EHD effects on periodic bubble formation and coalescence in ethanol under non-uniform electric field

Abstract

This paper focus on the effects of electrohydrodynamic (EHD) on bubble dynamic characteristics generated on a submerged capillary in ethanol under non-uniform electric field, using high-speed photography and with a particular interest in the effect of electrical Bond number (BoE) on the bubble behaviors. The obtained results ranges of BoE from zero to 5.52 and Weber number (We) from 0.0006 to 0.1365 show that the bubble formation process associated with three stages at the low electric field strengths, including the nucleation, stable growth and necking stages, while the stable growth stage is absent for the high field strengths. With the increase of both We and BoE, the bubble period and waiting times are shortened rapidly, while the frequency is accelerated remarkably. The bubble dynamic behavior, which is characterized by the bubble volume and curvature radius, depends primarily on the BoE, and the increase in the We slightly raises the bubble volume and curvature radius at the departure time. Furthermore, it is found that with the increasing of BoE, bubbles coalescence evidenced at high We is weakened and eventually disappeared. Nevertheless, this phenomenon has the tendency to subsequently reappear at the higher We and BoE.