The voxelized photon Monte Carlo method for hypersonic radiation modeling

A novel method of solving for radiative energy transfer at hypersonic speeds, the voxelized photon Monte Carlo (voxPMC) method, is presented. The voxPMC method is implemented in the Discrete Adaptive Radiative Transport (DART) code and results are given for radiative heat transfer of Mach 9.6 flow over a cylinder. Simulation parameters for this method were tuned to determine requirements for accurate solutions, using benchmark results from NASA's Nonequilibrium Radiative Transport and Spectra Program (NEQAIR). It was found that of the tuning parameters, the mesh resolution and number of simulated photon packets had the largest effect on the resulting solution accuracy. It was found that 108 photon packets, or 5 photon packets per smallest mesh cell dimension, produced accurate results. Voxel resolution refinement and optical boundary conditions were also tested and 2 voxels per smallest mesh cell dimension and an optical symmetry boundary condition produced results that aligned with those given by NEQAIR. Future work will determine if recommendations for these parameters hold for a wider range of applications. Loose coupling between flowfield results and radiation analysis resulted in radiative cooling, which smeared the shock gradients and led to a slight increase in convective heating at the stagnation point.