Transonic Cascade Measurements to Support Analytical Modeling

Turbulence measurements were made in a transonic turbine cascade using PIV in a unique two-passage model consisting of a single full blade and two shaped outer walls. The outer wall shapes were prescribed using an inverse design procedure that gave the correct infinite-cascade pressure and mean velocity distribution around the blade. The outer surfaces of the curved walls were shaped to steer a laser sheet to provide uniform illumination for the PIV. The PIV measurements were performed over a large number of small domains providing excellent spatial resolution over most of the flow field. Measurements in the free stream above the blade boundary layers showed that the absolute magnitude of the turbulent stresses changed little through the strong acceleration and curvature. This means that the relative turbulence intensity falls rapidly as the flow accelerates through the cascade. Detailed comparison to various turbulence models is underway.