Large Scale Experimental Study of the Scour Protection Damage Around a Monopile Foundation Under Combined Wave and Current Conditions

Minghao Wu,Carlos Emilio Arboleda Chavez,Leen De Vos,Peter Troch,Paulo Rosa-Santos,Tiago Fazeres-Ferradosa,Francisco Taveira-Pinto,Vasiliki Stratigaki

doi:10.3390/jmse8060417

Minghao Wu, Carlos Emilio Arboleda Chavez + Show 6 more

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https://doi.org/10.3390/jmse8060417

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Abstract

This paper presents a series of large-scale wave flume experiments on the scour protection damage around a monopile under combined waves and current conditions with model scales of 1:16.67 and 1:8.33. The main objective is to compare the damage data obtained from these large-scale models with existing monopile scour protection design approaches, which were proposed based on small scale wave flume experiments, and to study the applicability of the existing approaches. The static stability (onset of motion and bed shear stress) and the dynamic stability (three-dimensional damage numbers) of the scour protection are investigated. Both results show that the existing design approaches can be conservative when applied to large scale models, which highlights the need of further investigations on scale and model effects. In addition, this paper also analyses the scour protection damage depth. It is observed that damage depths of the scour protection layer under low Keulegan–Carpenter number (KC) conditions are smaller than predictions. The study provides valuable large scale experimental data for future research on the monopile scour protection design.

Highlights

Wind energy has become increasingly important over recent years as one of the primary sources of renewable energy
Based on the data acquired from the PROTEUS project, this paper aims to achieve three objectives: (1) To conduct a thorough data analysis regarding the damage to scour protections around a large scale monopile, (2) to check the applicability of using the state-of-the-art design approaches for large scale monopile scour protection, and (3) to analyze the damage depth of the scour protection layer based on the hydrodynamic conditions and the bed shear stresses
Regarding the scour protection of a monopile, various design approaches have been proposed based on small scale tests

Summary

Introduction

Wind energy has become increasingly important over recent years as one of the primary sources of renewable energy. As the technology developed rapidly, harvesting wind energy offshore is a reality and a very promising option with regard to the decreasing cost of installation. It is reported that the EU will invest 20 billion Euros in the wind energy market, of which 60% is aimed at offshore wind by 2030 [1]. The annual report of offshore wind in Europe [2] reveals that, by the end of 2019, new offshore wind installations hit a record of 3.6 GW. Due to the relatively low cost and easy construction procedure, monopile foundations are widely used in wind farms. The scour problem around the monopile foundation triggers engineering challenges [1]

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