Multigroup radiation hydrodynamics with flux-limited diffusion and adaptive mesh refinement

TL;DR

This paper introduces a multigroup flux-limited diffusion algorithm integrated into the RAMSES code, enabling efficient multi-frequency radiation-hydrodynamics simulations crucial for modeling star formation and proto-stellar collapse.

Contribution

The authors developed and implemented a novel multigroup radiative transfer method with an implicit solver in RAMSES, improving simulation accuracy for frequency-dependent radiation effects in star formation.

Findings

The scheme performs well in standard tests.

Preliminary 3D proto-stellar collapse simulation with 20 frequency groups.

Differences observed between grey and multigroup results.

Abstract

Radiative transfer plays a key role in the star formation process. Due to a high computational cost, radiation-hydrodynamics simulations performed up to now have mainly been carried out in the grey approximation. In recent years, multi-frequency radiation-hydrodynamics models have started to emerge, in an attempt to better account for the large variations of opacities as a function of frequency. We wish to develop an efficient multigroup algorithm for the adaptive mesh refinement code RAMSES which is suited to heavy proto-stellar collapse calculations. Due to prohibitive timestep constraints of an explicit radiative transfer method, we constructed a time-implicit solver based on a stabilised bi-conjugate gradient algorithm, and implemented it in RAMSES under the flux-limited diffusion approximation. We present a series of tests which demonstrate the high performance of our scheme in dealing with frequency-dependent radiation-hydrodynamic flows. We also present a preliminary simulation of a three-dimensional proto-stellar collapse using 20 frequency groups. Differences between grey and multigroup results are briefly discussed, and the large amount of information this new method brings us is also illustrated. We have implemented a multigroup flux-limited diffusion algorithm in the RAMSES code. The method performed well against standard radiation-hydrodynamics tests, and was also shown to be ripe for exploitation in the computational star formation context.