A SPHERICAL-HARMONICS METHOD FOR MULTIGROUP OR NONGRAY RADIATION TRANSPORT

The spherical-harmonics method, also called the P(N) method, is used to develop solutions to a class of multi-group or non-gray radiation transport problems. The multi-group model considered allows an anisotropic scattering law and transfer from any group to any group. In addition to a spherical-harmonics solution for the case of a homogeneous radiative-transfer equation, a particular solution for the P(N) method is derived for the case of multi-group radiative transfer in a homogeneous plane-parallel medium that contains group sources that vary with position and direction. Computational aspects of the developed solutions are discussed, and numerical results for a test case are reported.