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片岡 武大学院工学研究科 機械工学専攻准教授
研究活動情報
■ 論文- Elsevier BV, 2022年07月, Physica D: Nonlinear Phenomena, 435, 133272 - 133272研究論文(学術雑誌)
- Wiley, 2021年04月, International Journal for Numerical Methods in Fluids研究論文(学術雑誌)
- AbstractCambridge University Press (CUP), 2020年11月, Journal of Fluid Mechanics, 907研究論文(学術雑誌)
- American Physical Society (APS), 2020年01月, Physical Review Fluids, 5(1) (1)[査読有り]研究論文(学術雑誌)
- Wiley, 2019年10月, International Journal for Numerical Methods in Fluids, 91(4) (4), 183 - 197[査読有り]研究論文(学術雑誌)
- 2019年03月, Studies in Applied Mathematics, 142, 419 - 432, 英語On mean flow generation due to oblique reflection of internal waves at a slope[査読有り]研究論文(学術雑誌)
- 2018年, 日本応用数理学会 学会誌『応用数理』, 28(1) (1), 11 - 17, 日本語大気・海洋中の内部重力波ビーム[査読有り]研究論文(学術雑誌)
- 2018年, Theoretical and Applied Mechanics, 64, 9 - 14, 英語The stability of internal gravity waves of finite width[査読有り]研究論文(学術雑誌)
- 2018年, Theoretical and Applied Mechanics, 64, 31 - 39, 英語Improvement of stability of Free-Molecular Type LBM by Using Median Filter[査読有り]研究論文(学術雑誌)
- 2018年01月, Journal of Fluid Mechanics, 838, R1 (12pages), 英語On the interaction of an internal wavepacket with its induced mean flow and the role of streaming[査読有り]研究論文(学術雑誌)
- The generation of internal gravity waves by a vertically oscillating cylinder that is tilted to the horizontal in a stratified Boussinesq fluid of constant buoyancy frequency, N, is investigated. This variant of the widely studied horizontal configuration - where a cylinder aligned with a plane of constant gravitational potential induces four wave beams that emanate from the cylinder, forming a cross pattern known as the 'St. Andrew's Cross' - brings out certain unique features of radiated internal waves from a line source tilted to the horizontal. Specifically, simple kinematic considerations reveal that for a cylinder inclined by a given angle phi to the horizontal, there is a cutoff frequency, N sin phi, below which there is no longer a radiated wave field. Furthermore, three-dimensional effects due to the finite length of the cylinder, which are minor in the horizontal configuration, become a significant factor and eventually dominate the wave field as the cutoff frequency is approached; these results are confirmed by supporting laboratory experiments. The kinematic analysis, moreover, suggests a resonance phenomenon near the cutoff frequency as the group-velocity component perpendicular to the cylinder direction vanishes at cutoff; as a result, energy cannot be easily radiated away from the source, and nonlinear and viscous effects are likely to come into play. This scenario is examined by adapting the model for three-dimensional wave beams developed in Kataoka & Akylas ( J. Fluid Mech., vol. 769, 2015, pp. 621-634) to the near-resonant wave field due to a tilted line source of large but finite length. According to this model, the combination of three-dimensional, nonlinear and viscous effects near cutoff triggers transfer of energy, through the action of Reynolds stresses, to a circulating horizontal mean flow. Experimental evidence of such an induced mean flow near cutoff is also presented.CAMBRIDGE UNIV PRESS, 2017年11月, JOURNAL OF FLUID MECHANICS, 830, 660 - 680, 英語[査読有り]研究論文(学術雑誌)
- The free-molecular-type kinetic scheme is a new lattice Boltzmann model which can simulate supersonic flows described by the compressible Euler and Navier-Stokes equations. We simulate two-dimensional supersonic flows over a wedge and a circular cylinder using this scheme. Numerical results agree well with the corresponding theories and experiments and show that this scheme can capture shock waves sharply without using any spatial fitting method.National Committee for IUTAM, 2015年06月, Theoretical and Applied Mechanics, 63, 3 - 8, 英語[査読有り]研究論文(学術雑誌)
- The three-dimensional propagation of internal gravity wave beams in a uniformly stratified Boussinesq fluid is discussed, assuming that variations in the along-beam and transverse directions are of long length scale relative to the beam width. This situation applies, for instance, to the far-field behaviour of a wave beam generated by a horizontal line source with weak transverse dependence. In contrast to the two-dimensional case of purely along-beam variations, where nonlinear effects are minor even for beams of finite amplitude, three-dimensional nonlinear interactions trigger the transfer of energy to a circulating horizontal time-mean flow. This resonant beam mean-flow coupling is analysed, and a system of two evolution equations is derived for the propagation of a small-amplitude beam along with the induced mean flow. This model explains the salient features of the experimental observations of Bordes et al. (Phys. Fluids, vol. 24, 2012, 086602).CAMBRIDGE UNIV PRESS, 2015年04月, JOURNAL OF FLUID MECHANICS, 769, 621 - 634, 英語[査読有り]研究論文(学術雑誌)
- We numerically study a point sink flow of stratified viscous fluid in a reservoir of finite depth under a rigid rotation of the whole system. In the initial stage after starting a discharge, selective withdrawal is formed and only a layer of fluid adjacent to the sink level is withdrawn. As time elapses more, this withdrawal layer increases its thickness gradually. The speed of such withdrawal-layer thickening is found to be a function of the Reynolds number only and does not depend on the other parameters if the time is non-dimensionalized using the rotating speed of the system. Based on our numerical results, we also discuss the effect of the earth's rotation on sink flow in the actual situation.Science Council of Japan, 2014年, Theoretical and Applied Mechanics Japan, 62, 31 - 37, 英語[査読有り]研究論文(学術雑誌)
- The linear stability of uniform, plane internal wave beams with locally confined spatial profile, in a stratified fluid of constant buoyancy frequency, is discussed. The associated eigenvalue problem is solved asymptotically, assuming perturbations of long wavelength relative to the beam width. In this limit, instability is found only for oblique disturbances which vary in the along-beam and the horizontal transverse directions. The mechanism of instability is a first-harmonic-mean resonant interaction between the underlying wave beam and three-dimensional perturbations that comprise a time-harmonic component, with the beam frequency, and a mean flow. Progressive beams which transport energy in one direction, in particular, are unstable if the beam steepness exceeds a certain threshold value, whereas purely standing beams are unstable even at infinitesimal steepness. A distinguishing feature of this three-dimensional modulational instability is the generation of circulating horizontal mean flows at large distances from the vicinity of the beam.CAMBRIDGE UNIV PRESS, 2013年12月, JOURNAL OF FLUID MECHANICS, 736, 67 - 90, 英語[査読有り]研究論文(学術雑誌)
- The instability due to resonant interactions of finite-amplitude water waves is examined in the long-wave limit. In contrast to the well-known case of a small-amplitude limit in which the resonance is considered for a flat surface, here we consider a periodic approximate of the finite-amplitude solitary wave which is the long-wave limit of the periodic wave. The resonance conditions for the corresponding perturbations yield a new family of resonance curves that are totally different from those of the small-amplitude limit obtained by Phillips and Mclean. Under these resonance conditions, we conduct a systematic asymptotic analysis for small wavenumbers to obtain the growth rates of the perturbations explicitly and clarify whether each resonance curve is associated with instability. These results are verified numerically by showing that the instability bands for finite-amplitude periodic waves in shallow water are located along these unstable resonance curves. © 2013 Cambridge University Press.Cambridge University Press, 2013年05月, Journal of Fluid Mechanics, 722, 461 - 495, 英語[査読有り]研究論文(学術雑誌)
