Regime map of non-coalescence between two equal-sized uncharged water droplets suspended in oil: A numerical study

Abstract

This paper is devoted to numerical simulation of collision and consequent separation of conductive same-sized droplets of different sizes (from 0.3 to 2 mm) under the effect of a constant voltage exceeding the threshold of the transition from coalescence to non-coalescence. The computations were based on the arbitrary Lagrangian–Eulerian method—the interface between the two phases was represented as a geometry line that moves in accordance with the calculated fluid velocity throughout the solution of the problem. Four possible modes and ranges of electric field strength values corresponding to them were identified, ranked by their negative impact on the demulsification process: rebound, separation into three or multiple drops, and electrospraying. This includes the narrow ranges of electrospraying beside the “coalescence-non-coalescence” threshold and during the “rebound-multidrops” transition. A “regime map”—a diagram of possible outcomes depending on the size of drops and the electric field strength—was formed and analyzed to summarize the results and identify the most favorable modes of demulsification processes. The map revealed an area when coalescence is substituted with only rebound when drop radius increases, i.e., when there will be no smaller drops after the interaction.