Splash and Bounce of Droplet on Liquid Layer under Low-Gravity

Abstract

Fluid motions after an impact of a droplet on a thin liquid layer were investigated by experimental observation under low gravity condition using the parabolic flight of an airplane. Whether the droplet bounces or coalesces on the liquid layer was found to be dependent on the Weber number and also on the Bond number, which represents the relative importance of gravity. In the plane of the Weber and the Bond numbers, droplet bouncing occurred for larger Weber numbers when the Bond number was small. The appearance of secondary droplets, which are caused by a symmetry-breaking of the growing cylindrical liquid sheet, was found to be independent to gravity. Our experimental results do not find gravity-dependent instability to be a cause of the symmetry-breaking, because it was observed even under microgravity conditions.