Corners, cusps, and pearls in running drops.
Small drops sliding down a partially wetting substrate bifurcate between different shapes depending on their capillary number Ca. At low Ca, they are delimited by a rounded, smooth contact line. At intermediate values they develop a corner at the trailing edge, the angle of which evolves from flat to 60 degrees with increasing velocity. Further up, they exhibit a cusped tail that emits smaller drops ("pearls"). These bifurcations may be qualitatively and quantitatively recovered by considering the dynamic contact angle along the contact line.
Podgorski
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Physique et Mécanique des Milieux Hétérogènes, UMR 7636 CNRS-ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05, France.
Flesselles
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Limat
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