- Line sink flow in a stratified streamLine sink flow in a linearly stratified stream, bounded by the top and bottom two horizontal boundaries, is investigated on the basis of the Euler set of equations. The initial-value problem after start-up of discharge is solved numerically, and propagation of internal wave modes generated by the discharge and steady-state withdrawal-layer thickness are investigated. It is foun2012年, Theoretical and Applied Mechanics, 60, 43 - 50, 英語[査読有り]研究論文(学術雑誌)
- 2011年02月, Theoretical and Applied Mechanics, Vol.59, pp.221-227, 英語Gas-flow simulations by novel lattice Boltzmann method[査読有り]研究論文(学術雑誌)
- 2010年12月, Physical Review E, Vol.82, 056709, 英語Accuracy of the lattice Boltzmann method for describing the behavior of a gas in the continuum limit[査読有り]研究論文(学術雑誌)
- 2010年06月, Journal of Fluid Mechanics, Vol.657, pp.126-170, 英語Transverse instability of surface solitary waves. Part 2. Numerical linear stability analysis[査読有り]研究論文(学術雑誌)
- The breaking of a water solitary wave over a sloping-step geometry is studied both experimentally and numerically. There are three parameters for this breaking phenomenon, but we find that the breaker type can be sorted primarily by a single parameter, i. e., the ratio of the solitary-wave height to water depth above the step. As this parameter increases, breaker type changes from spilling to plunging and finally to collapsing if the sloping angle of the step is not small (30° or greater). If the sloping angle is small (about 10°), breaker type changes from spilling to plunging but no collapsing occurs. Flow velocities in the water measured by PIV show that the mechanism of collapsing breaker is quite different from that of spilling and plunging breakers.Japan Society of Mechanical Engineers, 2010年, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 76(769) (769), 1346 - 1354, 日本語[査読有り]研究論文(学術雑誌)
- We revisit the Bénard problem for a gas in the continuum limit. It was recently shown that the behavior of a gas with finite temperature difference is not described by the usual NS equations but by the SB equations, which are derived systematically from the Boltzmann equation in the continuum limit. The SB equations include the thermal-stress term which does not appear in the NS equations. In the present study, we investigate the linear stability of the quiescent state of the system on the basis of the SB equations and the results are compared with those on the basis of the NS equations. It is found that the critical Rayleigh number for the onset of instability is always smaller and growth rate of a disturbance is always larger in the framework of the SB equations. Thus, the thermal-stress term has a role of accelererating the Rayleigh-Taylor instability, and increasing the strength of thermal convection. These features are commonly observed not only for no-slip boundary conditions but also for free-slip boundary conditions.Japan Society of Mechanical Engineers, 2010年, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 76(768) (768), 1144 - 1151, 日本語[査読有り]研究論文(学術雑誌)
- In this paper, we investigated an advantage of the finite difference lattice Boltzmann method (FDLBM) to direct numerical simulations of sound propagation including scattering by a body. In order to incorporate monopole sound source into the flow, a new FDLB formulation was proposed using the Chapman-Enskog expansion. We calculated the acoustic scattering problem around a circular cylinder using the FDLBM discretized by non-compact finite difference scheme which is faster than compact finite difference scheme. The results agreed with both the exact solution and the accurate calculation by the macroscopic equations based on the discretizations of compact finite difference scheme. As a result, the FDLBM was proved to have a merit to a calculation of sound propagation. Also, we estimated error of the FDLBM in the acoustic pulse problem.Japan Society of Mechanical Engineers, 2010年, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 76(765) (765), 733 - 740, 日本語[査読有り]研究論文(学術雑誌)
- 2010年, 58, 235 - 242, 英語On the Critical Rayleigh Number of the Benard Problem for a Gas[査読有り]研究論文(学術雑誌)
- 2010年, 日本機械学会論文集(B編), Vol.76, No.768, pp.1144-1151, 日本語適切な支配方程式に基づく気体のべナール問題の再検討[査読有り]研究論文(学術雑誌)
- 2010年, 日本機械学会論文集(B編), Vol.76, No.765, pp.733-740, 日本語差分格子ボルツマン法による円柱周りの放射音解析[査読有り]研究論文(学術雑誌)
- 2010年, 土木学会論文集B, Vol.66, No.3, pp.280-288, 日本語剛体回転系における密度成層流体の点吸い込み流れ[査読有り]研究論文(学術雑誌)
- 2010年, 日本機械学会論文集(B編), Vol.76, No.769, pp.1346-1354, 日本語傾斜ステップ型地形を過ぎる孤立波の砕波に関する実験・数値的研究[査読有り]研究論文(学術雑誌)
- The Lattice Boltzmann Method (LBM) is used to study the propagation of high amplitude progressive sound wave radiated from a piston in a duct. The discretised Boltzmann equation for the 2 D 21 V thermal BGK model is solved using a second-order Runge-Kutta scheme in time and a fifth order upwind difference scheme in space. The formation of a shock front and the development of saw tooth waves are simulated for the dimensionless distance x̄ up to 3. The Fourier component amplitudes of computed waveforms are obtained. The simulations are compared with the solution of Burgers' equation. The results show good agreement with Burgers' equation for non-linearity factor I'̃O(1). For I'»1 i.e. when the effect of non-linearity is strong relative to thermo-viscous dissipation, the feature describing the occurrence of acoustic streaming in the direction of wave propagation after shock formation is observed. These results suggest that the LBM is useful for studying a wider range of nonlinear acoustical problems than Burgers' equation.Japan Society of Mechanical Engineers, 2009年, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 75(752) (752), 718 - 723, 日本語[査読有り]研究論文(学術雑誌)
- 2009年, 日本機械学会論文集(B編), 75巻752号718-723頁, 日本語差分格子ボルツマン法による有限振幅音波の伝播計算[査読有り]研究論文(学術雑誌)
- 2009年, Theoretical and Applied Mechanics, Vol.57, pp.323-330Numerical simulation of transversely distorted surface solitary wave[査読有り]研究論文(学術雑誌)
- The linear stability of finite-amplitude interfacial solitary waves in a two-layer fluid of finite depth is examined analytically on the basis of the Euler equations. Ail asymptotic analysis is performed, which provides an explicit criterion of instability in the case of long-wavelength transverse disturbances. This result leads to the general statement that, when the amplitude of the solitary wave is increased, the solution becomes transversely unstable before an exchange of longitudinal stability Occurs.CAMBRIDGE UNIV PRESS, 2008年09月, JOURNAL OF FLUID MECHANICS, 611, 255 - 282, 英語[査読有り]研究論文(学術雑誌)
- An unsteady two-dimensional inviscid blade-vortex interaction has been calculated using the finite difference lattice Boltzmann method of the compressible Enter model. The perturbed discrete Boltzmann equation based on a prescribed vortex approach has been proposed to prevent a vortex from diffusing by numerical dissipation. The discretization of the governing equation is based on a second-order-accurate explicit Runge-Kutta time integration and a fifth-order-accurate upwind scheme that includes additional terms to capture the shock waves clearly. Subsonic and transonic flows around an airfoil were simulated to validate the perturbed discrete Boltzmann equation system. The numerical results were compared with other numerical data, and good agreement has been obtained. In the simulation of the transonic blade-vortex interaction, an instantaneous pressure coefficient, a time history of a lift coefficient, and patterns of acoustic waves were compared with other numerical results, and were found to agree with them very well. We have also investigated a generation mechanism of acoustic wave caused by the blade-vortex interaction, the effect or the flow Mach number, and the influence of the vortex miss distance.AMER INST AERONAUT ASTRONAUT, 2008年09月, AIAA JOURNAL, 46(9) (9), 2235 - 2247, 英語[査読有り]研究論文(学術雑誌)
- 2008年03月, Bulletin of the Institute of Mathematics, Academia Sinica, New series, vol.3, no.1, pp.153-166The superharmonic instability of finite-amplitude interfacial waves[査読有り]研究論文(学術雑誌)
