Interfaces mobiles : friction en mouillage nul et dynamiques de fronts

Abstract : Through several experiments, we investigate situations for which interfaces play a major role on the dynamics of either drops or liquid fronts. First, we study several non wetting drops: Leidenfrost drops, drops on a superhydrophobic surfaces and liquid marbles. When a drop is on a substrate hotter than the boiling point, a vapor layer prevents contact by isolating the drop from the solid. On a superhydrophobic surface, which is a rough and hydrophobic surface, the bottom surface of the drop touches only a fraction of the solid, and thus is mostly in contact with air. Finally, when one deposits a drop on hydrophobic grains, the interface captures the grains and they isolate completely the drop from its substrate. In all these situations, we study the friction of these drops when they run down inclines. This friction is lower than the one usually observed for partial wetting, and of different physical nature. The second part of this work focuses on different studies of mobile fronts. When we pour a liquid on a grains pile, it can either soak it or stay at its surface. The transition between these situations occurs for a critical contact angle. When we deposit a drop on hydrophobic grains, it produces an erosion of the pile: the amount of grains taken away by the drop is discussed. Besides, dripping water on a surface colder than the freezing point lead to the growth of an ice stalagmite. Finally, the confinement of a Leidenfrost drop between two parallel plates causes a succession of instabilities: it first takes a ring shape, which then expands before breaking up into droplets.
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Pascal Raux. Interfaces mobiles : friction en mouillage nul et dynamiques de fronts. Matière Molle [cond-mat.soft]. Ecole Polytechnique X, 2013. Français. ⟨pastel-00945753⟩

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