The Effect of Turbulence on a Multi-Hole Pitot Calibration

Abstract- Accurate calibrations of multi-hole Pitot tubes require thousands of measurements spanning ranges of the fluid’s velocity, and the pitch and yaw angles. When calibrating a commercially-manufactured multi-hole Pitot tube in NIST’s low-turbulence wind tunnel, we found hysteresis in certain ranges of airspeed, pitch angle, and yaw angle. In the worst case, the hysteresis caused a calibration error of 30 %. We demonstrate that the hysteresis was caused by a flow instability associated with flow separation. A turbulence intensity of only 1 % removes the hysteresis; however, the calibration dependends on the turbulence intensity over the entire range of our measurements (0.25 % to 2 %). Therefore, multi-hole Pitot tubes should be calibrated and used at the same turbulence levels.