Sticking and splashing in yield-stress fluid drop impacts on coated surfaces
Sticking and splashing in yield-stress fluid drop impacts on coated surfaces
复制标题
屈服应力流体滴对涂层表面的影响中的粘附和飞溅
DOI：
10.1063/1.4916620
复制
发表时间：
2015
影响因子：
4.6
通讯作者：
R. Ewoldt
中科院分区：
文献类型：
--
作者：
Brendan C. Blackwell;Marc E. Deetjen;Joseph E. Gaudio;R. Ewoldt
屈服应力流体，包括凝胶和糊剂，在高应力下有效地为流体，在低应力下为固体。在液-固冲击中，流体运动可以在事件的不同点处被屈服应力停止，并且这些流体因此可以在它们冲击的地方粘附和积聚，从而激发了这些流变学复杂材料的几种应用。在这里，我们使用高速成像实验研究液-固屈服应力流体预涂水平表面的影响。通过预涂相同材料，我们可以观察到大型长寿命喷射片，其动量重新定向，远离撞击位置延伸。在临界飞溅条件下，发生片材破裂，并且喷射的液滴可以是非球形的和线状的，这是由于毛细管应力不能使材料在一定长度尺度以上变形。通过改变液滴尺寸、冲击速度、表面涂层厚度和流变材料特性，我们开发了适当的无量纲参数，并提出了一个低维的冲击行为区域图。
Yield-stress fluids, including gels and pastes, are effectively fluid at high stress and solid at low stress. In liquid-solid impacts, the fluid motion can be halted by the yield stress at different points of the event, and these fluids can therefore stick and accumulate where they impact, motivating several applications of these rheologically complex materials. Here, we use high-speed imaging to experimentally study liquid-solid impact of yield-stress fluids on pre-coated horizontal surfaces. With a pre-coating of the same material, we can observe large long-lifetime ejection sheets with redirected momentum which extend away from the impact location. Under critical splash conditions, sheet breakup occurs and ejected droplets can be nonspherical and threadlike due to the inability of capillary stresses to deform material above a certain lengthscale. By varying the droplet size, impact velocity, surface coating thickness, and rheological material properties, we develop appropriate dimensionless parameters and present a low-dimensional regime map of impact behaviors.