Vapor condensation induced by fast-moving liquid film in the presence of noncondensable gas molecules

Abstract

In this study, vapor condensation phenomena at the surface of a fast-moving planar liquid film in a gas mixture (vapor and noncondensable (NC) gas), aimed to imitate a cavitation bubble collapse, were simulated to investigate the evaporation and condensation coefficients of vapor molecules based on the Enskog–Vlasov equation. These coefficients indicate the evaporation and condensation rates of vapor molecules, and they were incorporated into the kinetic boundary condition (KBC) for the vapor/gas–liquid interface. We employed the Enskog–Vlasov direct simulation Monte Carlo method to simulate the condensation phenomena. Based on the results, we confirmed that the obtained coefficients decreased with an increase in the liquid temperature and NC gas content at the condensing interface. Additionally, the coefficients had the same values as those in the equilibrium state, even for such a moving system. Notably, the nonequilibrium effect on condensation phenomenon discussed in the field of cavitation bubble dynamics, whereby vapor molecules fail to condense when the liquid velocity is significantly high, could not be confirmed in this simulation. Furthermore, we conducted an analysis based on the Boltzmann equation using the direct simulation Monte Carlo method to verify the obtained coefficients.