Liquid Jet and Droplet Impaction on a Moving Substrate

在许多工业过程中，液体射流或液滴撞击移动的固体表面。当液体撞击表面时，会产生一层薄层。对于液体射流撞击的情况，如果薄片附着在表面上，并且所有液体都留在表面上，则撞击结果被描述为‘沉积’。相反，如果液体破碎成细小的液滴，就会发生“飞溅”或“飞溅”。在大多数应用中，例如表面涂层，沉积是期望的结果，而飞溅和飞溅是不希望的。射流是否干净地沉积在表面是液体和表面性质的函数，令人惊讶的是，也是周围空气的函数。将使用几种实验方法来研究射流和液滴的撞击。为了确定喷射或液滴相互作用的整体特征(例如，飞溅与沉积以及薄片半径和宽度)，将进行高速视频成像和图像处理。将使用光学吸收、傅里叶变换轮廓术或激光干涉测量来确定作为位置函数的薄片厚度。最后，将使用粒子跟踪测速仪来测量薄层内颗粒速度的空间变化。对于牛顿液体射流，这些测量将作为射流方向、表面粗糙度、表面静态接触角、射流雷诺数和韦伯数以及射流与表面速度比的函数进行。对于含有悬浮颗粒的非牛顿液体射流，还将确定颗粒浓度和尺寸对射流薄片扩散特性的影响，以及可能的飞溅。在一些工业应用中，固体表面覆盖着一层薄薄的液体。我们将在定制的装置中研究具有这种运动表面的液体射流的冲击。人们还知道，周围空气的疏散可以抑制液滴在静止表面上的飞溅。我们计划测量液滴撞击移动表面时飞溅抑制的程度。*这项研究应该为一个重要的工业问题提供洞察力，并与一个引起强烈科学兴趣的问题相关--发生在表面液膜与空气交界处的移动接触线。

In numerous industrial processes a liquid jet or liquid droplets impact on a moving solid surface. As the liquid impacts the surface a thin lamella is generated. For the case of liquid jet impaction, if the lamella adheres to the surface and all liquid remains on the surface, the impaction outcome is described as ‘deposition'. In contrast, if the liquid breaks into fine droplets, ‘splattering' or ‘splash' occurs. In most applications, for example surface coating, deposition is the desired outcome whereas splash and splattering are undesirable. Whether the jet deposits cleanly on the surface is a function of the liquid and surface properties, and surprisingly, also a function of the surrounding air.*******Several experimental methods will be used to study jet and droplet impaction. In order to determine the bulk characteristics of the jet or droplet interaction (e.g., splash versus deposition and lamella radius and width), high speed video imaging and image processing will be performed. Optical absorption, Fourier transform profilometry, or laser interferometry measurements will be used to determine the lamella thickness as a function of position. Finally, Particle Tracking Velocimetry will be used to measure the spatial variation of particulate velocity within the lamella. For Newtonian liquid jets, these measurements will be made as a function of the jet orientation, surface roughness, static contact angle of the surface, the jet Reynolds and Weber numbers, and the jet-to-surface velocity ratio. For non-Newtonian liquid jets with suspended particulates, the influence of particulate concentration and size on the spreading characteristics of the jet lamella, and possible splash, will also be determined.****In some industrial applications, the solid surface is coated with a thin film of liquid. The impaction of a liquid jet with such a moving surface will be studied in a custom apparatus. It is also known that evacuation of the surrounding air can suppress droplet splash on stationary surfaces. We plan to measure the magnitude of the splash suppression for droplet impaction on a moving surface.*******This research should provide insight into both an important industrial problem and be relevant to a problem of intense scientific interest – the moving contact line that occurs at the location where the liquid lamella on the surface interfaces with the air.*********