A two-phase cinematic PIV method for bubbly flows

A cinematic particle image velocimeter (PIV) for measurement of time varying fields in two-phase flow is described. This system has the capability to track detailed characteristics of individual bubbles moving through a turbulent flow field, e.g., size, shape, velocity, and acceleration, and simultaneously to measure the instantaneous fluid velocity field on a two-dimensional plane. The system employs an argon-ion laser, a rotating polygonal mirror and a single 35 mm movie camera. Two features of this technique are the ability to capture bubble trajectories for long periods of time and the use of bubble images which appear as two fine point images for each instant, from which centroid and diameter can be deduced. The instrument is evaluated in an experiment on the dispersion of nominally 3.5 mm diameter bubbles from a point source in a two stream, turbulent, planar free-shear layer. Characteristics of the fluid field and the bubble motion are described.