- A new scheme for the finite difference lattice Boltzmann method is proposed, in which negative viscosity term is introduced to reduce the viscosity and the calculation time can be remarkably reduced for high Reynolds number flows. A model with additional internal degree of freedom is also presented for diatomic gases such as air, in which an additional distribution function is introduced. Direct simulations of aero-acoustics by using the proposed model and scheme are presented. Speed of sound is correctly recovered. As typical examples, the Aeolian tone emitted by a circular cylinder is successfully simulated even very low Mach number flow. Full three-dimensional sound emission is also given. (C) 2006 Elsevier Ltd. All rights reserved.PERGAMON-ELSEVIER SCIENCE LTD, 2008年01月, COMPUTERS & FLUIDS, 37(1) (1), 79 - 89, 英語[査読有り]研究論文(学術雑誌)
- The linear stability of finite-amplitude interfacial gravity solitary waves propagating in a two-layer fluid is investigated analytically focusing on the occurrence of an exchange of stability. We make an asymptotic analysis for small growth rates of infinitesimal disturbances, and explicitly obtain their growth rates near an exchange of stability. The result indicates that an exchange of stability occurs at every stationary value of the total energy of the solitary waves. It also gives us information whether the number of growing modes increases or decreases after experiencing the exchange of stability. We apply these analytical results to specific interfacial solitary waves, and find various features on their stability that are not seen in the case of surface solitary waves. (c) 2006 The Japan Society of Fluid Mechanics and Elsevier B.V. All rights reserved.ELSEVIER SCIENCE BV, 2006年12月, FLUID DYNAMICS RESEARCH, 38(12) (12), 831 - 867, 英語[査読有り]研究論文(学術雑誌)
- The linear stability of two-dimensional Surface gravity waves on fluid of finite depth is investigated for superharmonic disturbances. For this problem, Zufiria & Saffman (Stud. Appl. Maths vol. 74, 1986, p. 259) Suggested that an exchange of stability occurs when the total wave energy becomes stationary as a function of wave speed for fixed 'Bernoulli constant'. In defining the potential energy of the above total wave energy, the Surface displacement was measured from the quiescent surface with the same 'Bernoulli constant. We have re-examined this problem both analytically and numerically, and found that the above 'Bernoulli constant' Must be replaced by 'mean surface height' for the statement to be valid.CAMBRIDGE UNIV PRESS, 2006年01月, JOURNAL OF FLUID MECHANICS, 547, 175 - 184, 英語[査読有り]研究論文(学術雑誌)
- The linear stability of finite-amplitude surface solitary waves with respect to long-wavelength transverse perturbations is examined by asymptotic analysis for small wavenumbers of perturbations. The sufficient condition for the transverse instability is explicitly derived, and it is found that there exist transversely unstable surface solitary waves whose amplitude-to-depth ratio is greater than 0.713. This critical ratio is well below that for the one-dimensional instability (= 0.781) obtained by Tanaka (Phys. Fluids, 1986, vol. 29, p. 650).CAMBRIDGE UNIV PRESS, 2004年08月, JOURNAL OF FLUID MECHANICS, 512, 211 - 221, 英語[査読有り]研究論文(学術雑誌)
- The present paper is a more detailed article of the previously published Letter [ Phys. Rev. Lett. 84, 3065 (2000) ], which discovered the transversely unstable solitary wave solutions of the generalized Kadomtsev-Petviashvili (GKP) equation with negative dispersion. In addition to detailed explanation of stability analysis to long-wavelength transverse perturbations, numerical calculation of the GKP equation is carried out here to study the transverse stability to perturbations of finite wavelength. The numerical results show that there is a short-wavelength cutoff to the transverse instability. Moreover, we reveal the existence of transversely unstable solitons.AMER PHYSICAL SOC, 2004年07月, PHYSICAL REVIEW E, 70(1) (1), 英語[査読有り]研究論文(学術雑誌)
- The lattice Boltzmann model for the compressible Euler equations is proposed together with its rigorous theoretical background. The proposed model has completely overcome the defects of the previous model that the specific-heat ratio cannot be chosen freely. The macroscopic variables obtained from the solution are shown to satisfy, in the limit of the small Knudsen number, the compressible Euler equations if the variation of the solution is moderate. This is the case where no shock waves or contact discontinuities appear. In contrast, when the solution makes steep variation at several localized regions due to the appearance of shock waves and contact discontinuities, the corresponding macroscopic variables satisfy the weak form of the Euler equations. Their derivation is carried out rigorously by taking into account the scale of variation of the solution correctly. This is the first study that has laid the theoretical foundation of the lattice Boltzmann model for the simulation of flows with shock waves and contact discontinuities. Numerical examples and the error estimates are also given, which are consistent with the above theoretical arguments.AMER PHYSICAL SOC, 2004年05月, PHYSICAL REVIEW E, 69(5) (5), 英語[査読有り]研究論文(学術雑誌)
- A lattice Boltzmann model (LBM) for the compressible Navier-Stokes (NS) equations with flexible specific-heat ratio was discussed. The NS equations were characteristics by viscosity, bulk viscosity, and thermal conductivity. The NS equations of the LBM were solved by using the Crank-Nicolson and MacCormack scheme. The LBM was numerically calculated using the explicity finite-difference scheme. The explicit finite-difference scheme, which was used for the NS calculations, was using Courant number in order to make stable calculations.2004年03月, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 69(3) (3), 1 - 35701, 英語[査読有り]研究論文(学術雑誌)
- We have developed a lattice Boltzmann model for the compressible Navier-Stokes equations with a flexible specific-heat ratio. Several numerical results are presented, and they agree well with the corresponding solutions of the Navier-Stokes equations. In addition, an explicit finite-difference scheme is proposed for the numerical calculation that can make a stable calculation with a large Courant number.AMER PHYSICAL SOC, 2004年03月, PHYSICAL REVIEW E, 69(3) (3), 英語[査読有り]研究論文(学術雑誌)
- Two-dimensional direct numerical simulation of the edge-tones by the finite difference lattice Boltzmann method (FDLBM)is reported. We use anew lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted coordinates. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. It is clarified that the sound wave generated in rather wide region and. individual vortices do not affect the sound wave propagation. We showed that the frequency of edge-tones depend on the jet flow speed.一般社団法人日本機械学会, 2004年, 年次大会講演論文集, 2004, 69 - 70, 日本語
- The present paper is a more detailed article of the previously published Letter [Phys. Rev. Lett. 84 3065 2000], which discovered the transversely unstable solitary wave solutions of the generalized Kadomtsev-Petviashvili (GKP) equation with negative dispersion. In addition to detailed explanation of stability analysis to long-wavelength transverse perturbations, numerical calculation of the GKP equation is carried out here to study the transverse stability to perturbations of finite wavelength. The numerical results show that there is a short-wavelength cutoff to the transverse instability. Moreover, we reveal the existence of transversely unstable solitons. © 2004 The American Physical Society.2004年, Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 70(1) (1), 9, 英語[査読有り]研究論文(学術雑誌)
