Behavior of a Single Bubble in a Nonuniform D.C. Electric Field

The effects of a nonuniform electric field on the formation, detachment, and breakup of a single inert bubble surrounded by a dielectric liquid were studied experimentally and numerically. In experiments, air bubbles were injected into kerosene at a constant flow rate through an orifice at the bottom wall of the test cell. The liquid was subjected to a nonuniform electric field, applied between the horizontal and vertical electrodes. During the experiments, the behavior of bubbles was recorded continuously, and the position, shape, and volume departure of the bubbles were digitally extracted from the sequential frames with the aid of graphical software. The experimental results show that in the presence of the nonuniform electric field, bubbles take a prolate shape and skew to the opposite direction of the ground electrode. With an increase in the electric potential, the bubble growth time and departure volume will decrease continuously. Bubble breakup is also observed at high enough voltages. As a further study, a 3-D numerical simulation was performed, using a commercial finite element code (Comsol Multiphysics) to determine the distribution of electric stresses along the bubble surface. The numerical results show that the nonuniform electric field generates some inhomogeneous stresses at the bubble surface. The bubble is compressed and deviated by the horizontal component and elongated by the vertical component. Numerical outcomes prove the physical behavior of the bubble observed in the experiments.