8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Thu 811:10-14:00P7.81Bouncing jets on solid surfacesXavier Noblin, 1 Richard Kofman, 1 Mathieu Pellegrin, 1 and Franck Celestini 11 LPMC, UMR6622, CNRS-UNSA, Parc Valrose, Av. Vallot, 06108, Nice Cedex 2,FranceWhen a water jet impinges upon a solid surface it produces a so called hydraulic jump, characterizedby a thin liquid sheet bounded by a circular rise of the surface due to gravitational forces.In the common experiment, the liquid impacts normally the substrate and downstream of the impactregion sticks to it. Here we experimentally observed that a water jet, impacting at an anglea solid surface can bounce on it, when it is sufficiently hydrophobic, without being destabilized.Depending on the incident angle of the impinging jet, its velocity and the degree of hydrophobicityof the substrate, the jet can: i) Bounce on the surface with a reflected angle that depends on thesethree parameters. ii) Land on it and give rise to a supported jet. iii) Be destabilized, emittingdrops. We have built a simple model that describe the various cases observed and highlights theprominent role of surface tension forces normal to the solid surface and its hydrophobic nature.We also demonstrate various possible applications in order to reach a better control of liquid jetsin a microfluidics perspective.81