Singular jets in free-surface flows

July 17, 2008
  • Jets
  • 58A20
Free-surface 'singular jetting' occurs in geometries where flow focusing accelerates the free surface symmetrically towards a line or a point. This is known to occur in a number of configurations, such as during the collapse of free-surface craters and of granular cavities as well as for capillary waves converging at the apex of oscillating drops. Drops impacting onto super-hydrophobic surfaces also generate such jets. We will show recent work on characterizing such jetting, in well-known and new jetting configurations. High-speed video imaging, with frame-rates up to 1,000,000 fps, will be presented and used for precise measurement of jet size and velocity. The focus will be on three well-controlled flow-configurations: During the crater collapse following the impact of a drop onto a liquid pool and after the pinch-off of a drop from a vertical nozzle. Finally, we will show a new apex jet which is generated by the impact of a viscous drop onto a lower-viscosity pool.