Methods of nonequilibrium thermodynamics for description of multicomponent turbulent gas mixtures

An attempt is made to derive, by means of a continuum mechanics method, a closed system of hydrodynamic equations for the average turbulent motion of an ideal gas mixture in a gravitational field. The equations can be used to obtain the pulsating gas dynamic parameters for a numerical model of the planetary mesosphere and lower thermosphere in which structure and heat balance are determined primarily by molecular and turbulent transport processes. The choice of an averaging operator for the gas dynamic parameters is described and the balance equation for the total entropy of the turbulent air mixture, including the weight-average and turbulent superstructure entropies is obtained. The application of Onsager's formalism to nonequilibrium thermodynamics problems is discussed in detail. Formulas for the turbulent heat diffusion and heat fluxes are obtained in order to generalize the homogeneous hydrodynamic equations to the case of a multicomponent medium. A technique for semiempirical simulation of transport coefficients in the turbulent multicomponent gas flow is proposed, based on the transport equations for the second moments of the velocity and enthalpy pulsations. Analytical formulas for the transport equations are derived, and the numerical computations are carried out for the turbulent viscosity and diffusivity coefficients of the earth turbopause.