Hybrid Approach for Multi-Scale Modeling of Radiation Transfer in Three-Dimensional Non-Gray Media

In this STTR project, an efficient and high-fidelity computational module to predict non-gray radiative transfer will be developed and validated. The proposed hybrid approach to solve the radiative transport equation (RTE) is a combination of the spherical harmonics (PN) method and the Monte-Carlo method. Non-gray gases will be treated using the full spectrum correlated k-distribution (FSCK) method. The proposed approach is unique and innovative for: (1) its ability to efficiently handle orders of magnitude variation in the medium optical thickness, and (2) its ability to solve the non-gray RTE at a small fraction of the computational cost of line-by-line calculations. CFDRC has teamed with Ohio State University (Prof. Sandip Mazumder) to develop the proposed module. In Phase I, the modified differential approximation (MDA) approach, along with the non-gray FSCK method, will be implemented and validated for simple 2-D geometries. MDA combines the lower-order spherical harmonics (i.e., P1) method for the diffusive component with a simplified view-factor based method for the ballistic component of radiative intensity. In Phase II, the view-factor method will be replaced with the more accurate and general Monte-Carlo method. The hybrid approach will be extended to three-dimensional geometry with arbitrary unstructured mesh topology. The radiation module will also be parallelized and demonstrated for practical cases to be determined in consultation with AFOSR.