Technical note | Calibration of the DST Group Research Wind Tunnel Pressure Rings

Abstract

A calibration of the pressure rings in the DST Group Research Wind Tunnel was performed for an empty test section and with an elevated ground plane installed. This pressure ring system is similar in principle to the piezo-rings utilised in the DST Group Low Speed Wind Tunnel for calculating nominal test-section wind speed with a calibration factor. Calibration factors were obtained for both the empty test section and when the elevated ground plane is installed. It is found that the addition of the elevated ground plane changes the calibration factor significantly.

Executive Summary

The DST Group Research Wind Tunnel (RWT) has high- and low-pressure rings (i.e. circumferential pressure tappings) installed, similar in principle to the piezo-rings in the DST Group Low Speed Wind Tunnel (LSWT). The high-pressure ring is located before the wind tunnel contraction and the low-pressure ring after the contraction, where the average static pressure is lower than before the contraction. This pressure differential can be measured and calibrated to provide the average wind speed at a downstream station, thus obviating the need for a local wind speed measurement using an intrusive instrument such as a Pitot-static tube.

A calibration of the RWT pressure rings was carried out with a method similar to the LSWT piezo-ring calibration, for the cases of an empty test section and when an elevated ground plane is installed. A first order least-squares fit accounting for errors in both coordinates was used and a calibration constant obtained for each case. The uncertainties in measurements were assessed and found to be within acceptable limits. Thus, the calibration constants may be applied to the pressure ring data and ultimately used for determining wind speed in the RWT test section with or without the elevated ground plane, instead of relying on a pitot-static tube for wind speed measurements.