Smoothed particle hydrodynamics simulations of the evaporation of suspended liquid droplets

Abstract

The ordinary evaporation and explosive vaporization of equilibrium, van der Waals, liquid drops subjected to uniform heating at supercritical temperatures are investigated by means of numerical simulations with the aid of a modified version of the DualSPHysics code. The models include the effects of surface tension, thermocapillary forces, mass transfer across the interface, and liquid–vapor interface dynamics by means of a diffuse-interface description. In contrast to previous simulations in this line, a new non-classical source term has been added to the internal energy equation to deal with the vaporization rate through the diffuse interface. This term is related to the diffusion of the latent heat in the interface zone and is, therefore, necessary for a correct physical description of the liquid–vapor interface structure. As the heating temperature increases the drops undergo surface evaporation, nucleation of an interior vapor bubble, nucleation followed by fragmentation of the liquid, and explosive vaporization. Heating at supercritical temperatures brings the drop out of equilibrium and forces it to rapid quenching into either the miscibility gap, where it undergoes surface evaporation by spinodal decomposition, or the metastable region bounded by the binodal and spinodal curves, where it nucleates a vapor bubble. The results also indicate that at comparable heating, drops of lower density experience faster evaporation rates than drops of higher density.