- The lattice Boltzmann model for the compressible Euler equations is proposed together with its rigorous theoretical background. The proposed model has completely overcome the defects of the previous model that the specific-heat ratio cannot be chosen freely. The macroscopic variables obtained from the solution are shown to satisfy, in the limit of the small Knudsen number, the compressible Euler equations if the variation of the solution is moderate. This is the case where no shock waves or contact discontinuities appear. In contrast, when the solution makes steep variation at several localized regions due to the appearance of shock waves and contact discontinuities, the corresponding macroscopic variables satisfy the weak form of the Euler equations. Their derivation is carried out rigorously by taking into account the scale of variation of the solution correctly. This is the first study that has laid the theoretical foundation of the lattice Boltzmann model for the simulation of flows with shock waves and contact discontinuities. Numerical examples and the error estimates are also given, which are consistent with the above theoretical arguments. © 2004 The American Physical Society.2004年, Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, 69(5) (5), 14, 英語[査読有り]研究論文(学術雑誌)
- 2004年, 計算数理工学論文集, Vol.4,37-42, 日本語差分格子ボルツマン法によるエッジトーンの直接計算[査読有り]研究論文(学術雑誌)
- 2004年, 日本機械学会論文集(B編), 70(699),2681-2688, 日本語回転二重同心円筒内流体の吸込みわき出し流れ[査読有り]研究論文(学術雑誌)
- 2004年, Theoretical and applied mechanics Japan, 53,155-161, 英語Knudsen pump and its possibility of application to satellite control system[査読有り]研究論文(学術雑誌)
- Three-dimensional direct numerical simulation of aerodynamic sound by the finite difference lattice Boltzmann method (FDLBM) is reported. We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted co-ordinates. We have succeeded in capturing very small pressure fluctuations in a uniform flow over a circular cylinder. They were generated with same frequency of Karman vortex street. We can also succeed to detect the aerodynamic sound which is generated by a three-dimensional body and propagates in radial direction. We clarified that we can calculate the aerodynamic sound directly using by the finite difference lattice Boltzmann method.一般社団法人日本機械学会, 2003年, 年次大会講演論文集, 2003, 287 - 288, 日本語
- In this paper, three-dimensional numerical simulation around a calculation model of the part of vehicle's front pillar (wedge-box) by the finite difference lattice Boltzmann method (FDLBM) is reported. We use a new lattice BGK incompressible fluid model that has an additional term to manipulate a viscous term. As a result, we have confirmed the generation of the spiral flow by the sidepiece of wedge box, and captured the reattachment line of the spiral flow.一般社団法人日本機械学会, 2003年, 年次大会講演論文集, 2003, 289 - 290, 日本語
- 2003年01月, Computational Fluid Dynamics Journal, 11(1) (1), 486 - 493, 英語[査読有り]研究論文(学術雑誌)
- 2003年, 日本機械学会論文集(B編), 69(680),841-847, 英語差分格子ボルツマン法による音波の直接計算[査読有り]研究論文(学術雑誌)
- 2003年, Theoretical and Applied Mechanics., Vol.52,239-246, 英語Stability of small-amplitude internal solitary waves in stratified fluids.[査読有り]研究論文(学術雑誌)
- 2002年, Theoretical and Applied Mechanics, 51, 315 - 322, 英語Reflection of internal solitary wave by a vertical wall in a stratified fluid[査読有り]研究論文(学術雑誌)
- 2002年, 日本機械学会論文集(B編), 68(667) (667), 666 - 671, 日本語差分格子ボルツマン法による圧縮性成層流体の数値シミュレーション[査読有り]研究論文(学術雑誌)
- Selective withdrawal through a line sink of non-rotating and rotating stratified fluid in a reservoir of finite depthSelective withdrawal through a line sink of both non-rotating and rotating stratified fluid in a reservoir of finite depth is studied under an assumption that viscosity and diffusivity of the fluid are negligible. This flow is characterized by the two parameters: the Froude number F; and the ratio of the inertial frequency f to the buoyancy frequency N. Following the initiation of discharge from the sink, internal (or inertial) gravity wave modes propagate upstream. We first consider the case of F --> 0 to get linearized governing equations and seek a linear asymptotic solution for large t* (where t* is time after starting the discharge) which is uniformly valid in space. The obtained solution shows the propagation of the individual modes clearly and it is found that the amplitude of the modal front is kept constant with time t* when f = 0, whereas it decreases as t*(-1/3) when f > 0. Next, numerical calculation is conducted to study the case of F > 0. Specifically, the validity of both our linear solution and the theory suggested by Clarke and Imberger in describing the mode propagation for F > 0 is explored. Investigations are also made of the how patterns constructed by the passage of these modes. It is then found that the withdrawal-layer thickness shows strong time dependence whose period is about 6/f. (C) 2001 Editions scientifiques et medicales Elsevier SAS.GAUTHIER-VILLARS/EDITIONS ELSEVIER, 2001年03月, EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, 20(2) (2), 167 - 186, 英語[査読有り]研究論文(学術雑誌)
- The Japan Society of Fluid Mechanics, 2001年02月, ながれ : 日本流体力学会誌, 20(1) (1), 7 - 17, 日本語
- Effect of the body force in the finite difference lattice Boltzman method (FDLBM) is studied. A simple one-dimensional model is employed, and the error is estimated to be order of the square of the acceleration due to the body force. Spin-up phenomenon is calculated by FDLBM, the lattice BGK model with introducing the Colioris force in the local equilibrium distribution function. The convection terms are discretized by third order up-wind scheme. The spin-up time is compared with the theoretical one, and both agree well.Japan Society of Mechanical Engineers, 2001年, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 67(660) (660), 1912 - 1917, 日本語[査読有り]研究論文(学術雑誌)
- Effect of the body force in the finite difference lattice Boltzmann method (FDLBM) is studied Inertial waves in a rotating field are calculated by FDLBM, the 3D15V lattice BGK model with introducing the Coriolis force in the local equilibrium distribution function of the collision term The phase velocity and the group velocity of the inertial wave are compared with the theoretical one obtained by the dispersion relation of an incompressible inviscid fluid, and both agree well.Japan Society of Mechanical Engineers, 2001年, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 67(663) (663), 2662 - 2669, 日本語[査読有り]研究論文(学術雑誌)
- 2001年, 日本機械学会論文集(B編), 67(663) (663), 2662 - 2669, 日本語差分格子BOLTZMANN法による回転流体における慣性波の解析[査読有り]研究論文(学術雑誌)
- 2001年, Theoretical and Applied Mechanics, 50, 295 - 301, 英語Effects of stratification and rotation on a sink flow[査読有り]研究論文(学術雑誌)
- 2001年, 日本機械学会論文集(B編), 67(660) (660), 1912 - 1917, 日本語差分格子ボルツマン法による回転場における流体運動の解析[査読有り]研究論文(学術雑誌)
- The evolution of selective withdrawal through a point sink of horizontally unbounded, linearly stratified fluid of finite depth is studied as an initial-value problem. Following the initiation of discharge from the sink, internal gravity wave modes propagate radially upstream to change the flow pattern. These modes are called cylindrical modes. We first consider the case of F → 0 (where F is the Froude number) to get linearized governing equations, and seek a linear asymptotic solution for large times t(*) after starting the discharge, of the cylindrical modes in a stratified fluid where viscous and diffusive effects are negligible. The obtained solution shows that the strength of the modal front grows like t(*1/3), unlike the case of two-dimensional modes whose strength at the front is kept constant. Numerical calculations are also performed to study the case of F> 0. The results then indicate that all the cylindrical modes can propagate upstream for any F except infinity. The steady-state withdrawal-layer thickness and time to steady state are also investigated over the full parameter range considering the viscous and diffusive effects. The obtained results are then compared with both the analytical and experimental results of prior works. (C) 2000 American Institute of Physics.American Inst of Physics, 2000年11月, Physics of Fluids, 12(11) (11), 2775 - 2786, 英語[査読有り]研究論文(学術雑誌)
