On sonic anemometer measurement theory

Cuerva Tejero, Alvaro and Sanz Andres, Angel Pedro (2000). On sonic anemometer measurement theory. "Journal of Wind Engineering and Industrial Aerodynamics", v. 88 (n. 1); pp. 25-55. ISSN 0167-6105.


Title: On sonic anemometer measurement theory
  • Cuerva Tejero, Alvaro
  • Sanz Andres, Angel Pedro
Item Type: Article
Título de Revista/Publicación: Journal of Wind Engineering and Industrial Aerodynamics
Date: 2000
Volume: 88
Faculty: E.T.S.I. Aeronáuticos (UPM)
Department: Vehículos Aeroespaciales [hasta 2014]
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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In this paper a model for the measuring process of sonic anemometers (ultrasound pulse based) is presented. The differential equations that describe the travel of ultrasound pulses are solved in the general case of non-steady, non-uniform atmospheric flow field. The concepts of instantaneous line-average and travelling pulse-referenced average are established and employed to explain and calculate the differences between the measured turbulent speed (travelling pulse-referenced average) and the line-averaged one. The limit k1l=1 established by Kaimal in 1968, as the maximum value which permits the neglect of the influence of the sonic measuring process on the measurement of turbulent components is reviewed here. Three particular measurement cases are analysed: A non-steady, uniform flow speed field, a steady, non-uniform flow speed field and finally an atmospheric flow speed field. In the first case, for a harmonic time-dependent flow field, Mach number, M (flow speed to sound speed ratio) and time delay between pulses have revealed themselves to be important parameters in the behaviour of sonic anemometers, within the range of operation. The second case demonstrates how the spatial non-uniformity of the flow speed field leads to an influence of the finite transit time of the pulses (M≠0) even in the absence of non-steady behaviour of the wind speed. In the last case, a model of the influence of the sonic anemometer processes on the measurement of wind speed spectral characteristics is presented. The new solution is compared to the line-averaging models existing in the literature. Mach number and time delay significantly distort the measurement in the normal operational range. Classical line averaging solutions are recovered when Mach number and time delay between pulses go to zero in the new proposed model. The results obtained from the mathematical model have been applied to the calculation of errors in different configurations of practical interest, such as an anemometer located on a meteorological mast and the transfer function of a sensor in an atmospheric wind. The expressions obtained can be also applied to determine the quality requirements of the flow in a wind tunnel used for ultrasonic anemometer calibrations.

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Item ID: 39886
DC Identifier: http://oa.upm.es/39886/
OAI Identifier: oai:oa.upm.es:39886
Deposited by: Biblioteca ETSI Aeronauticos
Deposited on: 11 Apr 2016 11:55
Last Modified: 11 Apr 2016 11:55
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