Modification of the first approximation of the Chapman-Enskog method for a gas mixture

Abstract

The authors propose a transformation of the equations of the first approximation of the Chapman-Enskog method for a gas mixture with frozen internal degrees of freedom. As a result, the solution for the perturbation of the distribution functions can be written in terms of the diffusion velocities and temperature gradient, and the derivation of the Stefan-Maxwell relations and the heat flux calculations can be much simplified. The transformations are extended to a mixture of polyatomic gases with nonequilibrium excitation of the internal degrees of freedom of the molecules. The modification of the first approximation of the Chapman-Enskog method does not affect the relations used for calculating the viscosity of the mixture. Accordingly, that part of the solution is not considered.