Abstract
This study describes experimental results on the wake structure generated by a bubble swarm using LDV. The authors have considered the individual bubble motion of a bubble swarm and the liquid-phase motion driven by the buoyancy. The bubbles were simultaneously released from 19 needles under precise control; two bubbles were released from each needle at a short interval; as a result a total of 38 bubbles composed the bubble swarm. The 38 bubbles were almost uniform and 2.6mm in equivalent diameter. The center-gravity motion of the each bubble was obtained from high-speed visualization. The liquid-phase motion induced by the dispersed bubble buoyancy was measured via LDV. The following results were obtained: in the frontal region of the bubble swarm, the liquid-phase motion induced by the individual bubbles of the swarm did not interact with each other; in the rear region of the bubble swarm, the liquid-phase motion intensively interacts with each other through the wakes; inside of the bubble swarm, the liquid-phase motion was affected by the center-gravity motion of each bubble.
