Statistics of compound droplets generated by fragmentation of immiscible buoyant oil jet in the water

Very little experimental data exists on the droplet formation and morphology in the near field of a crude oil jet fragmenting in water because of the inability to probe dense droplet cloud. PIV and PLIF measurements are made possible by using a surrogate refractive index matched liquid pair: silicone oil in sugar water. The oil jet fragmentation is visualized by fluorescently tagging the oil. Compound oil ligaments and droplets, which contain smaller water droplets, form regularly during the fragmentation process. In some cases, the droplets consist of multiple layers of oil and water, creating a “Russian Doll” like phenomenon. They affect the buoyancy and interfacial areas, which might affect associated biochemical interactions. A random forest-based trainable model is applied to distinguish between phases within the droplets and to quantify the resulting volume fractions and interfacial areas. While rarely occurring in a low Reynolds number jet (Re=594), the fraction of compound droplets increases to 21% and 26% as the jet Reynolds number increases to Re=1358 and 2122, respectively. The probability distributions of water fraction indicate a characteristic 4% decrease in droplet buoyancy and 12% increase in the interfacial area.