硬球-拟颗粒模拟高超声速稀薄气体流动

发展了适应高超声速稀薄流动的硬球-拟颗粒模拟(HS-PPM)，并分别采用硬球分子动力学模拟(HS)、HS-PPM和直接模拟蒙特卡洛(DSMC)对马赫数为5、努森数为0.8的圆球绕流进行模拟，证明了HS-PPM可以得到更接近HS的模拟结果。对雷诺数100、马赫数5~19的三维圆球绕流，采用HS-PPM模拟得到了填充率0.01~0.08、完全热边界和完全滑移边界条件下的曳力系数，与HS模拟结果的一致性较好；模拟了马赫数24、努森数0.11~4.55的零攻角三维尖锥绕流，结果与文献中DSMC的模拟结果相符。研究验证了HS-PPM处理高超声速稀薄气体流动的可行性。

Hard-sphere/pseudo-particle modeling (HS-PPM) for hypersonic rarefied gas flow

Hard-sphere/pseudo-particle modeling (HS-PPM) has been demonstrated as an effective discrete simulation method for supersonic gas flow, but the simulated flow was limited to relatively low Mach number (Ma?3~5) yet. Recently, hypersonic rarefied gas flow has attracted great attention in aerospace and material engineering under extreme conditions. In this work, flow past some objects with simple geometry was simulated in HS-PPM. The geometric method was used to describe the wall and specular, and diffuse reflection was coupled to represent the slip thermal boundary condition. The tangential accommodation coefficient was introduced to adjust the proportion of slip and thermal accommodation. The simulated domain size was analyzed to determine the optimal values and the influence of tangential accommodation coefficient on the drag coefficient was considered. The hard sphere (HS) modeling, HS-PPM and direct simulation Monte Carlo (DSMC) method were used to simulate the flow past a sphere with a Mach number of 5 and a Knudsen number (Kn) of 0.8, which proved that the HS-PPM results were closer to those of the HS model. On this basis, 14 cases of the flow past a three-dimensional sphere with a Reynolds number (Re) of 100 were simulated, and Mach numbers change from 5 to 19. The upper and lower limits of the simulated drag coefficient were obtained by using the fully diffuse boundaries and the slip boundaries respectively, and were in good agreement with the corresponding results of the HS model. In addition, the simulated drag coefficient of cones with axial flow at a Mach number of 24 and Knudsen numbers from 0.11 to 4.55 was also obtained. The attack angle was zero and the results were consistent with the results of DSMC. This study demonstrated that HS-PPM was effective for hypersonic rarefied gas flow. Furthermore, the error caused by the invariable collisional cross of hard spheres in simulating hypersonic flow was found, indicating the direction of future improvement.