An investigation of the aerodynamic response of a wind anemometer

Abstract

An experimental investigation was made to determine the aerodynamic response of a wind anemometer to unsteady air loads. The anemometer, a perforated drag sphere mounted upon a cylindrical pedestal, sensed dynamic pressure by a strain gage balance system. The anemometer response was calibrated for static and dynamic mechanical inputs and for steady aerodynamic loads prior to the unsteady investigation. The unsteady environment was obtained in an oscillating flow wind tunnel which utilizes a rotating shutter valve to superimpose a harmonically varying velocity upon a mean free stream. For steady flow conditions the anemometer drag coefficient remained essentially constant, apparently independent of Reynolds number. The anemometer responded well to the unsteady air loads at frequencies up to 20 cycles per second and mean dynamic pressures to 8.85 pounds per square foot. Unsteady aerodynamic response was qualitatively substantiated by a quasi-steady approximation to the measured unsteady drag.