An Investigation of Factors Influencing the Calibration of 5-Hole Probes for 3-D Flow Measurements

Abstract

The effects of Reynolds number, Mach number and turbulence on the calibrations of commonly used types of 5-hole probe arc discussed. The majority of the probes were calibrated at the exit from a transonic nozzle over a range of Reynolds numbers (7x103 < 80x103 based on probe tip diameter) at subsonic and transonic Mach numbers. Additional information relating to the flow structure were obtained from a large scale, low speed wind tunnel. The results confirmed the existence of two distinct Reynolds number effects. Row separation around the probe head affects the calibrations at relatively low Reynolds numbers while changes in the detailed structure of the flow around the sensing holes affects the calibrations even when the probe is nulled. Compressibility is shown to have little influence upon the general behaviour of these probes in terms of Reynolds number sensitivity but turbulence can effect the reliability of probe calibrations at typical test Reynolds numbers.