A numerical model for multigroup radiation hydrodynamics

TL;DR

This paper introduces a multigroup radiation hydrodynamics model that captures frequency-dependent gas opacities and energy exchanges, improving accuracy over traditional grey models, and validates it through various tests including realistic Xe gas simulations.

Contribution

The paper develops and validates a multigroup radiation hydrodynamics model with frequency-dependent opacities and energy exchange, enhancing previous grey models.

Findings

Excellent agreement with kinetic models in Marshak wave tests

Successful coupling of multigroup transfer with hydrodynamics

Realistic Xe gas radiative shock simulations achieved

Abstract

We present in this paper a multigroup model for radiation hydrodynamics to account for variations of the gas opacity as a function of frequency. The entropy closure model (M1) is applied to multigroup radiation transfer in a radiation hydrodynamics code. In difference from the previous grey model, we are able to reproduce the crucial effects of frequency-variable gas opacities, a situation omnipresent in physics and astrophysics. We also account for the energy exchange between neighbouring groups which is important in flows with strong velocity divergence. These terms were computed using a finite volume method in the frequency domain. The radiative transfer aspect of the method was first tested separately for global consistency (reversion to grey model) and against a well established kinetic model through Marshak wave tests with frequency dependent opacities. Very good agreement between the multigroup M1 and kinetic models was observed in all tests. The successful coupling of the multigroup radiative transfer to the hydrodynamics was then confirmed through a second series of tests. Finally, the model was linked to a database of opacities for a Xe gas in order to simulate realistic multigroup radiative shocks in Xe. The differences with the previous grey models are discussed.