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|Title : CONSTRAINED SIMULATION OF CRITICAL WIND SPEED GUSTS BY MEANS OF WAVELETS
Authors : Gunner Chr. Larsen, Kurt S. Hansen, and Bo Juul Pedersen
For most structures exposed to wind loading, extreme response is associated with extreme wind
speeds. However for wind turbines - especially for pitch regulated wind turbines - the design driving thrust loading is
often associated with severe wind gust situations occurring during normal operation and these are thus related to the
mean wind speed regime [5m/s; 25m/s].
Based on knowledge on the load response characteristic of the wind turbine (in terms of aerodynamics and pitch
action) it is possible to identify a general critical mean gust shape that may potentially result in ultimate thrust loading.
In the IEC 61400-1 design code, this particular load case is defined as Extreme Operational Gust (EOG). This
(coherent deterministic) gust has a characteristic “Mexican hat” shape with prescribed time extend and magnitude. The
time constant depends on the return period of the extreme wind speed gusts, whereas the magnitude depends on the
return period as well as the mean wind speed.
The present paper presents a rational method to calibrate the wind speed gust magnitudes specified in the IEC
61400-1 code. The method combines a wavelet expansion with extreme statistics and results in consistent estimates of
wind speed gust magnitudes for arbitrary return period, mean wind speed and gust time scale. In addition the method
offers to embed the resulting extreme wind gust consistently in a (coherent) stochastic wind field.
Based on measured data, extracted from “Database on Wind Characteristics” (http://www.winddata.com/), the
method has been applied to estimate the magnitudes of wind speed gusts with similar shape, time extend and return
period as the gusts specified in the IEC 61400-1 code.
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