Dynamics of phase inclusion during rotational oscillations of simply connected annulus

Abstract

The dynamics of a phase inclusion in a coaxial liquid layer divided with a radial partition is studied experimentally. The working volume of the container is filled with a viscous liquid, inside which an air bubble, immiscible with the main phase, is injected. This inclusion has a lower density than the surrounding liquid does. The container performs rotational oscillations as a whole with the zero average rotation. Such a motion brings to the generation of a harmonically oscillating azimuthal shear flow, which, as a consequence, excites the oscillations of the phase inclusion. During the bubble’s oscillations, the displacement of its geometric center follows the sinusoidal law. On the background of such a motion a periodic deformation of the bubble is observed, i.e. the phase boundary starts oscillating. A new and surprising result of the experiments is found, when the light bubble sinks and takes a quasi-steady position near the inner wall of the layer.