II - RECIRCULATION FLOW-INDUCED BY A BUBBLE STREAM RISING IN A VISCOUS-LIQUID

The recirculation flow induced by the rising motion of a bubble stream in a viscous fluid within an open-top rectangular enclosure is studie d. The three-dimensional volume averaged conservation equations are so lved by a control-volume method using a hybrid finite differencing sch eme to describe the liquid phase hydrodynamics. The momentum exhange b etween the bubbles and the liquid phase is modeled with a source term equals to the volumetric buoyancy force acting on the gas in the bubbl e stream. The volumetric buoyancy force accounts for in line interacti ons between bubbles through the average gas volume fraction in the gas liquid column which depends on the size and the rising velocity of bu bbles. The fluid flow within all open-top rectangular enclosure is fur ther investigated by particle image velocimetry for a bubble stream ri sing in a water-glycerol solution. The measured fluid velocities in a vertical plane are compared with the predictions of the numerical mode l over a wide range of fluid viscosity (43 mPa s-800 mPa a) and gas fl ow rates. Finally, the recirculation flows resulting from the interact ion of two neighbouring vertical bubble streams are studied.