Influence of a Boundary Condition on Steady Flows of a Vapor Evaporating from or Condensing on Its Plane Condensed Phase

A semi-infinite expanse of a vapor in contact with its plane condensed phase is considered. The steady one-dimensional flow caused by evaporation or condensation is investigated numerically on the basis of the BGK model Boltzmann equation with the new kinetic boundary condition (KBC) proposed recently in Ishiyama, T., Yano, T., and Fujikawa, S., Phys. Rev. Lett. 9,084504 (2005). By comparison with the corresponding results with the conventional KBC (complete condensation condition), it is found that the vapor flow may be drastically influenced by the new KBC in the case of the strong condensation. The first-order approximation formula for the relation between parameters at infinity and those of the condensed phase that allows a steady solution is also constructed.