Measurement of Three-Dimensional Unsteady Flows Using an Inexpensive Multiple Disk Probe

Abstract

A novel velocimeter consisting of multiple orthogonal disks fitted with pressure transducers has been developed. In such a velocimeter the pressure difference is measured between the center of each disk face and the center of its other face for each of the three orthogonal disks. The three components of fluid velocity can be deduced from the three measured pressure differences. While previously developed anemometers based on dynamic pressure differences (such as yawhead or five-hole probes) can only measure velocities with a small range of directions, the new disk probe can measure three components of velocity, even in highly three-dimensional flows where the approximate direction of the flow is not known. Previous work demonstrated that in steady flows the device could measure velocities to ±1.4% and angles to ±4°. In the present work, involving both field trials and wind tunnel tests, it is shown that the disk probe can measure three-dimensional unsteady flows with accuracy suitable for many meteorological applications. The disk probe tested has a flat frequency response up to 3 or 4 Hz and can measure velocity magnitudes with an accuracy of better than ±0.3 m s?1. Simple modifications to the disk probe would increase its frequency range to 10 Hz or better.