Electrohydrodynamic effects on the bubble ascent in quiescent liquid using charge conservation approach

Abstract

The current study investigates bubble ascent under the influence of an applied electric field. To accomplish this, an electrohydrodynamic solver is developed and integrated with the open-source multiphase flow solver interFoam. The numerical model accurately calculates charge distribution and Coulomb force by solving the charge convection equation. This numerical model is utilized to study the effect of electric capillary number (CaE), electrical conductivity ratio (R), and permittivity ratio (S). The electrical force comprises dielectrophoretic force (DEF) and Coulomb force, which increases with higher values of CaE, R, and S. As the bubble begins to ascend in the presence of an electric field, the tangential component of the electrical force induces vortices in the vicinity of the bubble, which interact with the bubble's motion. These interactions result in various phenomena: the ascent of undeformed and deformed bubbles, the ascent of wall-attached bubbles, bubble ascent with path instability, and bubble breakup. The strength of the vortices increases with higher CaE and R/S values. The direction of the vortices depends on the R/S, with vortices flowing from the equator to the pole for R/S<1 and from the pole to the equator for R/S>1. The vortices become stronger as moving away from R/S=1. The vortices flowing from the pole to the equator cause horizontal deformation of the bubble, reducing rising velocity by providing resistance to the bubble's motion along with DEF. Conversely, vortices flowing from the equator to the pole cause vertical deformation of the bubble, increasing the rising velocity by facilitating the bubble's motion.