Shun Takahashi | Tokai University (original) (raw)
Papers by Shun Takahashi
International Journal for Numerical Methods in Fluids, 2020
It is well known that the lateral vibration of the trains running in tunnel becomes larger than t... more It is well known that the lateral vibration of the trains running in tunnel becomes larger than that at open section, where we cannot find strong relevance to track irregularity in contrast to the vibration at open section. This vibration has been explained mainly by the aerodynamic flow separation and vortex shedding from the surface of trains. In this paper we focus on lateral vibration of the high-speed train (Shinkansen), and try to investigate not only flow separation but also expansion wave effect from the tail part of the trains on the vibration when they enter the tunnel. We have started to investigate with compressible and two-dimensional numerical analysis of aerodynamic flows around the trains. For the trains entering the tunnel, we performed the CFD with ghost cells and level set functions. As a result of interference of expansion waves and aerodynamic flow separation and alternating periodical expansion waves passing the train sides, large pressure difference on both sides of the trains moving forwards from the tail to the top is raised, which causes the lateral vibration.
Computational and Experimental Simulations in Engineering, 2019
In the design and development of tires, the robust grip performance is a key role in different ro... more In the design and development of tires, the robust grip performance is a key role in different road conditions such as dry or wet load. The objective of this study is accurate prediction of friction coefficient on the wet road by using numerical analysis. Therefore, we developed a finite element analysis (FEA) solver for hyperelastic materials to apply flow–structure coupling simulations. In this paper, we investigated the validity and applicability of the structure and flow solver. As a result, present numerical method we developed showed good agreements with theoretical and experimental values.
The Proceedings of The Computational Mechanics Conference, 2019
The exhaust gas from rocket motors generates severe acoustic waves. The acoustic waves reflected ... more The exhaust gas from rocket motors generates severe acoustic waves. The acoustic waves reflected from the ground and launch facility is cause of vibration of the payload in the fairing. Therefore, prediction and reduction of acoustic level at the lift-off is quite important. Traditionally, acoustic level has been predicted by an empirical method, NASA SP-8072 [1] or subscale tests [2] . In recent, prediction of acoustic level by CFD is required, because an empirical methods does not have enough accuracy. The alumina particles released from solid rocket motors might attenuate acoustic wave, but the mechanism is not well known. Therefore, a new model for prediction of drag force at the highMach-number and low-Reynolds-number condition is necessary, in order to perform high accuracy prediction on acoustic wave generated by exhaust gas from solid rocket motors. In this study, the high-Mach-number and low-Reynolds-number flow analysis of the around a sphere by direct numerical simulation...
2018 AIAA Aerospace Sciences Meeting, 2018
The Proceedings of Conference of Hokuriku-Shinetsu Branch, 2020
The Proceedings of the National Symposium on Power and Energy Systems, 2014
The Proceedings of Mechanical Engineering Congress, Japan, 2012
The Proceedings of the Fluids engineering conference, 2015
Applied Thermal Engineering, 2016
Computational fluid dynamics (CFD) simulations have become prevalent tools in the numerical model... more Computational fluid dynamics (CFD) simulations have become prevalent tools in the numerical modeling of complex thermoacoustic phenomena. The basic problem concerning a CFD simulation of a complete system is the computational cost. To overcome this problem, a CFD simulation tool using an impedance matching boundary (IMB) condition has been developed to analyze the characterization of the flow field in a looped-tube travelling-wave thermoacoustic engine. The thermodynamic processes were simulated using a two-dimensional numerical solution for the compressible Navier-Stokes equations. By imposing an impedance matching boundary condition, flow fields around the regenerator and heat-exchanger plates were simulated. The boundary condition being defined as an acoustic load which was derived from experimental data. From the simulations, features of the flow field such as nonlinear vortex generation around the regenerator and heat-exchanger plates were observed that were not present in the analytical solutions. Furthermore, the temperature oscillations were obtained around regenerator plates, and the operating mechanism of a looped-tube travelling-wave thermoacoustic engine was characterized both qualitatively and quantitatively. The CFD tool was validated by obtaining good agreement when comparing results with those from experimental data and analytical solutions. As a result, it was concluded that CFD
54th AIAA Aerospace Sciences Meeting, 2016
In this study, direct numerical simulation of the flow around a sphere at the high Mach number an... more In this study, direct numerical simulation of the flow around a sphere at the high Mach number and the low Reynolds number condition is carried out in order to investigate the flow properties. The three-dimensional compressible Navier-Stokes equations are solved on boundary fitted coordinate system. It is confirmed to have sufficient accuracy from the results of the previous study. Analyses are performed at the Reynolds number of between 50 and 300, the freestream Mach number of between 0.3 and 2.0, and the temperature ratio of the sphere surface and freestream of between 0.5 and 2.0. As the results, we clarified the following points: 1) the freestream Reynolds number and the temperature ratio influence the flow properties, 2) the effect of the temperature ratio can be summarized by the effective Reynolds number that is a newly proposed parameter.
