Encounters with Vortices in a Turbine Nozzle Passage

Experiments were conducted on the flow through a transonic turbine cascade. A wide range of vortices was encountered including horseshoe vortices, secondary flows, shock-induced passage vortices and streamwise vortices on the suction surface. In the separation region on the suction surface, a large roll-up of passage vorticity occurred. The blunt leading edge gave rise to strong horseshoe vortices and secondary flows. The suction surface had a strong convex curvature over the forward portion and was quite flat further downstream. Surface flow visualization was performed and this convex surface displayed coherent streamwise vorticity. At subsonic speeds strong von Kármán vortex shedding resulted in a substantial base pressure deficit. For these conditions time-resolved measurements were made of Eckert-Weise energy separation in the blade wake. At transonic speeds, exotic shedding modes were observed. These phenomena all occurred in experiments on the flow around one particular turbine nozzle vane in a linear cascade.