Progress in the numerical study on the aerodynamic and thermal characteristics of hypersonic vehicles: High-temperature chemical non-equilibrium effect

Abstract

In this paper, the progress in the numerical study of high-temperature chemical non-equilibrium effects on the aerodynamic and thermal characteristics of hypersonic vehicles is reviewed. First, the influence of physicochemical models on the numerical simulation of high-temperature chemical non-equilibrium flow is analyzed. The results show that the diffusion coefficient model will affect the aerodynamic heating under the full catalytic wall; the difference between the predicted heat flux peak values of different chemical kinetic models for complex flow areas, such as in the case of shock wave/shock wave interference is greater than 20%. The wall catalytic effect on the aerodynamic heating is considerable. Finite catalytic models are still under development; among them, models using finite-rate chemical reaction kinetic methods for the gas-solid surface to obtain catalytic reaction rates have greater developmental potential. Material ablation introduces the mass injection effect into the boundary layer, while pyrolysis gases result in complex chemical reactions with the high-temperature air in the boundary layer, significantly reducing the overall aerodynamic heating. There are two main mechanisms of high-temperature chemical non-equilibrium effect on the surface pressure of aircraft. One is that the decrease in the specific heat ratio after the shock wave will cause an increase in pressure after the shock wave, and the other is that the decrease of detached shock wave angle will reduce the pressure after the shock wave. Although the high-temperature chemical non-equilibrium effect on the lift and drag of typical shapes, such as space shuttle and re-entry capsule, is relatively small, the effect on the moment is considerable. Finally, high-temperature chemical non-equilibrium affects the fluctuation characteristics of the physical quantity in the hypersonic turbulent boundary layer and increases the wall friction while reducing the heat flux; however, it does not change the scaling laws of velocity, density, temperature, and component concentration of the turbulent boundary layer.