Planar Laser Induced Fluorescence Experiments and Modeling Study of Jets in Crossflow

Abstract

Planar laserinduced fluorescence (PLIF) with acetone seeding was applied to measure the scalar fields of an axisymmetric freejet and an inclined jet in crossflow as applicable to film cooling. From the scalar fields, jetmixing and trajectory characteristics were obtained. In order to validate the technique, the canonical example of a nonreacting freejet of Reynolds numbers 900–9000 was investigated. Desired structural characteristics were observed and showed strong agreement with computational modeling. After validating the technique with the axisymmetric jet, the jet in crossflow was tested with various velocity ratios and jet injection angles. Results indicated the degree of wall separation for different injection angles and demonstrated both the timeaveraged trajectories as well as select nearwall concentration results for varying jet momentum fluxes. Consistent with literature findings, the orthogonal jet trajectory for varying blowing ratios collapsed when scaled by the jettofreestream velocity ratio and hole diameter, rd. Similar collapsing was demonstrated in the cases of a nonorthogonal jets. Computational fluid dynamic (CFD) simulations using the openfoam software were used to compare predictions with select experimental cases and yielded reasonable agreement. Insight into the importance and structure of the counterrotating vortex pair (CVP) and general flow field turbulence was highlighted by cross validation between CFD and experimental results.