Reynolds Number Effects on the Calibration of a Subminiature Four Hole Three Dimensional Wake Probe

A subminiature four-hole probe is designed and fabricated to be used specifically to measure wakes that occur in turbomachinery and its components. The probe has a nominal measuring area of 0.413 mm² and has a nominal dimension of 0.254 mm in the direction across the wake downstream the trailing edge of a blade thus minimizing spatial and flow gradient errors in this direction. The non-nulling calibration of the probe is carried out in the pitch and yaw angle range of ±30° at 5° interval. The probe is calibrated at four different velocities, viz., 10 m/s, 20 m/s, 30 m/s and 50 m/s corresponding to the probe thickness Reynolds numbers in the range of 159 to 794 with objective of finding the effect of Reynolds number on the calibration coefficients. In addition to these, for practical importance the actual changes in yaw angle, pitch angle, static pressure, total pressure and velocity magnitude due to Reynolds number variation has been investigated. A method to incorporate the effect of Reynolds number for minimum interpolation errors is described.