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Master of Wind Energy
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MSc in Wind Energy


EWEM
European Wind Energy Master


Danish Center for Computational Wind Turbine Aerodynamics and Atmospheric Turbulence

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Title : Validity of the Assumption of Gaussian Turbulence
Authors : Morten Nielsen, Jørgen Højstrup, Kurt S Hansen, and Leo Thesbjerg

Summary :
Wind turbines are designed to withstand the impact of the turbulent wind, which usually is modelled as a Gaussian process. Based on a large number of measurements from many sites, this seems a reasonable assumption in flat homogeneous terrain, whereas it may fail in complex terrain. At these sites, the wind speed often has a skewed distribution with more frequent lulls than gusts. In order to simulate aerodynamic loads on wind turbine rotors, a numerical turbulence simulation method was developed and implemented in a user-friendly PC program (iGSIM). This program simulates multiple correlated time series of non-Gaussian variables without distorting the spectrum or coherence. The simulated time series were used as input to the dynamic-response simulation program Vestas Turbine Simulator (VTS). We simulated the dynamic response of systems exposed either Gaussian or extreme, yet realistic, non-Gaussian turbulence. Some of the equivalent fatigue load components, on turbines with active pitch regulation, were enhanced by up to 15% compared to purely Gaussian turbulence. The increased loads depend on the dynamic system, and it might be reduced by optimisation of the wind turbine regulation system after site-specific turbulence characteristics.

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