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Entraînements visqueux

Abstract : We study experimentally different configuration of Newtonian viscous entrainment and drainage. We show that surface roughness drastically affects the coating laws of the dip- coating experiment : the entrained thickness is equal to the texture height below a critical capillary number, then increases and tends towards the smooth limit when it becomes much larger than the roughness. Th drainage is also affected, and features a sharp decrease. A two layer model is able to quantitatively reproduce all these observations. We then study the coating by an elastic sheet. When the scraper is just tangent to the deposition surface, a model reproduces the experimental results within a prefactor, which is part due to finite width effetcs. We then show that the deposition is very different when using a rigid scraper, and arrises from the stress divergence at scraper's tip. This study features the crucial role of the shape of the scraper. Lastly, we consider the filament withdrawn from a bath of viscous oil with a cylinder, and show the its size comes from a balance between viscous and gravity forces. The observed drainage law strongly depends on the size of the thread. This characteristic is also found when considering a horizontal viscous thread in the gravity field. We explain why "thick" filaments keep a catenary-like shape throughout their fall, whereas "small" ones evolve toward a "U" shape.
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Contributor : Jacopo Seiwert Connect in order to contact the contributor
Submitted on : Monday, December 6, 2010 - 8:26:23 PM
Last modification on : Friday, August 5, 2022 - 11:54:07 AM
Long-term archiving on: : Saturday, December 3, 2016 - 12:18:58 AM


  • HAL Id : tel-00512382, version 2


Jacopo Seiwert. Entraînements visqueux. Dynamique des Fluides [physics.flu-dyn]. Ecole Polytechnique X, 2010. Français. ⟨tel-00512382v2⟩



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