Oil drop shedding from solid substrates by a shearing liquid

Abstract

The present work deals with the shedding of liquid drops by a liquid shear flow, which is still not adequately addressed experimentally in the literature. The effect of surface wettability, physical properties of the oil drop, flow velocity, and drop size on single drop detachment was studied. A force balance analogy was carried out to theoretically better understand the phenomena. Through an experimental study the shedding of series of silicone oil drops of varying viscosities from oleophilic Teflon and oleophobic PMMA subjected to a shearing water flow, was investigated. The drop motion was tracked using two cameras. The position of upstream and downstream drop contact points, drop height and baselength, was measured using image processing. The main results show that at high viscosities oil drops detach more easily from Teflon than PMMA. Different regimes of drop shedding have been observed including: (1) drop deformation in the flow direction followed by drop sliding, (2) sliding along the substrate without any significant deformation, and (3) drop deformation and sliding followed by lift-off from the surface.