Transport properties of nonequilibrium gas mixtures

Abstract

Transport properties of binary mixtures of diatomic gases in vibrational nonequilibrium are analyzed and the corresponding terms are established. In order to solve the Boltzmann equation, a generalized Chapman-Enskog method is used, valid whatever the degree of nonequilibrium, contrarily to previous analyses in which only the extreme regimes were considered, at weak or strong nonequilibrium, and generally for pure gases only. The transport coefficients, first written in terms of collision integrals, are finally expressed as functions of macroscopic quantities, known or experimentally attainable, following Mason and Monchick type approximations and with the harmonic-oscillator model. Finally, examples of calculations are given for ${\mathrm{N}}_{2\mathrm{\ensuremath{-}}}$${\mathrm{H}}_{2}$ and ${\mathrm{O}}_{2\mathrm{\ensuremath{-}}}$${\mathrm{N}}_{2}$ mixtures. Results are in good agreement with available experimental data. Comparisons with approximate formulas, extensively used in the literature, show also that, at least for the investigated mixtures, the use of these formulas seems roughly justified.