Modified method of characteristics in transient radiation transfer

This paper presents the modified method of characteristics for simulating multidimensional transient radiative transfer in emitting, absorbing and scattering media. The method is based on the method of characteristics that follows photons along their pathlines. It makes use of a fixed set of points, and unlike the conventional method of characteristics, it follows the photons backward in space. Test problems involving diffuse irradiation in 1-D and 3-D participating media and collimated irradiation in 1-D participating media were considered. The results show good agreement with analytical and numerical solutions reported in literature. The scheme is fast and was able to capture the sharp discontinuities associated with the propagation of a radiation front in transient radiation transport.