Investigation on Transient Oscillation of Droplet Deformation before Conical Breakup under Alternating Current Electric Field

Abstract

In this paper, the conical breakup of a water droplet suspended in oil under the alternating current (ac) electric field was experimentally studied with the help of a high-speed video camera. We observed three stages of transient oscillation of deformation characterized by deformation degree l* before the conical breakup that were described in detail. Then a theoretical model was developed to find out the dynamic mechanisms of that behavior. Despite a very small discrepancy, good agreement between model predictions and experimental observations of the evolution of the droplet deformation was observed, and the possible reasons for the discrepancy were discussed as well. Finally, the stresses on the interface were calculated with the theoretical model and their influence on the dynamic behavior before the breakup was obtained. The differences between the droplet breakup mode of ac and direct current electric field are also discussed in our paper.

Charge-Transfer-Induced Noncoalescence and Chain Formation of Free Droplets under a Pulsed DC Electric Field

“…The conductivity of silicone oil was measured by an oil conductivity meter (GD29YX1154B, China National Electric Apparatus Research Institute Co., Ltd., China), and the conductivity of water was measured by a conductivity meter (DDS-11A, Shanghai INESA Scientific Instrument Co., Ltd., China). The relative dielectric constants of silicone oil and water were obtained from the literature . The specific physical properties of silicone oil and water at 20 °C are presented in Table .…”

Droplet deformation under pulsatile electric fields

“…Droplet deformation in the presence of an externally applied electric field is very common in many industries, including electrospining [15], electrospraying [16] and electrowetting [17], etc. A good number of experimental and numerical works have been conducted on droplet deformation under an electric field [18][19][20][21][22][23][24]. Taylor [25] proposed an electrohydrodynamic model, generally referred as the "leaky dielectric model", for droplet deformation, with the assumptions of neutral droplets, quasi-static electric field, small deformation, and free convection charge.…”

Non‐coalescence and chain formation of droplets under an alternating current electric field

“…The camera was operated at the frame rate of 10,000 frames per second. Since the droplet radius is considerably smaller than the distance between electrodes, the external electric field can be regarded as uniform and the strength is calculated by: 24 where L is the distance between electrodes and equals 11 mm; d i is the thickness of insulation layer and equals 4 mm; ε c and ε i are the relative permittivities of continuous phase and insulation layer, respectively. Here, ε i equals 4.…”