Transport properties of collision-dominated dilute perfect gas mixtures at low pressures and high temperatures

Abstract

Atmospheric entry flights, combusting flows, experiments in high-enthalpy tunnels are examples of aerospace problems in which an accurate computation of the transport properties of gas mixtures are of crucial importance. Transport coefficients for collision-dominated dilute perfect gas mixtures can be obtained from the rigorous kinetic theory analysis of Chapman and Enskog. The full expressions needed for the computation are included, and all the practical details for an efficient implementation are discussed. The present method constitutes the current state-of-the-art and should be preferred to the use of mixture rules, which are slower and less accurate. The final accuracy depends on obtaining accurate sets of collision integrals for the specific mixture used in the actual computation (several such sets are available in the literature). In addition to the general expressions suited to thermal and chemical nonequilibrium conditions, the particular case of thermochemical equilibrium is also discussed, and the recent findings regarding taking into account mixing and demixing effects are included in the description. Finally, numerical values of the transport coefficients of air under equilibrium conditions at one atmosphere are presented in the range of 500–15 000 K.