Effects of chemical non-equilibrium models on stability analysis of blunt wedge boundary layer with high enthalpy

Boundary layer transition has a significant impact in the design of flight vehicles. At high Mach numbers, the temperature in the boundary layer rises rapidly, leading to a series of high-temperature effects, which affect the boundary layer transition process. Some physicochemical models are often introduced to reflect these effects in the numerical simulations, which greatly increases the computational cost. In the meantime, different models may give different results in the flow stability analysis. Currently, relevant research in this field is not sufficient, and the effects of typical physicochemical models have not been considered. In the present study, the linear stability theory (LST) for chemical non-equilibrium flow was developed, and the influence of chemical non-equilibrium effects on the flow stability of blunt wedge boundary layers was investigated. The differences in the boundary layer stability calculation results caused by physicochemical models such as the thermal models, the transport models, and the chemical models were analyzed. The results show that the chemical non-equilibrium effects mainly affect the N factors by changing the basic flow, thus, they can be considered merely in the basic flow calculation in order to improve the computational efficiency. The transition prediction result is insensitive to the selection of physicochemical models for second-mode dominant transition in the chemical non-equilibrium flow. However, when the contribution of the third mode to the N values is large, the influence of physicochemical model on the transition prediction cannot be ignored.