Scour mitigation measures around offshore wind structures using experimental models

Project Description:

Offshore wind infrastructure are frequently exposed to large wave and fast current conditions, which can result in erosion (scour) of mobile sediments where the foundation structure meets the seabed. The erosion and removal of sediment can expose part of the foundation and cause a reduction in the lateral load capacity of foundations. In extreme circumstances, this can result in the wind turbine being shutdown to prevent feedback mechanisms from causing damage to the structure itself.

To mitigate this effect, scour protection measures are often deployed around the base of foundation structures. These protection measures are designed to reduce sediment erosion; either by changing the flow pattern around the base of the structure to reduce the erosive effect of the flow or by stabilising the sediment substrate to effectively increase the threshold required for sediment entrainment. However, there are significant costs involved with such types of intervention and scour protection, therefore selecting the optimal form of protection and optimising the layout and extent for the specific offshore wind infrastructure is essential for managing the costs both of installation and operation.

In this project, we will compare different approaches to providing scour protection for different types of foundation, to quantify the performance and level of protection offered. In addition, the project will investigate potential changes in scour protection through the lifecycle of an offshore wind installation, focussing in particular on the potential failure mechanisms and the ease of decommissioning associated with different types of scour protection.

Testing will make use of both the experimental facilities at Hull University, and the purpose-built facilities at HR Wallingford.

Methodology

The PhD will use scaled experimental models to study both flow dynamics and sediment transport patterns associated with different approaches to scour reduction – particularly focusing on innovative solutions for scour protection such as artificially increased sediment cohesion and modifying flow around structures. The experimental studies will focus on reproducing extreme events to develop scour protection solutions that are cost-effective across a range of environmental conditions.

The PhD will make use of innovative new instrumentation, including Tomographic Particle Image Velocimetry to characterise the flow structure and to model how flow structures can be modified to reduce erosion and acoustic Doppler velocimetry to characterise flow in sediment laden flows with underwater laser scanning to quantify changes in seabed sediments.