A novel efficient hybrid DSMC–dynamic collision limiter algorithm for multiscale transitional flows

Abstract

Summary A new 2D parallel multispecies polyatomic particle–based hybrid flow solver is developed by coupling the Direct Simulation Monte Carlo (DSMC) method with a novel Dynamic Collision Limiter (DCL) approach to solve multiscale transitional flows. The hybrid DSMC‐DCL solver can solve nonequilibrium multiscale flows with length scales ranging from continuum to rarefied. The DCL method, developed in this work, dynamically assigns different number of collisions in cells, which is based on the local value of K‐S parameter such that the number of collisions per time step is limited in near‐equilibrium flow regions. Present hybrid solver uses the Kolmogorov‐Smirnov statistical test as the continuum breakdown parameter, based on which, the solution domain is decomposed into near‐equilibrium and nonequilibrium flow regions. Direct Simulation Monte Carlo is used where nonequilibrium flow regions are encountered, while the DCL method is used where flow regions are found to be in near‐equilibrium state. In this work, we have studied hypersonic flow of nitrogen over a blunt body with an aerospike and supersonic flow of argon through a micronozzle. The results obtained by the hybrid DSMC‐DCL solver are compared and shown to agree well with the experimental data and with those obtained from DSMC, with significant savings in the computational cost.

Improving computational efficiency in DSMC simulations of vacuum gas dynamics with a fixed number of particles per cell

“…Managing computational costs while maintaining accuracy is crucial in simulations involving a wide range of local Knudsen numbers or significant variations in local gradients. Various approaches have been explored, including CFD-DSMC hybrid methods [17,[21][22][23] and all-molecular hybrid methods such as DSMC-Equilibrium Particle Simulation Method (EPSM) [24], DSMC-Low Diffusion (LD) [25], DSMC-Dynamic Collision Limiter [26], and DSMC-Fokker-Planck [27][28][29] hybrid methods. These methods address challenges arising from significant variations in local rarefaction, concentrating primarily on the increased computational cost in DSMC simulations with decreasing local Knudsen numbers.…”