Bubble velocities induced by interactions in polydisperse confined inertial swarms
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In this experimental work we present a study on the collective dynamics of polydisperse swarms of inertial confined bubbles. The kinematics of unequal sized bubbles, constituting a population that rises in a thin-gap cell filled with liquid at rest and which evolves due to coalescence, is deeply analyzed by means of statistically well-converged data. A Bubble Tracking Algorithm (BTA) has been developed to follow the motion of bubbles in high-speed movies registered at different downstream locations of the cell. The detailed information provided by the BTA allows an individual analysis of the time evolution of bubble velocities together with the detection of collision events, prior to which strong bubble-bubble interactions take place. To determine the effects of the local distribution of sizes and of the gas volume fraction, various gas injection conditions have been tested. The different injected fluxes of bubbles induce various coalescence rates, giving rise to different distributions of sizes throughout the cell.