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Accueil > Actualités > Séminaires > Séminaires 2012

Mardi 23 octobre 2012, 11h00 LEGI salle A103

Evgeny Ermanyuk

Titre/Title :
Impact of a rigid sphere onto a free surface and a flat bottom of a liquid volume : air trapping and cavitation

Contact :
Bruno Voisin (Equipe Meige)

Résumé/Abstract :
The phenomena of liquid-to-solid and liquid-to-liquid impact are related to many applications such as ink-jet printing, coating, airplane icing, slamming of ships, etc. Its practical importance in processes covering very wide ranges of spatial and temporal scales stimulates an intense ongoing research.
The present talk is focused on two aspects of impact problems : i) air trapping by a body impacting onto a free surface and ii) cavitation at touchdown of a solid body moving through a liquid toward a solid wall.
First, we present an experimental and theoretical investigation of the air trapping. In the parameter regime previously studied theoretically by Hicks & Purvis (JFM 2010), excellent agreement between experimental data and theoretical modeling is obtained. Earlier data on the radius of the trapped air pocket are confirmed. At low impact speed we observe non-axisymmetric regimes of air trapping.
Second, we present the results of visual and instrumental studies of impact of circular disks with convex, flat and concave lower surface onto a thin liquid layer. We show that disks with flat and concave lower surfaces approach to a flat bottom asymptotically, with zero terminal velocity. Disks with convex lower surface have non-zero terminal velocity, with intense cavitation observed at touchdown to a flat bottom. The cavitation removes “the continuity paradox” : theory predicts that a locally spherical body in a continuous Newtonian fluid may approach a flat wall only asymptotically, with zero terminal velocity (Brenner (Chem. Eng. Sci. 1961), Starovoitov (2004)).
Some results of the above-mentioned studies are presented in Hicks, Ermanyuk, Gavrilov & Purvis (JFM 2012) and Ermanyuk & Gavrilov (J. Appl. Mech. & Tech. Phys. 2011).