Experimental and Large-Eddy Simulation Studies on Three-Dimensional Vortices Produced by an Impinging Transverse Jet

Abstract

The flow pattern and entrainment feature of highly three-dimensional vortices produced by an impinging jet in crossflow were investigated by means of LIF flow visualization, PIV measurement and LES computation. The distinctive vortex modes of the slightly skewed jet shear layer in the proximal region close to jet nozzle are identified mainly depending upon the velocity ratio between the jet and crossflow, namely changing from approximately axisymmetric mode to helical mode with the decreasing velocity ratios varying from 20 to 8. In the case of intense jet impingement upon the wall, the scarf vortex wrapped around the impinging jet in near-wall region is well reproduced showing somewhat asymmetry in respect of its bilateral spiral legs within near region. In addition, the entrainment of the ambient crossflow fluid by the scarf vortex occurs in large part on the surface of the spiral roller structures of itself due to the presence of smaller and unorganized eddies.