Bubble Motion in the Linear Shear Flow.

Abstract

The objective of the present study is to obtain fundamental knowledge of the influence of the lift force on the bubble and its motion induced by the surrounding flow field. We explored the flow structure in the vicinity of the bubble and also deformation of the bubble shape respectively by PIV/LIF and a projecting technique. As our system, we chose a single air bubble with an equivalent bubble diameter (Deq) 1∼8 mm, in a vertical shear flow. Velocity measurements were made using one digital high-speed CCD camera for Digital Paricle Image Velocimetry (DPIV) with fluorescent tracer particles. The recorded image data are analyzed by cross-correlation technique. A second CCD camera was used to detect the bubble's shape and translational motion via backlighting from a square array of infrared LEDs. We confirmed that the bubble deformation and surrounding flow induced lateral force on bubble. We proposed the lateral force parameter αr which consisted of the relative velocity of the bubble and the circulation around the flow structure in the vicinity of the bubble measured by PIV/LIF. Bubble motion can be estimated by αr with the phase which depends on the circulation around the bubble.