Measurement and numerical simulation of shock standoff distances over hypersonic spheres in CO2 in a ballistic range

Abstract

To gather test data of the nonequilibrium flow in CO2 and investigate the influence of the two-temperature nonequilibrium model on numerical simulations, measurements of shock standoff distances over hypersonic spheres in CO2 have been taken in the hypervelocity ballistic ranges of the Hypervelocity Aerodynamics Institute, China Aerodynamics Research and Development Center. Corresponding numerical simulations using the two-temperature model were also performed. The measurements were made for spheres with diameters of 10 mm and 20 mm, flight velocities between 2.122 and 4.220 km/s, and ambient pressures between 2.42 and 14.74 kPa. Test flow fields were visualized by the shadowgraphy for the measurement of shock standoff distances. The shock standoff distances generally decrease as ρR (freestream density × radius of the model, namely the binary scaling parameter) increases. The flow is mainly nonequilibrium when ρR is of the order of 10−4 kg/m2, and the two-temperature nonequilibrium model is applicable for the calculation of the flow field under such conditions. When ρR increases to the order of 10−3 kg/m2, the flow approaches the equilibrium state.