QUALITATIVE-ANALYSIS OF THE NAVIER-STOKES EQUATIONS FOR EVAPORATION-CONDENSATION PROBLEMS

The methods of qualitative theory of dynamical systems are used to pro vide new information of the Navier-Stokes solutions for gas flows driv en by evaporation and condensation at interphase surfaces. It is shown that these solutions correspond to separatrixes of the saddle point i n the (u,T) plane. The classification of solutions is given, and some special cases are studied in detail. The qualitative methods are appli ed to the problem of evaporation/condensation between two plates. It i s shown that the topology of the saddle point implies the following si tuation: one of the functions u(x) (velocity) or T(x) (temperature) is always non-monotone for sufficiently small Knudsen number. This expla ins some previously published numerical results. The case of finite Re ynolds number is considered separately, and relationship with the kine tic-theory results is discussed throughout. (C) 1996 American Institut e of Physics.