- Simulation of the stratified flows using the two-component lattice Boltzmann methodTwo-dimensional incompressible stratified flows are simulated by the two-component lattice Boltzmann method. The red and blue particles are miscible and the gravity acts on the blue particles only. The density fractuation is expressed by the ratio of the density of the blue particles and the total density. The Boussinesq equation is derived and the total density is confirmed not to vary much. The blocking and the selective withdrawal phenomena are successively simulated. (C) 2000 Elsevier Science B.V. All rights reserved.ELSEVIER SCIENCE BV, 2000年07月, COMPUTER PHYSICS COMMUNICATIONS, 129(1-3) (1-3), 131 - 137, 英語[査読有り]研究論文(学術雑誌)
- Transverse instability of solitary waves in the generalized Kadomtsev-Petviashvili equationThe linear stability of planar solitary waves with respect to long-wavelength transverse perturbations is studied in the framework of the generalized Kadomtsev-Petviashvili equation. It is newly discovered that for some nonlinearities in this family, the solitary waves could be transversely unstable even in a medium with negative dispersion. In the case of positive dispersion, they are found to be always unstable.AMERICAN PHYSICAL SOC, 2000年04月, PHYSICAL REVIEW LETTERS, 84(14) (14), 3065 - 3068, 英語[査読有り]研究論文(学術雑誌)
- Two-dimensional evolution equation of finite-amplitude internal gravity waves in a uniformly stratified fluidWe derive a fully nonlinear evolution equation that can describe the two-dimensional motion of finite-amplitude long internal waves in a uniformly stratified three-dimensional fluid of finite depth. The derived equation is the two-dimensional counterpart of the evolution equation obtained by Grimshaw and Yi [J. Fluid Mech. 229, 603 (1991)]. In the small-amplitude limit, our equation is reduced to the celebrated Kadomtsev-Petviashvili equation.AMERICAN PHYSICAL SOC, 2000年02月, PHYSICAL REVIEW LETTERS, 84(7) (7), 1447 - 1450, 英語[査読有り]研究論文(学術雑誌)
- Three-dimensional fluid flows are simulated numerically by the 3 D 15 V incompressible lattice Boltzmann model. In a rotating coordinate system, the effect of Coriolis force is incorporated into the local equilibrium distribution function at the collision stage. The force due to the pressure gradient is taken into consideration at the translating stage of the particles. The velocity fields are obtained by averaging these calculated two stage fields. The Taylor-Proudman column, the Ekman spiral and the spin-down are simulated. The existence of the Taylor-Proudman column is confirmed by the calculation. Results of the Ekman spiral and the spin-down agree well with theoretical ones obtained by an analysis with the boundary layer approximation.Japan Society of Mechanical Engineers, 2000年, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 66(651) (651), 2838 - 2844, 日本語[査読有り]研究論文(学術雑誌)
- 2000年, 日本機械学会論文集(B編), 66(651) (651), 2838 - 2844, 日本語格子ボルツマン法による回転場における流体運動の解析[査読有り]研究論文(学術雑誌)
- The time development of two-dimensional fluid motion induced by a line sink of a rotating linearly stratified Boussinesq fluid in a finite-depth reservoir is numerically studied. The flow is characterized by a Froude number, Fr and the ratio of the inertial frequency, f, to the buoyancy frequency, N. Following the initiation of the sink, the inertial gravity wave modes are generated to propagate upstream, which results in the narrowing of a withdrawal-layer thickness. Attention is focused on investigating the evolution of the mode propagation and the resultant flow patterns for various Fr and f/N. The numerical results clarify that the nature of the mode propagation has little dependence on the parameter Fr if the distance from the sink is larger than a critical one, Nd/f where d is the reservoir's depth. The withdrawal-layer thickness for Fr = 0 is linearly proportional to the distance from the sink and the nonlinear effect (Fr≠0) can be easily incorporated only by adding the term representing the thickness under no rigid rotation. Furthermore, profiles of the withdrawal -layer thickness show strong time-dependence whose period is about 2π/f.Japan Society of Mechanical Engineers, 1999年, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 65(635) (635), 2366 - 2373, 日本語[査読有り]研究論文(学術雑誌)
- 1999年, 日本機械学会論文集(B編), 65(635) (635), 2366 - 2373, 日本語回転密度成層場における線吸込流れに関する数値解析的研究[査読有り]研究論文(学術雑誌)
- 1999年, Theoretical and Applied Mechanics, 48, 295 - 301, 英語Two-dimensional selective withdrawal in a rotating stratified fluid[査読有り]研究論文(学術雑誌)
- 1999年, 日本機械学会論文集(B編), 65(629) (629), 152 - 158, 日本語密度成層場における点吸込流れによる選択取水形成過程[査読有り]研究論文(学術雑誌)
- Thermal free convection is simulated by the Lattice Boltzmann Method using two types of particles, that is red particles and blue ones. The gravitational force is introduced into the collision stage, at which the impulsive force is added by making the population of blue particles moving downward increase. The buoyancy force is taken into consideration in the translating stage of the particles. The velocity field and the density or the temperature field are obatained by averaging these calculated two stage fields. The results agree well with those obtained by the finite difference method.一般社団法人日本機械学会, 1998年07月, 日本機械学会論文集 B編, 64(623) (623), 1966 - 1972, 日本語[査読有り]研究論文(学術雑誌)
- 1998年, Theoretical and Applied Mechanics, 47, 191 - 195, 英語Axisymmetric withdrawal in a stratified fluid[査読有り]研究論文(学術雑誌)
- 日本流体力学会, 1998年, 日本流体力学会誌「ながれ」, 17(3) (3), 189 - 201, 日本語回転密度成層場における線形慣性内部重力モード波の水平伝播[査読有り]研究論文(学術雑誌)
- 1998年, 日本機械学会論文集(B編), 64(628) (628), 3942 - 3949, 日本語密度成層場における二次元選択取水に関する数値解析的研究[査読有り]研究論文(学術雑誌)
- 非粘性非拡散性線形密度成層場における線吸い込みおよび点吸い込み流れを考え, 最初静止した状態から, ある時刻より一定の取水を始めた後の長時間にわたる流れの振舞を解析的に明らかにした.内部Froude数が小さいとき, 上記流れは, 最終的には選択取水を形成し, 吸い込み口と同じ高さの流体のみが抜き取られるが, 本研究は, その選択取水形成において重要な役割を果たしている内部波の漸近的振舞を詳細に示した.また, 線吸い込みと点吸い込みとで, 選択取水に移行していくまでの内部波の挙動が大きく異なることを見いだした.The Japan Society of Fluid Mechanics, 1997年, 日本流体力学会誌「ながれ」, 16(3) (3), 248 - 258, 日本語[査読有り]研究論文(学術雑誌)
- 1994年, European Journal of Mechanics B/Fluids, 13, 573 - 589, 英語Numerical examination of applicability of the linearized Boltzmann equation[査読有り]研究論文(学術雑誌)
- 京都大学, 2016年04月, 数理解析研究所講究録, 1989, 113 - 118, 日本語傾斜円柱の振動により誘起される内部波 (非線形波動現象の数理に関する最近の進展)
- 一般社団法人日本機械学会, 2016年03月11日, 関西支部講演会講演論文集, 2016(91) (91), 278 - 278, 日本語M402 自由分子型運動学的スキームによる三次元圧縮性流体解析(GS5 流体工学(4),修士研究発表セッション)
- 一般社団法人日本機械学会, 2012年03月16日, 関西支部講演会講演論文集, 2012(87) (87), "1 - 25", 日本語104 浅水波列の共鳴不安定性について(OS-2 流れと熱と波動に関わる非線形現象(1))
- 一般社団法人日本機械学会, 2010年03月16日, 関西支部講演会講演論文集, 2010(85) (85), "10 - 28", 日本語1022 底面地形の違いによる孤立波の砕波形状に関する実験的数値的研究(OS-5 可変形性境界を含む流れ(2))
- 水面波列の長波長極限における線形安定性(波動(3),一般講演)Linear stability of finite-amplitude surface periodic waves in the long-wave limit is investigated. When the wavenumber (K_x,K_y,) of a perturbation is of the same order as that of the basic wave, resonance curves on the plane (K_x,K_y) are represented by a cross and ellipses. As the wavenumber of a perturbation becomes larger relative to that of the basic wave, the type of instability asymptotes to that of solitary wave.日本流体力学会, 2010年, 日本流体力学会年会講演論文集, 2010, 263 - 263, 日本語
- 一般社団法人日本機械学会, 2009年03月16日, 関西支部講演会講演論文集, 2009(84) (84), "1 - 12", 日本語112 水面孤立波の3次元的不安定性(OS-5 界面が関わる複雑熱流体現象(5))
- 有限振幅水面波の長波長極限における共鳴不安定性(対流・拡散・渦・波動 波動(4),一般講演)Resonant instability of finite-amplitude surface periodic waves in the long-wave limit is investigated. Two kinds of resonances are found. The first one is associated with the oscillation of a distorted solitary wave which is a long-wave limit of the periodic wave. A resonance between such a distorted long wave and a disturbance leads to four resonance lines on a parameter plane (k, l), where k and l are the wavenumbers of a disturbance in the longitudinal and transverse directions, respectively. A disturbance on the two smaller-gradient lines induces instability, while that on the remaining two does not. The second one is a resonance between two linear disturbances. The corresponding resonance curves are given by ellipses on the parameter plane (k, l).日本流体力学会, 2009年, 日本流体力学会年会講演論文集, 2009, 190 - 190, 日本語
