Study Of Rarefied Gas Flow Of Hybrid Dsmc / Epsm Algorithm

The Direct Simulation of Monte Carlo method (DSMC) is the only succeed numerical method used in rarefied gas dynamics[3]. But in the density dense regions, such as the region near the windward surfaces of a blunt re-entry spacecraft, the flow is collision dominated. The DSMC method is ineffective because prohibitively expensive amounts of CPU time can be spent calculating collisions. For that deficiency, the Equilibrium Particle Simulation method (EPSM) was proposed by Pullin[7] as a direct simulation method in the density dense region, which is shown to be computationally efficient. In his method the states of the particles after collision are dealt with as the state of the local Maxwell-Boltzmann equilibrium distribution. The works of this paper are based on the above, and the main achievements of this paper are as follows:The hybrid DSMC/EPSM code is made by using two kinds of 'hybrid parameter' to divide the different flow regions. The supersonic flow of flat plate, hypersonic flows of vertical plate and flat-nosed cylinder are simulated by using the hybrid DSMC/EPSM code and DSMC method respectively. Through the comparison of the results of the DSMC/EPSM code and the DSMC method, the availability of the DSMC/EPSM method is proved.The EPSM method is developed to build a EPSM model suited for chemical reaction flows in high temperature gas. The hybrid DSMC/EPSM method is developed to simulate the nonequilibrium thermodynamics and chemical reactions in the high temperature gas flow. The hypersonic gas flows of vertical plate and flat-nosed cylinder are simulated by using DSMC/EPSM code and the DSMC method. Through the comparison of the results, the effectiveness of the DSMC/EPSM code is proved.The computation efficiency of the DSMC/EPSM method and the DSMC method is compared. It is proved that in the region which is collision dominated the EPSM method is more efficient than the DSMC method.