that the outflow of OH radicals having a larger diffusion coefficient reduces the reaction rate at the high temperature point. In contrast, the reaction rate was enhanced by the influx of OH radicals at the low temperature point. Copyright © 2012 by the Japan Society of Mechanical Engineers.

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  • 2D Direct Numerical Simulation of Intermediate Species Diffusion in Low Temperature Oxidation Process Reviewed

    Atsushi Teraji, Takahiro Morikawa, Takashi Ishihara, Yukio Kaneda

    ICDERS 2011 Proceedings   - ( - )   -   2011

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  • Improvement of Reality of CG Motion Pictures by Hydrodynamic Effects Reviewed

    Takashi Ishihara, Yuji Hattori

    Proceedings of the Eleventh International Symposium on Advanced Fluid Information and Transdisciplinary Fluid Integration   48-49   2011

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  • Towards a separation of the elements in turbulence via the analyses withing MPDFT

    Toshihico Arimitsu, Naoko Arimitsu, Kohei Takechi, Yukio Kaneda, Takashi Ishihara

    arXiv.org[cond-mat.sta-mech]   1111   2011

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  • 高レイノルズ数等方乱流の直接数値シミュレーション -小スケールにおける統計的普遍性- Invited

    金田行雄, 石原 卓

    ながれ   29 ( 2 )   73-78   2010.4

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  • 乱流の大規模DNSデータ解析:速度差の統計の距離依存性とレイノルズ数依存性

    石原 卓

    九州大学応用力学研究所研究集会報告,   20ME-S6   176   2009.5

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  • Universality in Statistics at Small Scales of Turbulence: A Study by High Resolution DNS Reviewed

    Yukio Kaneda, Takashi Ishihara

    TURBULENCE AND INTERACTIONS   105   55 - 76   2009

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    A review is given of the basic idea and some results of data-analysis of recent high-resolution direct numerical simulations (DNSs) of incompressible turbulence in a periodic box with up to 4096(3) grid points. Emphasis is put on the possible universality of small-scale statistics in turbulence at high Reynolds numbers. An analogy of turbulence with systems at or near thermal equilibrium state is also discussed.

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  • Direct numerical simulation of turbulent channel flow at high Reynolds number Reviewed

    Koji Morishita, Takashi Ishihara, Yukio Kaneda

    Proceedings of International Symposium on Frontiers of Computational Science 2008   165-172   2008.11

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  • スーパーコンピュータを使おう(5)

    石原 卓

    名古屋大学情報連携基盤センター ニュース   7 ( 3 )   327-332   2008.8

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  • Attempts at computer-aided understanding of turbulence Reviewed

    Yukio Kaneda, Takashi Ishihara, Koji Morishita, Yoshinori Mizuno

    IUTAM SYMPOSIUM ON COMPUTATIONAL PHYSICS AND NEW PERSPECTIVES IN TURBULENCE   4   49 - 54   2008

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    A review is presented on some attempts to understand turbulence by using high-performance computing (HPC). Among them is the study of turbulence by the direct numerical simulation (DNS) of incompressible turbulence in a periodic box with the number of grid points up to 4096(3). The DNS data shed some light on the Reynolds number (Re)-dependence of the statistics of turbulence at high Re and on the intermittency of energy dissipation. HPC is shown to be useful also for solving a multidimensional singular partial differential equation that determines the anomalous scaling of a passive scalar field advected by a random velocity field with an infinitely small correlation time.

    DOI: 10.1007/978-1-4020-6472-2_7

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  • Multifractal analysis by using high-resolution direct numerical simulation of turbulence Reviewed

    Takashi Ishihara, Hirotaka Higuchi

    IUTAM SYMPOSIUM ON COMPUTATIONAL PHYSICS AND NEW PERSPECTIVES IN TURBULENCE   4   61 - 66   2008

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    Multifractal analysis based on the energy dissipation epsilon and the enstrophy Omega in isotropic turbulence is made by using high-resolution direct numerical simulation of turbulence with the number of grid points up to 20483. The analysis shows that the singularity exponents alpha and alpha' that characterize the intermittencies associated with epsilon and Omega, respectively, agree well with each other in the inertial subrange. This result is consistent with log epsilon(r) and log Omega(r) correlating well with each other for the scale r in the inertial subrange, where the subscript denotes the local average over a cubic domain of size r.

    DOI: 10.1007/978-1-4020-6472-2_9

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  • Attempts at Computational Science of Turbulence Invited

    26 ( 6 )   375-383   2007.12

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  • Small-scale statistics in high-resolution direct numerical simulation of turbulence Reviewed

    Yukio Kaneda, Takashi Ishihara

    PROGRESS IN TURBULENCE II   109   11 - +   2007

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    We performed high-resolution direct numerical simulations (DNSs) of incompressible turbulence in a periodic box with the number of grid points up to 4096(3). The DNS data shed some light on the nature, especially on the possible universality, of small-scale statistics of turbulence at high Reynolds number Re. We report some results of the analysis of the DNS data with an emphasis on the possible dependence of the statistics on Re.

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  • High-resolution direct numerical simulation of turbulence Reviewed

    Y Kaneda, T Ishihara

    JOURNAL OF TURBULENCE   7 ( 20 )   1 - 17   2006

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    We performed high-resolution direct numerical simulations (DNS) of incompressible turbulence in a periodic box by using a Fourier spectral method with the number of grid points up to 4096(3). The simulations consist of two series: one with k(max)eta similar to 1 ( series 1), and the other with k(max)eta similar to 2 (series 2), where k(max) is the highest wavenumber in each simulation, and. is the Kolmogorov length scale. In the 4096(3) DNS, the Taylor scale Reynolds number R-lambda similar to 1200 and the ratio of L/eta of the integral length scale L to eta is approximately 2200, in series 1. The DNS data analysis reveals simple scaling of various spectra, and also sheds some light on (i) the energy spectrum at high R-lambda, (ii) the asymptotic R-lambda-dependence of the normalized energy dissipation rate, (iii) the anomalous scaling of the spectra of energy dissipation and enstrophy, and so on. After some preliminary remarks on the methods and limitations of the DNS, this paper presents a review of the DNS data analysis. Discussions are also made on some questions invoked by the DNS.

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  • Statistical property of pressure fluctuation in fully developed turbulence Reviewed

    Yoshiyuki Tsuji, Takashi Ishihara

    IUTAM SYMPOSIUM ON ELEMENTARY VORTICES AND COHERENT STRUCTURES: SIGNIFICANCE IN TURBULENCE DYNAMICS   79   163 - +   2006

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    Pressure fluctuation is measured by using a condenser microphone and piezoresistive transducer. In order to confirm the experimental accuracy, measured data are compared with direct numerical simulation. This basic test encourages us to study small-scale statistics from the standpoint of Kohnogorov universal scaling. The power-law exponent and proportional constant of normalized pressure spectrum are discussed. The clear power law with scaling exponent -7/3 is confirmed in the range of R-lambda &gt;= 600. These Reynolds numbers are much larger than those in velocity fluctuation for achieving the Kolmogorov scaling. The spectral constant K-p is not universal but depends on Reynolds number.

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  • Statistics of energy transfer in high-resolution direct numerical simulation of turbulence in a periodic box Reviewed

    T Aoyama, T Ishihara, Y Kaneda, M Yokokawa, K Itakura, A Un

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   74 ( 12 )   3202 - 3212   2005.12

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    The statistics of energy transfer is studied by using the data of a series of high-resolution direct numerical simulations of incompressible homogeneous turbulence in a periodic box with the Taylor micro-scale Reynolds number R-lambda and grid points up to approximately 1130 and 4096(3), respectively. The data show that the energy transfer T across the wave number k is highly intermittent and the skewness S and flatness F of T increase with k approximately as S proportional to (kL)(alpha S), F proportional to (kL)(alpha F) in the inertial subrange, where alpha(S) similar to 2/3, alpha(F) similar to 1 and L the characteristic length scale of energy containing eddies. The comparison between the statistics of T, the energy dissipation rate epsilon and its average epsilon(r) over a domain of scale r shows that T is less intermittent than epsilon, while there is a certain similarity between the probability distribution functions of T and epsilon(r).

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  • Box 乱流の大規模 DNS 結果から見た Channel 乱流

    石原 卓, 長田將明, 金田行雄

    京都大学数理解析研究所講究録   ( 1434 )   188-194   2005.5

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  • 結合コンパクトスキームを用いたチャネル乱流の直接数値シミュレーション

    高林大作, 林 一樹, 石原 卓

    豊田研究報告   ( 58 )   155-160   2005.5

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  • Energy spectrum in the near dissipation range of high resolution direct numerical simulation of turbulence Reviewed

    T Ishihara, Y Kaneda, M Yokokawa, K Itakura, A Uno

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   74 ( 5 )   1464 - 1471   2005.5

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    The energy spectrum in the near dissipation range of turbulence is studied by analyzing the data of a series of high-resolution direct numerical simulations of incompressible homogeneous turbulence in a periodic box with the Taylor micro-scale Reynolds number R-lambda and resolution ranging up to about 675 and 4096(3), respectively. The spectra in the Reynolds number range fit well to the form C(k eta)(alpha) exp(-beta k eta) in the wavenumber range 0.5 less than or similar to k eta less than or similar to 1.5, where eta is the Kolmogorov dissipation length scale and C, alpha and beta are constants independent of k. The values of alpha and beta decrease monotonically with R-lambda, and they are consistent with the conjecture that they approach to constants as R-lambda -&gt; infinity, but the approach, especially that of beta, is slow.

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  • Scalability of hybrid programming for a CFD code on the Earth Simulator

    K Itakura, A Uno, M Yokokawa, T Ishihara, Y Kaneda

    PARALLEL COMPUTING   30 ( 12 )   1329 - 1343   2004.12

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    The Earth Simulator (ES) is an SMP cluster system. There are two types of parallel programming models available on the ES. One is a flat programming model, in which a parallel program is implemented by MPI interfaces only, both within an SMP node and among nodes. The other is a hybrid programming model, in which a parallel program is written by using thread programming within an SMP node and MPI programming among nodes simultaneously. It is generally known that it is difficult to obtain the same high level of performance using the hybrid programming model as can be achieved with the flat programming model.
    In this paper, we have evaluated scalability of the code for direct numerical simulation of the Navier-Stokes equations on the ES. The hybrid programming model achieves the sustained performance of 346.9Gflop/s, while the flat programming model achieves 296.4Gfiop/s with 16 PNs of the ES for a DNS problem size of 256 3. For small scale problems, however, the hybrid programming model is not as efficient because of microtasking overhead. It is shown that there is an advantage for the hybrid programming model on the ES for the larger size problems. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.parco.2004.09.006

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  • High-resolution direct numerical simulation of turbulence - Spectra of fourth-order velocity momenrs Reviewed

    Y Kaneda, T Ishihara, M Yokokawa, K Itakura, A Uno

    IUTAM SYMPOSIUM ON REYNOLDS NUMBER SCALING IN TURBULENT FLOW   74   155 - 162   2004

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    High-resolution direct numerical simulations (DNSs) of incompressible turbulence based on an alias-free spectral method were performed on the Earth Simulator. Statistics of turbulence are studied by a DNS on 1024(3) grid points with a special emphasis on the spectra of moments fourth order in velocity. A brief review is given on some results of the preliminary analysis of the data of DNSs with up to 2048(3) grid points.

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  • Ultra Direct Numerical Simulation of Turbulence on the Earth Simulator - Data Analyses- Reviewed

    Takashi Ishihara, Yukio Kaneda

    Proc. Russia-Japan International Workshop on Turbulence and Instabilities, Moscow, Russia   2004

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  • Ultra direct numerical simulation of turbulence on the earth simulator Reviewed

    T Ishihara

    COMPUTATIONAL MECHANICS, PROCEEDINGS   369 - 374   2004

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    Language:English   Publishing type:Research paper, summary (national, other academic conference)   Publisher:TSINGHUA UNIV PRESS  

    We recently carried out a series of DNSs of incompressible turbulence with number of grid points up to 4096(3) on the Earth Simulator (ES). The 4096(3) (ultra) DNS is 64 times the size of the largest DNS before the appearance of the ES. The DNSs consist of two groups; one is with K-max eta = 2 R-lambda = 1 and the Taylor micro scale Reynolds number R-lambda = 167 similar to 1131, while the other is with K-max eta = 2 and R-lambda = 94 similar to 675, where K-max is the maximum wave number and eta the Kolmogorov length scale. A review is given on the one-point and two-point statistics of the velocity derivatives, including the fourth-order rotational invariants I-alpha (alpha = 1...4) proposed by Siggia (1981) and the spectra of energy dissipation epsilon, enstrophy omega(2), and pressure p, obtained by the series of the DNSs on the ES. The series of the DNSs suggest that the spectra of epsilon, omega(2), and p exhibited a wave number range in which the spectra scaled with the wave number k as k(-a). Exponent a for p was in good agreement with the value obtained by assuming the joint probability distribution of the velocity field to be Gaussian, while a values for epsilon and omega(2) were very different from the Gaussian approximation values.

