Liquid Jet and Droplet Impaction on a Moving Substrate

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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.*********