- 水面波列の新しい共鳴不安定性(波動(3),一般講演)A new type of resonant instability for surface periodic waves is investigated in the long-wave limit. Resonance curves on a parameter plane (k,l), where k and l are the wavenumbers of a disturbance in the longitudinal and transverse directions respectively, become four lines of the form l=±c_1k and l=±c_2k (0
日本流体力学会, 2008年, 日本流体力学会年会講演論文集, 2008, 312 - 312, 日本語 2401 格子ボルツマン法による有限振幅音波の伝播計算(OS24.格子ボルツマン・ガス法(1))The Lattice Boltzmann Method (LBM) was used to study the propagation of high amplitude progressive sound wave radiated from a piston in a duct. The formation of a shock front and the development of saw tooth waves are simulated when the effect of nonlinearity is strong relative to thermoviscous dissipation. The wave deformation is compared with the solution of Burgers equation that describes the combined effects of nonlinearity and losses on the propagation of plane progressive waves. The results show good agreement with Burgers equation and suggest that the LBM is useful for studying nonlinear acoustics problems.一般社団法人日本機械学会, 2007年11月25日, 計算力学講演会講演論文集, 2007(20) (20), 631 - 632, 日本語409 回転二重同心円筒内流体の吸込み湧き出し流れ(OS-2 熱流体の数値シミュレーション(3),研究発表講演)Steady source-sink flows of viscous incompressible fluid in a rotating annulus are numerically studied The annulus is made of two concentric cylinders of different radius with finite axial length and solid-wall ends. The fluid is injected uniformly from the inner cylinder and the same amount is extracted uniformly from the outer cylinder. This flow is mainly characterized by the Ekman number (E) and dimensionless speed of extracted fluid (U). When U is small, the injected fluid moves through the annulus via the Ekman layer which is formed near the end walls of the annulus. The ratio of the volume rate of fluid that goes through the Ekman layer is investigated and it is newly found that this ratio can take an extremum value at some intermediate value of U for a fixed value of E. Moreover, we findthat, when E and U are very small, the torus flow appears, which was not found in the previous studies.一般社団法人日本機械学会, 2005年03月18日, 関西支部講演会講演論文集, 2005(80) (80), "4 - 23"-"4-24", 日本語京都大学, 2004年04月, 数理解析研究所講究録, 1368, 205 - 212, 日本語二層流体中を伝播する内部孤立波の横方向撹乱に対する安定性 (波動の非線形現象とその応用)1307 希薄気体におけるクヌッセンポンプの工学的応用に関する研究(GS-5 流れの数値解析(1))The Knudsen pump is a pump that utilizes a thermal transpiration flow that is peculiar to a rarefied gas. A thermal transpiration flow is induced when boundary wall have temperature gradient. There is no moving part in this pump and the mechanism is very simple. It is expected that it will be applied from now on from the viewpoint of engineering. But the Knudsen pump has demerits like low pressure and the severe condition for the pump to be workable. In this paper we investigate the basic features of the Knudsen pump. Then we suggest the more efficient Knudsen pump, and evaluate its performance. Therefore we investigate both numerically and experiment.一般社団法人日本機械学会, 2004年03月17日, 関西支部講演会講演論文集, 2004(79) (79), "13 - 13"-"13-14", 日本語808 密度成層流体中における内部孤立波の反射現象(GS-5 発振現象・ソリトン)Reflection of an obliquely incident internal solitary wave by a vertical wall in a stratified fluid is studied numerically. We employ the Euler equations, which are the equations for incompressible ideal fluids, as basic equations of the analysis. According to the numerical results, the reflection pattern approaches that of normal reflection in comparison with the analytical results of Kadomtsev-Petviashvili(KP) equation which is the model equation in a small amplitude limit. For example, the transition from Mach reflection to regular reflection occurs at smaller incident angle than that of the KP equation.一般社団法人日本機械学会, 2004年03月17日, 関西支部講演会講演論文集, 2004(79) (79), "8 - 13"-"8-14", 日本語F311 差分格子ボルツマン法によるスリット及び穴あき円柱から生じる空力音の直接計算(F-31 騒音(1),一般講演)Three dimensional direct simulation of aero acoustic waves emitted from slitted and holed circular cylinders by finite difference Boltzmann method (FDLBM) is reported. We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing the conventional FDLBM, and also use a boundary fitted co-ordinates. We have succeeded in capturing very small pressure fluctuations in a uniform flow over a circular cylinder. They generated with same frequency of Karman vortex street. We calculated directly aero acoustic waves emitted from slitted and holed circular cylinders by the finite difference lattice Boltzmann method, and compared pressure fluctuations generated from slitted and holed circular cylinders.日本流体力学会, 2004年, 日本流体力学会年会講演論文集, 2004, 656 - 657, 日本語221 乱流モデルを組み込んだ差分格子ボルツマン法に関する研究This paper reports the finite difference lattice Boltzmann method (FDLBM) built in the turbulence model. This model is built in the subgrid model, which incorporates the standard Smagorinsky model to damp the small-scale fluctuations from the flow field. First, we show the theory of the FDLBM subgrid model, and then we simulate three-dimensional fully developed turbulent channel flow at Re_τ=150 using this method, and compare it with DNS database. The result of FDLBM subgrid model shows appropriate agreement with that of DNS database if a shortage of calculation lattice is considered.一般社団法人日本機械学会, 2003年11月22日, 計算力学講演会講演論文集, 2003(16) (16), 137 - 138, 日本語213 差分格子ボルツマン法による界面活性剤の SIS に関する研究Drag reduction caused by surfactant solutions is considered. Surfactant contains threadlike micelles. At a critical shear rate the shear viscosity suddenly increases in this so-called shear-induced state (SIS). At high shear rates the increased shear viscosity gradually decreases. In this paper, two-dimensional numerical simulation in the surfactant solution containing threadlike micelles by the finite difference lattice Boltzmann method is reported. As a result, we formed SIS and checked the shear viscosity increasing at a critical shear rate and the increased shear viscosity decreasing at high shear rates.一般社団法人日本機械学会, 2003年11月22日, 計算力学講演会講演論文集, 2003(16) (16), 121 - 122, 日本語223 差分格子ボルツマン法による乱流の直接計算に関する研究Computation of 3-dimensional homogeneous isotropic turbulence by the Finite Difference Lattice Boltzmann Method (FDLBM) has been conducted with the grids of 64×64×64. In the case of freely decaying homogeneous turbulence, the energy spectrum obtained by the FDLBM is compared with the experimental result. In the case of forced turbulence, a comparison of turbulence by the FDLBM and FDS are conducted.一般社団法人日本機械学会, 2003年11月22日, 計算力学講演会講演論文集, 2003(16) (16), 141 - 142, 日本語一般社団法人日本機械学会, 2003年09月18日, 流体工学部門講演会講演論文集, 2003, 99 - 99, 日本語707 差分格子ボルツマン法によるエッジ音の直接計算京都大学, 2003年04月, 数理解析研究所講究録, 1311, 27 - 39, 英語瞬間的動作を受けた後の密度成層完全流体の支配方程式系導出 (非線形波動現象の数理とその応用)1504 二層流体中を伝播する内部孤立波の線形安定性についてLinear stability of interfacial solitary waves is studied under the assumption that the fluid is incompressible and inviscid with no interfacial tension. Solitary wave solutions are obtained by numerically solving the corresponding governing equations. Their stability is investigated by solving the eigen-value problem for linear perturbations.一般社団法人日本機械学会, 2003年, 関西支部講演会講演論文集, 2003(78) (78), "15 - 7"-"15-8", 日本語1503 取水口移動による選択取水効果の数値的研究We consider line sink flow in a reservoir of finite depth. When the fluid is stratified in the vertical direction, only a layer of fluid adjacent to the sink level is withdrawn. This phenomenon is called selective withdrawal, and there exists wide application to water quality management. We here describe the effect of selective withdrawal when the line sink moves in a horizontal direction.