SPIV investigations of correlation between streamwise vorticity and velocity in the wake of a vortex generator in a boundary layer

The current work describes the experimental parametric study of streamwise vortices generated in a boundary layer by a rectangular vane (commonly named vortex generator) mounted perpendicularly to the wall and at an angle to the oncoming flow. Stereoscopic Particle Image Velocimetry measurements have been conducted in cross-planes to obtain a full picture of the wake for each measured case. It is observed that this seemingly simple configuration produces a complicated vortex system consisting of 4 vortices: the tip vortex, a horseshoe vortex system consisting of two sleeves and a secondary vortex generated by the interaction between the tip vortex and the wall. Depending on the height and angle of the vane, some structures are enhanced and others are suppressed. Comparing the corresponding vorticity and velocity fields, a strong correlation between the two is found. Stream-wise vorticity induced velocity with the observed strong correlation found is not at all evident. This has previously been shown to be true for the primary (tip) vortex, but not for the remaining secondary structures.