Textures fonctionnelles : aérophilie, propulsion et friction spéciale

Abstract : This thesis deals with the influence of textures on wetting and propulsion. Three situations have been considered, depending on the texture size.Aerophilic surfaces can be obtained with hydrophobic nanometric structures. When immerged in a liquid bath, these surfaces remain covered by a thin plastron of air. This oppens a new class of problems where gas – liquid interfaces are exchanged, compared to usual studies. We described the spreading of an air bulle over an aerophilic surface, capillary depression and the dynamics of a bubble on a wire.Millimetric sutructures allow an efficient redirection of the air cushion between a levitating object and its substrate. Because the flux is controlled, a specific direction can appear, and the object is efficiently propelled. Depending on the textures location, viscous entrainement or rocket effect can be the propulsive mechanism.Hydrophobic nanotextures are used to generate non-wetting situation of water. A tiny angle of tilt of the surface is enough to see a drop mouving; its velocity is high because of the low friction. Macrotextures, as millimetric crennels slow down very efficiently the drop: the study optimized the control of the drop (possibly viscous) motion.
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Hélène De Maleprade. Textures fonctionnelles : aérophilie, propulsion et friction spéciale. Mécanique des fluides [physics.class-ph]. Université Paris-Saclay, 2016. Français. ⟨NNT : 2016SACLX035⟩. ⟨tel-01493125⟩

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