THE YAW RESPONSE OF HOT-WIRE PROBES AT ULTRA-LOW WIND SPEEDS

Measurements of effective angles of crossed hot-wire probes to determi ne their efficacy for characterizing turbulence, particularly the vert ical component and shear stress, in a boundary layer with mean wind sp eeds in the range 0.33 m s(-1) have been made. These results suggest t hat the effective angles change markedly at low wind speeds, but prope r calibrations and application of effective angles which are functions of the wind speed, although tedious, will yield results comparable to those from a laser-Doppler anemometer (LDA).