Heat transfer to a flat plate with arbitrary surface catalysis under partially dissociated nitrogen freestream

In the high-enthalpy shock tunnel experiments, the expansion flow starting from the high-temperature chamber accelerates drastically and rapidly. The flow exists in a state of thermochemical nonequilibrium for the characteristic time of the flow is relatively short compared with that of thermochemical processes. Because of the incomplete wall catalysis, the recombination reactions on the model surface are also in nonequilibrium. As a result, the effects of chemical nonequilibrium on aeroheating measurements should be taken into account in shock tunnel experiments. In the present investigation, computational fluid dynamics is employed to study the effect of chemical nonequilibrium and the finite-rate catalytic wall on heat flux to a flat plate under high-enthalpy shock tunnel conditions. Based on the microscopic analysis, a Damköhler number characterizing the nonequilibrium degree of catalytic reactions is introduced. Also, a formula is derived to further predict the wall catalysis nonequilibrium effect on the heat flux, which is distinctive from those described by the calorically perfect gas model. The theoretical result is further modified to consider viscous interaction at the leading edge of the flat plate. These results are useful for the establishment of a ground-to-flight extrapolation methodology for the chemical nonequilibrium flows.