Bubble-Bubble Interaction Observed in a Swarm of Wall-Sliding Bubbles. 1st Report. Measurement of the Interaction Pattern using Particle Tracking Velocimetry.

The bubble-bubble interaction in a swarm of wall-sliding bubbles is experimentally investigated using an image processing measurement. At first, the drag coefficient of a vertically sliding bubble is measured for the range of Reynolds number from 2 to 9. Secondly, the two-dimensional pattern of the bubble-bubble interaction in a layer of wall sliding bubbles is detected by using particle tracking velocimetry (PTV). The evolution of relative coordinates and the relative velocity vectors of the bubbles are clarified by the statistical data analysis. Also, hydrodynamic mechanism of the bubble-bubble interaction is discussed with the present data comparing literatures on twin bubble interactions.