Flexible scraping of viscous fluids
Abstract
We study the thickness h(d) of the liquid film left on a wet surface after scraping it with an elastic wiper (length L, rigidity B) moved at a velocity V. The scraper is clamped vertically at a given distance above the substrate, and h(d) is maximal when the tip of the scraper is just tangent to the surface. We show experimentally and theoretically that this maximum thickness is hmax similar or equal to 0.33L (eta VL2/B)(3/4) where eta is the liquid viscosity. The deposition law is found to be sensitive to the shape of the wiper: the film thickness can also be tuned by using wipers with a permanent curvature, and varying this curvature.
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