Theory of accommodation in hypersonic flows

The slip-flow boundary conditions for mixtures of monatomic gases were derived for small deviations from equilibrium within the Knudsen layer and are expressed in terms of first and second order accommodation coefficients. The effects of velocity slip, temperature slip, thermal creep, and diffusion slip are treated, as well as the influence of surface anisotropy (second thermal creep flow, second diffusion slip flow). The second order slip velocity was derived for a simple gas. Several models for the scattering kernel were investigated and the influence of their parameters on the accommodation coefficients and the boundary conditions was calculated. Possibilities of extending the present theory to regions of larger deviations from thermal equilibrium and methods of evaluating the accommodation coefficients are discussed.