Dynamics of isolated holes in sheets of oil-in-water emulsions

The addition of oil droplets in an aqueous phase modifies the atomization of the aqueous phase. A traditional method for studying atomization involves the fragmentation of self-suspended liquid sheets formed upon the impact of a free-falling drop on a small solid target. As a liquid sheet of an oil-in-water emulsion expands and retracts, holes form and are advected within the liquid sheets. Invariably, holes in sheets of these oil-in-water emulsions are preceded by preholes, or locally thin areas. We vary the emulsion composition by adjusting the oil phase viscosities, which range from 20 to 1000 mPa.s, and the surfactant formulation to observe the destabilization of liquid sheets of emulsion using a high-speed camera. By including dye in the aqueous phase, we take advantage of Beer's law to obtain thickness values from the light intensity of the recorded images. After selecting isolated holes, we examine the dynamics of these holes. We can track the position of the center of the hole and the pre-hole-to-hole transition, which is easily identified using thickness values across the heterogeneous patch as seen in the figure. We report on the position, velocity, and growth rate for pre-holes and holes forming in a liquid sheet resulting from the impact of emulsion drops.