Northwestern Polytechnical University, Xi'an, PR China.
J Colloid Interface Sci. 2011 Apr 1;356(1):286-92. doi: 10.1016/j.jcis.2010.12.087. Epub 2011 Jan 4.
The motion of droplets on surfaces is crucial to the performance of a wide range of processes; this study examines the initiation of droplet motion through a shearing mechanism generated here by a controlled air flow. Systematic experiments are carried out for a range of fluids and well defined surfaces. A model is postulated that balances surface tension forces at the contact line and the drag force due to the air motion. Experiments reveal that the critical velocity at which droplet motion is initiated depends on the contact angle and the droplet size. Visualizations highlight three modes of motion: (I) the droplet retains a footprint similar to that at the point of motion; (II) a tail exists at the rear of the droplet; (III) a trail remains behind the droplet (that can shed smaller droplets). The predictions of droplet initiation velocity are good for type I motion, in accordance with the assumptions inherent within the model. This model confirms the dominant physics associated with the initiation of droplet motion and provides a useful predictive expression.
液滴在表面上的运动对广泛的过程的性能至关重要；本研究通过这里产生的受控气流的剪切机制来检查液滴运动的开始。对一系列流体和明确定义的表面进行了系统的实验。提出了一个模型，该模型平衡了接触线处的表面张力和空气运动引起的阻力。实验表明，液滴开始运动的临界速度取决于接触角和液滴尺寸。可视化突出了三种运动模式：（I）液滴保持与运动点相似的足迹；（II）液滴的后部存在尾巴；（III）液滴后面留下痕迹（可能会脱落较小的液滴）。根据模型中固有的假设，对第一类运动，预测液滴初始速度的结果是很好的。该模型证实了与液滴运动开始相关的主要物理现象，并提供了有用的预测表达式。
