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Pyramidal and toroidal water drops after impact on a solid surface

Published online by Cambridge University Press:  20 May 2003

Y. RENARDY
Affiliation:
Department of Mathematics and ICAM, 460 McBryde Hall, Virginia Tech, Blacksburg, VA 24061-0123, USA
S. POPINET
Affiliation:
National Institute for Water and Atmospheric Research, PO Box 14 901, Kilbirnie, Wellington, New Zealand
L. DUCHEMIN
Affiliation:
Laboratoire de Modélisation en Mécanique, CNRS-UMR 7607, Université Pierre et Marie Curie, 8 rue du Capitaine Scott, 75015 Paris Cedex 05, France
M. RENARDY
Affiliation:
Department of Mathematics and ICAM, 460 McBryde Hall, Virginia Tech, Blacksburg, VA 24061-0123, USA
S. ZALESKI
Affiliation:
Laboratoire de Modélisation en Mécanique, CNRS-UMR 7607, Université Pierre et Marie Curie, 8 rue du Capitaine Scott, 75015 Paris Cedex 05, France
C. JOSSERAND
Affiliation:
Laboratoire de Modélisation en Mécanique, CNRS-UMR 7607, Université Pierre et Marie Curie, 8 rue du Capitaine Scott, 75015 Paris Cedex 05, France
M. A. DRUMRIGHT-CLARKE
Affiliation:
Department of Mathematics and ICAM, 460 McBryde Hall, Virginia Tech, Blacksburg, VA 24061-0123, USA
D. RICHARD
Affiliation:
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, UK
C. CLANET
Affiliation:
Institut de Recherche sur les Phénomènes Hors Équilibre, UMR 6594 du CNRS, BP 146, 13384 Marseille Cedex, France
D. QUÉRÉ
Affiliation:
Laboratoire de Physique de la Matire Condense, URA 792 du CNRS, Collège de France, 75231 Paris Cedex 05, France

Abstract

Superhydrophobic surfaces generate very high contact angles as a result of their microstructure. The impact of a water drop on such a surface shows unusual features, such as total rebound at low impact speed. We report experimental and numerical investigations of the impact of approximately spherical water drops. The axisymmetric free surface problem, governed by the Navier–Stokes equations, is solved numerically with a front-tracking marker-chain method on a square grid. Experimental observations at moderate velocities and capillary wavelength much less than the initial drop radius show that the drop evolves to a staircase pyramid and eventually to a torus. Our numerical simulations reproduce this effect. The maximal radius obtained in numerical simulations precisely matches the experimental value. However, the large velocity limit has not been reached experimentally or numerically. We discuss several complications that arise at large velocity: swirling motions observed in the cross-section of the toroidal drop and the appearance of a thin film in the centre of the toroidal drop. The numerical results predict the dry-out of this film for sufficiently high Reynolds and Weber numbers. When the drop rebounds, it has a top-heavy shape. In this final stage, the kinetic energy is a small fraction of its initial value.

Type
Research Article
Copyright
© 2003 Cambridge University Press

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