低韦伯数下电场强度对液滴撞击固体表面影响的实验研究

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

  • 摘要: 液滴在电场作用下撞击固体表面这一物理现象在静电喷涂、微流控、高压输电线结冰等领域得到了广泛应用。本文通过可视化实验研究了液滴在外加电场下撞击壁面的运动过程及形态变化,尤其是回缩、拉伸及喷射阶段,同时考虑了电场强度、低韦伯数和表面润湿性对液滴动态行为的影响。结果表明:当撞击速度一定时,由于惯性力、重力、表面张力、静电力和黏滞耗散的共同作用,液滴撞击壁面的行为会随着场强的增大展现出3种不同的模态;电场强度的变化对液滴铺展系数无明显影响,但会显著促进液滴拉伸系数的增加;进一步得到了低韦伯数、电毛细数与模态之间的阈值关系;在强电场条件下,液滴的喷射现象导致液量损失,且随着壁面润湿性的改变,液滴残留的液量和达到喷射状态的时间均展现出差异性。本文结果可为电场调控液滴动力学行为提供理论依据,并对优化静电喷涂精度、开发新型微流控芯片具有参考价值。

     

    Abstract: 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.

     

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