Ab Initio Based Rate Coefficients For Two-Temperature Nonequilibrium Models In Hypersonic Blunt Body Flow

摘要

In this paper we explore the impact of different rate coefficients on the widely used two-temperature nonequilibrium model on the flowfield dynamics of hypersonic flows. Equilibrium dissociation rate coefficients for O_2 + O collisions are calculated based on the earlier work of Grover et al. We propose curve fits for ab initio-based characteristic excitation times and dissociation rate coefficients for N_2 + N_2, N + N_2, O_2 + O_2, and O + O_2 for accurate predictions of aerodynamic coefficients and surface properties. We consider an oxygen shock wave corresponding to the experiments by Ibraguimova et al, where the free stream velocity is v = 4400 m/s and free stream pressure is p = 0.8 torn We also consider Mach 11 and 15 oxygen flow over a hemisphere. Finally we compare shock stand-off distance with experiments conducted by Nonaka et al for freestream velocities of v = 3850 m/s, 3490 m/s, and 3160 m/s and the binary scaling for these cases is ρR = 1 × 10~(-4), 4 × 10~(-4), 1.7 × 10~(-3) respectively. We compare translational and vibrational temperatures and the composition of the gas for the two-temperature Park dissociation model with rate coefficients proposed by Park and the newly proposed ab initio-based. Furthermore, we compare computational predictions of the shock-standoff distance with experiments by Nonaka et al. to delineate the role of rates from the Park two-temperature model.