A volume of fluid framework for interface-resolved simulations of vaporizing liquid-gas flows

Abstract

This work demonstrates a computational framework for simulating vaporizing, liquid-gas flows. It is developed for the general vaporization problem [1] which solves the vaporization rate based as from the local thermodynamic equilibrium of the liquid-gas system. This includes the commonly studied vaporization regimes of film boiling and isothermal evaporation. The framework is built upon a Cartesian grid solver for low-Mach, turbulent flows [2] which has been modified to handle multiphase flows with large density ratios [3]. Interface transport is performed using an unsplit volume of fluid solver [4]. A novel, divergence-free extrapolation technique is used to create a velocity field that is suitable for interface transport. Sharp treatments are used for the vapor mass fractions and temperature fields [5]. The pressure Poisson equation is treated using the Ghost Fluid Method [6]. Interface equilibrium at the interface is computed using the Clausius-Clapeyron relation, and is coupled to the flow solver using a monotone, unconditionally stable scheme.It will be shown that correct prediction of the interface properties is fundamental to accurate simulations of the vaporization process. The convergence and accuracy of the proposed numerical framework is verified against solutions in one, two, and three dimensions. The simulations recover first order convergence under temporal and spatial refinement for the general vaporization problem. The work is concluded with a demonstration of unsteady vaporization of a droplet at intermediate Reynolds number.

Numerical simulation of boiling on unstructured grids

“…In 2019, Palmore and Desjardins [61] presented numerical simulations of vaporizing two-phase flows with large density ratios using an unsplit VOF method to transport the interface. The mass transfer rate is computed from the thermal fluxes at the interface.…”

A weakly-compressible DNS formalism dedicated to evaporating turbulent liquid-gas flows

“…The idea of this method is to compute a divergence-free liquid-velocity field for advecting of the liquid volume fraction, by subtracting the velocity jump at the interface from the original velocity field. Another method has been proposed by [8]. Similar to [9], its purpose is to construct a divergence-free velocity field to advect the liquid volume fraction.…”

“…Similar to [9], its purpose is to construct a divergence-free velocity field to advect the liquid volume fraction. In this case, [8] takes the original velocity field and extend the velocity of the liquid phase into the gas phase using the Aslam's extension method [1]. A third method is the one proposed by [12], here, the ghost fluid method is used for extending both the liquid and gas velocity fields, and this way obtaining a continuous liquid velocity field.…”

Numerical simulation of droplet evaporation using interface tracking methods: phase change modelling

“…The sharp treatment of the interface seems to be a promising method to deal with such discontinuities. Numerous recent numerical approaches have shown very encouraging results using either Volume of fluid (VOF) [1], Level set (LS) [2] or Front tracking [3]. However, some numerical aspects of droplet evaporation simulations remain open subjects.…”

“…The comparison relies on the work of Palmore at al. [1] in the context of Volume of fluid and on the phase change procedure of Rueda Villegas et al [2] in the Level set framework. Both approaches have been implemented and coupled to the same two-phase low Mach solver.…”