On a droplet levitation due to evaporation during thermal interaction with the substrate

Abstract

We study the possibility of levitation of a water droplet in the presence of excess pressure beneath it due to intensive evaporation resulting from thermal interaction with a solid heated substrate. It is shown that water vapor, even if it displaces air when the condition of constancy of the vapor-air mixture density is imposed, leads to the occurrence of excess pressure under the droplet and, as a consequence, can cause its levitation above the substrate. The distributions of pressure, water vapor concentration, and the velocity field of the vapor-air mixture under the droplet in the steady-state outflow regime were found numerically by the finite difference method. The distance between the droplet and the substrate was determined. The vapor flow density necessary to keep the droplet in equilibrium was calculated.