| 17 Dec 2025
Comparison of measured and simulated fatigue loads on a multi-megawatt wind turbine
Abstract. The Mann turbulence model is widely used in the design and certification of multi-megawatt wind turbines. However, these turbines operate in a region of the atmosphere where the model’s assumptions are violated. One of the most significant assumptions is that of neutral stability conditions, which raises concerns about the model's accuracy for load simulations. To investigate this, we compare fatigue loads measured on a 15 MW wind turbine with simulations performed using an aeroelastic solver. The inflow was characterized using data from a meteorological mast equipped with sonic and cup anemometers. The turbulence model was fitted to measurements of auto-spectra under varying wind speeds and stability conditions, while the vertical profile of wind speed was represented by a power law. The resulting wind fields were then used as input to the aeroelastic simulations.
We first present a comparison of measured fatigue loads on the tower and blades across different atmospheric stability regimes. The difference in loads between unstable and stable conditions was found to be 98 % for the tower and 20 % for the blades, underscoring the importance of accounting for atmospheric stability in wind turbine siting and load verification campaigns. A subsequent comparison of measurements and simulations revealed that loads from the two sources tend to fall within three standard deviations of each other, even under non-neutral stability conditions. However, the simulated fatigue loads on the tower were overestimated by a margin of five standard deviations under some stable conditions, likely due to incorrect predictions of the spectral coherence made by the turbulence model. Shear extrapolation based on the power law might also lead to overestimation of blade loads in the simulations.
These results indicate that, despite its simplifying assumptions, the Mann model when fitted to measurements of turbulence auto-spectra, does not introduce significant errors in fatigue load simulations for solitary multi-megawatt wind turbines.
Competing interests: One of the authors is a chief editor in Wind Energy Science. Two of the authors are employed by Vestas Wind Systems A/S.
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