A 2-PHASE CINEMATIC PIV METHOD FOR BUBBLY FLOWS

A cinematic particle image velocimeter (PIV) for measurement of time v arying fields in two-phase flow is described. This system has the capa bility to track detailed characteristics of individual bubbles moving through a turbulent flow field, e.g., size, shape, velocity, and accel eration, and simultaneously to measure the instantaneous fluid velocit y field on a two-dimensional plane. The system employs an argon-ion la ser, a rotating polygonal mirror and a single 35 mm movie camera. Two features of this technique are the ability to capture bubble trajector ies 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 di ameter can be deduced. The instrument is evaluated in an experiment on the dispersion of nominally 3.5 mm diameter bubbles from a point sour ce in a two stream, turbulent, planar free-shear layer. Characteristic s of the fluid field and the bubble motion are described.