Accelerated simulation of multiscale gas-radiation coupling flows via a general synthetic iterative scheme

TL;DR

This paper introduces a novel synthetic iterative scheme that significantly accelerates the simulation of multiscale gas-radiation flows, crucial for designing thermal protection systems in hypersonic reentry vehicles.

Contribution

The study develops a general synthetic iterative scheme combining kinetic and macroscopic equations, achieving asymptotic-preserving, fast convergence across flow regimes for radiative gas dynamics.

Findings

Achieves orders-of-magnitude speedup over traditional methods.

Accurately captures non-equilibrium effects in hypersonic flows.

Validates approach with 3D hypersonic reentry simulations.

Abstract

Gas-radiation coupling critically influences hypersonic reentry flows, where extreme temperatures induce pronounced non-equilibrium gas and radiative heat transport. Accurate and efficient simulation of radiative gas dynamics is therefore indispensable for reliable design of thermal protection systems for atmospheric entry vehicles. In this study, a Boltzmann-type kinetic model for radiative gas flows is solved across a broad spectrum of flow and radiation transport regimes using the general synthetic iterative scheme (GSIS). The approach integrates an unstructured finite-volume discrete velocity method with a set of macroscopic synthetic equations. Within this framework, the kinetic model provides high-order closures for the constitutive relations in the synthetic equations. Simultaneously, the macroscopic synthetic equations drive the evolution of the mesoscopic kinetic system, significantly accelerating steady-state convergence in near-continuum regimes, as substantiated by linear Fourier stability analysis. Crucially, the algorithm is proven to be asymptotic-preserving, correctly recovering the continuum and optically thick limits, represented by the radiative Navier-Stokes-Fourier equations governing distinct translational, rotational, vibrational, and radiative temperatures, on coarse meshes independent of the mean free path. Numerical simulations of challenging benchmarks, including three-dimensional hypersonic flow over an Apollo reentry capsule, demonstrate that GSIS achieves orders-of-magnitude speedup over conventional iterative schemes in multiscale simulations of radiative gas flows while accurately capturing non-equilibrium effects and radiative heat transfer in hypersonic environments.