Drop-vapour coexistence in smoothed particle hydrodynamics

The formation of a bare droplet of a liquid obeying the van der Waals equation of state (vEoS), its properties, evaporation processes, and equilibration with the surrounding vapour are studied using Smoothed particle hydrodynamics (SPH). An impenetrable wall boundary condition is considered. Equilibrated droplet-vapour system is energized to start evaporation. Binodal curves obtained from vapourization of droplet mimic the corresponding theoretical curves. The boiling temperature is found to be independent of the size of the droplet if the relative size (box to droplet) is kept constant. Dependence of the droplet's properties, such as density, surface tension, radius, etc., on temperature is discussed. A liquid droplet in a box filled with vapour particles (not in equilibrium) is allowed to evolve to reach the equilibrium. Effects of the existing vapour on the droplet's properties are studied. It is observed that the temperature evolutions of density, radius, and coefficient of surface tension for the equilibrated drop-vapour system follow the same curves obtained from the evaporation of a bare drop with the same total number of particles.