Jets in crossflow - Scalar mixing via PLIF

The scalar concentration field of the round jet in a uniform crossflow is studied for a range of jet to crossflow velocity ratios; r, with emphasis on r = 10 and 20, using planar laser-induced fluorescence (PLIF) of acetone. For a top-hat jet exit velocity profile, the emerging presence of jet fluid in the wake structures is seen for for r > 10. The near-field region is characterized by a centerline concentration decay Of s(-1.3), an. improvement over the mixing rate s(-1) of the free jet. The far-field is marked by a branching away from the s(-1.3) decay and approaching a decay of s(-2/3) a rate derived from modelling efforts. When normalized by r(2)d, the branch points occur at a uniform jet position, x/r(2)d similar to 0.2. The view of the branch points as points of transition in the flow is reinforced by the probability density function (pdf) results along the upper edge of the jet.