Ring wire anemometer. I - Calibrations and cooling laws. II - Measurement of small-scale turbulence

A hot-wire anemometer probe with a circular shape, developed for measuring the magnitude of the instantaneous velocity vector, is described. The ring- wire probe relies on the same hot-wire anemometry technique as the straight wire, with similar heat transfer laws and frequency transfer functions. The theoretical cooling law and the calibration curves showed that a ring wire is less sensitive to the lateral components of the velocity, i.e., less sensitive to positioning errors than the straight-wire anemometers. The ring-wire probe was applied for measurements of higher-order statistics in turbulent flows, i.e., the statistics of the higher wave-number microstructures in the dissipative scale range. The ring wire was shown to have a much higher sensitivity and frequency response than the straight wire of similar spatial resolution. (I.S.)