BUBBLE CHARACTERISTICS IN THE BUOYANCY REGION OF A VERTICAL BUBBLING JET

The flow field in a vertical bubbling jet in a cylindrical vessel with bottom blowing can be divided into four regions. They are named the momentum, transition, buoyancy and surface regions in order of increasing distance from the nozzle exit. In a previous paper, bubble behavior characterized by gas holdup, bubble frequency, bubble rising velocity and so on was clarified for the momentum region in which the inertia force of injected gas played an important role. In the present study, bubble behavior in the buoyancy region in which the buoyancy force of bubbles governed the flow was investigated by means of two kinds of electro-resistivity porbes, a high-speed video camera, and a laser Doppler velocimeter. The bubble behavior was not affected by the nozzle diameter and the bath diameter. Therefore, correlations for gas holdup, bubble frequency and bubble rising velocity were proposed as functions of gas flow rate.