Modified steady discrete unified gas kinetic scheme for multiscale radiative heat transfer

In this work, a steady discrete unified gas kinetic scheme (SDUGKS) is proposed to solve the radiative transfer equation (RTE), which an improvement of original SDUGKS [X. F. Zhou et al., J. Comput. Phys. 423, 109767 (2020)]. The trapezoidal rule other than rectangular used in adopted method reconstruction energy flux across cell interface, just as unsteady DUGKS. By way, length characteristic line modified establishes relationship with Courant-Friedrichs-Lewy (CFL) number transient DUGKS, guarantees accuracy SDUGKS. Furthermore, no longer limited by extinction coefficient like As result, more accurate SDUGKS, and efficient DUGKS for radiation problems. smooth linear interpolation van Leer limiter are problems discontinuous optical thicknesses, respectively. Several numerical tests thickness varying from thin thick conducted validate present scheme. Numerical results demonstrate that can serve effective tool study multiscale heat participating media.