HIGH-ORDER SPHERICAL HARMONICS METHOD FOR RADIATIVE TRANSFER IN SPHERICALLY SYMMETRIC PROBLEMS

Abstract

A matrix formulation of the spherical harmonics method to predict radiative transfer in participating layer and layered media within spherical geometry is presented. This formulation combines forward finite-difference spatial discretization and the conjugate gradient squared methods to solve the resulting partial differential equations of radiative intensity moments. Henceforth, a high-order spherical harmonics solution has been obtained without difficulty. Comparisons with other methods are carried out for boundary radiative fluxes, transmittance, and reflectance associated with radiative heat transfer through homogeneous/inhomogeneous, isotropic/anisotropic participating spherical layer and layered media. The comparisons show excellent agreement between exact and very high-order spherical harmonics predictions. It was found that a high order of the PN approximation is necessary to produce accurate results at the inner boundary of hollow spherically symmetric media, while low- or moderate-order of the PN approximation is sufficient to obtained accurate results at the outer boundary of both hollow and solid spherically symmetric media.