The evaporation–condensation problem for a binary mixture of rarefied gases

Half space problems of evaporation and condensation for a binary mixture of inert gases are investigated when the dynamics is governed by a system of Navier–Stokes equations, obtained as hydrodynamic limit of a BGK-type description with dominant elastic collisions. Typical methods of qualitative theory of dynamical systems are used to investigate the one-dimensional stationary problem and to classify the solutions both in subsonic and supersonic cases. Numerical results for a mixture of noble gases are presented; the shock wave structure, representing transition between a subsonic and a supersonic steady flow in thermodynamic equilibrium, and the occurrence of under- and overshoots are discussed.