An Improved Parallelized Hybrid DSMC-NS Algorithm

Abstract

An improved parallelized hybrid DSMC-NS algorithm presented and verified. In previous work [11, it showed the slow convergence of coupling between two numerical solvers if the normal velocities across the breakdown interfaces are very low. By detailed kinetic velocity sampling study from the pure DSMC simulation of a two-dimensional supersonic nitrogen flow (M-infinity=4) past a 25 finite wedge, we have found most of boundary layer region is in nearly thermal equilibrium, even with very high continuum breakdown Kn(max)[10]. Thus, a new continuum breakdown parameter based on pressure gradient, pressure and local mean free path, which can be used to effectively "exclude" the "false" breakdown region like the boundary layer, is proposed in this paper. Results show that the improved algorithm can greatly reduce the computational cost while maintaining essentially the same accuracy.