Multiscale simulation of rarefied gas dynamics via direct intermittent GSIS-DSMC coupling

TL;DR

This paper introduces a hybrid multiscale simulation method combining GSIS and DSMC to efficiently model rarefied gas dynamics, overcoming traditional limitations of cell size and convergence speed.

Contribution

It develops an intermittent coupling scheme that leverages GSIS's properties to accelerate DSMC simulations and remove cell size restrictions.

Findings

Rapid convergence to steady state

Elimination of cell size constraints

Validated accuracy and efficiency

Abstract

The general synthetic iterative scheme (GSIS) has proven its efficacy in modeling rarefied gas dynamics, where the steady-state solutions are obtained after dozens of iterations of the Boltzmann equation, with minimal numerical dissipation even using large spatial cells. In this paper, the fast convergence and asymptotic-preserving properties of the GSIS are harnessed to remove the limitations of the direct simulation Monte Carlo (DSMC) method. The GSIS, which leverages high-order constitutive relations derived from DSMC, is applied intermittently, which not only rapidly steers the DSMC towards steady state, but also eliminates the requirement that the cell size must be smaller than the molecular mean free path. Several numerical tests have been conducted to validate the accuracy and efficiency of this hybrid GSIS-DSMC approach.