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  • Similarity scaling of pressure fluctuation in turbulence Reviewed

    Y Tsuji, T Ishihara

    PHYSICAL REVIEW E   68 ( 2 )   2630968-1-5   2003.8

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    Pressure fluctuation was measured in a turbulent jet using a condenser microphone and piezoresistive transducer. The power-law exponent and proportional constant of normalized pressure spectrum are discussed from the standpoint of Kolmogorov universal scaling. The clear power law with scaling exponent close to -7/3 was confirmed in the range of 600less than or equal toR(lambda). These Reynolds numbers are much larger than those in velocity fluctuation to achieve Kolmogorov scaling. The spectral constant is not universal but depends on Reynolds numbers. Measured pressure probability density functions are compared with direct numerical simulation.

    DOI: 10.1103/PhysRevE.68.026309

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  • Anisotropic spectrum of homogeneous turbulent shear flow in a Lagrangian renormalized approximation Reviewed

    K Yoshida, T Ishihara, Y Kaneda

    PHYSICS OF FLUIDS   15 ( 8 )   2385 - 2397   2003.8

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    An analytical study of the anisotropic velocity correlation spectrum tensor in the inertial subrange of homogeneous turbulent shear flow is performed using a Lagrangian renormalized spectral closure approximation. The analysis shows that the spectrum in the asymptotic limit of infinitely large Reynolds numbers Re is determined by two nondimensional universal constants; theoretical estimates for the constants are provided. The anisotropic component of the spectrum at finite Re is more sensitive to large-scale turbulence structures than the isotropic component. A preliminary analysis of the effect of finite Re or the width of the inertial subrange is in qualitative agreement with direct numerical simulations. (C) 2003 American Institute of Physics.

    DOI: 10.1063/1.1588307

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  • Spectra of energy dissipation, enstrophy and pressure by high-resolution direct numerical simulations of turbulence in a periodic box Reviewed

    T Ishihara, Y Kaneda, M Yokokawa, K Itakura, A Uno

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 5 )   983 - 986   2003.5

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    The spectra of the squares of velocity quadratics including the energy dissipation rate epsilon per unit mass, the enstrophy omega(2) and the pressure p were measured using the data obtained from direct numerical simulations (DNSs) of incompressible turbulence in a periodic box with number of grid points up to 2048(3). These simulations were performed using the Earth Simulator computing system. The spectra for epsilon, omega(2) and p exhibited a wave number range in which the spectra scaled with the wave number k as proportional to k(-a). Exponent a for p was about 1.81, which is in good agreement with the value obtained by assuming the joint probability distribution of the velocity field to be Gaussian, while a values for epsilon and omega(2) were about 2/3, and very different from the Gaussian approximation values.

    DOI: 10.1143/JPSJ.72.983

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  • 大規模DNSによる乱流物理現象の解明

    金田行雄, 石原卓

    日本流体力学会数値流体力学部門Web会誌   11 ( 2 )   25-30   2003.5

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  • Energy dissipation rate and energy spectrum in high resolution direct numerical simulations of turbulence in a periodic box Reviewed

    Y Kaneda, T Ishihara, M Yokokawa, K Itakura, A Uno

    PHYSICS OF FLUIDS   15 ( 2 )   L21 - L24   2003.2

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    High-resolution direct numerical simulations (DNSs) of incompressible homogeneous turbulence in a periodic box with up to 4096(3) grid points were performed on the Earth Simulator computing system. DNS databases, including the present results, suggest that the normalized mean energy dissipation rate per unit mass tends to a constant, independent of the fluid kinematic viscosity nu as nu--&gt;0. The DNS results also suggest that the energy spectrum in the inertial subrange almost follows the Kolmogorov k(-5/3) scaling law, where k is the wavenumber, but the exponent is steeper than -5/3 by about 0.1. (C) 2003 American Institute of Physics.

    DOI: 10.1063/1.1539855

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  • Performance tuning of a CFD code on the earth simulator

    K Itakura, A Uno, M Yokokawa, M Saito, T Ishihara, Y Kaneda

    NEC RESEARCH & DEVELOPMENT   44 ( 1 )   115 - 120   2003.1

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    High-resolution direct numerical simulations (DNSs) of incompressible turbulence with numbers of grid points up to 2048(3) have been executed on the Earth Simulator (ES). The DNSs are based on the Fourier spectral method, so that the equation for mass conservation is accurately solved. In DNSs based on the spectral method, most of the computation time is consumed in calculating the three-dimensional (3D) Fast Fourier Transform (FFT). In this paper, we tuned the 3D-FFT algorithm for the Earth Simulator and have achieved DNS at 16ATFLOPS on 2048(3) grid points.

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  • High resolution DNS of incompressible homogeneous forced turbulence - Time dependence of the statistics Reviewed

    T Ishihara, Y Kaneda

    STATISTICAL THEORIES AND COMPUTATIONAL APPROACHES TO TURBULENCE   177 - 188   2003

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    Language:English   Publishing type:Research paper, summary (national, other academic conference)   Publisher:SPRINGER-VERLAG TOKYO  

    Results of direct numerical simulation (DNS) of incompressible homogeneous and isotropic forced turbulence with grid points up to 1024 3 are presented with emphasis on the time dependence of the turbulence statistics. The Taylor micro scale Reynolds number at a quasi-stationary state is 283 in the DNS with 1024 3 grid points, and the energy spectrum exhibits an universal equilibrium range. The results suggest that for R-lambda &gt; 280 or so, the energy dissipation rate normalized by the integral length scale and root-mean-square velocity is almost independent of R-lambda and is 0.44 - 0.45.

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  • Ultra Direct Numerical Simulation of Turbulence on the Earth Simulator Reviewed

    Takashi Ishihara

    Proc. Japan-Russia Seminar, TIT   2003

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  • Comparison of a spectral method with a higher-order finite difference method in direct numerical simulations of three-dimensional homogeneous turbulence Reviewed

    Katsunori Yoshimatsu, Takashi Ishihara, Yukio Kaneda, Satoshi Nakai, Hidetoshi Nishida, Nobuyuki Satafuka

    Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B   69 ( 679 )   541 - 546   2003

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    A finite difference method (FDM) is easier and cheaper to use than a spectral method (SM) in flows with complicated geometry, but is inferior to a SM in both accuracy and resolution. In this paper, effects of both accuracy and resolution in a FDM on the quality of incompressible turbulent flow description were studied by comparing a SM with a FDM in direct numerical simulations (DNS) of the three-dimensional freely decaying homogeneous turbulence with 1283 and 2563 grids. We adopted the higher-order method of lines and Fourier spectral method as a FDM and a SM, respectively. The value of the kinematic viscosity was determined so that the minimum value of Kmaxη in time was about 2 in the SM with 2563 grids. Here, Kmax and η are the maximum resolved wavenumber and the Kolmogorov length scale, respectively. The statistical quantities, such as the total energy, the energy dissipation ratio, obtained by the higher-order method of lines were in good agreement with those by the SM. Furthermore, comparing their DNS fields, we found that the performance of the 4th-order method of lines with 2563 grids was comparable to that of the SM with 1283 grids in which the minimum value of Kmaxη in time was about 1.

    DOI: 10.1299/kikaib.69.541

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  • LES modelings based on the Lagrangian renormalized approximation Reviewed

    K Yoshida, T Ishihara, D Fujita, T Yamahira, Y Kaneda

    STATISTICAL THEORIES AND COMPUTATIONAL APPROACHES TO TURBULENCE   203 - 218   2003

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    A systematic way for formulating large-eddy simulation (LES) models based on the Lagrangian renormalized approximation is presented. A spectral LES to simulate the energy spectrum and a probabilistic LES to simulate both the energy spectrum and the error spectrum are formulated for 3-dimensional turbulence and 2-dimensional turbulence with the inverse energy cascading range. The derived models axe free from any ad hoc parameters. The models are verified using high resolution numerical simulations with 512(3) grid points for 3-dimension and 1024(3) for 2-dimension.

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  • Predictability of 3D isotropic turbulence - Effect of data assimilation Reviewed

    K Hayashi, T Ishihara, Y Kaneda

    STATISTICAL THEORIES AND COMPUTATIONAL APPROACHES TO TURBULENCE   239 - 247   2003

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    In numerical simulation of turbulent flows, it is usually difficult to obtain exact initial conditions and it is well known that initial uncertainty in high wavenumbers spreads toward large scale through nonlinear dynamics. These imply the limitation of the numerical prediction. We present here a series of numerical experiments to study the effect of data assimilation on the predictability of isotopic 3D turbulence. In the experiment we have two parameters K-c and T to control the data assimilation, where K-c is the maximum of the assimilated wavenumber range and T is the time interval of the assimilation. It is found not only that we can suppress the growth of uncertainty by data assimilation but also that we can reduce it under appropriate conditions on K-c and T. It is also found that there exists a critical K-c* such that if K-c &lt; K-c*, the uncertainty grows for any T.

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  • Relative diffusion of a pair of fluid particles in the inertial subrange of turbulence Reviewed

    T Ishihara, Y Kaneda

    PHYSICS OF FLUIDS   14 ( 11 )   L69 - L72   2002.11

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    Turbulent diffusion of a pair of fluid particles in 3-dimensional homogeneous and isotropic turbulence was studied using a high-resolution direct numerical simulation (DNS) with 1024(3) grid points. The DNS showed that the mean square of the distance deltax between the two fluid particles grows with time t as &lt;\deltax\(2)&gt;similar toCepsilont(3) in the inertial subrange, which is in agreement with Richardson (1926) and Obukhov (1941), where Capproximate to0.7 and epsilon is the mean dissipation rate per unit mass. A simple Lagrangian closure approximation for &lt;\deltax\(2)&gt; is shown to be in good agreement with the DNS. (C) 2002 American Institute of Physics.

    DOI: 10.1063/1.1508443

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  • LES of Stably Stratified Turbulence Reviewed

    Kyo Yoshida, Takashi Ishihara, Yukio Kaneda

    Proc. International Workshop on Statistical Theories and Computational Approaches to Turbulence   219-228   2002.11

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  • Scalability Evaluation of Direct Numerical Simulation on Earth Simulator

    UNO ATSUYA, ITAKURA KEN'ICHI, YOKOKAWA MITSUO, ISHIHARA TAKASHI, KANEDA YUKIO

    IPSJ SIG Notes   91   55 - 60   2002.8

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    There are two programming models on the shared-memory architecure. One, called the flat programming, is using MPI, and the other, called the hybrid programming, is using MPI and shared-memory models simultaneously. In general, it is difficult that the hybrid programming outperforms the flat programming. In this study, we evaluated a scalability of large-scale direct numerical simulations of the Navier-Stokes equations on the Earth Simulator. As a result, the hybrid programming could outpeform the flat programming on the Earth Simulator. Also, we discuss the tuning strategies to obtain higher performance on the Earth Simulator.

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  • Anisotropic velocity correlation spectrum at small scales in a homogeneous turbulent shear flow Reviewed

    T Ishihara, K Yoshida, Y Kaneda

    PHYSICAL REVIEW LETTERS   88 ( 15 )   154501 - 1545014   2002.4

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    A simple theoretical analysis and direct numerical simulations on 512(3) grid points suggest that the velocity correlation spectrum tensor in the inertial subrange of homogeneous turbulent shear flow at high Reynolds number is given by a simple form that is an anisotropic function of the wave vector. The tensor is determined by the rate of the strain tensor of the mean flow, the rate of energy dissipation per unit mass, the wave vector, and two nondimensional constants.

    DOI: 10.1103/PhysRevLett.88.154501

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  • 25aXB-4 Anisotropic spectrum in homogeneous shear turbulent flow

    Ishihara T., Yoshida K., Kaneda Y.