Journal of Applied Mathematics, 2014
A computational code adopting immersed boundary methods for compressible gas-particle multiphase ... more A computational code adopting immersed boundary methods for compressible gas-particle multiphase turbulent flows is developed and validated through two-dimensional numerical experiments. The turbulent flow region is modeled by a second-order pseudo skew-symmetric form with minimum dissipation, while the monotone upstream-centered scheme for conservation laws (MUSCL) scheme is employed in the shock region. The present scheme is applied to the flow around a two-dimensional cylinder under various freestream Mach numbers. Compared with the original MUSCL scheme, the minimum dissipation enabled by the pseudo skew-symmetric form significantly improves the resolution of the vortex generated in the wake while retaining the shock capturing ability. In addition, the resulting aerodynamic force is significantly improved. Also, the present scheme is successfully applied to moving two-cylinder problems.
The Proceedings of Conference of Kanto Branch
The Proceedings of Conference of Hokuriku-Shinetsu Branch
The Proceedings of The Computational Mechanics Conference
The Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME
JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES
The proceedings of the JSME annual meeting
International Journal for Numerical Methods in Fluids, 2020
It is well known that the lateral vibration of the trains running in tunnel becomes larger than t... more It is well known that the lateral vibration of the trains running in tunnel becomes larger than that at open section, where we cannot find strong relevance to track irregularity in contrast to the vibration at open section. This vibration has been explained mainly by the aerodynamic flow separation and vortex shedding from the surface of trains. In this paper we focus on lateral vibration of the high-speed train (Shinkansen), and try to investigate not only flow separation but also expansion wave effect from the tail part of the trains on the vibration when they enter the tunnel. We have started to investigate with compressible and two-dimensional numerical analysis of aerodynamic flows around the trains. For the trains entering the tunnel, we performed the CFD with ghost cells and level set functions. As a result of interference of expansion waves and aerodynamic flow separation and alternating periodical expansion waves passing the train sides, large pressure difference on both sides of the trains moving forwards from the tail to the top is raised, which causes the lateral vibration.
Computational and Experimental Simulations in Engineering, 2019
In the design and development of tires, the robust grip performance is a key role in different ro... more In the design and development of tires, the robust grip performance is a key role in different road conditions such as dry or wet load. The objective of this study is accurate prediction of friction coefficient on the wet road by using numerical analysis. Therefore, we developed a finite element analysis (FEA) solver for hyperelastic materials to apply flow–structure coupling simulations. In this paper, we investigated the validity and applicability of the structure and flow solver. As a result, present numerical method we developed showed good agreements with theoretical and experimental values.
