Influence of thermochemical modelling of CO2-N2 mixtures on the shock interaction patterns at hypersonic regimes

The effect of finite-rate internal energy transfer on shock interaction mechanisms of CO2-dominated flows is investigated. The polyatomic molecule has a relatively low characteristic vibrational temperature that causes vibrational degrees of freedom to be excited across a shock wave at hypersonic regimes. In this paper, the impact of accounting for the time associated to the relaxation of this process, as opposed to assuming instant thermal equilibrium, on the shock structures occurring in the flowfield over a double-wedge geometry is numerically studied. A Mach 9 flow over two different geometries is simulated with two different models, the two-temperature model of Park and the thermally perfect gas model. Simulations are carried out with the SU2 software that is coupled to the Mutation++ library, providing thermodynamic, chemical kinetic and transport properties of any mixture of gases for a given state of the flow. Anisotropic mesh adaption is used with the AMG library to accurately capture highly directional and high-gradient localized flow features. Results show that different ways of modelling the effect of vibrational relaxation have a major impact on the size of the compression corner separation bubble, leading to different shock wave systems in this region. As a consequence, the obtained shock interaction mechanisms differ as well. The shock patterns obtained for the thermally perfect gas model result in stronger impingement on the surface and higher aerodynamic loads of pressure and heat flux.