The drag force acting on a small evaporating particle exposed to a high-temperature diatomic gas flow

Kinetic-theory analytical results are presented concerning the effect of intense evaporation on the drag force acting on a spherical particle exposed to a high-temperature diatomic gas for the case of a free-molecule regime. Molecule dissociation and atom recombination are included in the analysis. It has been shown that evaporation may substantially enhance the drag force acting on a particle, especially for the case of the particle materials with low-evaporation latent heat and small molecular mass at high gas temperatures. The values of the recombination fraction of atoms at the particle surface and of the fraction of the specularly reflected molecules or atoms significantly affect the drag force acting on a particle. Neglecting gas dissociation may appreciably overestimate the drag force acting on a nonevaporating or evaporating particle at high gas temperatures. (C) 1998 Academic Press.