An Lda Study Of Longitudinal Vortices Embedded In A Turbulent Boundary Layer

A three-component Laser Doppler Anemometry (LDA) system was used to investigate the complex flow field generated by vortex generator jets in a turbulent boundary layer. The prominent feature of the flow is longitudinal vortices embedded in the boundary layer. The study was performed in a 3:5m \Theta 2:6m low speed wind tunnel. The non-intrusive measurement technique allows for reliable and accurate measurement of the velocity and turbulent stress field. Data obtained include timeaveraged velocity and turbulent stress distributions on cross planes downstream of the jet exit. It was found that (i) the flow field of the longitudinal vortex generated by a rectangular jet is significantly different from that generated by a round jet in the magnitude of the cross velocity, but quite similar to that generated by a solid vortex generator; (ii) a strong injection flow from the surface between two contra-- rotating longitudinal vortices generated by a row of contra--rotating jets can be observed..