Splash formation by spherical drops

The impact of a spherical water drop onto a water surface has been studied experimentally with the aid of a 35 mm drum camera giving high-resolution i mages that provided qualitative and quantitative data on the phenomena. Sca ling laws for the time to reach maximum cavity sizes have been derived and provide a good fit to the experimental results. Transitions between the reg imes for coalescence-only, the formation of a high-speed jet and bubble ent rapment have been delineated. The high-speed jet was found to occur without bubble entrapment. This was caused by the rapid retraction of the trough f ormed by a capillary wave converging to the centre of the cavity base. The converging capillary wave has a profile similar to a Crapper wave. A plot s howing the different regimes of cavity and impact drop behaviour in the Web er-Froude number-plane has been constructed for Fr and We less than 1000.