Topic：Asymptotic preserving schemes for radiative transfer systems

Speaker：Mr. Jiang Song （academician）, from Institute of Applied Physics and Computational Mathematics

Date：Nov 19, 2018

Time：7:00pm

Venue：Room 224, Nanhai Building

Introduction：Radiative transfer systems find a wide range of applications, for example, in the inertial constrained fusion research and in astrophysics. The solution of a radiative transport system can cover both optical thin and optical thick regimes due to the large variation of photon's mean-free path and its interaction with the material. In the small mean free path limit, a nonlinear time-dependent radiative transfer system can converge to an equilibrium diffusion equation due to the intensive interaction among radiation and material. In the optical thin limit, the photon free transport mechanism will emerge.

In this talk, we are going to develop an asymptotic preserving unified gas kinetic scheme (AP-UGKS) for both grey and frequency-dependent radiative transfer systems, where the radiation transport equation is coupled with the material thermal energy equation. The newly developed scheme has the asymptotic preserving property in the optically thick regime to capture the diffusive solution without using a cell size being smaller than the photon's mean free path and time step being less than the photon collision time. Besides the diffusion limit, the scheme can capture the exact solution in the optical thin regime as well. Due to the direct modeling for the time evolution of the interface radiative intensity, a smooth transition of the transport physics from optical thin to optical thick can be accurately recovered. A number of numerical examples are included to validate the current approach. Extensions to more complex systems will be presented.