    Meeting abstracts of the Physical Society of Japan   57 ( 1 )   248 - 248   2002.3

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  • 25aXB-5 Simulation of 3D homogeneous turbulence:spectral method vs. higher order method of lines

    Yoshimatsu K, Ishihara T., Yamazaki Y., Kaneda Y., Nishida H., Nakai S., Satofuka N.

    Meeting abstracts of the Physical Society of Japan   57 ( 1 )   248 - 248   2002.3

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  • Effects of wavenumber truncation on high-resolution direct numerical simulation of turbulence Reviewed

    Y Yamazaki, T Ishihara, Y Kaneda

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 3 )   777 - 781   2002.3

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    The effects of wavenumber truncation on the direct numerical simulation (DNS) of incompressible turbulence at high Reynolds numbers using the Fourier spectral method were studied by comparing DNS fields with different truncation wavenumbers, K-max. The comparison suggests that the error due to truncation increases faster at higher wavenumbers, k, and the increase obeys a simple scaling law in the inertial subrange k much less than K-max. Some statistics, such as the energy and dissipation spectra, may remain insensitive to the error, even in the later period, provided that K(max)eta similar to 1 (eta is the Kolmogorov length scale), although DNS fields with different K-max are then essentially uncorrelated to each other.

    DOI: 10.1143/JPSJ.71.777

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  • 地球シミュレータによる乱流のUltra Simulation

    金田行雄, 石原 卓, 横川三津夫, 板倉憲一, 宇野篤也

    九大応力研研究集会報告 14ME-S1   90-97   2002

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  • 乱流の謎にせまる計算科学

    後藤俊幸, 石原卓

    パリティ   17 ( 10 )   27-33   2002

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  • 16.4TFlops direct numerical simulation of turbulence by a Fourier spectral method on the Earth Simulator Reviewed

    Mitsuo Yokokawa, Ken'ichi Itakura, Atsuya Uno, Takashi Ishihara, Yukio Kaneda

    Proc. IEEE/ACM SC2002 Conf.   2002-November   -   2002

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    The high-resolution direct numerical simulations (DNSs) of incompressible turbulence with numbers of grid points up to 40963 have been executed on the Earth Simulator (ES). The DNSs are based on the Fourier spectral method, so that the equation for mass conservation is accurately solved. In DNS based on the spectral method, most of the computation time is consumed in calculating the three-dimensional (3D) Fast Fourier Transform (FFT), which requires huge-scale global data transfer and has been the major stumbling block that has prevented truly high-performance computing. By implementing new methods to efficiently perform the 3D-FFT on the ES, we have achieved DNS at 16.4 Tflops on 20483 grid points. The DNS yields an energy spectrum exhibiting a wide inertial subrange, in contrast to previous DNSs with lower resolutions, and therefore provides valuable data for the study of the universal features of turbulence at large Reynolds number.

    DOI: 10.1109/SC.2002.10052

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  • 乱流のUltra Simulation

    金田行雄, 石原 卓, 横川三津夫, 板倉憲一, 宇野篤也

    第6回シミュレーション・サイエンス・シンポジウム及び核融合科学研究所共同研究「大型シミュレーション研究」合同研究会集録NIFS-PROC-52   24-27   2002

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  • 地球シミュレータ上の一様等方性乱流シミュレーション

    横川三津夫, 斎藤 実, 石原 卓, 金田行雄

    ハイパフォーマンスコンピューティングと計算科学シンポジウムHPCS2002   125-131   2002

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  • Frequency shifts of Rossby waves in the inertial subranges of beta-plane turbulence Reviewed

    T Ishihara, Y Kaneda

    PHYSICS OF FLUIDS   13 ( 8 )   2338 - 2349   2001.8

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    Nonlinear interactions between waves and turbulence cause systematic frequency shifts in Rossby waves. The frequency shifts in the inertial subranges of statistically steady beta -plane turbulence were examined theoretically and numerically. The theoretical analysis is based on the Lagrangian closure called the Lagrangian renormalized approximation and predicts that when the beta effect is small, the frequency shifts of Rossby waves are proportional to k(x)/k(4/3) in the inverse energy transfer range, while they are proportional to k(x) with or without a log-correction term in the enstrophy transfer range, depending on the flow conditions, where k(x) is the wave number in the eastward direction. Numerical simulations using 1024(2) grid points of forced beta -plane turbulence that exhibit the inertial subranges, show fairly good agreement with theoretical predictions. (C) 2001 American Institute of Physics.

    DOI: 10.1063/1.1384468

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  • 乱流の慣性小領域におけるラグランジュ統計

    石原卓, 金田行雄

    京都大学数理解析研究所講究録   ( 1226 )   86-93   2001.7

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  • Nonuniversal k(-3) energy spectrum in stationary two-dimensional homogeneous turbulence Reviewed

    Y Kaneda, T Ishihara

    PHYSICS OF FLUIDS   13 ( 5 )   1431 - 1439   2001.5

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    A spectral closure analysis and numerical simulations suggest that there may be a class of two-dimensional turbulence in which the energy spectrum E(k) scales with the wave number k like E(k)=Ak(-3) in the enstrophy transfer range in accordance with the Kraichnan-Leith-Batchelor (KLB) spectrum, but the prefactor A is different from the KLB spectrum and depends in a nontrivial way on the flow conditions at large scales. (C) 2001 American Institute of Physics.

    DOI: 10.1063/1.1359187

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  • Energy spectrum in the enstrophy transfer range of two-dimensional forced turbulence Reviewed

    T Ishihara, Y Kaneda

    PHYSICS OF FLUIDS   13 ( 2 )   544 - 547   2001.2

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    Numerical simulations of two-dimensional forced turbulence suggest that the enstrophy transfer range energy spectrum E(k) a little steeper than k(-3) is robust in the sense that it may be realized in a wave number range under different run conditions. It is shown that such energy spectra fit well E(k)=C(K)eta (2/3)k(-3)[ln(k/k(1))](-1/3), where C-K is a dimensionless constant, eta the enstrophy transfer rate per unit mass and k(1) a wave number at the bottom of the range. The simulations give C(K)approximate to1.9 in fairly good agreement with the existing theoretical estimates. (C) 2001 American Institute of Physics.

    DOI: 10.1063/1.1336149

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  • Statistics of small-scale structure of homogeneous isotropic turbulence Reviewed

    T Ishihara, Y Yamazaki, Y Kaneda

    IUTAM SYMPOSIUM ON GEOMETRY AND STATISTICS OF TURBULENCE   59   133 - 138   2001

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  • 乱流の大規模DNSデータ可視化ツールの開発

    石原 卓

    第4回「シミュレーション・サイエンス・シンポジウム」及び核融合科学研究所共同研究「大型シミュレーション研究」合同研究会集録   61-65   2001

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  • 大規模乱流DNSデータの可視化

    大野哲也, 森建策, 末永康仁, 石原 卓, 石井克哉, 金田行雄

    九州大学応用力学研究所研究集会報告   11ME-S3   2000.12

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  • Taylor expansions in powers of time of Lagrangian and Eulerian two-point two-time velocity correlations in turbulence Reviewed

    Y Kaneda, T Ishihara, K Gotoh

    PHYSICS OF FLUIDS   11 ( 8 )   2154 - 2166   1999.8

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    A method is developed for generating the Taylor expansions in powers of the time difference of the Lagrangian and Eulerian two-point two-time velocity correlations in turbulence. The expansions are based on the Taylor series of the Eulerian and Lagrangian velocity fields subject to given dynamics along with initial and boundary conditions. The lowest few coefficients in the expansions enable us to construct approximations to the correlations. An application of the method to turbulence obeying the Navier-Stokes dynamics yields approximations, particularly Padi approximations that agree well with direct numerical simulations of homogeneous isotropic turbulence at moderate Reynolds numbers. The ratios of the second-order to the zeroth-order coefficients of the Taylor series of the Lagrangian and Eulerian correlations give, respectively, the estimates for the Lagrangian and Eulerian micro time scales tau(L) and tau(E). An analysis of a high resolution (512(3) grid points) direct numerical simulation database at large Reynolds number suggests the scalings tau(L)proportional to k(-2/3) and tau(E) proportional to k(-1) for wave numbers k in the inertial subrange. The role of flow structures in turbulence in determining the time scales is also discussed. (C) 1999 American Institute of Physics. [S1070-6631(99)02508-8].

    DOI: 10.1063/1.870077

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  • 乱流の大規模数値実験

    石原 卓

    九大応力研研究集会「流体方程式の解と縮約解析」   ?   1999

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  • Statistics of small-scale structure of homogeneous isotropic turbulence

    10ME-S4   131   1999

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  • 乱流の大規模数値シミュレーション

    石原 卓

    名古屋大学大型計算機センターニュース   30 ( 4 )   ?   1999

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  • Numerical Studies of Large Scale Turbulent Flows in Two and Three Dimensions Reviewed

    Kamen N. Beronov, Takashi Ishihara, Yukio Kaneda

    Proceedings of Oxford Kobe Seminars: The Second Scientific Meeting on Systems Engineering and Applied Mathematics   145-151   1998.12

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  • Fine-scale structure of thin vortical layers Reviewed

    T Ishihara, Y Kaneda

    JOURNAL OF FLUID MECHANICS   364   297 - 318   1998.6

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    A class of exact solutions of the Navier-Stokes equations is derived. Each of them represents the velocity field v = U + u of a thin vortical layer (a planar jet) under a uniform strain velocity field U in three-dimensional infinite space, and provides a simple how model in which nonlinear coupling between small eddies plays a key role in small-scale vortex dynamics. The small-scale structure of the velocity field is studied by numerically analysing the Fourier spectrum of u. It is shown that the Fourier spectrum of rr falls off exponentially with wavenumber k for large k. The Taylor expansion in powers of the coordinate (say y) in the direction perpendicular to the vortical layer suggests that the solution may be well approximated by a function with certain poles in the complex y-plane. The Fourier spectrum based on the singularities is in good agreement with that obtained numerically, where the exponential decay rate is given by the distance of the poles from the real axis of y.

    DOI: 10.1017/S0022112098001293

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  • Taylor expansions and pade approximations of Lagrangian and Eulerian two-time velocity correlations in turbulence Reviewed

    Y Kaneda, K Gotoh, T Ishihara

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   67 ( 4 )   1075 - 1078   1998.4

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    The time-derivatives up to the Gth-order of Eulerian and Lagrangian velocity fields in homogeneous and isotropic turbulence are computed. The Taylor expansions in powers of the time difference of the Eulerian as well as the Lagrangian two-time velocity correlations, and their Pade approximations are constructed from the time-derivatives. The Pade approximations are found to be in good agreement with direct numerical simulations.

    DOI: 10.1143/JPSJ.67.1075

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  • Fine scale structure of thin vortex layers

    Takashi Ishihara, Yukio Kaneda

    Proc. ICTAM   -   -   1996

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  • Singularity Formation in the Shape of a Vortex Sheet in Three Dimensions - Numerical Simulation Reviewed

    Takashi Ishihara, Yukio Kaneda

    ESAIM:Proceedings   1   463-479   1996

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  • Analytic Structure of a vortical layer in uniform strain field

    974   248-259   1996

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  • SINGULARITY FORMATION IN 3-DIMENSIONAL MOTION OF A VORTEX SHEET Reviewed

    T ISHIHARA, Y KANEDA

    JOURNAL OF FLUID MECHANICS   300   339 - 366   1995.10

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    The evolution of a small but finite three-dimensional disturbance on a flat uniform vortex sheet is analysed on the basis of a Lagrangian representation of the motion. The sheet at time t is expanded in a double periodic Fourier series: R(lambda(1),lambda(2),t) = (lambda(1),lambda(2),0) + Sigma(n,m) A(n,m) exp[i(n lambda(1) + delta m lambda(2))], where lambda(1) and lambda(2) are Lagrangian parameters in the streamwise and spanwise directions, respectively, and delta is the aspect ratio of the periodic domain of the disturbance. By generalizing Moore's analysis for two-dimensional motion to three dimensions, we derive evolution equations for the Fourier coefficients A(n,m). The behaviour of A(n,m) is investigated by both numerical integration of a set of truncated equations and a leading-order asymptotic analysis valid at large t. Both the numerical integration and the asymptotic analysis show that a singularity appears at a finite time t, = O(1n epsilon(-1)) where epsilon is the amplitude of the initial disturbance. The singularity is such that A(n,0) = O(t(c)(-1)) behaves like n-(5/2), while A(n)+/-1 = O(epsilon t(c),) behaves like n-(3/2) for large n. The evolution of A(0,m),(spanwise mode) is also studied by an asymptotic analysis valid at large t. The analysis shows that a singularity appears at a finite time t = O(epsilon(-1)) and the singularity is characterized by A(0,2k) proportional to k(5/2) for large k.

