The interaction between two electrohydrodynamics phenomena when an electric field affects a two-phase immiscible liquid

Abstract

Electrohydrodynamic (EHD) phenomena in two-phase immiscible liquids—droplet electrodeformation and electrical coalescence—underpin several technologies, e.g., electrostatic phase separation of water-oil emulsions. The corresponding devices' development calls for a deeper understanding of the underlying physics and reliable mathematical and numerical models. However, another EHD phenomenon that has to take place under the same conditions and can affect the results is unfairly overlooked. The phenomenon is the emergence of near-interface dissociation–recombination layers and EHD conduction pumping inside the dielectric phase. The present paper considers the electrical deformation of a conducting droplet suspended in a low-conducting liquid. A numerical simulation is used to show an EHD conduction pumping (like that emerging near an electrode in low-conducting fluid) to emerge near the interface of two immiscible liquids when one of them is a low-conducting medium. The space charge that causes this EHD flow also affects the Coulomb force applied to the interface and therefore changes droplet electrodeformation. Moreover, both the increase and decrease of electrodeformation are possible outcomes, which can be explained by a concurrent effect on the electric field distribution of charged layers emerging near both the interface and electrodes.