Oil drop impact on stratified oil-water layers

The impact of liquid droplets onto liquid films plays an important role in a wide variety of natural systems and industrial processes, which include raindrop-assisted soil erosion, oil-water emulsions, spray deposition and coating and chemical dispersant application on oil spills. This work investigates the oil drops impacting on stratified oil-water layers with the aid of two high-speed video cameras, using different magnifications to capture both the initial details and overall evolution of the splash at later times. We show that the droplet velocity, the thickness of the silicone oil surface layer and its viscosity have substantial impact on the crown formation and the creation of a bubble canopy that sends liquid jets upwards and downwards from its radially collapsing apex. The results obtained with high-speed visualization provide new insights into the evolution of the liquid jet emerging from the bubble canopy. The effects of key parameters including Weber number, Ohnesorge number, viscosity ratio and the dimensionless film thickness are carefully examined to elucidate the crown formation and the jet breakup.