Discrete unified gas kinetic scheme on unstructured meshes

TL;DR

This paper extends the discrete unified gas kinetic scheme (DUGKS) to unstructured meshes, demonstrating its effectiveness in simulating multiscale gas flows across various regimes.

Contribution

The paper introduces the extension of DUGKS to unstructured meshes, enabling accurate simulation of complex multiscale gas flows without mesh restrictions.

Findings

Successfully simulated cavity flows from continuum to free molecular regimes.

Accurately modeled high-speed flow over a cylinder in slip and transitional regimes.

Demonstrated DUGKS's capability in multiscale flow problems across different regimes.

Abstract

The recently proposed discrete unified gas kinetic scheme (DUGKS) is a finite volume method for deterministic solution of the Boltzmann model equation with asymptotic preserving property. In DUGKS, the numerical flux of the distribution function is determined from a local numerical solution of the Boltzmann model equation using an unsplitting approach. The time step and mesh resolution are not restricted by the molecular collision time and mean free path. To demonstrate the capacity of DUGKS in practical problems, this paper extends the DUGKS to arbitrary unstructured meshes. Several tests of both internal and external flows are performed, which include the cavity flow ranging from continuum to free molecular regimes, a multiscale flow between two connected cavities with a pressure ratio of 10000, and a high speed flow over a cylinder in slip and transitional regimes. The numerical results demonstrate the effectiveness of the DUGKS in simulating multiscale flow problems.