Multi-phase plumes in uniform and stratified crossflow

Laboratory experiments of multiphase plumes in uniform and stratified crossflows are presented. In uniform crossflow, multi-phase plumes behave as mixed single-phase plumes up to a critical height, h s , where the entrained fluid separates from the dominant dispersed phase. From the experimental results, an empirical relationship for h s was calibrated giving u ∞ /(B/ s ) 1/3 =6.3(u s /(B/h s ) 1/3 ) -2.4 , where u ∞ is the crossflow velocity, B is the total kinematic buoyancy flux of the mixed plume, and u s is the slip velocity. Above h s the separated continuous-phase plume behaves like a momentum jet and the bubble column follows the trajectory of the vector sum of u s and u ∞ In stratified crossflow. the trap height in quiescent water, h T , was compared to h s . For h T « h s , the plumes are stratification-dominated and separation occurs at h T = (2.8-0.27 u s /(B/N) 1/4 )(B/N 3 ) 1/4 , where N is the Brunt- Vaisala buoyancy frequency. For h T , » h s . the plumes are crossflow-dominated, and separation occurs at h s . A simple single-phase model was modified to predict the fate of the separated plume above h s .