Vapor mediated interaction of two condensing droplets

Abstract

The present work investigates the internal flow structure of two condensing droplets of aqueous solution during interaction. Velocity of fluid inside the droplets was investigated by confocal micro-PIV technique. Simulation study has also been carried out to supplement the understanding of internal hydrodynamics inside droplets. Condensation on the droplets was carried out inside a closed chamber by generating a difference in vapor pressure between the droplet interface and a reservoir fluid surrounding the droplet in the room temperature without any cooling. Condensation on the droplet leads to spatial variation of solute concentration inside the droplet causing buoyancy driven Rayleigh convection. Fluid flow pattern inside a single condensing droplet is symmetric in nature whereas the fluid flow pattern for two condensing droplets is asymmetric in nature. The neighboring droplet influences the internal convection through vapor mediated interaction between the two condensing droplets. The condensing droplet senses the neighboring droplet from a distance without any physical contact. The asymmetric nature of the flow pattern is attributed to the modification in the distribution of condensation flux of the droplet in the presence of the neighboring droplet. The flow pattern observed for interacting droplets during condensation is opposite to that of evaporating droplets. The effect of the neighboring droplet on the internal convection of the condensing droplet reduces with increase in separation distance between the droplets.