Boundary condition at a gas-liquid interphase

R. Meland
2001 AIP Conference Proceedings  
We have used a molecular dynamics simulation to determine the velocity distributions at equilibrium for molecules evaporated from the liquid and for molecules incoming from the gas reflected in the interphase. The evaporated molecules have a larger velocity normal to the interphase than might be expected, the evaporation distribution resembles a Maxwellian with outward drift-velocity of the order of the thermal velocity. The distribution for the reflected molecules is similar to a drifting
more » ... llian toward the interphase with a velocity shift of the order of the thermal velocity. Not even for equilibrium can reflection be interpreted as specular reflection, diffuse reflection or a combination of both, since it would imply in all cases a Maxwellian with zero drift velocity. We believe significant modifications to the boundary conditions used in the kinetic theory approach to evaporation and condensation are warranted. We discuss two possible representations of new boundary conditions.
doi:10.1063/1.1407612 fatcat:beaqcm5gfzhejiulbltkxpq5hm