一般社団法人日本機械学会, 2003年, 関西支部講演会講演論文集, 2003(78) (78), "15 - 5"-"15-6", 日本語D-214 内部孤立波の安定性The linear stability of finite-amplitude internal solitary waves propagating in a two-layer fluid is studied. As a first step, in the present work, we try to reveal the critical surface that divides the region of stability and instability in a parameter space of solitary waves. It is then revealed that the linear stability and instability regions are divided by the surface of dE/dv=0,where E is the total energy of solitary wave and v is the propagating speed of solitary wave. We also derived explicitly the stability criterion that can prescribe which sides of critical surface are stable or unstable.日本流体力学会, 2003年, 日本流体力学会年会講演論文集, 2003, 278 - 279, 日本語1318 内部孤立波の鉛直壁面による反射形態Reflection of an obliquely incident internal solitary wave by a vertical wall in a stratified fluid is studied numerically. We employ two different types of equations for the analysis, that is, the equation for incompressible ideal fluids and the Modified Kadomtsev-Petviashvili (MKP) equation derived from the former equation under the assumption of small wave amplitude, small incident angle, large horizontal lengthscale of variation, and the condition for stratification profile specified in the main text, According to the numerical results of the MKP equation, the reflection pattern approaches that of normal reflection in comparison with analyses of Kadomtsev-Petviashvili (KP) equation as the wave amplitude increases.一般社団法人日本機械学会, 2002年, 関西支部講演会講演論文集, 2002(77) (77), "13 - 39"-"13-40", 日本語C111 圧縮性 Euler 方程式系を基とした長波長非線形内部重力波の時間発展The higher-order KdV equations that describe the motion of long nonlinear internal waves are derived on the basis of the compressible Euler set of equations. We consider the case where the following three parameters are of the same order of magnitude : (i) the degree of stratification, (ii) the degree of pressure gradient caused by the gravitational acceleration, and (iii) the amplitude of waves. The terms representing compressibility of fluids are clarified and propagation of the radiated waves is also discussed.日本流体力学会, 2002年, 日本流体力学会年会講演論文集, 2002, 86 - 87, 日本語一般社団法人日本機械学会, 2001年09月28日, 流体工学部門講演会講演論文集, 2001, 157 - 157, 日本語1113 一般化KP方程式による孤立波解の不安定性(O.S.11-3 乱流現象とEFD(その3))(O.S.11 乱流現象とEFD)307 平面孤立波の不安定牲に関する研究(FM-4 流れ解析の基礎について)The linear stability of planar solitary waves with respect to long-wavelength transverse perturbations is studied in the framework of the generalized Kadomtsev-Petviashvili (KP) equation. It is newly discovered that for some nonlinearities in this family, the solitary waves could be transversely unstable. The results of numerical simulation also confirm the instability.一般社団法人日本機械学会, 2001年03月16日, 関西支部講演会講演論文集, 2001(76) (76), "3 - 21"-"3-22", 日本語1028 密度成層流体における平面内部孤立波の垂直壁面によるMach反射(GS-5 低レイノルズ数流れ)Mach reflection of internal solitary waves by a vertical wall in a stratified fluid is studied numerically. There are some studies about Mach reflection, but they assume a weakly and nearly uniformly stratified fluid or a two layer fluid or free surface waves. Here, we suppose a weakly and nonuniformly stratified fluid. We use the SMAC method for calculations. And a comparison with solutions of model equations is made.一般社団法人日本機械学会, 2001年03月16日, 関西支部講演会講演論文集, 2001(76) (76), "10 - 55"-"10-56", 日本語907 差分格子BOLTZMANN法による回転流体における慣性波の解析(OS-2 格子ボルツマン法ほか)Effect of the body force in the finite difference lattice Boltzmann method (FDLBM) is studied. Inertial waves in a rotating field are calculated by FDLBM, the 3D15V lattice BGK model with introducing the Coriolis force in the local equilibrium distribution function. The phase velocity and the group velocity of the inertial wave are compared with the theoretical one obtained by the dispersion relation of an incompressible inviscid fluid, and both agree well.一般社団法人日本機械学会, 2001年03月16日, 関西支部講演会講演論文集, 2001(76) (76), "9 - 19"-"9-20", 日本語F231 一定速度で水平方向に流れる密度成層流体の線吸い込み流れLine sink flow in a linearly stratified stream, bounded by the top and bottom two horizontal plates, is investigated numerically by the finite-difference method. The unsteady behavior of fluids, especially the propagation of internal waves generated by the start-up of discharge, is examined computationally. The flow approaches steady state where a layer of withdrawn fluids is concentrated near the bottom and a thickness of this withdrawn layer is also presented.日本流体力学会, 2001年, 日本流体力学会年会講演論文集, 2001, 367 - 368, 日本語1301 三次元性地形効果により励起される有限振幅内部重力波の振舞(OS-7 密度成層・自由境界)Finite-amplitude internal waves resonantly excited by three-dimensional topography in the flow of a weakly and nearly uniformly stratified fluid are studied. This flow is mainly governed by a stratification profile and the Froude number. The numerical solutions of Navier-Stokes equations show various wave patterns, such as the Mach reflection and upstream propagation of solitary waves, depending on the values of these parameters. A comparison with solutions of fully nonlinear model equation is also made.一般社団法人日本機械学会, 2000年03月16日, 関西支部講演会講演論文集, 2000(75) (75), "13 - 1"-"13-2", 日本語1303 差分格子ボルツマン法による重力下の密度成層流れの解析(OS-7 密度成層・自由境界)Stratified fluids in gravitational field show some peculiar behavior different from homogeneous fluids. Free convection is one of such typical phenomena in stratified flows. The phenomenon is of practical importance in civil engineering or geophysical fluid dynamics. In this paper Finite Difference Lattice Boltzman Method and the thermal Lattice BGK model is applied to the compressible stratified fluid and we have simulated the free convection.一般社団法人日本機械学会, 2000年03月16日, 関西支部講演会講演論文集, 2000(75) (75), "13 - 5"-"13-6", 日本語E213 差分格子ボルツマン法による圧縮性成層流体の数値シミュレーションFor a compressible fluid under gravitational force, the density stratification is not enough and the entropy stratification is essential. In this report, we present the numerical simulation of a line sink compressible stratified flow in two-dimensional channel by the finite difference lattice Boltzmann method. The results show that selective withdrawal is established when the entropy increase upward that is predicted by theoretical consideration.日本流体力学会, 2000年, 日本流体力学会年会講演論文集, 2000, 357 - 358, 日本語B345 内部孤立波の二次元的不安定性The linear stability of finite-amplitude internal solitary waves in a weakly and nearly uniformly stratified fluid with respect to long-wavelength transverse perturbations is studied analytically. The two-dimensional (three-dimensional in the physical space) version of the strongly nonlinear evolution equation derived by Grimshaw and Yi^<4)> is used as a basic equation of the stability analysis. We derived the condition for transverse stability of solitary waves and newly found that one-dimensionally stable internal solitary waves could be transversely unstable. In the small-amplitude limit, our results agree with those obtained by using the weekly-nonlinear evolution equation as a basic model.日本流体力学会, 2000年, 日本流体力学会年会講演論文集, 2000, 495 - 496, 日本語神戸大学, 2000年, 神戸大学大学院自然科学研究科紀要, 18, 81 - 90, 日本語陰的シンプレクティック法の有効性に関する研究速報,短報,研究ノート等(大学,研究機関紀要)2000年, Mem. Grad. School Sci. Technol., Kobe Unbiv., 18-A, 131 - 148Numerical simulation of thermal convections using the lattie Boltzmann method京都大学, 1999年11月, 数理解析研究所講究録, 1115, 111 - 119, 日本語格子ボルツマン法による熱対流の数値解析 (熱対流の数理 : 流れ場の構造)1999年07月29日, 年会一般講演, 18, 333 - 334, 日本語熱格子Boltzmann法によるレーリベナール対流の数値計算1999年07月29日, 年会一般講演, 18, 469 - 470, 日本語一般化KP方程式による孤立波の二次元的不安定性1999年07月29日, 年会一般講演, 18, 467 - 468, 日本語三次元性地形効果により励起された有限振幅内部重力波の振舞 - 強非線形モデル方程式の導出とその特徴 -1998年07月, 年会一般講演, 17, 345 - 346, 日本語密度成層場における線形モード波の水平伝播1997年07月, 年会一般講演, 16, 523 - 524, 日本語密度成層場における吸い込み流れの際, 上流へ伝播するColumnar Disturbancesに関する数値解析的研究1996年07月, 年会一般講演, 15, 473 - 474, 日本語密度成層場における点すい込み流れ1996年07月, 年会一般講演, 15, 477 - 478, 日本語密度成層場におけるブロッキング形成過程
■ 講演・口頭発表等- 第30回数値流体力学シンポジウム, 2016年12月, 日本語, 国内会議海洋中を伝わる内部波ビームの3次元的安定性口頭発表(一般)
- 69th Annual Meeting of the APS Division of Fluid Dynamics, 2016年11月, 英語, 国際会議3D instability of internal gravity wave beams口頭発表(一般)
- 日本流体力学会年会2016, 2016年09月, 日本語, 国内会議内部波ビームの3次元的不安定性(粘性を伴う新しいメカニズム)口頭発表(一般)
- Mini-Workshop on Nonlinear Waves in Fluids, Kyoto, 2016年05月, 英語, 国際会議Three-dimensional Instability of Internal Wave Beams口頭発表(一般)
