Surface catalytic effect on the boundary layer stability over a high-enthalpy blunt wedge

High-enthalpy flows can induce complex surface catalytic reactions influencing the boundary-layer stability and transition. The influence is still a lack of in-depth study. In this work, various boundary conditions consisting of noncatalytic wall, fully catalytic wall, and finite-rate catalytic wall, are considered in the linear stability analysis method with chemical non-equilibrium effects. The basic flow over a high-enthalpy blunt wedge is computed at the freestream Mach number of 15 and 20. The surface catalytic effect is found to significantly affect the basic flow. As the catalytic recombination coefficients increase, the catalytic reactions intensify decreasing the adiabatic wall temperature and thinning the boundary layer. The effect on the boundary-layer stability can be ignored at the Mach number of 15. While at the Mach number of 20, the differences in boundary-layer stability caused by the surface catalytic effect will be marked. There are significant distinctions in the growth rates and N factors of instability modes. Moreover, unstable supersonic modes would even appear when the catalytic recombination reactions are vigorous. The general influence is similar to that of wall cooling in the calorically perfect gas. The behavior of the mode instabilities is mainly dependent on the change of the basic flow characteristics in the boundary layer caused by the surface catalytic effect.