DSMC Simulation of Hypersonic Flows over a Compression Ramp in Subcell Scheme

Accurate prediction of the surface properties and the recirculation zone is very imperative for the design of advanced hypersonic vehicles and thermal protection. The objective of this paper is to identify the predominant factor affecting the accuracy of the calculation and to propose a more efficient way to simulate the shock wave/boundary layer interaction flow. First, the hypersonic flow over a compression ramp of 35-degree is calculated by the parallel direct simulation Monte Carlo (DSMC), and the results are compared with the benchmark to get a grid resolution. Then, the subcell scheme is implemented and the computational efficiency is highly improved. It is recommended to use a relatively coarse grid with subcell scheme to get a reliable result efficiently in engineering. It also can be found that the SOF, which is the ratio of mean collision separation (MCS) of the particles to mean free path (MFP), plays an important role in the accurate prediction of the recirculation zone, surface pressure and heat flux coefficient. Furthermore, further study show it is not a necessary condition to maintain the SOF value below unity throughout the flow field. More attention should be given to the SOF value in the cells close to the wall.