- Kinetic Theory and Fluid Dynamics: From micro to macroscopic modeling, 2016年05月, 英語, 国際会議Stability of internal wave beams to 3D perturbations口頭発表(一般)
- 日本機械学会関西支部 第91期定時総会講演会, 2016年03月, 日本語, 寝屋川, 国内会議自由分子型運動学的スキームによる三次元圧縮性流体解析口頭発表(一般)
- 第29回数値流体力学シンポジウム, 2015年12月, 日本語, 福岡, 国内会議内部波ビームの弱3次元的な時間発展とその特徴口頭発表(一般)
- 神戸大学工学フォーラム2015, 2015年10月, 日本語, 神戸, 国内会議孤立波の横方向不安定性と波の崩れる仕組み公開講演,セミナー,チュートリアル,講習,講義等
- 京都大学数理解析研究所研究集会”非線形波動現象の数理に関する最近の進展”, 2015年10月, 日本語, 京都, 国内会議傾斜円柱の振動により誘起される内部波口頭発表(一般)
- 日本流体力学会年会2015, 2015年09月, 日本語, 東京, 国内会議有限長さの円柱振動により誘起される内部波口頭発表(一般)
- 第47回流体力学講演会/第33回航空宇宙数値シミュレーション技術シンポジウム, 2015年06月, 日本語, 東京, 国内会議自由分子型運動学的スキームによる圧縮性流体解析口頭発表(一般)
- 第28回数値流体力学シンポジウム, 2014年12月, 日本語, 東京, 国内会議内部波ビームの弱3次元的な時間発展とその特徴口頭発表(一般)
- 京都大学数理解析研究所研究集会 非線形波動現象のメカニズムと数理, 2014年10月, 日本語, 京都, 国内会議3次元内部波ビームと誘起される平均流口頭発表(一般)
- 第63回理論応用力学講演会, 2014年09月, 日本語, 東京, 国内会議自由分子型運動学的スキームによる鈍頭物体まわりの超音速流れシミュレーション口頭発表(一般)
- 日本流体力学会年会2014, 2014年09月, 日本語, 仙台, 国内会議空間3次元的な依存性をもつ内部波ビームの時間発展口頭発表(一般)
- Seminar presentation in University of Oslo, 2014年08月, 英語, 国際会議Three-dimensional instability of solitary water waves公開講演,セミナー,チュートリアル,講習,講義等
- Theory of water waves, Isaac Newton institute for mathematical Sciences, 2014年07月, 英語, Cambridge, 国際会議Resonance curves of finite-amplitude gravity waves in shallow-water limit口頭発表(一般)
- 第27回数値流体力学シンポジウム, 2013年12月, 日本語, 日本流体力学会, 東京都, 内部波ビームの空間3次元的な時間発展を表す非線形方程式を,振幅が小,ビームに沿っての空間依存性が緩やか,という仮定の基で導出し,その計算結果について報告。, 国内会議内部波ビームの空間3次元的な時間発展口頭発表(一般)
- 京都大学数理解析研究所研究集会”非線形波動現象の数理と応用”, 2013年10月, 日本語, 京都大学数理解析研究所, 京都市, 一様な密度成層流体中を伝播する内部波ビームの3次元撹乱に対する線形安定性を取り扱った。具体的には,撹乱の波長がビームの幅に比べて十分長い場合を仮定し,漸近理論を駆使してEuler方程式系を基に変調安定性を調べた。その結果,一方向のみにエネルギーを伝える進行波ビームは,振幅がある値を超えると変調不安定となり,両方向にエネルギーを伝える定在波ビームは,任意の振幅において変調不安定となることが分かった., 国内会議内部波ビームの3次元的安定性口頭発表(一般)
- 日本流体力学会年会2013, 2013年09月, 日本語, 日本流体力学会, 東京都, 内部波ビームは海洋中での伝播がよく観測されているが、その変調安定性をEuler方程式系を基に調べた結果を報告., 国内会議内部波ビームの変調安定性口頭発表(一般)
- 第26回数値流体力学シンポジウム, 2012年, 日本語, 国内会議内部波ビームの不安定性口頭発表(一般)
- 第90期日本機械学会流体工学部門講演会, 2012年, 日本語, 国内会議回転系における密度成層流体の吸い込み流れ口頭発表(一般)
- 第39回流体力学講演会, 2007年06月, 日本語, 日本航空宇宙学会, 東京都, 国内会議差分格子ボルツマン法によるBVI の数値解析口頭発表(一般)
- 日本流体力学会年会2004, 2004年08月, 日本語, 日本流体力学会, 名古屋大学, 国内会議差分格子ボルツマン法によるスリット及び穴あき円柱から生じる空力温の直接計算口頭発表(一般)
- 日本機械学会関西支部第80期定時総会講演会, 2004年03月, 日本語, 日本機械学会関西支部, 京都大学, 国内会議二層流体中を伝播する内部孤立波の線形安定性に関する研究口頭発表(一般)
- 日本機械学会関西支部第80期定時総会講演会, 2004年03月, 日本語, 日本機械学会関西支部, 京都大学, 国内会議回転二重同心円筒内流体の吸い込み湧き出し流れ口頭発表(一般)
- 日本機械学会関西支部第79期定時総会講演会, 2004年, 日本語, 日本機械学会, 未記入, 国内会議内部孤立波の鉛直壁面による反射口頭発表(一般)
- 日本機械学会2004年度年次大会, 2004年, 日本語, 日本機械学会, 北海道大学, 国内会議差分格子ボルツマン法によるエッジ音の直接計算口頭発表(一般)
- 第53回理論応用力学講演会, 2004年, 日本語, 日本学術会議, 日本学術会議, 国内会議差分格子ボルツマン法における数値拡散について口頭発表(一般)
- 日本機械学会関西支部第79期定時総会講演会, 2004年, 日本語, 日本機械学会, 未記入, 国内会議希薄気体におけるクヌッセンポンプの光学的応用に関する研究口頭発表(一般)
- 第53回理論応用力学講演会, 2004年, 日本語, 日本学術会議, 日本学術会議, 国内会議クヌッセンコンプレッサーの宇宙空間利用に関する研究口頭発表(一般)
- 日本機械学会関西支部第78期定時総会講演会, 2003年03月, 日本語, 日本機械学会関西支部, 大阪, 国内会議二層流体中を伝播する内部孤立波の線形安定性について口頭発表(一般)
- 日本機械学会関西支部第78期定時総会講演会, 2003年03月, 日本語, 日本機械学会関西支部, 大阪, 国内会議取水口移動による選択取水効果の数値的研究口頭発表(一般)
- 日本機械学会関西支部第78期定時総会講演会, 2003年03月, 日本語, 日本機械学会関西支部, 大阪, 国内会議希薄気体におけるクヌッセンポンプの応用に関する研究口頭発表(一般)
- 日本機械学会第16回計算力学講演会, 2003年, 日本語, 日本機械学会, 神戸大学, 国内会議乱流にデルを組み込んだ差分格子ボルツマン法に関する研究口頭発表(一般)
- 第51回理論応用力学講演会, 2003年, 日本語, 日本学術会議 メカニクス・構造研究連絡委員会, 日本学術会議, 国内会議密度成層流体中の内部孤立波の安定性口頭発表(一般)
- 第17回数値流体力学シンポジウム, 2003年, 日本語, 日本流体力学会, 国立オリンピック記念青少年センター, 国内会議内部自由度を持つ差分格子ボルツマンモデルによる低マッハ数における空力音の直接計算口頭発表(一般)
- 日本流体力学年会’03, 2003年, 日本語, 日本流体力学会, 工学院大学, 国内会議内部孤立波の安定性口頭発表(一般)
- 2003年度日本機械学会年次大会 Mechanical Engineering Congress, 2003年, 日本語, 日本機械学会, 徳島大学, 国内会議差分格子ボルツマン法の3次元圧縮性モデルによる流体音の直接計算口頭発表(一般)
- 日本機械学会第16回計算力学講演会, 2003年, 日本語, 日本機械学会, 神戸大学, 国内会議差分格子ボルツマン法による乱流の直接計算に関する研究口頭発表(一般)
- 日本機械学会第16回計算力学講演会, 2003年, 日本語, 日本機械学会, 神戸大学, 国内会議差分格子ボルツマン法による界面活性剤のSISに関する研究口頭発表(一般)
- 第81回日本機械学会流体工学部門講演会, 2003年, 日本語, 日本機械学会, 関西大学, 国内会議差分格子ボルツマン法によるエッジ音の直接計算口頭発表(一般)
- 2003年度日本機械学会年次大会 Mechanical Engineering Congress, 2003年, 日本語, 日本機械学会, 徳島大学, 国内会議差分格子ボルツマン法によるウェッジボックス周りの流れの数値解析口頭発表(一般)
- 第40回日本航空宇宙学会関西・中部支部合同秋期大会, 2003年, 日本語, 日本航空宇宙学会, 神戸大学, 国内会議差分格子ボルツマン法による3次元物体周りから発生する音波の直接計算口頭発表(一般)
- 第35回流体力学講演会, 2003年, 日本語, 日本流体力学会, 東京工業大学, 国内会議格子ボルツマン法における比熱比可変モデルの提案口頭発表(一般)
- 日本学術振興会, 科学研究費助成事業, 基盤研究(B), 茨城大学, 2024年04月01日 - 2027年03月31日海洋波の強非線形・非定常現象に対する数理モデルとその検証
- 日本学術振興会, 科学研究費助成事業, 基盤研究(B), 茨城大学, 2022年04月01日 - 2027年03月31日海洋波の強非線形・非定常現象に対する数理モデルとその検証
- 学術研究助成基金助成金/基盤研究(C), 2018年04月 - 2023年03月, 研究代表者競争的資金
- 日本学術振興会, 科学研究費助成事業, 基盤研究(B), 茨城大学, 2017年04月01日 - 2022年03月31日海洋における大振幅・非線形波動の数理モデルと解析本研究の目的は,海洋における大振幅波動の本質(非線形性と分散性)をとらえた数理モデルを導出し,その数理解析を行うことである.令和3年度(最終年度)は以下の三つのテーマについて研究を実施した.研究成果は,発表論文6件(査読有5件,国際共著4件),学会発表21件(招待講演2件,国際講演6件)で公表されている.研究の概要は以下の通りである. 1. 数学モデル:(1)水面上に浮体がある場合の浅水波モデルの適切性を示した(井口).(2)航跡波(一定速度で動く波源から放射される定常波)の定式化と数値計算を行い,非線形性が強いことを明らかにした(片岡).(3)KP方程式の曲線波ソリトンの高次解を導出し,直線波ソリトンとの相互作用を調べた(太田).(5)KP方程式の2重線ソリトンの安定性を明らかにした(水町). 2. 内部波:密度の異なる2層流体の界面波の線形安定性を複素解析の手法を用いて数値的に調べ,Kelvin-Helmholtz タイプの不安定性が支配的であることを示した(村重). 3. 大振幅・非線形波動の数値計算:(1)鉛直方向に流速が変化するシアー流上で発生する parasitic capillary waves(進行波の前面で発生する波長の短い表面張力波)の特徴を数値計算で明らかにした(村重).(2)表面波・内部波共存場の孤立波の特徴を,磯部・柿沼モデルの数値計算を用いて示した(柿沼).(3)津波(地すべり津波,河川を遡上する津波,浅瀬が存在する島嶼に入射する津波)の大振幅・非定常運動の特徴を数値計算で示した(柿沼).(4)自己適合移動格子(急激に波形が変化する領域で格子間隔を自動的に調節する方法)の一般化(境界条件,時空間変数の全離散化)を行った(丸野).(5)前進する船の先端付近で発生する砕波の特徴を,Navier-Stokes 方程式の直接計算により明らかにした(日野).
- 科学研究費補助金/基盤研究(C), 2012年04月 - 2015年03月, 研究代表者競争的資金
- 科学研究費補助金/若手研究(B), 2010年, 研究代表者競争的資金
- 科学研究費補助金/挑戦的萌芽研究, 2009年競争的資金
- 科学研究費補助金/若手研究(B), 2005年, 研究代表者競争的資金
- 日本学術振興会, 科学研究費助成事業, 若手研究(B), 神戸大学, 2003年 - 2004年熱遷移流を利用した常圧空気のポンプおよびコンプレッサーの試作常圧下における実験を行う前の準備段階として,まずは低度に希薄な気体中で熱遷移流を生じさせるための実験をおこなった.流れを生じさせるデバイスとして,微小な間隔で並べた平板を用いた.平板同士の間隔は0.1mmのオーダーのものを数パターン採用した.ヒーターおよび冷半導体を用いて平板列の両端に温度差を与え,その温度勾配により熱遷移流が生じることを確認した.次にこの平板列を1ユニットとし,長い直管内に等間隔で数ユニット配置した.数ユニット配置することにより,上流,下流間の圧力差を大きくするようにした.この装置では,管内に配置されたユニット間のつなぎ目の空間に逆の温度勾配が働くが,そこでは代表長さが長いために流れに対する駆動力が働かない.つまり逆方向の熱遷移流は誘起されない.よって温度分布を周期的に設定することができ,装置全体の温度差を低く押さえることができた.円管の上流側を,新たに製作した気密容器につなぎ,下流側を大気に解放し,上流側の圧力を測定することにより,排気装置としての性能を調べた.1.1倍程度の圧力上昇を測定した. 次にユニット間の距離,平板間距離,温度分布,および様々な運転条件における圧力上昇の依存性を知るために,モンテカルロ直接シミュレーションによる数値実験をおこなった.それによると,系の希薄度を表すパラメータであるKnudsen数が0.1程度のときに最大の圧力上昇度が得られることなどを明らかにした.今後は,上記した基礎実験,および数値実験による知見をもとにして,常圧下における熱遷移流を利用したコンプレッサーを試作する予定である.
- 日本学術振興会, 科学研究費助成事業, 萌芽研究, 神戸大学, 2002年 - 2003年格子ボルツマン法による界面活性物質の流体摩擦抵抗減メカニズムの解明差分格子ボルツマン法での計算では、層流計算において見かけ上の粘性係数が変化するSIS 現象を再現することができた。2次元クエット流れに、界面活性剤の棒状ミセルのモデルとして、自由な変形を許すひも状の物体を潜入し壁面に働く平均の努断応力を求めた。それにより、あるレベルまで剪断が強くなると剪断応力が急増し、見かけ上の粘性係数が増加する現象がみられた。それ以上剪断が強くなると、ミセル表面で液の滑りが生じ、見かけ上の粘性係数は減少に転じることも確認された。一方、乱流の直接計算では2次元及び3次元等方性乱流のシミュレーションを行った。2次元計算ではエネルギースペクトルが時間によって-3乗則および-4乗側と変化する。また逆カスケード現象もとらえられた。3次元では-5/3乗側の成立する領域が存在することが確認できた。また実験や、他の計算との比較も良好であった。サブグリッドモデルを組み込んだ計算では、チャネル流れ正方形物体周りの流れも、満足のいく結果が得られた。 2次元クエット乱流に、界面活性物質を混入した計算では、流れ方向の乱れはそれほど抑えられていないが、流れに垂直な方向の乱れは大きく抑制され、実験により得られている結果を再現した。 実験では、水の場合にレイノルズ数Re=14000まで層流を維持できる管路の助走区間にリング状突起物を設置して強制的に乱れを与え,遷移の初期段階で断続的に発生しはじめる乱流塊の性質や挙動に及ぼす界面活性剤添加の影響を調べた.界面活性剤としてCH_3(CH_2)_<13>N(CH_3)_3Brを用いた.LDVと参照用熱線流速計により成長速度を測定した.その結果,(1)濃度250ppm以下では界面活性剤添加の影響は現れない,(2)250ppm以上では乱流塊が発生しはじめるReは濃度とともに増大するが,400ppmを越えると明確な乱流塊は発生しない,(3)300〜400ppm水溶液では遷移初期に発生しはじめる乱流塊はスラグからパフに転化する,ことがわかった.
- 日本学術振興会, 科学研究費助成事業, 基盤研究(B), 神戸大学, 2001年 - 2003年水蒸気を直接の駆動源とする船舶推進装置の性能向上に関する研究高速度カメラによりノズル内流れを観測し、これまで考えていた気泡と水が混合した流れではなく、気相と液層が分離した流れであり、高圧空気の噴出部下流の気液界面に大きな振幅をもつ波が現れる。この波の頂部がノズル上面に近付くことにより空気の流路が遮断され、その上流部の圧力が増加し、水を下流へと加速する構造が明らかとなった。この流れの条件は、圧力の上昇のタイミングが早すぎる事によるが、運転条件の適正化に対する指針が得られた。もっとも極端な場合として、高圧空気を断続的に噴出する方法であるが、この場合ノズルの推力自体は連続的に噴出する場合よりも小さいが、空気の噴出時間をベースに換算し直すと、その推力が増加することがわかった。 ノズル内の圧力分布の履歴を測定し,上記ノズル内流れの構造を確認した.すなわち,ノズル内の界面に現れる波の前方は圧力が高い.しかし詳細な測定では波直前の位置でもっとも高く,それより上流では圧力が下がっていることが確認された. これらのことからノズル内での水の加速は,乱流混合に依るのではなく,空気により直接水塊を加速しており,損失の少ないメカニズムであると考えられる. 数値シミュレーションにおいては、2種類の粒子を用いた差分格子ボルツマンモデルにより、ノズル内2相流れを計算した。その結果噴出した気相と液層の界面に、観測で得られた波動が生じ下流へと流れていくことが確認された。またノズル内の圧力変動は、この波動と連動しているようであるが、必ずしもそれらの相関はすべての場合に対して高くはない。この事実は実験的に検証が必要である。ただ波の形成に同期して、噴出気流の揺動がみられることなど、流れ場全体として定性的には実験結果と良い一致を示し、計算によるシミュレーションを注意深く調べることにより、ノズル内流れの知見を得ることが可能であることがわかった。また気液の密度比は約800であり,この大きな密度比に対応するモデルの駆逐を試みた.現時点では単相において30倍程度の密度変化を実現することができた.圧縮性流体の安定でかつ比熱比を多原子気体にまで拡張しうるモデルの提案を行った.