PIV study of the Influence of Large Scale Streamwise Vortices on a Turbulent Boundary Layer

Vortex generator jets were used to generate large-scale longitudinal vortices embedded in a flat-plate turbulent boundary layer. The investigation was performed in a water tunnel, measuring instantaneous flow fields in planes parallel and normal to the flat plate, using particle image velocimetry. The objective of the research was to observe the response of near-wall turbulence to the imposed perturbing flow. It was shown that a small-amplitude forcing vortical flow had significant influence on the mean and fluctuating velocity profiles. Moreover, particle image velocimetry permitted speculation upon the behaviour of the wall velocity streaks under the action of the perturbing vortical flow.