Robust Post-Processing Procedure for Multi-Hole Pressure Probes Available to Purchase

Aerodynamic probes have been extensively used in turbine performance measurements for over 60 years to provide flow direction and Mach numbers. In turbomachinery applications the absence of adequate optical access prevents the use of laser-Doppler-anemometry (LDA), laser-two-focus velocimetry, particle-image-velocimetry (PIV). Moreover, multi-hole pressure probes are more robust than hot-wire or hot-fiber probes, and less susceptible to gas contamination. The pressure readings are converted into flow direction using calibration maps. Some researchers tried to model theoretically or numerically the calibration map to speed up the process. Due to manufacturing abnormalities, experimental calibration is still essential. The calibration map is obtained in a wind tunnel varying the yaw and pitch angles, while recording the hole-pressures. With the advent of powerful computers, researchers introduced sophisticated techniques to process the calibration data. Depending on the geometry or manufacturing imperfections a conventional calibration map is distorted, with multiple crossings resulting in the inability to identify a unique flow direction. In the current paper, a new calibration and data processing procedure is introduced for multi-hole probe measurements. The new technique relies on a set of calibration data rather than a calibration map. The pressure readings from each hole are considered individually through a minimization algorithm. Hence, the new technique allows computing flow direction even when a hole is blocked during the test campaign. The new methodology is demonstrated in a five-hole probe including estimates on the uncertainty.