    DOI: 10.1017/S0022112095003715

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  • SPONTANEOUS SINGULARITY FORMATION IN THE SHAPE OF VORTEX SHEET IN 3-DIMENSIONAL FLOW Reviewed

    T ISHIHARA, Y KANEDA

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   63 ( 2 )   388 - 392   1994.2

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    The three-dimensional motion of a flat uniform vortex sheet slightly perturbed initially in both streamwise and spanwise directions is studied on the basis of a Lagrangian representation of the motion. The vortex sheet at time t is represented as R(lambda1, lambda2, t) (lambda1, lambda2, 0) + SIGMA(n,m) A(n,m) (t) exp i(nlambda1 + mdeltalambda2), where lambda1 and lambda2 are Lagrangian parameters in the streamwise and spanwise directions, respectively, and delta is the aspect ratio of the periodic domain of the disturbance. The behaviour of A(n,0) and A(n,1) is studied by an asymptotic analysis valid at large t. The analysis shows that singularity appears on the sheet at a critical time 0 (In (epsilon1(-1))), where epsilon1 is the initial amplitude of the streamwise disturbance. The singularity is such that A(n,0) behaves like n-5/2 while A(n,1) behaves like n-3/2, for large n. The latter is associated with the vortex stretching intrinsic in three-dimensional dynamics of the sheet.

    DOI: 10.1143/JPSJ.63.388

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  • Spontaneous singularity formation in the shape of vortex sheet in three-dimensional flow-analysis and numerical simulation

    石原 卓, 金田行雄

    数理解析研究所講究録   888   64-72   1994

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  • 3次元的渦面の運動の解析と数値シミュレーション

    石原 卓, 金田行雄

    京大数理研講究録   866   149-160   1994

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  • TIME MICRO-SCALES OF LAGRANGIAN STRAIN TENSOR IN TURBULENCE Reviewed

    T ISHIHARA, Y KANEDA

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   62 ( 2 )   506 - 513   1993.2

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    Estimations of the time micro scales of Lagrangian strain tensors are obtained by dynamical analysis based on the Navier-Stokes equation for three dimensional turbulence at very high Reynolds number.

    DOI: 10.1143/JPSJ.62.506

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  • STRETCHING AND DISTORTION OF MATERIAL LINE ELEMENTS IN 2-DIMENSIONAL TURBULENCE Reviewed

    T ISHIHARA, Y KANEDA

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   61 ( 10 )   3547 - 3558   1992.10

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    A study is made of the stretching and distortion of material line elements in turbulence both analytically and numerically. Approximations for the statistics of these processes derived by perturbative expansions are tested by comparison with dynamical simulations in two dimensions. An integral time scale associated with the Lagrangian statistics of the velocity gradients plays a key role in the approximations. A rough estimation of the time scale is obtained by a dynamical short-time analysis by making use of the Navier-Stokes equation.

    DOI: 10.1143/JPSJ.61.3547

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  • Time micro scales of Lagrangian Strain Tensor in Turbulence

    800   147-156   1992

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Presentations

  • Temporal Behavior of Significant Shear Layers in High Reynolds Number Turbulence

    Takashi Ishihara

    Eighteenth International Conference on Flow Dynamics  2021.10.28 

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  • 乱流の大規模数値シミュレーション Invited

    石原 卓

    山梨大学大学院医工農総合教育部,修士課程(工学専攻)特別講義  2021.9.27 

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    Event date: 2021.9.27 - 2021.9.28

    Language:Japanese   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

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  • Significant thin shear layers in high Reynolds number turbulence Invited

    Takashi Ishihara, Gerrit E. Elsinga, Julian C. R. Hunt

    COLLOQUIUM 620 EXTREME DISSIPATION AND INTERMITTENCY IN TURBULENCE  2021.5.18 

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    Event date: 2021.5.17 - 2021.5.19

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  • 乱流の慣性小領域の渦構造についてのDNSデータ解析

    宮本 理史, 石原 卓, 金田 行雄

    日本流体力学会 年会2021  2021.9.22 

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  • 高レイノルズ数乱流中の慣性粒子の運動の直接数値シミュレーション

    森中 宏樹, 石原 卓

    日本流体力学会 年会2021  2021.9.22 

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  • 高レイノルズ数乱流中の流体粒子と慣性粒子の拡散過程のDNSデータ解析

    浦覚斗, 石原 卓

    日本流体力学会 年会2021  2021.9.21 

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  • 乱流中の微細渦構造周りの慣性粒子の運動の数値解析

    元塚 博貴, 石原 卓

    日本流体力学会 年会2021  2021.9.21 

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  • 乱流中の慣性粒子の分布の位相的データ解析

    岡 省吾, 石原 卓

    日本応用数理学会 2021年度年会  2021.9.9 

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  • 宇宙物理における乱流現象解明のための計算科学 ー原始惑星系円盤乱流中のダスト成長ー Invited

    石原 卓

    GFD オンラインセミナー (第 6 回)  2021.7.12 

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  • On the role of turbulence in the dust coagulation process in a protoplanetary disk

    Takashi Ishihara, Hiroki Shiraishi, Hiroki Morinaka, Hiroki Mototsuka, Yoshiki Sakurai

    2021.6.4 

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  • 原始惑星系円盤の高レイノルズ数 乱流中でのダスト成長

    石原 卓, 森中宏樹, 奥住 聡, 梅村雅之

    日本天文学会2021年春季年会  2021.3.16 

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  • 乱流中の慣性粒子の衝突過程に対する重力の影響のDNSデータ解析

    浅井 瑞貴, 石原 卓

    第34回数値流体力学シンポジウム  2020.12.21 

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  • テイラー長に基づくレイノルズ数2250までの乱流DNSにおける2次の速度構造関数

    石原 卓, 金田 行雄, 森下 浩二, 横川 三津夫, 宇野 篤也

    第34回数値流体力学シンポジウム  2020.12.21 

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  • 乱流中の多重スケール流れ構造と粒子衝突統計の関係についての数値解析

    櫻井 幹記, 石原 卓

    日本流体力学会 年会2020  2020.9.20 

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  • 乱流中の慣性粒子の衝突・付着現象理解のための数値解析2

    白石 啓貴, 櫻井 幹記, 石原 卓

    日本流体力学会 年会2020  2020.9.19 

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  • 台風に伴う気象現象と流れ構造の関係のデータ解析

    森中 宏樹, 石原 卓, 稲津 將

    日本流体力学会 年会2020  2020.9.18 

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  • Multi-scale turbulent flow structures and particle collision statistics on planetesimal formation

    JpGU-AGU Joint Meeting 2020  2020.5.20 

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  • nヘプタン予混合気の自己着火過程における乱流と反応の相互作用

    久野 僚介, 石原 卓

    第33回数値流体力学シンポジウム  2019.11.28 

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  • 乱流中の慣性粒子の衝突・付着現象理解のための数値解析

    白石啓貴, 櫻井幹記, 石原 卓

    第33回数値流体力学シンポジウム  2019.11.28 

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  • 乱流現象の計算・数理科学 Invited

    石原 卓

    大阪大学MMDSワークショップ 工学と数学の接点を求めて  2019.11.14 

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  • Collision Statistics of Dust Particles in Compressible Turbulence International conference

    Y. Sakurai, T. Ishihara, H. Furuya, M. Umemura, K. Shiraishi

    16th International Conference on Flow Dynamics  2019.11.6 

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  • Drastic Changes of Turbulence in the Ignition Process of an n-Heptane Air Mixture International conference

    Takashi Ishihara, Ryousuke Kuno

    The 5th Symposium on Fluid-Structure-Sound Interactions and Control  2019.8.29 

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  • Effect of the compressibility of turbulent flows on dust particle collision statistics in a protoplanetary disk

    Yoshiki Sakurai, Hitomi Furuya, Naoki Kobayashi, Takashi Ishihara, Naoya Okamoto, Kenji Shiraishi, Masayuki Umemura

    JpGU2019  2019.5.28 

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  • Numerical simulations on the collision, adhesion, and growth of dust particles in turbulent gas in a protoplanetary disk

    Takashi Ishihara, Kohei Hamabata, Yoshiki Sakurai, Masayuki Umemura

    JpGU 2019  2019.5.28 

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  • Thin shear layers in high resolution Direct Numerical Simulations of turbulence International conference

    T. Ishihara, K. Morishita, J.C.R. Hunt

    IUTAM Symposium “Critical flow dynamics around moving/deformable structures with design applications”  2018.6.22 

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  • 乱流の計算科学

    石原 卓

    第23回計算工学講演会  2018.6.7 

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  • 乱流中の微細スケールにおける流体運動と慣性粒子クラスタリングの関係

    櫻井幹記, 石原 卓

    流体力学会中四国九州支部講演会  2018.6.2 

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  • スーパーコンピュータを用いた乱流の大規模直接数値シミュレーションについて Invited

    石原 卓

    流体力学会中四国九州支部講演会  2018.6.2 

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  • Vortex clusters and their time evolution in high-Reynolds-number turbulence, Invited International conference

    ISHIHARA, Takashi

    Fundamental Aspects of Geophysical Turbulence III  2018.3.19 

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  • Motion of inertial particles in high-Reynolds-number turbulence Invited International conference

    Takashi Ishihara, Naoki Kobayashi, Kei Enohata, Masayuki Umemura, Kenji Shiraishi

    NITech Lectures on Turbulence and Cloud  2018.3.8 

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  • 原始惑星系円盤乱流とダスト成長

    石原 卓

    ポスト「京」萌芽的課題・計算惑星 調査研究・準備研究フェーズ成果報告会  2017.12.20 

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  • HCCI乱流燃焼の直接数値計算を用いたnヘプタン予混合気の自己着火過程の数値解析

    久野 僚介, 石原 卓

    第28回内燃機関シンポジウム  2017.12.8 

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  • 乱流と壁の影響を受けたnヘプタンHCCI燃焼の直接数値シミュレーション

    清水 聖有, 久野 僚介, 石原 卓

    第28回内燃機関シンポジウム  2017.12.8 

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  • 原始惑星系円盤乱流場中のダスト粒子運動

    櫻井幹記, 古谷眸, 小林直樹, 岡本直也, 石原卓, 白石賢二, 梅村雅之

    日本天文学会 2017年秋季年会  2017.9.11 

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  • 乱流の直接数値計算を用いた原始惑星系円盤中の岩石ダストの衝突付着成長シミュレーション

    濱端航平, 石原卓, 白石賢二, 梅村雅之

    日本天文学会 2017年秋季年会  2017.9.11 

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  • 乱流中の微細渦構造と慣性粒子クラスタリングの関係のDNSデータ解析

    櫻井 幹記, 小林 直樹, 石原 卓

    日本流体力学会 年会2017 (東京理科大学)  2017.8.30 

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  • 高レイノルズ数乱流中の強い剪断層と圧力場のデータ解析

    石原 卓

    日本流体力学会 年会2017  2017.8.30 

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  • Reynolds Number Dependence Of Straining Motions In Turbulence International conference

    G.E. Elsinga, T. Ishihara, M.V. Goudar, C.B. da Silva, J.C.R. Hunt

    16th European Turbulence Conference  2017.8.21 

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  • Applications of Persistent Homology to Simulated Turbulent Fluid Flows on a 3D Domain International conference

    Rachel Levanger, Takashi Ishihara, Paweł Dłotko, Miroslav Kramár, Konstantin Mischaikow

    Applied Algebraic Topology 2017,  2017.8.8 

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  • Internal interfaces in turbulence Invited International conference

    ISHIHARA, Takashi

    Euromech colloquium on Turbulent/nonturbulent interfaces: from laboratory to geophysical scales  2017.7.5 

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  • Direct numerical simulations of incompressible and compressible turbulence

    Takashi Ishihara

    JAPAN-RUSSIA WORKSHOP ON INNOVATIVE APPROACHES AND SUPERCOMPUTER TECHNOLOGIES IN COMPUTATIONAL PHYSICS  2017.3.14 

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  • 原始惑星系円盤乱流場中のダスト成長過程 International conference

