Session MC - Micro-Fluid Dynamics IX.
MIXED session, Tuesday afternoon, November 23
Grand III, Westin Seattle
Evaporation and condensation at an interface between argon vapor and its condensed phase is analyzed with the numerical method of molecular dynamics (MD) to construct the kinetic boundary condition, i.e., boundary condition for the Boltzmann equation, at a vapor-liquid interface. The interface realized in the MD simulation is planar and the temperature of bulk liquid phase is kept with the velocity control technique. The kinetic boundary condition prescribes the velocity distribution function of molecules leaving the interface. We obtain the velocity distribution by counting the number of the molecules and sampling their velocities for various steady and nonequilibrium states of vapor-liquid two phase system accompanied with evaporation or condensation. It is found that, when the temperature of the bulk liquid phase is 85K, the probability density of velocity component normal to the interface is a Gaussian with the temperature of bulk liquid phase and that of tangential component is a Gaussian with different temperature, which increases with increase in the net condensing mass flux. The resulting kinetic boundary condition can be expressed in the form of the product of the probability densities and a constant including the evaporation and condensation coefficients defined properly.