Influence of State-to-State Transport Coefficients on Surface Heat Transfer in Hypersonic Flows

摘要

A numerical study is performed to assess the influence of two state-to-state kinetic approaches on the prediction of surface heat transfer of Mach 7 hypersonic external flowfields. One approach consists of a simplified state-to-state kinetic model which utilizes Eucken's relation for calculating thermal conductivity and a constant Lewis number assumption for calculating self-diffusion in the vibrational quantum levels. The other approach uses a rigorous kinetic theory based model for which collision integrals are used to determine transport coefficients related to thermal diffusion, heat conductivity, self-diffusion, and diffusion of vibrational energy. Inclusion of self-diffusion results in an increase in the surface heat flux of up to 6.5% upstream of a shoulder region. Thermal conductivity is found to be the primary contributor to surface heat flux. The differences in heat flux predictions between the two state kinetic models highlight the sensitivity of surface heat transfer rate to the thermal conductivity models used. As a starting point for future determination of transport coefficient model sensitivities, a probabilistic global sensitivity analysis is performed for a simplified set of hypersonic flow calculations involving the Sutherland viscosity model.