Droplet Impact on a Micro-structured Hydrophilic Surface: Maximum Spreading, Jetting, and Partial Rebound
Droplet Impact on a Micro-structured Hydrophilic Surface: Maximum Spreading, Jetting, and Partial Rebound
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DOI：
10.1016/j.ijmultiphaseflow.2022.104235
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发表时间：
2022-08-27
影响因子：
3.8
通讯作者：
Siddique, Anayet Ullah
中科院分区：
文献类型：
--
作者：
Asai, Brooklyn;Tan, Hua;Siddique, Anayet Ullah
在本文中，我们对液滴撞击由圆柱形微柱组成的部分润湿亲水基底进行了实验研究。水和甘油以不同比例混合，主要改变液体粘度并保持表面张力大致恒定。我们表明，我们的微结构亲水表面可以表现出许多与疏水表面相同的冲击结果，包括铺展、反冲、喷射和部分回弹。构建状态图来传达冲击速度和粘度对冲击结果的总体影响。我们的数据表明，最大扩频因子 Amax 通常遵循幂律，韦伯数 We 为 beta(max) -We(0.25)。然而，β(max)-We(0.2)Re(0.04) 的比例关系为 Amax 提供了更好的相关性，因为由于流过基底上的微柱而产生的粘性耗散效应对于粘性较大的流体变得越来越重要。反冲阶段气腔塌陷引起的快速射流以自相似模式增长。发现顶部射流液滴的尺寸和射流速度之间的关系遵循最初为气泡破裂射流提出的相同缩放定律。部分回弹仅发生在冲击速度相对较高的低粘度流体中。发现部分回弹中惯性拉伸的浓液丝破裂所发射的回弹液滴的尺寸几乎与冲击速度无关。液滴撞击和部分回弹事件之间经过的时间与毛细管时间成比例。
In this paper, we perform an experimental study of droplet impact on a partially wetting hydrophilic substrate composed of cylindrical micro-pillars. Water and glycerol are mixed at different ratios to primarily change liquid viscosity and keep surface tension approximately constant. We show that our microstructured hydrophilic surface can exhibit many of the same impact outcomes as hydrophobic surfaces including spreading, recoiling, jetting, and partial rebound. A regime map is constructed to convey the overall effects of the impact velocity and viscosity on the impact outcomes. Our data indicate that the maximum spreading factor Amax generally follows the power law with the Weber number We as beta(max) -We(0.25). However, the scaling relation of beta(max)-We(0.2)Re(0.04) provides a better correlation for Amaxbecause the viscous dissipative effect due to flow through the micro-pillars on the substrate becomes increasingly important for more viscous fluids. The rapid jet caused by the collapse of the air cavity in the recoil phase grows in a self-similar pattern. The relationship between the size of the top jet droplet and jet velocity is found to obey the same scaling law originally proposed for the bubble bursting jet. The partial rebound occurs only for low viscosity fluids with relatively high impact velocity. The size of the rebounding droplet emitted by the breakup of inertially stretched thick liquid thread in the partial rebound is found to be nearly independent of the impact velocity. The elapsed time between droplet impingement and partial rebound event scales with the capillary time.