The Proceedings of The Computational Mechanics Conference, 2019
The exhaust gas from rocket motors generates severe acoustic waves. The acoustic waves reflected ... more The exhaust gas from rocket motors generates severe acoustic waves. The acoustic waves reflected from the ground and launch facility is cause of vibration of the payload in the fairing. Therefore, prediction and reduction of acoustic level at the lift-off is quite important. Traditionally, acoustic level has been predicted by an empirical method, NASA SP-8072 [1] or subscale tests [2] . In recent, prediction of acoustic level by CFD is required, because an empirical methods does not have enough accuracy. The alumina particles released from solid rocket motors might attenuate acoustic wave, but the mechanism is not well known. Therefore, a new model for prediction of drag force at the highMach-number and low-Reynolds-number condition is necessary, in order to perform high accuracy prediction on acoustic wave generated by exhaust gas from solid rocket motors. In this study, the high-Mach-number and low-Reynolds-number flow analysis of the around a sphere by direct numerical simulation...
2018 AIAA Aerospace Sciences Meeting, 2018
The Proceedings of Conference of Hokuriku-Shinetsu Branch, 2020
The Proceedings of the National Symposium on Power and Energy Systems, 2014
The Proceedings of Mechanical Engineering Congress, Japan, 2012
The Proceedings of the Fluids engineering conference, 2015
Applied Thermal Engineering, 2016
Computational fluid dynamics (CFD) simulations have become prevalent tools in the numerical model... more Computational fluid dynamics (CFD) simulations have become prevalent tools in the numerical modeling of complex thermoacoustic phenomena. The basic problem concerning a CFD simulation of a complete system is the computational cost. To overcome this problem, a CFD simulation tool using an impedance matching boundary (IMB) condition has been developed to analyze the characterization of the flow field in a looped-tube travelling-wave thermoacoustic engine. The thermodynamic processes were simulated using a two-dimensional numerical solution for the compressible Navier-Stokes equations. By imposing an impedance matching boundary condition, flow fields around the regenerator and heat-exchanger plates were simulated. The boundary condition being defined as an acoustic load which was derived from experimental data. From the simulations, features of the flow field such as nonlinear vortex generation around the regenerator and heat-exchanger plates were observed that were not present in the analytical solutions. Furthermore, the temperature oscillations were obtained around regenerator plates, and the operating mechanism of a looped-tube travelling-wave thermoacoustic engine was characterized both qualitatively and quantitatively. The CFD tool was validated by obtaining good agreement when comparing results with those from experimental data and analytical solutions. As a result, it was concluded that CFD
54th AIAA Aerospace Sciences Meeting, 2016
In this study, direct numerical simulation of the flow around a sphere at the high Mach number an... more In this study, direct numerical simulation of the flow around a sphere at the high Mach number and the low Reynolds number condition is carried out in order to investigate the flow properties. The three-dimensional compressible Navier-Stokes equations are solved on boundary fitted coordinate system. It is confirmed to have sufficient accuracy from the results of the previous study. Analyses are performed at the Reynolds number of between 50 and 300, the freestream Mach number of between 0.3 and 2.0, and the temperature ratio of the sphere surface and freestream of between 0.5 and 2.0. As the results, we clarified the following points: 1) the freestream Reynolds number and the temperature ratio influence the flow properties, 2) the effect of the temperature ratio can be summarized by the effective Reynolds number that is a newly proposed parameter.
Journal of Applied Mathematics, 2014
A computational code adopting immersed boundary methods for compressible gas-particle multiphase ... more A computational code adopting immersed boundary methods for compressible gas-particle multiphase turbulent flows is developed and validated through two-dimensional numerical experiments. The turbulent flow region is modeled by a second-order pseudo skew-symmetric form with minimum dissipation, while the monotone upstream-centered scheme for conservation laws (MUSCL) scheme is employed in the shock region. The present scheme is applied to the flow around a two-dimensional cylinder under various freestream Mach numbers. Compared with the original MUSCL scheme, the minimum dissipation enabled by the pseudo skew-symmetric form significantly improves the resolution of the vortex generated in the wake while retaining the shock capturing ability. In addition, the resulting aerodynamic force is significantly improved. Also, the present scheme is successfully applied to moving two-cylinder problems.
The Proceedings of Conference of Kanto Branch
The Proceedings of Conference of Hokuriku-Shinetsu Branch
The Proceedings of The Computational Mechanics Conference
The Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME
JOURNAL OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES
The proceedings of the JSME annual meeting