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Prof. Dr. sc. techn. Klaus Thiele
Technische Universität Braunschweig Institut für Stahlbau Beethovenstraße 51 Braunschweig Germany sekretariat@is.tu-braunschweig.de www.is.tu-braunschweig.de
20 Years of Wind Measurements in Germany
Results and Future Developments
M. Clobes, T. Höbbel, K. Thiele
Institut für Stahlbau, Technische Universität Braunschweig, Deutschland
Wind loading is a relevant issue in the design of high and slen-der steel structures. Due to this fact since 1989, the Institute of Steel Structures at Braunschweig University has been op-erating a data acquisition system on a 344 m high guyed mast called Gartow II, which is owned by Deutsche Telekom AG. The guyed mast is located in the north of Germany at 53°03´55´´N, 11°26´33´´E and was formerly used as a directional radio an-tenna for broadcasting phone calls to West Berlin. This measur-ing system is one of the best equipped worldwide and provides the possibility to get an inside view of the wind’s structure. With the installed equipment it is possible to measure wind ve-locities and directions from a height of 30 m above the ground, with a vertical distance of 18 m up to a height of 341 m. For measuring meteorological data, 14 cup anemometers, four pro-peller anemometers, four ultrasonic anemometers, seven wind vanes, and four PT-100 temperature sensors are installed. The wind sensors are located on the western side of the mast shaft and are mounted on 7.5 m long stayed cantilevers. In addition the mast’s response is measured with 17 strain gauges, five ac-celerometers and 32 force sensors.
In this paper the equipment for the measuring of wind flow is presented and an overview of the measured data and their analysis from the past two decades is presented. The meas-ured data is compared with theoretical and empirical models
for the height dependent wind speed and turbulence intensi-ty profiles. In addition measured time series of wind speed are analysed with respect to their statistical characteristics using correlation- and coherence functions.
Using Hellmann’s power law for the description of the mean wind speed profile, the profile exponent shows a large scat-ter and is dependent from absolute wind velocity. Scatscat-ter re-duces for higher wind velocities, the profile exponent fits to the on-site topography. Compared to the log-law profile the Hellmann’s law is adequate for heights up to 350 m. For low wind velocities, the wind speed profile can differ significant-ly from the power law profile. Thus wind speed profile shapes have been identified and sorted to six classes using a neural network.
It can be shown that the distribution of the turbulent energy can be described well using the von Kármán-spectra for the longi-tudinal and for the lateral velocity component respectively. Co-herence functions are very much dependent on the numerical evaluation process.
At the moment, the mast is being equipped with 48 addition-al Ultrasonic-Anemometers, fixed on the guy-cables. This up-grading of the measuring equipment will allow for 3D meas-urement and analysis of the wind flow. The measuring concept and technical details will be presented in the paper.
