Experimental evidence of flow destabilization in a two-dimensional bidisperse foam.
Liquid foam flows in a Hele-Shaw cell were investigated. The plug flow obtained for a monodisperse foam is strongly perturbed in the presence of bubbles whose sizes are larger than the average bubble size by an order of magnitude, at least. Above a velocity threshold, the large bubbles migrate faster than the mean flow. We evidence experimentally this instability and, in the case of a single large bubble, we compare the large bubble velocity to the prediction deduced from scaling arguments. In the case of a bidisperse foam, an attractive interaction between large bubbles induces segregation and the large bubbles organize themselves in columns oriented along the flow.
GMCM, UMR 6626, Université de Rennes (CNRS), 263 av. du Général Leclerc, 35042 Rennes Cedex, France. isabelle.cantat@univ-rennes1.fr
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Cantat
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Poloni
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Delannay