PIV in two-phase flows: Simultaneous bubble sizing and liquid velocity measurements

A two-phase measurement technique based on the simultaneous sizing of the dispersed phase and PIV measurement of the continuous phase is presented. The referred technique has been applied to study the formation of bubbles, when air is injected into quiescent water through a single needle. The efficient application of the PIV technique to measure the liquid velocity field in bubbly flows is based on the use of fluorescent tracers combined with optical filters. Strong optical effects at the air/water interface limit the use of the PIV image for the accurate determination of the bubble contour. Therefore, a supplementary CCD-camera acquires simultaneously the bubble shadow images. The results show the evolution of the liquid velocity field around a growing bubble during its formation cycle, as well as a comparison between the PIV measurements in the vicinity of the bubble interface and the theoretical predictions using a potential flow solution.