Bouncing water drops
Laboratoire de Physique de la Matière Condensée, URA 792 du CNRS
Collège de France - 75231 Paris Cedex 05, France
Accepted: 7 April 2000
When a liquid drop impacts a solid, it spreads (with possibly beautiful fingering patterns) up to the point when kinetic energy is dissipated by viscosity. Then, it can retract (if the solid is partially wetted by the liquid), or not. A very different behaviour can be observed on highly hydrophobous solids. On such solids, the contact angle is close to , so that the kinetic energy of the impinging drop can be transferred to surface energy, without spreading. Thus, the drop can fully bounce. However, the liquid nature of this kind of spring imposes a limit for the restitution coefficient, which is due to the fact that the drop, after the lift-off, oscillates.
PACS: 68.10.Cr – Surface energy (surface tension, interface tension, angle of contact, etc.) / 68.45.Gd – Wetting / 83.50.Lh – Interfacial and free surface flows; slip
© EDP Sciences, 2000