Higher order minimum entropy approximations in radiative transfer

In this paper we approximate the radiative transfer equations by the method of moments, constructing mesoscopic approximations of arbitrary order of the otherwise microscopic system. To define the necessary closure a minimum entropy approach is utilized. While in radiative transfer, the minimum entropy closure for moment systems up to the first-order moment is well known, higher-order minimum entropy closures have not been implemented. This is probably due to the fact that the closure cannot be expressed in analytical form. Our focus thus lies in developing some general results about the minimum entropy system and in deriving a numerical closure. By extending to higher order, among increasing the precision, we are able to overcome difficulties that arise for the first order minimum entropy method. Numerical experiments in a 1-dimensional domain irradiated by two beams or with internal source show the accuracy of this approach.