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Development and prediction of scour around offshore wind turbine monopile foundations in ebb and flow tides

Lookup NU author(s): Fei Geng, Dr Wenxian YangORCiD, Dr Sadegh NadimiORCiD, Professor Zhiqiang Hu

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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).


Abstract

© 2024 The Authors. Monopile foundations are commonly used to support offshore wind turbines (OWTs) in nearshore shallow waters, where the periodic ebb and flow of tides can cause severe seabed erosion around these foundations. Accurately predicting the progression of scour depth under these tidal conditions is crucial for the safety of OWTs. While a few empirical formulas for equilibrium scour depth in periodic tides have been proposed, they often overlook the backfilling effects during their derivation. Consequently, these methods fail to predict the progression of scour depth characterized by recurring scouring and backfilling processes. In this study, the scour progression under different tidal patterns, including square tides, symmetrical sinusoidal tides, and asymmetrical sinusoidal tides with various periods, is investigated using numerical methods. It is indicated by the results that deeper scour depths are produced by symmetrical tides compared to asymmetrical tides, while the highest scour depth is observed under square tides, potentially slightly exceeding that under unidirectional currents. Additionally, asymmetric scour depths at the front and back sides of the pile can result from the asymmetry of tides. Although scour progression is affected by tide periods, their impact on the equilibrium scour depth is limited. Furthermore, a new concept called normalized cumulative effective flow intensity is introduced, which plays a primary role in governing equilibrium scour depth. Based on this concept, prediction methods for both equilibrium scour depth and scour progression under sinusoidal tides, which closely resemble natural tidal patterns, are proposed. The accuracy of these methods is validated by experimental data from previous studies. These findings not only provide a method to optimize the design of monopile burial depth but also aid in the development of appropriate maintenance measures to prevent scour-induced damage to OWT foundations over their long lifespans.


Publication metadata

Author(s): Geng F, Yang W, Nadimi S, Hu Z

Publication type: Article

Publication status: Published

Journal: Ocean Engineering

Year: 2024

Volume: 311

Issue: Part 2

Print publication date: 01/11/2024

Online publication date: 17/08/2024

Acceptance date: 03/08/2024

Date deposited: 28/08/2024

ISSN (print): 0029-8018

ISSN (electronic): 1873-5258

Publisher: Elsevier Ltd

URL: https://doi.org/10.1016/j.oceaneng.2024.118905

DOI: 10.1016/j.oceaneng.2024.118905


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Funding

Funder referenceFunder name
China Scholarship Council (CSC): 202106220076

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