Bubble induced mixing in a vertically vibrating bubble column*

A homogeneous bubble swarm rising in quiescent liquid generates liquid velocity agitations different from that of grid generated isotropic turbulence. Dispersion of a passive scalar using the mixing effect of bubble-induced turbulence was studied. In addition, the effect of vibration on the mixing performance of a bubble swarm was investigated. An instrumented vibrating bubble column test facility was used to study the mixing time of a non-reactive dye. Mixing time was measured by tracking the temporal evolution of a batch of dye using optical photography. In the present work gas superficial velocity, vibration frequency, and amplitude are the independent variables. In addition to the mixing time and independent parameters, measurements of the bulk void fraction, bubble size, and rise velocity were acquired. Effect of vibration frequency and amplitude on mixing time was investigated independently. In a bubble swarm, mixing was observed to occur via capture and transport in the bubble wake and via direct interaction of bubble induced liquid agitations with the dye. The mixing performance of the bubble swarm will be presented and compared with and without vibration while matching the specific input power.