Jets in Crossflow - Scalar Mixing via PLIf

摘要

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~2d, the branch points occur at a uniform jet position, x/r~2d ～ 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.