Oily jets by bubble bursting at an air/water/oil interface

Bursting of bubbles at a fluid-fluid interface is ubiquitous in nature and many industrial processes, relevant to foam stability, cell cultures in bioreactors as well as ocean spray generation. In particular, bubble bursting plays a key role in mediating the mass transport across the interface and has consequently received significant attention. Here, we report the dynamics of an oily jet produced by bubble bursting at an aqueous surface covered by a layer of oil, which finally ejects oily aerosols into the air. With high-speed imaging, we document the dynamics of the cavity collapse and jet formation with different oil viscosities and layer thicknesses. We observe that the oil layer damps the capillary waves during cavity collapse, hence decreasing the jet radius and increasing the jet velocity. We further propose an effective Ohnesorge number to quantify the jet radius and velocity by taking into account the viscous dissipation from the oil layer. Our study not only advances the fundamental understandings of bubble bursting at a compound interface, but may also shed light on the formation of oily aerosols in the ocean regarding pollutant transport.