Liquid Entrainment by Round Turbulent Gas Jets Submerged in Water

Entrainment characteristics of two-phase flow (liquid-gas) buoyant jets differ significantly from their single-phase flow counterparts. Past studies have not adequately described the mechanisms that cause the gas jet to entrain liquid from its surroundings and expand. In this work, Particle Image Velocimetry (PIV) and shadowgraph flow visualization experiments have been conducted on submerged round gas jets of varying speeds and nozzle diameters with the goal of improving our understanding of the processes of entrainment and expansion in a two-phase jet. We hypothesize that liquid is entrained into the gas column through (1) shear entrainment due to instabilities at the interface between the fast-moving gas jet and stagnant liquid, and (2) convective entrainment that occurs when the jet begins to pinch off and transform into a bubbly plume. The total entrainment estimated using the PIV measurements is higher than the respective values that single-phase buoyant jet theory suggests, especially at low jet speeds. This may be an effect of increased convective entrainment as the jet slows down. The shadowgraph flow visualization experiments provide valuable information pertaining to the structure of the jet and the interfacial dynamics.