Dynamic response of novel floating wind turbine to freak waves during uninterrupted operation

Huiwen Meng, Yongqian Liu, De Tian, Kai Long, Zhang Han, Yi Su and Ke Sun

Renewable Energy, 2025, vol. 239, issue C

Abstract: This study focuses on the dynamic responses of a novel 15 MW deep-sea Floating Offshore Wind Turbine (FOWT) equipped with a specific heave plate and low-ballast (SHLB) to freak waves while in operation. To gain a more comprehensive understanding of the impact of freak waves on FOWTs, a three-column wave superposition model is employed to simulate abnormal waves. A fully coupled time-domain model of the innovative 15 MW semi-submersible FOWT is developed utilizing the FAST code. The transient dynamic performance of the FOWT is evaluated under both random and freak waves. The analysis covers foundation motion, blade and tower force, nacelle acceleration, and fairlead tension, among other responses. Based on this, wavelet analysis is applied to explore the time-frequency properties of freak waves as opposed to random waves. Furthermore, the effects of freak wave incidence angle and wind speed fluctuations on wind turbine operational efficacy are analyzed. The results unequivocally indicate that the peak responses in the impact zones across various components increase under freak waves. Freak waves exacerbate the maximum foundation motion, particularly in heave, surge, and pitch, and produce a shift in the high-frequency energy core of the wavelet transform. Fairlead tension is greatly raised due to surge amplification. The impact of freak waves generates a dramatic rise in nacelle axial acceleration. Moreover, under freak wave conditions, variations in wind speed have no discernible effect on the foundation motion excitation at the wave frequency but exhibit enhanced responses in the wind energy and natural frequency ranges. Wind speed predominantly affects the blade response, exerting minimal influence on tower base loads. The peaks of the foundation and blade follow a similar pattern in cases of wind-wave misalignment, whereas the tower differs slightly, with all responses reaching a maximum at 0°. These findings are significant in providing guidelines for the safe design and failure analysis of ultra-large FOWTs.

Keywords: Floating offshore wind turbine; Freak wave; Fully-coupled analysis; 15 MW-Novel foundation; Wavelet analysis (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:renene:v:239:y:2025:i:c:s0960148124020524

DOI: 10.1016/j.renene.2024.121984

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