Bubble characteristics of air-water bubbly jets in crossflow

This paper presents a detailed experimental study on bubble characteristics of bubbly jets in crossflow by injecting air-water mixtures vertically via a circular nozzle. Bubbles were observed to separate from the water jets after some distance from the nozzle. Bubble properties were measured at different sections along the gas-phase centerline trajectory. The results show that the radial distributions of void fraction, bubble frequency and bubble specific interfacial area generally follow the Gaussian distribution. The distribution of bubble velocity was found to be larger in the downstream side of a cross-section, but Gaussian in the transverse direction. The distribution of bubble diameter was found to be affected primarily by air and water injection rates and the distance from the nozzle. At a cross-section, the gas-phase exhibits an ellipse-shape for pure air injection, while a kidney-shape for a mixture of air-water injection. Bubble properties along the gas-phase centerlines were also investigated, and their values decay along the centerlines until reaching some terminal values. Finally, relation of bubble slip velocity with bubble diameter in crossflow was found close to that of single isolated bubbles in stagnant water, rather than that of bubbly jets in stagnant water. (C) 2013 Elsevier Ltd. All rights reserved.