State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China.
Phys Rev E. 2019 Nov;100(5-1):053108. doi: 10.1103/PhysRevE.100.053108.
It is generally accepted that a Worthington jet occurs when a droplet impacts onto a liquid pool. However, in this experimental study of the impact of viscous droplets onto a less-viscous liquid pool, we identify another jet besides the Worthington jet, forming a two-jet phenomenon. The two jets, a surface-climbing jet and the Worthington jet, may appear successively during one impact event. By carefully tuning the impact conditions, we find that the two-jet phenomenon is jointly controlled by the droplet-pool viscosity ratio, the droplet Weber number, and the droplet-pool miscibility. The mechanism of the surface-climbing jet is completely different from that of the Worthington jet: the liquid in the pool climbs along the surface of the droplet and forms a liquid layer which converges at the droplet apex and produces the surface-climbing jet. This surface-climbing jet has a very high speed, i.e., an order of magnitude higher than the droplet impact speed. The effects of the impact speed, droplet viscosity, droplet size, and surface tension on the surface-climbing jet are also analyzed. This study not only provides physical insights into the mechanism of droplet and jet dynamics but also will be helpful in the optimization of the droplet impact process in many relevant applications.
人们普遍认为，当液滴撞击液池时，会产生沃辛顿射流。然而，在这项关于粘性液滴撞击粘性较小的液池的冲击实验研究中，我们除了沃辛顿射流之外，还发现了另一种射流，形成了双射流现象。这两种射流，即表面爬升射流和沃辛顿射流，可能会在一次冲击事件中相继出现。通过仔细调整冲击条件，我们发现双射流现象由液滴-液池粘度比、液滴韦伯数和液滴-液池混溶性共同控制。表面爬升射流的机理与沃辛顿射流完全不同：池中的液体沿着液滴的表面爬升，并形成一层液体，在液滴顶点汇聚并产生表面爬升射流。这种表面爬升射流的速度非常高，即比液滴冲击速度高一个数量级。还分析了冲击速度、液滴粘度、液滴尺寸和表面张力对表面爬升射流的影响。本研究不仅为液滴和射流动力学的机理提供了物理见解，而且有助于优化许多相关应用中液滴冲击过程。
