A semi-Lagrangian gas-kinetic scheme for smooth flows

TL;DR

This paper introduces a semi-Lagrangian gas-kinetic scheme for smooth flows that couples collision and transport mechanisms, allowing for larger time steps and accurate simulation across various flow regimes.

Contribution

The novel scheme combines Lagrangian flux construction with Eulerian control volume evolution, enabling larger time steps independent of collision times and accurate modeling of viscous flows.

Findings

Second-order spatial accuracy with low numerical dissipation

Accurately captures Navier-Stokes solutions for various flow regimes

Time step independent of particle collision time

Abstract

In this paper, a semi-Lagrangian gas-kinetic scheme is developed for smooth flows based on the Bhatnagar-Gross-Krook (BGK) equation. As a finite-volume scheme, the evolution of the average flow variables in a control volume is under the Eulerian framework, whereas the construction of the numerical flux across the cell interface comes from the Lagrangian perspective. The adoption of the Lagrangian aspect makes the collision and the transport mechanisms intrinsically coupled together in the flux evaluation. As a result, the time step is independent of the particle collision time and solely determined by the Courant-Friedrichs-Lewy (CFL) conditions. A set of simulations are carried out to validate the performance of the new scheme. The results show that with second-order spatial accuracy, the scheme exhibits low numerical dissipation, and can accurately capture the Navier-Stokers solutions for the smooth flows with viscous heat dissipation from the low-speed incompressible to hypersonic compressible regimes.