Sphere Falling Onto A Liquid Jet

Abstract

Abstract The history of interfacial fluid dynamics is intertwined with the origins of flash photography from the 'Worthington Jet' of Aurthur Worthington [1] to the 'Milk drop coronets' of Harold Edgerton[2] , with this technique capturing ephemeral fluid impacts in their awe-inspiring beauty. Although camera technology has come far from the days of giant flash bulbs, this elegant technique still provides a uniquely focused window into the fleeting impact events that often seem chaotic in real time, but in the suspended reality of flash-photography are found to be surprisingly well patterned. We apply a similar technique with the help of a laser-controlled photo-receptor in a dark room at night with flashes going off when the light received by the photo-receptor is disturbed. The resultant sequential images of Figure 1 are achieved by the timed release of a 50 mm diameter steel sphere falling from 750 mm plunging through an upward moving Worthington Jet that was created by a 38 mm sphere dropped from 230 mm in line with the second sphere. The jet envelopes the sphere from all sides, with thin water films hugging and moving across the sphere surface continuously until they meet at the sphere apex creating beautiful fluid sheets and ligaments in Figure 2. This image not only captures the beauty of the impact but also reveals a novel mechanism of reducing the impact impulse force of falling objects. The sphere in this particular case experiences an almost 70% reduction in impact force compared to a quiescent pool impact [3, 4].