Flow visualization on the linear compressor cascade endwall using oil flows and laser Doppler anemometry

Surface oil flow visualizations were conducted in the VPI&SU Department of AOE Low Speed Linear Cascade Wind Tunnel on the endwall. Oil flow visualizations of the endwall flow features (passage flow, cross flow and tip leakage vortex) for tip gap to chord ratios ( t / c ) of 1.65% and 3.3% are discussed in detail. For the first time, quantitative comparisons are made between the oil-flow direction and the wall shear stress direction obtained from laser Doppler anemometer experimental results. The oil flow streaks are aligned with the wall shear stress direction, except near separation, which is proved theoretically and experimentally. Wall shear stress directions in the oil-flow images are measured and the separation line in the oil flow is calibrated based on the skin friction results from the LDA measurement.