2pPAb8. Measurements of wind turbulence spectra near ground and implications for sound propagation calculation.

Session: Tuesday Afternoon, May 14

Time: 3:15

Author: Michael R. Stinson
Author: Gilles A. Daigle
Author: David I. Havelock
Location: Inst. for Microstructural Sciences, Natl. Res. Council, Ottawa, ON K1A 0R6, Canada


Measurements of horizontal wind speed variations have been made at a local airfield using three different techniques and the resulting power spectra compared. The instruments used were a rotating three-cup anemometer, a sonic anemometer, and a hot-wire anemometer. The instrument sampling rates and frequency responses lead to upper frequency limits for the spectra of 0.5, 10, and at least 100 Hz, respectively. Good agreement was obtained between the techniques for those frequencies where they overlap. Knowledge of the shape of the turbulence spectrum is necessary for the incorporation of turbulence scattering into outdoor sound propagation calculations. The observed spectra tend to vary with frequency f as f[sup -5/3] over the range 0.001 to 100 Hz (corresponding to turbulence length scales between 5000 and 0.05 m, for a mean wind speed of 5 m/s) although there are significant deviations from this simple dependence. The observed results are consistent with the analysis of Hojstrup [J. Atmos. Sci. 39, 2239--2248 (1982)].

from ASA 131st Meeting, Indianapolis, May 1996