Kinetic modeling of non-equilibrium gas flows due to phase change

Abstract

The aim of the present project is the kinetic modeling of non-equilibrium gas flows caused by phase transition on a spherical interface with basis on kinetic models for the linearized Boltzmann equation. Firstly, the temperature and pressure jump coefficients used in the boundary conditions to solve the fluid dynamic equations in case of low and moderate gas rarefaction will be calculated for the problem of evaporation/condensation from/to a liquid sphere and its monocomponent vapor. The influence of the geometry on the jump coefficients will be analyzed by comparing the results with those available in the literature for planar geometry. Secondly, the sublimation and deposition processes in a helium-argon mixture will be studied numerically in the temperature range where helium is a background gas while argon can sublimate and deposit from/to a sphere of its own solid state. The influence of the intermolecular interaction potential on the solution of the problem will be analyzed by considering the rigid-spheres and Lennard-Jones models as well as ab initio potential available in the literature. The macroscopic characteristics of the gas flow around the sphere, such as bulk velocity, heat flux, pressure and temperature, induced by phase transition at the interface will be calculated in a wide range of the gas rarefaction and molar concentration of the mixture. Thirdly, a hybrid scheme based on both the kinetic modeling inside the Knudsen layer and the fluid dynamic equations outside the Knudsen layer will be proposed to be used in the continuum and near continuum regimes of the gas flow. (AU)