Unsteady Turbine Blade Wake Characteristics

The paper presents an experimental investigation of large coherent structures, commonly referred to as “von Karman vortex street,” in the wake of a turbine blade at high subsonic Mach number M2,is=0.79 and high Reynolds number (RE=2.8×106 and their effect on the steady and unsteady pressure and temperature distribution in the wake. Ultra short smoke visualizations and two interferometric measurement techniques, holographic interferometry and white light differential interferometry provide insight into the vortex formation and shedding process. In addition, the interferometric measurement provides quantitative information on the stream wise evolution of the minimum density associated with the vortices and on their lateral spreading. Wake traverses are performed with a four-head fork probe carrying a Kiel probe and a fast response Kulite pressure probe for pressure measurements and a thermocouple probe and a cold wire resistance probe for temperature measurements. The results confirm the observation of energy separation in the wake as found by other researchers. The experimental data are a unique source for the validation of unsteady Navier-Stokes codes.