An automated vorticity surveying system using a rotating hot-wire probe

A simple method is described whereby a standard `X´ hot-wire probe is used to obtain streamwise vorticity in a steady flow, while at the same time giving the mean flow velocity components, flow angles, and some turbulence data. The probe, with its measuring plane parallel to the probe axis, is rotated about this axis but with a small eccentricity so that the measuring plane is displaced slightly from the axis. Measurements are taken at four orientations of the probe at 90° intervals in order to define the tangential velocity along the four sides of a small square region in the plane perpendicular to the stream direction, from which vorticity is obtained directly. The rotating probe is combined with a two-axis traversing rig to produce an automated flow survey system, using a microcomputer to control all the measurement, data processing, and stepper motor drive functions. Results from flow surveys behind wing tips are presented and compared directly to results obtained with a nonaligning five-hole yawmeter vorticity survey system. These show the method proposed to give results of comparable quality, but with some advantages. These include the lower flow interference of the hot-wire probe and its faster response, which allows turbulence data to be obtained in parallel to the mean flow data