    石原 卓

    ポスト「京」萌芽的課題・計算惑星 第1回 公開シンポジウム:惑星の起源・進化と環境変動の解明を目指して  2017.3.6 

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    Venue:神戸大学先端融合研究環統合研究拠点 コンベンションホール  

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  • 原始惑星系円盤乱流とダスト成長

    石原 卓

    ポスト「京」萌芽的課題・計算惑星 調査研究・準備研究フェーズ成果報告会  2017.2.20 

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  • Rapid Dust Coagulation expedited by Turbulent Clustering in Protoplanetary Disks Invited

    Takashi Ishihara

    Formation of the Solar System and the Origin of Life  2017.2.20 

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    Venue:Lorentz Center@Oort  

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  • 圧縮性乱流直接数値シミュレーション手法の検討 International conference

    櫻井 幹記, 古谷 眸, 岡本 直也, 石原 卓

    第30回数値流体力学シンポジウム  2016.12.12 

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    Venue:タワーホール船堀, 東京  

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  • 乱流燃焼の2次元直接数値計算による等温壁近傍のnヘプタン自己着火過程の数値解析 International conference

    清水 聖有, 加藤正人, 石原 卓

    第27回内燃機関シンポジウム  2016.12.5 

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    Venue:東京工業大学  

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  • Vortex Clusters and Their Time Evolution in High- Reynolds-Number Turbulence

    Takashi Ishihara, Atsuya Uno, Koji Morishita, Mitsuo Yokokawa, Yukio Kaneda

    69th Annual Meeting of the APS Division of Fluid Dynamics  2016.11.20 

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  • カノニカル乱流の大規模直接数値シミュレーション International conference

    石原 卓

    第3回「京」を中核とするHPCIシステム利用研究課題成果報告会  2016.10.21 

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    Venue:コクヨホール  

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  • 大規模直接数値シミュレーションによる 乱流の速度構造関数 International conference

    石原 卓, 森下 浩二, 横川 三津夫, 宇野 篤也, 金田 行雄

    日本流体力学会 年会2016  2016.9.26 

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    Venue:名古屋工業大学  

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  • 一様等方性乱流中の渦構造の動的統計解析 International conference

    服部 裕司, 石原卓

    日本流体力学会 年会2016  2016.9.26 

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    Venue:名古屋工業大学  

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  • 乱流の直接数値計算を用いた原始惑星系円盤ダストの衝突付着成長シミュ レーション International conference

    濱端航平, 江野畑圭, 石原卓, 白石賢二, 梅村雅之

    日本天文学会2016年秋季年会  2016.9.14 

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    Venue:愛媛大学  

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  • 微惑星形成過程解明のための乱流の大規模直接数値計算と粒子追跡 International conference

    小林直樹, 江野畑圭, 石原卓, 白石賢二, 梅村雅之

    日本天文学会2016年秋季年会  2016.9.14 

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    Venue:愛媛大学  

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  • 超多自由度複雑流動現象解明のための計算科学 International conference

    石原卓

    JHPCN:学際大規模情報基盤共同利用・共同研究拠点 第8回 シンポジウム  2016.7.14 

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    Venue:THE GRAND HALL(品川)  

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  • Three types of thin shear layers observed in high Re turbulence

    Takashi Ishihara, Koji Morishita, J.C.R. Hunt

    IMA Conference on Turbulence, Waves and Mixing  2016.7.6 

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  • Thin shear layers observed in the DNS of high Reynolds number turbulence International conference

    Takashi Ishihara, Koji Morishita, Julian, C.R. Hunt

    International Symposium on Near-Wall Flows: Transition and Turbulence  2016.6.20 

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  • 原始惑星系円盤乱流中のダストの運動の数値シミュレーション International conference

    石原 卓

    宇宙生命計算科学連携拠点 第2回ワークショップ  2016.4.27 

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    Venue:筑波大学  

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  • 乱流の「第一原理計算」による原始惑星系円盤中のダスト粒子衝突過程に対する鉛直重力の影響の解析 International conference

    小林直樹, 江野畑圭, 石原卓, 白石賢二, 梅村雅之

    日本天文学会2016年春季年会  2016.3.14 

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  • 原始惑星系円盤乱流と微惑星成長 Invited International conference

    石原 卓, 江野畑圭, 小林直樹, 白石賢二, 中本泰史, 梅村雅之

    日本天文学会2016年春季年会  2016.3.14 

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  • 原始惑星系円盤における圧縮性乱流場中の粒子運動 International conference

    古谷眸, 江野畑圭, 石原卓, 白石賢二, 芳松克則, 岡本直也, 梅村雅之

    日本天文学会2016年春季年会  2016.3.14 

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  • Vortex Clusters and Their Time Evolution in High--‐Reynolds--‐Number Turbulence

    Takashi Ishihara

    A3 workshop:Vortex Dynamics and Turbulence  2016.3.13 

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    Venue:沖縄青年会館(那覇市)  

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  • カノニカルな古典乱流の大規模直接数値シミュレーション International conference

    石原 卓

    平成27年度物性研究所短期研究会「量子乱流と古典乱流の邂逅」  2016.1.5 

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    Venue:東京大学 物性研究所  

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  • 高レイノルズ数乱流中の渦の組織 構造とその時間発展 International conference

    石原 卓, 宇野 篤也, 森 下 浩二, 横川 三津夫, 金田 行雄

    第29回数値流体力学シンポジウム  2015.12.15 

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    Venue:九州大学 筑紫キャンパス  

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  • Turbulent/non-turbulent interface in turbulent magnetohydrodynamic channel flows at low magnetic Reynolds number

    Naoya Okamoto, Yusuke Otake, Takashi Ishihara

    2015 Japan-Russia Workshop  2015.12.10 

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  • Direct numerical simulations of canonical high Reynolds number turbulence

    T. Ishihara, K.Morishita, M.Yokokawa, A.Uno, Y.Kaneda

    2015 Japan-Russia Workshop  2015.12.10 

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  • General mechanisms of thin layers in high Reynolds number turbulent flows

    Julian Hunt, Takashi Ishihara, Koji Morishita

    American Physical Society 68th Annual DFD Meeting (APS-DFD2015)  2015.11.22 

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  • Thin shear layers in homogeneous high Reynolds number turbulence and in turbulent boundary layers

    Takashi Ishihara, Koji Morishita, Julian Hunt

    American Physical Society 68th Annual DFD Meeting (APS-DFD2015)  2015.11.22 

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  • Relative diffusion of a pair of inertial particles in the inertial sub-range of turbulence

    Kei Enohata, Koji Morishita, Takashi Ishihara

    American Physical Society 68th Annual DFD Meeting (APS-DFD2015)  2015.11.22 

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  • Energy spectrum in high Reynolds number turbulence - high resolution DNS results

    Koji Morishita, Takashi Ishihara, Yukio Kaneda, Mitsuo Yokokawa, Atsuya Uno

    American Physical Society 68th Annual DFD Meeting (APS-DFD2015)  2015.11.22 

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  • Analysis of Complex Spatiotemporal Structures of Vortices in High Reynolds Number Turbulence International conference

    Takashi Ishihara, Yuji Hattori

    Twelfth International Conference on Flow Dynamics (ICFD2015)  2015.10.27 

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  • カノニカル乱流の大規模直接数値シミュレーション International conference

    石原 卓

    第2回「京」を中核とするHPCIシステム利用研究課題 成果報告会  2015.10.26 

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    Venue:日本科学未来館  

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  • 宇宙規模流動現象解明のための計算科学 International conference

    石原 卓

    第7回「学際計算科学による新たな知の発見・統合・創出」シンポジウム」  2015.10.19 

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    Venue:筑波大学  

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  • 平行二等温壁間のノルマルヘプタンの自 己着火過程の直接数値シミュレーション International conference

    加藤 正人, 石原 卓, 芳松 克則

    日本流体力学会 年会2015  2015.9.26 

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  • ノルマルヘプタン予混合気自己着火過程 の温度場のパーシステントホモロジーを 用いた解析 International conference

    石原 卓, 末吉史弥, 荒井 迅, Mischaikow Konstantin

    日本流体力学会 年会2015  2015.9.26 

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  • ノルマルヘプタンの予混合自己着火過程 における流れの役割解明のための数値 実験 International conference

    末吉 史弥, 石原 卓, 芳松 克則

    日本流体力学会 年会2015  2015.9.26 

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  • 大規模直接数値シミュレーションによる乱流のエネルギースペクトル International conference

    石原卓, 森下浩二, 横川三津夫, 宇野篤也, 金田行雄

    日本物理学会2015年秋季大会  2015.9.16 

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    Venue:関西大学  

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  • 一様等方性乱流中の高渦度領域の動的形状解析II International conference

    服部裕司, 石原卓

    日本物理学会2015年秋季大会  2015.9.16 

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    Venue:関西大学  

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  • 乱流の直接数値計算による原始惑星 系円盤中の粒子運動に対する鉛直重力の影響の解析 International conference

    小林直樹, 江野畑圭, 石原卓, 白石賢二, 梅村雅之

    日本天文学会 2015年秋季大会  2015.9.9 

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    Venue:甲南大学  

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  • 電磁流体乱流の直接数値シミュレー ションによる原始惑星系円盤内の粒子運動の解析 International conference

    高橋良輔, 江野畑圭, 岡本直也, 芳松克則, 石原卓, 白石賢二, 梅村雅之

    日本天文学会 2015年秋季大会  2015.9.9 

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  • 微惑星形成過程解明のための乱流の直接数値計算と粒子追跡 International conference

    江野畑圭, 石原 卓, 白石賢二, 森下浩二, 中本泰史, 梅村雅之

    日本天文学会 2015年秋季大会  2015.9.9 

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    Venue:甲南大学  

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  • Accurate Parallel Algorithm for Tracking Inertial Particles in Large-Scale Direct Numerical Simulations of Turbulence

    Takashi Ishihara, Kei Enohata, Koji Morishita, Mitsuo Yokokawa, Katsuya Ishii

    PaCT2015 13th International Conference on Parallel Computing Technologies  2015.8.31 

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  • Direct numerical simulation and dissipation element analysis of an auto-ignition process in a homogeneous n-heptane/air mixture turbulence with temperature fluctuations

    Takashi Ishihara

    Workshop on Conditional statistics along lines and trajectories in turbulence  2015.8.24 

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  • 超多自由度複雑流動現象解明のための計算科学 International conference

    石原 卓

    学際大規模情報基盤共同利用・共同研究拠点第7回 シンポジウム  2015.7.9 

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    Venue:THE GRAND HALL(品川)  

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  • Coherent vorticity in turbulent channel flow: a wavelet viewpoint

    Katsunori Yoshimatsu, Teluo Sakurai, Kai Schneider, Marie Farge, Koji Morishita, Takashi Ishihara

    Ninth International Symposium on Turbulence and Shear Flow Phenomena  2015.6.30 

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  • 超多自由度複雑流動現象解明のための高効率な並列計算コード開発 International conference

    石原 卓

    名古屋大学HPC 計算科学連携研究プロジェクト成果報告シンポジウム  2015.6.3 

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    Venue:名古屋大学ES 総合館1 階ES ホール  

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  • Scalar and momentum transfer processes across stratified sheared turbulent interfaces

    J.C.R. Hunt, M. Moustaoui, A. Mahalov, T. Ishihara, J. Westerweel, M. Braza

    EUROMECH Colloquium 567: Turbulent mixing in stratified flows  2015.3.22 

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  • Direct numerical simulation of high reynolds number turbulence by the K computer

    T. Ishihara, K.Morishita, M.Yokokawa, A.Uno, Y.Kaneda

    JAPAN-RUSSIA WORKSHOP ON SUPERCOMPUTER MODELING, INSTABILITY AND TURBULENCE IN FLUID DYNAMICS  2015.3.4 

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  • カノニカル乱流の大規模直接数値計算 International conference

    石原 卓

    第27回 理論懇シンポジウム 「理論天文学・宇宙物理学と境界領域」  2014.12.24 

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    Venue:国立天文台 三鷹キャンパス すばる棟大セミナー室  

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  • 乱流燃焼の大規模直接数値シミュレーション International conference

    石原 卓

    第22回LBM研究会  2014.12.19 

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    Venue:名古屋大学  

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  • 乱流境界層における慣性粒子の運動の直接数値シミュレーション International conference

