Effects of tangential speed on low-normal-speed liquid drop impact on a non-wettable solid surface

Abstract

A stream of water drops colliding on a rotating cylindrical Teflon surface was observed. The collision resulted in partial rebound, deposition, and split deposition. The collision outcome was found to depend on the normal Weber number and the tangential Weber number, which represent the collision momentum in the normal and the tangential direction, respectively. The extent of influence of the centrifugal acceleration induced by the rotation was kept negligibly under 2% compared with the impact momentum change. Through careful measurements on the elongation of the liquid drop after impact, the impact regime boundaries are seen to be governed by the long and short axes of the elliptical-disk shape at the maximal spread. Partial rebound first changes to deposition when the long axis is 1.1 times the short axis; and then changes to split deposition when the long axis is 1.46 times the short axis. Furthermore, the dimensionless excess spread area was found to be directly proportional to the tangential Weber number.