Vorticity Measurements Using Calibrated Vane-Vorticity Indicators and Cross-Wires

Abstract

Vane-type vorticity indicators of various sizes have been constructed, calibrated, and used for direct and rapid measurement of local mean streamwise vorticity in several swirling flows. The dependence of the calibration factor, which relates the vane rotational speed to the local angular velocity of the fluid, on the trees (ream velocity, the fluid rotational speed, and the transverse vorticity gradient was determined. When the vanes were calibrated carefully and checked and maintained regularly, good agreement was achieved with vorticity profiles obtained using cross-wire data. Otherwise, a vane could be used only to give an indication of vorticity. Nomenclature Nj- = angular velocity of the fluid, rpm Nv = angular velocity of the vane-vorticity indicator, rpm r = radial distance measured from the center of the test section Ux = freestream mean velocity W — vertical velocity in the fluid normal to the streamwise direction x - axial or streamwise distance y = lateral distance normal to streamwise direction and measured from the center of the test section z = vertical distance normal to streamwise direction and measured from the center of the test section a = half-angle setting between the airfoils rj = vane indicator ratio T = delay time in autocorrelation function Qv = vorticity in the streamwise direction