    平田 亮介, 石原 卓

    第28回数値流体力学シンポジウム  2014.12.9 

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    Venue:タワーホール船堀, 東京  

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  • ノルマルヘプタン予混合気のHCCI乱流燃焼の散逸要素解析 International conference

    浅田 宗志, 石原 卓, 芳松 克則

    第28回数値流体力学シンポジウム  2014.12.9 

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    Venue:タワーホール船堀, 東京  

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  • 一様等方性乱流の直接数値シミュレーションコードの京コンピュータ向け最適化 International conference

    森下 浩二, 横川 三津夫, 宇野 篤也, 石原 卓, 金田 行雄

    第205回ARC・第147回HPC合同研究発表会(HOKKE-22)  2014.12.9 

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    Venue:小樽経済センター  

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  • Computational science of high Reynolds number turbulence International conference

    2014.12.8 

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  • Coherent vorticity extraction in turbulent channel flow using anisotropic wavelets

    Katsunori Yoshimatsu, Teluo Sakurai, Kai Schneider, Marie Farge, Koji Morishita, Takashi Ishihara

    67th Annual Meeting of the APS Division of Fluid Dynamics  2014.11.23 

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  • Interfacial phenomena in turbulent magnetohydrodynamic channel flows at low magnetic Reynolds number

    Naoya Okamoto, Yusuke Otake, Takashi Ishihara

    67th Annual Meeting of the APS Division of Fluid Dynamics  2014.11.23 

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  • Energy Spectra of Higher Reynolds Number Turbulence by the DNS with up to 122883 Grid Points

    Takashi Ishihara, Yukio Kaneda, Koji Morishita, Mitsuo Yokokawa

    67th Annual Meeting of the APS Division of Fluid Dynamics  2014.11.23 

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  • カノニカル乱流の大規模直接数値シミュレーション International conference

    石原 卓

    第1回「京」を中核とするHPCIシステム利用研究課題 成果報告会  2014.10.31 

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    Venue:コクヨホール  

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  • 宇宙規模流動現象解明のための計算科学 International conference

    石原 卓

    第6回「学際計算科学による新たな知の発見・統合・創出」シンポジウム  2014.10.22 

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    Venue:筑波大学 計算科学研究センター  

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  • Thin shear layers in homogeneous high Reynolds number turbulence and in turbulent boundary layer

    Takashi Ishihara, Julian, C.R. Hunt

    Takashi Ishihara, Julian C.R. Hunt  2014.10.10 

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  • Vortical Structures in High Reynolds Number Turbulence (Re~105) by Large-Scale DNS on K computer

    Takashi Ishihara

    Seminar at Imperial College London  2014.10.8 

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  • Dissipation element analysis of an auto-ignition process in a homogeneous n-heptane/air mixture turbulence with temperature fluctuations

    Takashi Ishihara

    JSPS Supported Meeting on Interscale Transfers and Flow Topology in Equilibrium and Nonequilibrium Turbulence  2014.9.15 

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  • Coherent vorticity extraction in turbulent channel flow using orthogonal wavelets

    T. Sakurai, K. Yoshimatsu, K. Schneider, M. Farge, K. Morishita, T. Ishihara

    European Fluid Mechanics Conference 10  2014.9.14 

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  • Vortical Structures in the DNS of Turbulence at Reynolds Number Higher Than 104

    Takashi Ishihara

    Mini-Workshop for Turbulence Research  2014.7.11 

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  • Vortical structures in homogeneous high Reynolds number turbulence International conference

    Takashi Ishihara

    2014.4.17 

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  • 大気境界層乱流現象解明のための計算科学 International conference

    石原 卓

    平成25年度地球シミュレータ利用報告会 プログラム  2014.1.27 

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  • 高レイノルズ数乱流中の薄い剪断層とその時間変化について International conference

    石原 卓, Pradeep Jha, 金田行雄, Julian Hunt

    大スケール流体運動と乱流揺らぎ 京大 数理解析研究所 共同研究集会  2014.1.8 

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    Venue:京大 数理解析研究所  

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  • 「京」コンピュータを用いたカノニカル乱流の大規模直接数値シミュレーション International conference

    石原 卓, 森下浩二, 横川三津夫, 宇野篤也, 金田行雄

    第27回 数値流体力学シンポジウム  2013.12.17 

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    Venue:名古屋大学  

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  • 低磁気レイノルズ数MHDチャネル乱流における乱流・非乱流界面 International conference

    大竹悠介, 岡本直也, 石原 卓

    第27回 数値流体力学シンポジウム  2013.12.17 

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    Venue:名古屋大学  

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  • ノルマルヘプタンの自己着火過程の3次元DNSと温度場に着目したデータ解析 International conference

    伊藤貴政, 石原 卓

    第27回 数値流体力学シンポジウム  2013.12.17 

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    Venue:名古屋大学  

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  • Structure of the turbulent/non-turbulent interface of turbulent boundary layers - DNS results

    Takashi Ishihara, Hiroki Ogasawara, Julian C.R. Hunt

    APS-66th Annual DFD meeting  2013.11.24 

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  • Inertial Subrange Spectra in the Log-Law Layer of Turbulent Channel Flow

    Yukio Kaneda, Koji Morishita, Takashi Ishihara

    APS-66th Annual DFD meeting  2013.11.24 

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  • Temporal behavior of strong shear layers in high Reynolds number turbulence

    Pradeep K. Jha, Takashi Ishihara

    APS-66th Annual DFD meeting  2013.11.24 

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  • カノニカル乱流の大規模直接数値シミュレーション (hp120242) International conference

    石原 卓

    平成25年度 「京」を中核とするHPCIシステム利用研究課題 中間報告会  2013.10.2 

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    Venue:タイム24ビル(東京都江東区)  

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  • 一様等方性乱流中の高渦度領域の動的形状解析 International conference

    服部裕司, 石原 卓

    日本物理学会 2013年秋季大会  2013.9.25 

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    Venue:徳島大学  

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  • 高レイノルズ数乱流中の剪断層の時間発展 International conference

    石原 卓, Jha Pradeep, 金田行雄, Julian Hunt

    日本流体力学会 年会2013  2013.9.12 

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    Venue:東京農工大  

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  • Structure of the turbulent/non-turbulent interface of turbulent boundary layers-DNS results

    Takashi Ishihara

    Turbulence Colloquium TCM2013  2013.9.5 

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  • Dynamic Geometrical Analysis of High-Enstrophy Structures in Isotropic Turbulence

    Yuji Hattori, Takashi Ishihara

    European Turbulence Conference(ETC)14  2013.9.1 

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  • Thin Shear Layers In High Reynolds Number Turbulence- A Coherent-structure Model

    Julian Hunt, Takashi Ishihara, Yukio Kaneda

    ETC14  2013.9.1 

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  • Thin Shear Layers In High Reynolds Number Turbulence-Dns Results

    Takashi Ishihara, Julian Hunt, Yukio Kaneda

    ETC14  2013.9.1 

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  • 超多自由度複雑流動現象解明のための計算科学 International conference

    石原 卓

    学際大規模情報基盤共同利用・共同研究拠点第5回シンポジウム  2013.7.11 

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    Venue:THE GRAND HALL(東京)  

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  • 高レイノルズ数乱流の渦構造について International conference

    石原 卓

    「宇宙生命計算科学連携拠点」ワークショップ  2013.6.28 

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    Venue:筑波大学計算科学研究センター ワークショップ室  

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  • Conditional Analysis of Statics Obtained Near the Turbulent/Non-Turbulent Interface of Turbulent Boundary Layers

    T. Ishihara, H. Ogasawara

    ERCOFTAC SYMPOSIUM on Unsteady Separation in Fluid-Structure Interaction  2013.6.17 

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  • Turbulence Near Interfaces- Modelling and Simulations

    J.C.R. Hunt, T. Ishihara, Y. Hoarau, M. Braza

    ERCOFTAC SYMPOSIUM on Unsteady Separation in Fluid-Structure Interaction  2013.6.17 

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  • 乱流境界層の乱流・非乱流界面近傍の条件付き統計解析 International conference

    石原 卓, 小笠原浩樹

    九大応力研共同利用研究集会「壁乱流における大規模構造の統計法則と動力学に果たす役割」  2013.2.23 

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    Venue:九州大学  

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  • 高レイノルズ数チャネル乱流の非等方スペクトル International conference

    森下 浩二, 石原 卓, 金田 行雄

    九大応力研共同利用研究集会「壁乱流における大規模構造の統計法則と動力学に果たす役割」  2013.2.23 

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    Venue:九州大学  

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  • 高レイノルズ数乱流中の強い渦の組織構造 International conference

    石原 卓

    RIMS 共同研究 研究集会「偏微分方程式の背後にある確率過程と解の族が示す統計力学的な現象の解析」  2013.2.14 

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    Venue:京都大学  

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  • ノルマルヘプタンの自己着火過程における反応と乱流の相互作用の3次元DNSとデータ解析 International conference

    三木貴史, 生田博也, 寺地 淳, 石原 卓

    第26回数値流体力学シンポジウム  2012.12.18 

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    Venue:国立オリンピック記念青少年総合センター  

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  • 乱流境界層のDNSにおける乱流・非乱流界面近傍の構造と統計 International conference

    小笠原浩樹, 石原 卓

    第26回数値流体力学シンポジウム  2012.12.18 

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    Venue:国立オリンピック記念青少年総合センター  

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  • Strong Shear Layer in High Re Turbulence - DNS Results

    Takashi Ishihara

    Mini Workshop on Urban Research a Review & Outlook on the Hong Kong Built Environment  2012.12.7 

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  • n-Heptane予混合圧縮自己着火過程の3次元直接数値シミュレーションに基づくデータ解析 International conference

    三木貴史, 生田博也, 寺地 淳, 石原 卓

    第50回燃焼シンポジウム  2012.12.5 

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    Venue:愛知県産業労働センターウインクあいち  

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  • Small-scale statistics in direct numerical simulation of turbulent channel flow up tp Ret=5120

    Koji Morishita, Takashi Ishihara, Yukio Kaneda

    APS 65th annual DFD meeting  2012.11.18 

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  • Intense dissipative mechanisms of strong thin shear layers in high Reynolds number turbulence

    Takashi Ishihara, Julian C.R.Hunt, Yukio Kaneda

    APS 65th annual DFD meeting  2012.11.18 

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  • Conditional analysis of the statistics near the turbulent/non-turbulent interface of turbulent boundary layers

    Hiroki Ogasawara, Takashi Ishihara

    APS 65th annual DFD meeting  2012.11.18 

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  • ノルマルヘプタン自己着火過程における反応と乱流の相互作用の三次元DNS 解析 International conference

    寺地 淳, 生田博也, 三木貴史, 石原 卓

    第23回内燃機関シンポジウム  2012.10.31 

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    Venue:北海道大学  

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  • Strong thin shear layers in homogeneous high Re turbulence- structures and statistics

    Takashi Ishihara, Julian, C.R. Hunt, Yukio Kaneda

    First Multiflow Conference on the Turbulent-Non turbulent interface, Madrid, Spain  2012.10.25 

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  • 4D visualization of isotropic turbulence and dynamics of high-enstrophy structures

    Yuji Hattori, Takashi Ishihara

    2012.9.27 

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  • Interactive visualizations of the large-scale data generated by the DNS of isotropic turbulence on 40963 grid points

    Takashi Ishihara, Kensaku Mori

    JSST2012 International Conference on Simulatin Technology  2012.9.27 

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  • Improvement of Reality of CG Motion Pictures by Hydrodynamic Effects

    Takashi Ishihara, Yuji Hattori

    Ninth International Conerence on Flow Dynamics  2012.9.19 

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  • レイノルズ数の異なる 4096 3 DNS 乱流のマルティフラクタルPDF理論による比較解析 International conference

    武智公平, 有光直子, 有光敏彦, 金田行雄, 石原 卓

    日本物理学会 2012年秋季大会  2012.9.18 

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    Venue:横浜国立大学  

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  • 乱流境界層の直接数値シミュレーションを用いた乱流・非乱流界面の解析 International conference

    小笠原浩樹, 石原 卓, 金田行雄

    日本流体力学会年会2012  2012.9.16 

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    Venue:高知大学  

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  • 一様磁場中における電磁流体チャネル乱流の直接数値計算 International conference

