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N. E. Busch and L. Kristensen

Abstract

Statistical considerations are applied to a general equation of motion for cup anemometers in a turbulent wind. It is shown that the relative overspeeding ΔS/S can be expressed as ΔS/S = Ih2 · Js(l0s) + cIw2, where Is and Iw are the horizontal and the vertical turbulence intensifies, respectively. The function Js depends on the shape of the spectrum of horizontal turbulent energy, l 0 is the distance constant for the anemometer, and Λs is a characteristic length scale of the horizontal turbulence. The constant c is of order unity.

If Λs is suitably chosen as the scale of the energy-containing eddies, then Js is satisfactorily approximated by Js = (1 + Λs/l 0)−1 in most atmospheric applications.

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N. E. Busch, R. M. Brown, and J. A. Frizzola

Abstract

The response characteristics obtained through wind tunnel tests of the Brookhaven National Laboratory bivane are presented and used in correcting the measured values of (ω′2/u*2), the variance of the vertical wind velocity fluctuations normalized by the square of the friction velocity. In neutral through unstable atmospheres the corrected values appear to be independent of thermal stability and height of observation, except for extreme instability at heights >46 m. The average value based on measurements at heights of 23, 46 and 92 m is 1.48 with a standard deviation of 0.38.

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