Computation of a nonequilibrium expansion flow in a single expansion ramp nozzle

The simulation of the flow inside the propulsion system is of essential int erest, for the design of airbreathing hypersonic vehicles. To compute accur ately the expansion flow of a hydrogen/air mixture at high temperatures, th e chemical and vibrational nonequilibrium effects must be taken into accoun t A finite element code is used to model chemical reactions considering fin ite-rate chemistry and vibrational relaxations according to the Landau-Tell er theory (Landau, L., and Teller, E., "Zur Theorie der Schalldispersion," Physikatische Zeitschrift der Sowjetunion. Vol. 10, No. 1, 1936, pp. 34-43) . The computational domain is discretized by applying unstructured adaptive grids. Different test cases are computed, and the results are compared wit h measured and numerical data. In one test case, a remarkable difference be tween the rotational and vibrational temperature of a hydrogen/air nozzle f low is seen. This difference in the experiment is also supported by the com putation. Because the applied relaxation rates are small compared to other data given in literature, the thermal nonequilibrium effects gain more impo rtance.