Beijing Institute of Mathematical Sciences and Applications

Zhen Li , Xin Liang , Zhi Ting Ma , Hamid Mofidi , Li Wang , Fan Sheng Xiong , Shuo Yang , Wu Yue Yang

Weiming Li

Monday, October 21, 2024 3:00 PM - 4:00 PM

A3-4-312

Zoom 928 682 9093 (BIMSA)

Radiative transfer equation has important applications in astrophysics, nuclear engineering and biomedicine. In this talk, we develop the unified gas-kinetic particle method (UGKP) and the unified gas-kinetic wave-particle method (UGKWP) for frequency-dependent radiative transfer equation. In this method, the photon free streaming and collision processes are treated in an un-splitting way. The photon distribution is described by both discrete simulation particle and analytic distribution function. The proposed method presents a smooth transition for photon transport from optically thin to optically thick regimes according to the cell’s Knudsen number. In the optically thin regime, the method performs as a Monte Carlo type particle tracking method, while in the optically thick regime it recovers a diffusion process without particles. Compared to the implicit Monte Carlo (IMC) method, the statistical noise of the UGKP and UGKWP method is greatly reduced, and the computational efficiency is significantly improved in the optically thick regime. Several numerical examples covering all transport regimes from the optically thin to optically thick ones are computed to validate the accuracy and efficiency of the proposed method.