Heat and radiative fluxes in strongly nonequilibrium flows behind shock waves

Abstract

State-to-state and two-temperature theoretical models for high-temperature strongly nonequilibrium reacting and radiating air flows are developed in the framework of the generalized Chapman—Enskog method. In the theoretical approach, the sets of governing equations for coupled fluid dynamics, chemical kinetics, internal energy transitions and radiation are derived; the algorithms for the calculation of state-resolved transport coefficients are developed and implemented. The proposed models are applied for 1-D simulations of shock waves in air under high-temperature conditions observed in flight experiments. Nonequilibrium mixture composition, temperatures and pressure profiles are obtained and compared for various models of chemical reaction rate coefficients. Flow variables strongly depend on both the kinetic-theory approach and chemical reaction model; species molar fractions and temperature show significantly different behaviour for the state-to-state and two-temperature simulations. Transport properties and radiative fluxes are calculated as functions of the distance from the shock front. It is found that diffusion provides a major contribution to the total energy flux whereas the role of heat conduction is weak due to the compensation effects. It is shown that under considered conditions, two-temperature models are not applicable for correct predictions of radiative heating.