Sensitivity Analysis Study of Expanding Hypersonic Flows of Nitrogen and Oxygen

Abstract

Sensitivity analysis studies of expanding high-enthalpy binary flows of nitrogen and oxygen in hypersonic nozzles are carried out for a variety of conditions. The polynomial chaos expansion (PCE) methodology is utilised to assess the sensitivity of the free-stream conditions to vibrational and chemical relaxation rates, as well as the reservoir conditions. It is shown that for high-enthalpy conditions, the main contributors to uncertainty in the free-stream flow are uncertainties in the vibrational and chemical relaxation rates for molecule-atom collisions, as well as uncertainties in the reservoir conditions. The impact of high- temperature vibrational relaxation time corrections and the vibrational-chemical coupling was found to be negligible for the investigated cases. A preliminary analysis on the potential influence of ionization was also performed, which was found to have an insignificant effect on the free-stream conditions in nitrogen.