EXPERIMENTAL STUDY ON THE EFFECT OF ELECTRIC FIELD STRENGTH ON DROPLET IMPACT ON SOLID SURFACE AT LOW WEBER NUMBERS

The physical mechanism of droplet impact on solid surface under the action of electric field has found extensive applications in electrostatic spraying, microfluidic control, high voltage power lines icing, and other fields. Visual experiments were conducted to investigate the motion process and morphological changes of droplet impacting surfaces under an applied electric field, particularly during shrinkage, stretching and spraying stages. The study also analyzed the effects of electric field intensity, low Weber number and surface wettability on droplet dynamic behavior. Results show that at constant impact velocity, droplet wall-impact exhibits three distinct modes with the increase of field strength, governed by the interplay of inertia, gravity, surface tension, electrostatic force, and viscous dissipation. While electric field intensity has no significant effect on the droplet spreading coefficient, it significantly promotes an increase in the droplet stretching coefficient. A threshold relationship between the low Weber number, electric capillarity number, and impact modes was established. Under strong electric fields, droplet ejection causes liquid loss, with the remaining liquid volume and time to reach the ejection state varying for surfaces with different wettability. These findings provide a theoretical foundation for the electric field regulation of droplet dynamics and offer valuable insights for optimizing electrostatic spraying precision and developing innovative microfluidic chips.