A COMPARISON OF TURBULENCE LEVELS FROM PIV AND CTA DOWNSTREAM OF A LOW-PRESSURE TURBINE CASCADE AT HIGH-SPEED FLOW CONDITIONS

The development and verification of new turbulence models for RANS equations based numerical methods require reliable experimental data with a deep understanding of the underlying turbulence mechanisms. High accurate turbulence measurements are normally limited to simplified test cases under optimal experimental conditions. This work presents comprehensive three-dimensional data of turbulent flow quantities, comparing advanced constant temperature anemometry (CTA) and stereoscopic particle image velocimetry (PIV) methods under realistic test conditions. The experiments are conducted downstream of a linear, low-pressure turbine cascade at engine relevant high speed operating conditions. The special combination of high subsonic Mach and low Reynolds number results in a low density test environment, challenging for all applied measurement techniques. Detailed discussions about influences affecting the measured result for each specific measuring technique is given. The presented time mean fields, as well as total turbulence data demonstrate with an average deviation of Delta Tu < 0.4% and Delta C/C-ref < 0.9% an extraordinary good agreement between the results from the triple sensor hot-wire probe and the 2D3C-PIV setup. Most differences between PIV and CTA can be explained by the finite probe size and individual geometry.