Drag and lift forces on microscopic bubbles entrained by a vortex

The forces that act on bubbles as they are entrained by a vortex are measured using particle image velocimetry. Triple exposure images are used to measure the velocity and acceleration of the fluid and the bubbles simultaneously. Distinction between phases is achieved by using fluorescent particles as liquid flow tracers. The buoyancy, pressure, and inertia forces are computed from the data, while the drag and the lift forces are determined from a force balance on each bubble. It is found that in the present range of bubble diameters, 500 μm