Parallel particle simulation of the near-continuum hypersonic flows over compression ramps

This paper describes the simulation of the near-continuum hypersonic flow over a compression ramp using two-dimensional parallel direct simulation Monte Carlo (DSMC) method. Unstructured and triangular solution-based adaptive mesh depending on the local mean free path is used to improve the resolution of solution for the flow field with highly varying properties. In addition, a free-stream parameter is defined to help reduced the cell numbers in the free-stream area, resulting in appreciable decrease of the computational time (20~30%) without sacrificing the accuracy of the solution. Two-step multi-level graph partition technique is used for physical domain decomposition, employing estimated particle number distribution in each cell as the graph vertex weight. 32 IBM-SP2 processors are used throughout the study. Effects of outflow vacuum boundary condition, compression ramp angle, free-stream condition and length of the ramp to the flow field are investigated. Computational results are compared with previous numerical results whenever available.