Hypersonic nonequilibrium flow simulations of a hemispherical nose with a counterflowing jet

In this study, numerical analysis is performed to investigate a hemispherical nose with a counterflowing jet in hypersonic flow with a Mach 19 free stream at an altitude of 60 km. Three jet velocities (Mach = 0.91,1.82 and 3.63) corresponding to steady, unsteady and near steady jet states, respectively, are simulated to explore the mechanisms of these three jet states and the effects on aerodynamic drag and aerodynamic heat. Vibrational excitations, chemical reactions and nonequilibrium due to high-temperature effects are considered. To explore the influences of these factors on the two surface quantities (the drag coefficient (Cd) and heat flux), four simulation methods are used involving single temperature without reaction (SingleT-NR), single temperature with reaction (SingleT-R), two temperatures without reaction (TwoT-NR) and two temperatures with reaction (TwoT-R). The results show that different methods have little effect on the change trend of Cd with time and the values of average Cd, which indicates that high-temperature effects barely affect the jet state and the aerodynamic drag of hemispherical nose. For the heat flux, regardless of the unsteady state, the SingleT-R method which not considered the nonequilibrium effect significantly underestimate the results for the hemispherical nose with a high Mach number, while the TwoT-NR method which not include chemical reactions overestimates the results.