| Abstract: |
| The standard kinetic theory studies on evaporation and condensation processes focus on the vapor dynamics in the Knudsen layer and take into account the molecular exchanges with the liquid phase through phenomenological boundary conditions. These prescribe the velocity distribution function of atoms spontaneously leaving the liquid bulk and the ones back-scattered into the vapor after impinging on the liquid-vapor interface. A lot of effort has been expended in assessing the physical appropriateness of kinetic boundary conditions by using different approaches, including molecular dynamics and mean-field kinetic approximations of simple liquids. The present work complements previous studies on single-component liquids evaporating into near-vacuum conditions. In this process the back scattered vapor component is virtually absent and, therefore, one can evaluate the distribution function of evaporated atoms without any ambiguity. Preliminary results, based on the numerical solution of the Enskog-Vlasov equation, show that, no matter how low the temperature, the distribution function of evaporated atoms is approximated by an anisotropic Maxwellian with different characteristic temperatures for the velocity components normal and parallel to the liquid-vapor interface. |
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