Spectral Module for Photon Monte Carlo Calculations in Hypersonic Nonequilibrium Radiation

In this paper, efficient spectral modules and random number databases are developed for atomic and diatomic species for use in photon Monte Carlo (PMC) modeling of hypersonic nonequilibrium flow radiation. To model nonequilibrium flow conditions, the quasisteady state assumption was used to generate electronic state populations of atomic and diatomic gas species in the databases. For atomic species (N and O), both bound-bound transitions and continuum radiation were included and were separately databased as a function of electron temperature and number density as well as the ratio of atomic ion to neutral number density. For the radiating diatomic species of $N2+$⁠, $N2$⁠, $O2$⁠, and NO databases were generated for each electronic molecular electronic system. In each molecular electronic system, the rovibrational transition lines were separately databased for each electronic upper state population forming the electronic system. The spectral module for the PMC method was optimized toward computational efficiency for emission calculations, wavelength selections of photon bundles and absorption coefficient calculations in the ray tracing scheme.