The equation describing the transfer of radiant energy in semitransparent media is radiative transfer equation. In three-dimensional semitransparent media, radiative intensity is a function of 7 dimensions, which can only be solved through the numerical method in most circumstances. Numerical simulation has become an important way in the study and application of the theory of thermal radiative transfer in semitransparent media. This paper reviews the recent progress of Chinese scholars in the field of computational thermal radiative transfer, and proposes some important subjects in this field for future study.
thermal radiation, radiative transfer equation, computational methodFor theoretical study and engineering application of the theory of thermal radiative transfer in semitransparent media, the basic governing equation for the radiative energy transport process is radiative transfer equation (RTE). The RTE for a gray medium with uniform refractive index can be written as [in which r is the vector of spatial position; s is the vector of radiation direction; c 0 is speed of light in vacuum; n is the refractive index; I is the radiative intensity; I b is the black body emission intensity; a is the absorption coefficient, s is the scattering coefficient; is scattering phase function; and t is time. The RTE describes the temporal, spatial and angular variation of the radiative intensity. The last term at the right hand side of eq. (1) includes an angular integration over the whole 4 solid angular space. As such, the radiative intensity of every direction is coupled together for scattering media, which demands for a coupled solution.The RTE is an integral-differential equation. Taking s as a velocity vector, ( , , ) I t s r s serves the role as a convection term, hence the RTE can be considered as a special kind of convection diffusion equation. Because radiative intensity is related to wavelength, time, spatial coordinates, and angular direction, which is a function of 7 variables in three-dimensional semitransparent media. Hence it is difficult to obtain analytical results and only numerical methods can be used in most cases. Nowadays, with the popularization of high performance computers, numerical simulation has become a very important tool for theoretical studies and engineering applications of the theory of thermal radiative transfer in semitransparent media. The already developed numerical methods in recent years for solving the RTE can be divided into two groups [3] : (1) methods based on ray tracing technique, and (2) methods based on global discretization of the differential form of the RTE. For the first group of methods, to trace the ray trajectory is essential to obtaining