Three-Dimensional Wake of Nonconventional Vortex Generators

Abstract

The wakes of wishbone, doublet, and ramp-type vortex generators (VGs) were investigated. The VGs were placed in the thin laminar boundary layer of a flat plate at a Reynolds number of 930 based on the freestream velocity and VG height. The turbulence statistics of the wake were measured with high spatial resolution using planar particle image velocimetry (PIV) and stereoscopic PIV. Three-dimensional time-resolved tomographic PIV was also carried out to visualize the evolution of vortices. The fastest recovery of the wake deficit was observed for the wishbone VG. The peak of turbulence production in the wake of the wishbone and doublet VGs had a similar magnitude and was 1.5 times stronger than that of the ramp VG. The hairpin vortices generated by the ramp VG formed the largest percentage of the wake turbulent kinetic energy, and their size is about half of the hairpins produced by the wishbone and doublet VGs. The wishbone and ramp VGs had the best overall performance. The wishbone VG generated the strongest mixing in the wake region, whereas the ramp VG had the smallest drag coefficient. The doublet VG had the weakest overall performance due to low mixing and the largest drag.