    大竹悠介, 岡本直也, 石原 卓

    日本流体力学会年会2012  2012.9.16 

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    Venue:高知大学  

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  • 高レイノルズ数一様等方性乱流中の強い剪断層 International conference

    石原 卓, Hunt Julian C.R, 金田行雄

    日本流体力学会年会2012  2012.9.16 

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    Venue:高知大学  

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  • 大規模直接数値シミュレーションによる周期境界乱流中のエネルギー散逸率とエネルギースペクトル International conference

    金田行雄, 石原 卓, 横川三津夫, 板倉憲一, 宇野篤也

    日本流体力学会年会2012  2012.9.16 

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    Venue:高知大学  

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  • 直接数値計算による三次元レイリー・ベナール対流乱流の渦構造 International conference

    丹羽佑太, 星野邦雄, 芳松克則, 石原 卓

    日本流体力学会年会2012  2012.9.16 

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    Venue:高知大学  

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  • Numerical Analysis of Effect of Intermediate Species Diffusion on Low Temperature Oxidation Process in a Homogeneous n-Heptane Mixture

    Atsushi Teraji, Takashi Ishihara, Yukio Kaneda

    COMODIA 2012  2012.7.23 

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  • 高レイノルズ数乱流の計算科学 International conference

    石原 卓

    流体若手夏の学校2012  2012.7 

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    Venue:京都  

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  • Volume Penalization 法による翼果まわりの流れの数値解析 International conference

    澤村陽一, 石原 卓

    研究集会「生物流体力学における同期および関連する現象」  2012.5.21 

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    Venue:京都大学数値解析研究所  

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  • 乱流の計算科学 International conference

    石原卓

    九州大学大学院総合理工学府 大気海洋環境システム学専攻 集中講義  2012.1 

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    Venue:九州大学大学院総合理工学府  

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  • nヘプタンの簡略反応モデルを用いた自己着火過程の3次元直接数値シミュレーション International conference

    生田博也, 石原 卓, 寺地 淳

    第25回数値流体力学シンポジウム  2011.12.19 

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    Venue:大阪大学コンベンションセンター  

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  • Volume Penalization 法による翼果モデルまわりの流れの数値解析 International conference

    澤村陽一, 石原 卓

    第25回数値流体力学シンポジウム  2011.12.19 

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    Venue:大阪大学コンベンションセンター  

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  • High-performance computing of canonical high-Reynolds-number turbulent flows

    Takashi Ishihara

    ICTS-TIFR Discussion Meeting-2011  2011.12.12 

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  • Strong thin shear layers in high Reynolds number turbulence

    Takashi Ishihara, Julian, C.R. Hunt, Yukio Kaneda

    64th annual meeting of the APS division of fluid dynamics  2011.11.20 

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  • The structure of the vorticity field in the near-wall region of turbulent channel flow at high-Reynolds number

    Koji Morishita, Takashi Ishihara, Yukio Kaneda

    64th annual meeting of the APS division of fluid dynamics  2011.11.20 

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  • 高レイノルズ数平行平板間乱流DNSにおける小スケール統計 International conference

    森下浩二, 石原 卓, 金田行雄

    平成23年度共同利用研究集会「乱流現象及び非平衡系の多様性と普遍性」  2011.11.10 

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    Venue:九州大学応用力学研究所  

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  • nヘプタンの簡略反応モデルを用いた乱流中の自己着火現象の直接数値計算 International conference

    生田博也, 石原 卓, 寺地 淳

    平成23年度共同利用研究集会「乱流現象及び非平衡系の多様性と普遍性」  2011.11.10 

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    Venue:九州大学応用力学研究所  

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  • Improvement of reality of CG motion pictures by hydrodynamic effects

    Takashi Ishihara, Yuji Hattori

    2011.11.9 

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  • DNS study of the small-scale statistics in turbulent channel flow at high-Reynolds numbers International conference

    Koji Morishita, Takashi Ishihara, Yukio Kaneda

    CCS Symposium Autumn 2011  2011.11.1 

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  • Strong shear layers in high Reynolds number homogeneous turbulence

    Takashi Ishihara

    CCS Symposium Autumn 2011  2011.11.1 

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  • 40963DNS乱流のマルティフラクタル確率密度関数理論による解析 International conference

    有光直子, 武智公平, 有光敏彦, 金田行雄, 石原 卓

    日本物理学会2011年秋季大会  2011.9.21 

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  • Conditional analysis near strong shear layers in DNS of isotropic turbulence at high Reynolds number

    Takashi Ishihara, J.C.R. Hunt, Yukio Kaneda

    13 European Turbulence Conference  2011.9.12 

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  • Small-scale statistics in direct numerical simulation of turbulent channel flow at high-Reynolds number

    Koji Morishita, Takashi Ishihara, Yukio Kaneda

    13 European Turbulence Conference  2011.9.12 

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  • 渦・境界相互作用の大規模数値計算による研究 International conference

    石原 卓

    第2回数学領域シンポジウム  2011.9.7 

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    Venue:アキバプラザ  

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  • 2D direct numerical simulation of intermediate species diffusion in low temperature oxidation process

    Atsushi Teraji, Takahiro Morikawa, Takashi Ishihara, Yukio Kaneda

    ICDERS  2011.7.24 

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  • 超多自由度複雑流動現象解明のための計算科学 International conference

    石原 卓

    学際大規模情報基盤共同利用・共同研究拠点第3回シンポジウム  2011.7.14 

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    Venue:東京  

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  • Conditional statistics near strong thin shear layers in DNS of high Reynolds number turbulence

    Takashi Ishihara

    Seminar at the University of Hong Kong  2011.6.16 

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  • 超多自由度複雑流動現象解明のための高効率な並列計算コード開発 International conference

    石原 卓

    名古屋大学HPC計算科学連携研究プロジェクト成果報告シンポジウム  2011.5.10 

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    Venue:名古屋大学高等研究院  

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  • Conditional statistics near strong thin shear layers in DNS of high Re turbulence

    Takashi Ishihara

    KITP Program: The Nature of Turbulence  2011.4.20 

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  • Conditional statistics near strong thin shear layers in DNS of isotropic turbulence at high Reynolds number

    Takashi Ishihara, Julian C.R. HUNT, Yukio Kaneda

    The School of Mathematical & Statistical Sciences (SoMSS) Seminar  2011.4.13 

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  • Local-isotropy in direct numerical simulation of turbulent channel flow at high-Reynolds number

    Koji Morishita, Takashi Ishihara, Yukio Kaneda

    SIAM Conference on Computational Science and Engineering  2011.2.28 

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  • Nヘプタンの簡略化反応モデルを用いた自己着火過程の2次元直接数値計算 - 自己着火過程の温度依存性の検討 International conference

    森川貴弘, 西田成志, 寺地 淳, 石原 卓, 金田行雄

    第24回数値流体力学シンポジウム  2010.12.20  日本流体力学会

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    Venue:慶應義塾大学日吉キャンパス  

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  • 高レイノルズ数チャネル乱流の局所等方性のDNSによる検証 International conference

    森下浩二, 石原 卓, 金田行雄

    第24回数値流体力学シンポジウム  2010.12.20  日本流体力学会

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    Venue:慶應義塾大学日吉キャンパス  

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  • Conditional statistics near strong thin shear layers in DNS of isotropic turbulence at high Reynolds number

    Takashi Ishihara, Julian, C.R. Hunt, Yukio Kaneda

    63rd Annual Meeting of the APS Division of Fluid Dynamics  2010.11.21 

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  • 乱流混合層DNSを用いた乱流/非乱流界面近傍の渦構造の条件付き統計の解析 International conference

    石原 卓, 後藤 崇, 金田行雄

    平成22年度共同利用研究集会「乱流現象及び非平衡系の多様性と普遍性」  2010.11.11 

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    Venue:九州大学応用力学研究所  

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  • ノルマルヘプタン均質予混合場における中間生成物拡散が低温酸化反応過程に与える影響の数値解析 International conference

    寺地 淳, 西田成志, 森川貴弘, 石原 卓, 金田行雄

    第21回内燃機関シンポジウム  2010.11.10 

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    Venue:岡山大学  

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  • Large-scale and high-resolution direct numerical simulation of turbulent boundary layer: dynamics of hairpin vortex structures

    Takashi Ishihara

    Japan-Russia Workshop on Numerical Investigation of Hydrodynamic Instabilities and Turbulence with High-performance Computing  2010.10.6 

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  • 高レイノルズ数乱流の大規模直接数値シミュレーション -乱流の大規模データベースの生成・解析・可視化- International conference

    石原 卓

    第一回計算科学セミナー  2010.9.27 

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    Venue:名古屋大学環境総合館, 名古屋市  

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  • 乱流の大規模直接数値計算データを用いた4次速度構造関数及び圧力勾配・速度構造関数の解析 International conference

    中西崇仁, 石原 卓

    日本物理学会 平成22年度 秋季大会  2010.9.23  日本物理学会

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    Venue:大阪府立大学  

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  • 乱流境界層の直接数値シミュレーションにおけるヘアピン渦構造の力学 International conference

    石原 卓, 加藤雅之, 金田行雄

    日本流体力学会 年会2010  2010.9.9  日本流体力学会

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    Venue:北海道大学  

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  • 乱流混合層における乱流/非乱流界面近傍の渦構造と条件付き統計 International conference

    後藤 崇, 石原 卓, 金田行雄

    日本流体力学会 年会2010  2010.9.9  日本流体力学会

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    Venue:北海道大学  

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  • nヘプタンの簡略化反応モデルを用いた自己着火過程の2次元直接数値シミュレーション International conference

    西田成志, 寺地淳, 石原 卓, 金田行雄

    第23回数値流体力学シンポジウム  2009.12.16 

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  • スペクトル法を用いた乱流境界層の直接数値計算 International conference

    石原 卓, 加藤雅之, 金田行雄

    第87期日本機械学会流体工学部門講演会  2009.11.7 

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  • Computational analysis of high Reynolds number turbulence using pressure gradient vector field

    Takashi Ishihara, Kazuki Takahashi

    RIMS Workshop on Mathematics and Physics across the Diversity of Turbulence Phenomena, the Kobe Institute  2009.7.9 

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  • Examination of Kolmogorov's 4/5 law by high-resolution DNS data of turbulence International conference

    2007.12.19 

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  • 大規模DNSデータを用いたKolmogorovの4/5法則の検証 International conference

    吉野 順也, 石原 卓, 金田 行雄

    九州大学応用力学研究所平成19年度共同利用研究集会「乱流現象及び多自由度系の動力学,構造と統計法則」  2007.11.23 

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    Venue:九州大学応用力学研究所, 福岡県春日市  

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  • Some Attempts at Computer Aided Understanding of Turbulence

    IUTAM Symposium 2006 NAGOYA `Computational Physics and New Perspectives in Turbulence'  2006.9.12 

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  • Ultra Direct Numerical Simulation of Turbulence on the Earth Simulator

    Takashi Ishihara

    6th World Congress on Computational Mechanics, Beijing, China  2004.9 

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  • 乱流のUltra DNSデータの解析 International conference

    石原 卓

    統計数理解析研究所 研究集会:乱流の統計理論とその応用  2004.3 

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  • 乱流の Ultra DNS データの解析 -エネルギースペクトルのレイノルズ数依存性- International conference

    石原 卓, 金田 行雄

    第17回数値流体力学シンポジウム  2003.12.17 

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    Venue:国立オリンピック記念青少年センター, 東京  

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  • 大規模直接数値計算による非圧縮乱流場のデータ解析ーエネルギー散逸・エンストロフィー・圧力のスペクトルについて International conference

    石原 卓, 金田行雄

    九州大学応用力学研究所 研究集会:乱流研究の異分野融合と新たな創成  2003.12 

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  • Reynolds number dependence of the one-point statistics of velocity-derivatives in high-resolution DNS of incompressible turbulence

    Takashi Ishihara, Yukio Kaneda

    The American Physical Society, 56th Annual Meeting of the Division of Fluid Dynamics  2003.11.23 

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  • 一様せん断乱流における慣性小領域の非等方的構造 International conference

    吉田 恭, 石原 卓, 金田 行雄

    第52回理論応用力学講演会  2003.1.28 

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    Venue:東京  

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  • 地球シミュレータによる乱流の ultra simulation International conference

    金田 行雄, 石原 卓, 横川 三津夫, 板倉 憲一, 宇野 篤也

    九州大学応用力学研究所研究集会「乱流現象の多様性と普遍性」  2002.12.11 

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    Venue:九州大学応用力学研究所, 春日市  

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  • 乱流のUltra Simulation International conference

