Preprints
https://doi.org/10.5194/wes-2023-149
https://doi.org/10.5194/wes-2023-149
18 Dec 2023
 | 18 Dec 2023
Status: a revised version of this preprint is currently under review for the journal WES.

Fatigue life evaluation of offshore wind turbines considering scour and passive structural control

Yu Cao, Ningyu Wu, Jigang Yang, Chao Chen, Ronghua Zhu, and Xugang Hua

Abstract. Offshore wind turbine (OWT) support structures are exposed to the risk of fatigue damages and scour, and this risk can be effectively mitigated by installing structural control devices such as tuned mass dampers (TMDs). However, time-varying scour altering OWTs’ dynamic characteristics has an impact on the TMD design and fatigue life, which was rarely studied before. In this paper, a simplified modal model was used to investigate the influence of scour and a TMD on the fatigue life evaluation of a 5 MW OWT’s support structure, and the parameters of the TMD were obtained by either a traditional method or a newly developed optimization technique. This optimization technique aims at finding optimal parameters of the TMD which maximizes the fatigue life of a hotspot at the mudline, and effect of time-varying scour can be considered. Results show that scour can decrease the fatigue life by about 26 %, and the TMD can effectively suppress vibration and increase the fatigue life. Further, it is found that the fatigue life can be extended by 7.2 % with the TMD optimized by the proposed optimization technique, compared to that with the traditionally optimized TMD which does not take the change of dynamic characteristics into account.

Yu Cao, Ningyu Wu, Jigang Yang, Chao Chen, Ronghua Zhu, and Xugang Hua

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wes-2023-149', Anonymous Referee #1, 21 Dec 2023
    • AC1: 'Reply on RC1', Chao Chen, 07 Feb 2024
  • RC2: 'Comment on wes-2023-149', Anonymous Referee #2, 05 Jan 2024
    • AC2: 'Reply on RC2', Chao Chen, 07 Feb 2024
Yu Cao, Ningyu Wu, Jigang Yang, Chao Chen, Ronghua Zhu, and Xugang Hua
Yu Cao, Ningyu Wu, Jigang Yang, Chao Chen, Ronghua Zhu, and Xugang Hua

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Short summary
This study investigates an offshore wind turbine support structure's fatigue life, by a rapid numerical model which considers the effect of scour and a tuned mass damper. An optimization technique is proposed to find the damper's optimal parameters, considering time-varying scour. Results show that scour makes the support structure more flexible. The damper optimized by the proposed optimization technique performs better than an initially designed damper in terms of fatigue life enhancement.
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