Parallel Computing of Non-equilibrium Hypersonic Rarefied Gas Flows

Abstract

This chapter presents multiscale analysis of nonequilibrium hypersonic rarefied diatomic gas flow by using parallel computers. DSMC (direct simulation Monte Carlo) simulations are employed with the dynamic molecular collision (DMC) model and the multi-stage (MS) model based on molecular dynamics (MD) simulation of nitrogen molecules. Those models do not need any empirical parameters such as inelastic collision parameter and can predict nonequilibrium between translational and rotational temperature rationality. In numerical simulation of the hypersonic flow in rarefied regime, DSMC is valid due to the treatment of particles directly. The important procedures in the DSMC method for diatomic molecular flow are the molecular collision and the gas-surface interaction. The DSMC simulations require significant amounts of computational time in near-continuum conditions and three-dimensional simulations because of the increase in the number of molecules and the collision frequency with increasing density. Therefore parallel implementation for the DSMC code is an efficient method to reduce CPU time per processor. The DSMC results over a flat plate in hypersonic rarefied gas flow show that nonequilibrium between translational and rotational temperature are obtained behind the leading edge over the plate and that the leading edge angle and the gas-surface interaction model has considerable effects on the flow structure.