Enhancement of electric field on bubble dispersion characteristics in leaky-dielectric liquid medium

Enhancement of the electric field on mixture has attached wide interests owing to its advantages in the terrestrial and space applications. In this paper, the dispersion characteristics of bubbles in leaky-dielectric liquid were investigated with a novel designed capillary electrode in the presence of a non-uniform electric field, employing high-speed photography and with a focus on the electrohydrodynamic (EHD) effects. The results show that the bubble dispersion is associated with three typical patterns in the manipulated parameter regions, including the dripping, mixed, and spraying patterns. With the increase of electrical Bond number (BoE), bubble size, characterized by the dimensionless bubble diameter zeta, is decreased significantly, while the evolution process of bubbles becomes faster and more complex. In particular, the size of the generated micro/nanobubbles in the spraying pattern is basically below 20 mu m. The rise of the dimensionless flow rate (Q/Q0) increases zeta. It is found that the transition of bubble dispersion patterns depends strongly on the BoE, and the rise in Q/Q0 tends to slow down the transition process. In addition, an empirical correlation of zeta as a function of BoE and Q/Q0 is established for the dripping pattern of bubbles based on the present experiment data, which is believed to be of significance for the modeling of bubble dispersion under electric field. The bubble shapes, characterized by aspect ratios, show a diversity of distribution in the cross-section close to the capillary orifice, while terminally tending to follow the conventional formulation in the literature as the bubbles develop in the vertical direction.