Ecoulement et distribution de liquide dans un bord de Plateau

Description

Our experimental configuration deals with an unique Plateau border positioned horizontally. The latter is supplied externally with a droplet of the same liquid, dropped from above. The droplet coalesces with the Plateau border. We study various liquids with different bulk and surface viscosities and surface tension, and Plateau borders of different sections and different drop radii. According to these parameters, two main limiting regimes of coalescence are identified. For large bulk viscosity or low surface mobility, the fluid in excess is slowly evacuated in the Plateau border according to a diffusion-like process. In contrast, for liquids of low viscosity and high surface mobility, measurements show that the Plateau border swells in the vicinity of the drop and attains a constant thickness, with a sharp front separating the swollen and the unperturbed parts of the Plateau border. The front is seen to propagate with a constant velocity. This velocity is shown to be controlled by a competition between capillary and inertial effects, without any noticeable effect of the viscosity. This last regime is reported here for the first time, and casts new insights on drainage and liquid flows in foams.

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