A Cartesian Cut Cell Method for Rarefied Flow Simulations around Moving Obstacles

TL;DR

This paper introduces a Cartesian cut cell method for simulating rarefied gas flows around moving obstacles, enabling accurate boundary treatment, conservation, and easy extension to 3D, demonstrated through various test cases.

Contribution

The paper presents a novel cut cell method that simplifies implementation and extends easily to 3D for rarefied flow simulations around moving obstacles.

Findings

Accurate boundary condition treatment in rarefied flow simulations.

Method enables extension to 3D problems.

Successful validation with test cases including a 3D radiometer.

Abstract

For accurate simulations of rarefied gas flows around moving obstacles, we propose a cut cell method on Cartesian grids: it allows exact conservation and accurate treatment of boundary conditions. Our approach is designed to treat Cartesian cells and various kind of cut cells by the same algorithm, with no need to identify the specific shape of each cut cell. This makes the implementation quite simple, and allows a direct extension to 3D problems. Such simulations are also made possible by using an adaptive mesh refinement technique and a hybrid parallel implementation. This is illustrated by several test cases, including a 3D unsteady simulation of the Crookes radiometer.