State-to-State Catalytic Models, Kinetics, and Transport in Hypersonic Boundary Layers

A new iterative model has been developed that couples, in the boundary layer of a reentering body, the equations for N2, N, O2, O and NO mass fractions, N2 and O2 vibrational distributions, and gas temperature with the surface state-to-state heterogeneous recombination coefficients has been developed. Results for SiO2 and metallic surfaces are presented and discussed. The non-Boltzmann behaviour of the vibrational distribution functions near the surface is found as well as the nonmonotonous behaviour of the NO density profile along the boundary layer coordinate. The transport coefficients and the heat flux to the surface are calculated using the Chapman-Enskog theory. A strong dependence of transport coefficients and energy flux on the vibrational-chemical kinetics in the boundary layer is shown. In particular the diffusion coefficients of the first and the last vibrational levels differ by several orders of magnitude, according to the shape of vibrational distributions, and the surface material noticeably influences diffusion coefficients of N and NO.