Combined PIV/PTV-measurements for the analysis of bubble interactions and coalescence in a turbulent flow

In order to allow more reliable modeling of coalescence processes in turbulent bubbly flows, detailed experiments in a double loop reactor were performed. Narrow and essentially monomodal bubble size distributions in the range of 2 to 4 mm were created. For simultaneous measurements of bubble size, bubble velocity and liquid velocity a combined system of PIV and PTV was developed and applied. It was possible to determine bubble size distributions and mean, as well as fluctuating velocities for both phases. The spatial changes of the bubble size distribution, due to the influence of bubble coalescence, was analyzed and coalescence rates were calculated.