TURBULENCE MEASUREMENTS FOR A LONGITUDINAL VORTEX INTERACTING WITH A 3-DIMENSIONAL TURBULENT BOUNDARY-LAYER

Turbulence measurements are reported for the case of a longitudinal vortex embedded in a pressure-driven, three-dimensional boundary layer. Previous measurements have shown that the distributed longitudinal vorticity of the three-dimensional boundary layer has a major effect on the mean flow development. The present measurements show that the turbulence development is very sensitive to the sign of the vortex. For one sign, the vortex-induced perturbation in the turbulence field decays quickly while for the opposite case the disturbance continues to grow producing high levels of turbulence kinetic energy and shear stress. This is caused by a strong velocity gradient in the outer part of the boundary layer. Generally, the structural parameter a1 is suppressed below conventional boundary-layer levels.