Europhys. Lett, 48 (3), pp. 286-291 (1999)
Viscous drops rolling on a tilted non-wettable solid
D. Richard and D. Quéré
Laboratoire de Physique de la Matière Condensée, URA 792 du CNRS, Collège
75231 Paris Cedex 05, France
(received 10 May 1999; accepted in final form 3 September 1999)
- Fluid surfaces and fluid-fluid
PACS. 68.15 - Liquid thin films.
A viscous liquid drop sliding down an inclined solid that it partially wets runs all the faster since it is large. Here we examine what happens in the limit of very high contact angles, on a so-called super-hydrophobic surface. It is shown that a droplet rolls instead of sliding, which leads to a surprising law for the velocity as a function of the drop radius: the smaller the droplet, the larger the running velocity. A recent model of Mahadevan and Pomeau allows us to propose an explanation for this paradoxical behaviour.
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