On the role of longitudinal vortices in turbulent flow over a curved surface

Experiments were conducted in two turbulent flows with streamline curvature, a convex wall-jet and a concave boundary layer. Two-point spatial crosscorrelation measurements separated in the spanwise direction clearly reveal the existence of large-scale longitudinal vortices in both experiments. Vortex generators (VGs) were used to enhance the streamwise vortices. The streamwise development of spanwise wavelength indicates these structures are related to the centrifugal or Görtler-type instability caused by the curvature. Surface pressure measurements show the vortices influence flow separation, which has implications for the future development of strategies for separation control and mixing enhancement.