Dynamics of an oil-coated bubble rising in a quiescent water medium

Bubbles encapsulated by an organic bulk phase are widely present in the ocean and many industrial processes. We present experiments on a rising oil-coated compound bubble in quiescent water. By immobilizing the compound bubble surface and increasing the compound bubble effective density, the oil coating causes a smaller bubble shape deformation, changing the wake dynamics and forces acting on the bubble, and thereby its drag coefficient and path oscillation. The compound bubble zigzag oscillation is observed to decay significantly with time above a critical oil volume fraction. These results may provide guidance for simulations and applications of bubbly flows with compound interfaces.