Unified gas-kinetic simulation for the system of multiscale radiation hydrodynamics

TL;DR

This paper develops a unified gas-kinetic scheme to simulate multiscale radiation hydrodynamics, effectively capturing phenomena from free streaming to diffusive regimes and ensuring accurate results across different optical depths.

Contribution

The paper introduces a combined gas-kinetic scheme that handles multiscale radiation transfer and fluid dynamics with asymptotic preserving properties, improving simulation accuracy in complex regimes.

Findings

Successfully simulates radiative shock waves.

Captures transition from free streaming to diffusive radiation.

Maintains accuracy in both optically thick and thin regions.

Abstract

This paper aims at the simulation of multiple scale physics in the system of radiation hydrodynamics. The system couples the fluid dynamic evolution equations with the radiative heat transfer. The coupled system is solved by the gas-kinetic scheme (GKS) for the compressible viscous and heat conducting flow and the unified gas-kinetic scheme (UGKS) for the non-equilibrium radiative transfer, together with the momentum and energy exchange between these two phases. For the radiative transfer, due to the possible large variation of fluid opacity in different regions, the transport of photons in the flow system is simulated by the multiscale UGKS, which is capable of naturally capturing the transport process from the free streaming to the diffusive propagation.Since both GKS and UGKS are finite volume methods,all unknowns are defined inside each control volume and are discretized consistently for the hydrodynamic and radiative variables. For the coupled system, the scheme has the asymptotical preserving (AP) property, such as recovering the equilibrium diffusion limit for the radiation hydrodynamic equations in the optically thick region, where the cell size is not limited by photon's mean free path. A few test cases, such as radiative shock wave problems, are used to validate the current approach.