New Approach for Radiative-Transfer Computations in Axisymmetric Scattering Hot Media

An atmospheric three-dimensional discrete ordinate method, called the Spherical Harmonics Discrete Ordinate Method (SHDOM), is extended to nonequilibrium and axisymmetric media such as rocket plumes, which contain hot reactive gases and metallic oxide particles like alumina. A spherical harmonics base is used to improve the source function evaluation while solving the radiative-transfer equation. The source function includes the chemiluminescence radiation produced by gas reactions, the particles thermal radiation, and the in-scattering term. During the iteration process, the in-scattering term is evaluated with a spherical harmonics base using the radiance field calculated along discrete ordinates until the source function converges. Test cases in simple geometries, like plane parallel media or square enclosures, show the accuracy of SHDOM results according to others calculated by reference models. An extended Arrhenius law is used to model the middle-ultraviolet chemiluminescent radiation produced by the CO + O recombination. Finally, SHDOM is applied to the radiance field emitted by realistic rocket plume sections represented by infinite cylinders or finite cylindrical media shadowed by a mask representing the rocket body.