    石原 卓, 金田行雄, 横川三津夫, 板倉憲一, 宇野篤也

    第6回シミュレーション・サイエンスシンポジウム  2002.12  核融合科学研究所

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  • 16.4-Tflops Direct Numerical Simulation of Turbulence by a Fourier Spectral Method on the Earth Simulator

    Mitsuo Yokokawa, Kenichi Itakura, Atsuya Uno, Takashi Ishihara, Yukio Kaneda

    Super Computing 2002  2002.11.16 

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  • High Resolution DNS of Incompressible Homogeneous Forced Turbulence -Time Dependence of the Statistics-Statistical Theories and Computational Approaches to Turbulence; Modern Perspectives and Applications to Global-Scale Flows

    Takashi Ishihara, Yukio Kaneda

    Yukio Kaneda and Toshiyuki Gotoh (Eds.), Springer-Verlag Tokyo  2002.11 

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  • Spectra of Fourth Order Velocity Moment in Homogeneous Isotropic Turbulence:Direct Numerical simulation and Lagrangian Theory

    Yukio Kaneda, Takashi Ishihara

    IUTAM Sympojium on Reynolds Number Scaling in Turbulent Flow  2002.9.11 

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  • 乱流の非等方スペクトルとそのReynolds数依存性 International conference

    吉田恭, 石原卓, 金田行雄

    日本流体力学会年会2002  2002.7 

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    Venue:仙台国際センター, 仙台市  

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  • 一様等方性乱流のシミュレーション:スペクトル法vs高次精度線の方法 International conference

    芳松克則, 石原卓, 山崎陽介, 金田行雄, 西田秀利, 中井聡, 里深信行

    日本物理学会第57回年次大会,  2002.3.24 

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    Venue:立命館大学, 草津市  

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  • 一様シアー乱流の非等方スペクトル International conference

    石原卓, 吉田恭, 金田行雄

    日本物理学会第57回年次大会  2002.3.24 

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    Venue:立命館大学, 草津市  

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  • 成層乱流のラージ・エディ・シミュレーションとサブグリッド・モデリング International conference

    吉田恭, 石原卓, 金田行雄

    第3回非静力学モデルに関するワークショップ  2001.9.18 

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    Venue:学術総合センター, 東京都  

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  • 三次元乱流場の予測可能性 ― 大規模渦のデータ同化の影響 International conference

    林一樹, 石原卓, 金田行雄

    日本物理学会2001年秋季大会  2001.9.17 

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    Venue:徳島分理大学, 徳島市  

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  • 三次元乱流場における二粒子拡散について ― 慣性小領域の有限性の影響 International conference

    石原卓, 金田行雄

    日本物理学会2001年秋季大会  2001.9.17 

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    Venue:徳島分理大学, 徳島市  

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  • 成層乱流のスペクトルLES International conference

    吉田恭, 石原卓, 金田行雄

    日本流体力学会年会2001  2001.7.31 

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    Venue:工学院大学, 東京都  

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  • 乱流の慣性小領域におけるラグランジュ統計 International conference

    石原卓, 金田行雄

    研究集会:乱流構造の数理 ― 発生・動力学・統計・応用(Study of Turbulence Structure ― Generation, Dynamics, Statistics and Application)  2001.7 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:京都大学数理解析研究所  

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  • 3次元等方性乱流の予測可能性の評価 International conference

    藤田大志, 吉田恭, 石原卓, 金田行雄

    日本物理学会第56回年次大会  2001.3.27 

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    Venue:中央大学多摩キャンパス, 八王子市  

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  • 2次元乱流における予測可能性とLES International conference

    山平倫道, 吉田恭, 石原卓, 金田行雄

    日本物理学会第56回年次大会  2001.3.27 

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    Venue:中央大学多摩キャンパス, 八王子市  

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  • 非等方性乱流のLESスペクトル理論モデルの a posteriori テスト International conference

    藤村宣昭, 山崎陽介, 石原卓, 金田行雄

    日本物理学会春の分科会  2001.3 

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    Venue:関西大学, 吹田市  

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  • 慣性小領域における3波相互作用の相似性 International conference

    石原卓, 金田行雄

    日本物理学会春の分科会  2001.3 

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    Venue:関西大学, 吹田市  

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  • 大規模乱流DNSデータの可視化 International conference

    石原卓, 大野哲也, 森建策, 末永康仁, 石井克哉, 金田行雄

    九州大学応用力学研究所研究集会  2000.12 

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  • 成層乱流のラージ・エディ・シミュレーション International conference

    藤村宣昭, 石原卓, 金田行雄

    日本物理学会第55回年次大会  2000.9 

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    Venue:新潟大学, 新潟市  

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  • 大規模乱流シミュレーションにおける高波数成分の取り扱い方の影響 International conference

    山崎陽介, 石原卓, 金田行雄

    日本物理学会第55回年次大会  2000.9 

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    Venue:新潟大学, 新潟市  

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  • Statistics of small-scale structure of homogeneous isotropic turbulence

    IUTAM Symposium on Geometry and Statistics of Turbulence  1999.11.1 

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  • 一様等方乱流中の微細構造の統計(大規模DNSデータベース解析) International conference

    石原卓, 山崎陽介, 金田行雄

    九州大学応用力学研究所研究集会  1999.11 

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  • 乱流の大規模数値実験 International conference

    石原 卓

    九州大学応用力学研究所 研究集会:流体方程式の解と縮約解析  1999.10 

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  • Leithによる2次元LESモデルの検証 International conference

    大川新太朗, 石原卓, 金田行雄

    日本物理学会秋の分科会  1999.9 

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    Venue:岩手大学, 盛岡市  

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  • 3次元乱流のLESスペクトル理論モデルの a posteriori テスト International conference

    石川綱一郎, 石原卓, 金田行雄

    日本物理学会秋の分科会  1999.9 

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    Venue:岩手大学, 盛岡市  

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  • Numerical studies of large scale turbulent flows in two and three dimensions

    Kamen N. Beronov, Takashi Ishihara, Yukio Kaneda

    Oxford-Kobe seminar: The Second Scientific Meeting on System Engineering and Applied Mathematics  1998.12.3 

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  • Numerical Studies of Large Scale Turbulent Flows in Two and Three Dimensions

    Kamen N. Beronov, Takashi Ishihara, Yukio Kaneda

    Oxford Kobe Seminars: The Second Scientific Meeting on Systems Engineering and Applied Mathematics  1998.12 

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  • 回転乱流中の粒子拡散 International conference

    山崎陽介, 石原卓, 金田行雄

    九州大学応用力学研究所研究集会「乱流現象とその周辺」  1998.11.26 

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    Venue:福岡県春日市  

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  • 一様等方乱流中の微細構造の統計(大規模DNSデータベース解析) International conference

    石原卓, 山崎陽介, 金田行雄

    九州大学応用力学研究所研究集会「乱流現象とその周辺」  1998.11.26 

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    Venue:福岡県春日市  

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  • 一様ストレイン場中の渦層の Analytic Structure International conference

    石原卓, 金田行雄

    研究集会:計算流体力学に関わる数理的諸問題  1996.6.24 

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    Venue:京都大学数理解析研究所  

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  • Singularity Formation in the Shape of a Vortex Sheet in Three-Dimensions - Numerical Simulation

    Takashi Ishihara, Yukio Kaneda

    Proceedings of the Second International Workshop on Vortex Flows and Related Numerical Methods  1995.8 

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  • Spontaneous Singularity Formation in the Shape of Vortex Sheet in Three-Dimensional Flow: Analysis and Numerical Simulation International conference

    1994.5.30 

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  • 3次元的渦面の運動の解析と数値シミュレーション International conference

    石原卓, 金田行雄

    研究集会:流体における波動現象の数理とその応用  1993.10.27 

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    Venue:京都大学数理解析研究所  

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  • Lagrange 的 Strain Tensor の相関時間 International conference

    石原卓, 金田行雄

    研究集会:乱流の発生と統計法則  1992.1.21 

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    Venue:京都大学数理解析研究所  

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Awards

  • JSST 2021 Best Author Award

    2021.8   Japan Society for Simulation Technology   Direct Numerical Simulations of Navier-Stokes Equation in Astrophysics : The Growth of Dust Grains in Protoplanetary Disk Turbulence

    Masayuki Umemura, Takashi Ishihara

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  • Award for Outstanding Paper in Fluid Mechanics

    2012.2   Energy Dissipation Rate and Energy Spectrum in High Resolution Direct Numerical Simulations of Turbulence in a Periodic Box

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  • SC2002 Gordon Bell Award

    2002.11   IEEE   16.4-Tflops Direct Numerical Simulation of Turbulence by a Fourier Spectral Method on the Earth Simulator

    M Yokokawa, K Itakura, A Uno, T Ishihara, Y Kaneda

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Research Projects

  • A new scenario of dust growth in protoplanetary disks explored through large-scale direct numerical simulations of turbulence

    Grant number:20H01948  2020.04 - 2024.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    石原 卓, 奥住 聡, 梅村 雅之

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    Authorship:Principal investigator 

    Grant amount:\16900000 ( Direct expense: \13000000 、 Indirect expense:\3900000 )

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  • Computational science of inertial particle clustering in high Reynolds number turbulence

    Grant number:15H03603  2015.04 - 2018.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    Ishihara Takashi, MORISHITA Koji, OKAMOTO Naoya, KANEDA Yukio, YOSHIMATSU Katsunori, ISHII Katsuya, HUNT Julian, ENOHATA Kei, KOBAYASHI Naoki, HAMABATA Kohei, SAKURAI Yoshiki

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    Grant amount:\16380000 ( Direct expense: \12600000 、 Indirect expense:\3780000 )

    By developing a highly accurate and efficient parallel program for analyzing the motion of inertial particles in turbulent flows, we realized large-scale numerical experiments for tracking the particles in direct numeical simulations of turbulence. The relationships between vortex-cluster structures, which are unique to high Reynolds number turbulence, and the motion of inertial particles were investigated. As a result, we showed that particles with large inertia tend to concentrate on the outside of the vortex cluster. We also clarified the Reynolds number dependence of the behavior of particles with large inertia and provided reliable results on the role of turbulence in the planetesimal formation process in protoplanetary disks.

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  • Computational Science for understanding the vortical structure and vortex dynamics in high Reynolds-number turbulence

    Grant number:23560194  2011.04 - 2015.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    ISHIHARA Takashi, YOSHIMATU Katsunori, OKAMOTO Naoya

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    Grant amount:\5200000 ( Direct expense: \4000000 、 Indirect expense:\1200000 )

    Using direct numerical simulation(DNS) of turbulence in a periodic box with a maximum of 4096^3 grid points and Taylor micro-scale Reynolds numbers Rλ up to 1131, it is shown that there is a transition in the forms of the significant vortical structures, from isolated vortices (when Rλ is less than 100) to complex thin-shear layers (when Rλ exceeds about 1000). Within the significant layers, strong vortices are generated with micro-scale thickness 10η (η is the Kolmogorov micro scale). The interfaces of the layers act partly as a barrier to the fluctuations outside the layer.
    We also performed the DNS of turbulent boundary layers (TBL) along a flat plate to study the properties of turbulent/non-turbulent (T/NT) interface of the TBL. Analysis of the conditional statistics near the interface shows that conditional cross correlations of the streamwise or the wall-normal velocity change sharply across the interface. This is consistent with the blocking mechanism of the interface.

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  • Development of the methods of large-scale, high-resolution direct numerical simulation of canonical problems of inhomogeneous turbulence

    Grant number:19560064  2007 - 2008

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    ISHIHARA Takashi, KANEDA Yukio, ISHII Katsuya, YOSHIMATSU Katsunori

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    Grant amount:\4550000 ( Direct expense: \3500000 、 Indirect expense:\1050000 )

    カノニカルな非一様性乱流の高精度・高解像度な大規模直接数値計算(DNS)実現に向け、スペクトル法コードの高効率化、Sinc関数を用いた新DNS手法の開発、精度と効率の比較検討を実施した。その結果、新DNS手法では適当なパラメータ選択により高精度計算可能なこと、チャネル乱流ではスペクトル法と同程度であるが壁乱流や乱流混合層では従来手法より効率的に高精度大規模DNSが実現しうることなど、大規模DNS実現のための重要な知見を得た。

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