Boundary conditions at vapor-liquid interfaces : existing results and possible developments
Orateur : Aldo Frezzotti
Dipartimento di Scienze e Tecnologie Aerospaziali - Politecnico di Milano - Italy
Abstract : In two-phase flows in which liquid and vapor regions coexist, hydrodynamic equation, based on Navier-Stokes-Fourier constitutive laws, provide an accurate description of liquid and vapor regions far from the interfaces. However, if the vapor phase is dilute, then Knudsen layers will form next to interfaces whenever evaporation and/or condensation processes will transfer mass, momentum and energy from one phase to the other, across interfaces. The existence of such kinetic layers produces finite jumps of macroscopic variables on the macroscopic scale, hence corrections to boundary conditions for hydrodynamic equations have to be made. In the years, kinetic theory methods have been extensively used to clarify the Knudsen layer structure for evaporation and condensation flows, for monatomic and polyatomic species as well as for mixtures, in an attempt to improve the classical Hertz-Knudsen and Schrage formulas. Most of the studies were based on simple models describing the spontaneous evaporation of molecules
from the liquid into the vapor and the scattering of vapor molecules from the liquid surface. Hence, a second and more recent research line has been devoted to validate such assumptions by molecular dynamics simulations. The talk will describe and discuss kinetic theory applications to evaporation/condensation flows as well as the results of molecular dynamics studies aimed at improving kinetic models for boundary conditions at vapor-liquid interfaces.
Date et lieu : le Vendredi 9 Septembre à 11h, salle 250, IUSTI