Yusuke Mizuno

A Simple Immersed Boundary Method for Compressible Flow Simulation around a Stationary and Moving Sphere

This study is devoted to investigating a flow around a stationary or moving sphere by using direct numerical simulation with immersed boundary method (IBM) for the three-dimensional compressible Navier-Stokes equations. A hybrid scheme developed to solve both shocks and turbulent flows is employed to solve the flow around a sphere in the equally spaced Cartesian mesh. Drag coefficients of the spheres are compared with reliable values obtained from highly accurate boundary-fitted coordinate (BFC) flow solver to clarify the applicability of the present method. As a result, good agreement was obtained between the present results and those from the BFC flow solver. Moreover, the effectiveness of the hybrid scheme was demonstrated to capture the wake structure of a sphere. Both advantages and disadvantages of the simple IBM were investigated in detail.

Analysis of the Temperature Ratio Effects on the Flow Properties of the Low Reynolds and High Mach number Flow around a Sphere

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.

Direct Numerical Simulation of Shock Waves Passed by Multiple Particles by Using Immersed Boundary Method

A flow containing multiple particles and the shock wave is investigated by the direct numerical simulation with immersed boundary method. The shock Mach number and the Reynolds numbers of particle behind the shock wave are set to be 1.5 to 2.0 and 300 to 600, respectively. The comparison of the present results with one-dimensional simulation results, shows good agreement. From the results, we clarified characteristic flow structure at different shock Mach and Reynolds number. The turbulence kinetic energy was enhanced from the vortex structure in the wake of particles for the high Reynolds number case. The drag coefficient from the present simulation and the previous prediction models shows almost the same values at Mach number 1.5. At Mach number 2.0, however, discrepancy is obtained for the drag coefficient between the present flow simulation and the previous prediction models.