Ring wire anemometer—Part II: Measurement of small‐scale turbulence

The ring wire, a circular hot‐wire anemometer probe, orientated normal to the flow, is useful to measure turbulent scales in the dissipative range. It is less sensitive to angular positioning errors than straight wire sensors. Following the rationale of Wyngaard [J. Phys. E. 52, 1, 1105 (1968)], theoretical expressions are derived for the high wave number attenuation due to spatial resolution (line averaging). The expressions are applied to the estimation of longitudinal velocity spectrum and dissipation rate. The ring wire is shown to present much smaller attenuations than the straight wire of the same length or, inversely, to have a much higher sensitivity and frequency response than the straight wire of similar spatial resolution. The theoretical results are confirmed by experimental data.