I - FORMATION AND RISE OF A BUBBLE STREAM IN A VISCOUS-LIQUID

The continuous emission of gas bubbles from a single ejection orifice immersed in a viscous fluid is considered. We first present a semi emp irical model of spherical bubble growth under constant flow conditions to predict the bubble volume at the detachment stage. In a second par t, we propose a physical model to describe the rise velocity of in-lin e interacting bubbles and we derive an expression for the net viscous force acting on the surrounding fluid. Experimental results for air/wa ter-glycerol systems are presented for a wide range of fluid viscosity (43 mPas - 800 mPas) and compared with theoretical predictions. An im agery technique was used to determine the bubble size and rise velocit y. The effects of fluid viscosity, gas from rate, orifice diameter and liquid depth on the bubble stream dynamic were analyzed. We have furt her studied the effect of large scale recirculation flow and, the infl uence of a neighbouring bubble stream on the bubble growth and rising velocity.