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，就会产生薄层。在液体喷射撞击的情况下，如果薄片附着在表面上，而所有液体都留在表面上，则撞击结果被描述为沉积。相反，如果液体破裂成细小的液滴，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。射流是否能干净地沉积在表面是液体和表面特性的函数，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。为了确定射流或液滴相互作用的总体特性（例如，飞溅与沉积以及片层半径和宽度），将进行高速视频成像和图像处理。光学吸收，傅里叶变换轮廓测量，或激光干涉测量将用于确定片层厚度作为位置的函数。最后，采用粒子跟踪测速技术测量颗粒速度在薄片内的空间变化。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。对于带有悬浮颗粒的非牛顿液体射流，还将确定颗粒浓度和大小对射流片层扩散特性的影响，以及可能的飞溅。****在一些工业应用中，固体表面涂有一层液体薄膜。液体射流与这种移动表面的碰撞将在定制的设备中进行研究。众所周知，疏散周围的空气可以抑制液滴在固定表面上的飞溅。我们计划测量液滴撞击运动表面时溅射抑制的大小。*******这项研究将为一个重要的工业问题提供见解，并与一个具有强烈科学兴趣的问题相关，即发生在表面上的液体薄片与空气界面处的移动接触线*********

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.*********