HR Wallingford has completed a ten week project with Oxford University’s Department of Engineering and Science and E.ON as part of the research aiming to minimise the effects of scour on wind turbine foundations.
The project included examining different forms of scour protection to assure the stability of offshore wind turbine monopiles and to help identify which scour remediation strategies are the most effective in maintaining foundation performance.
E.ON and HR Wallingford are jointly funding the research and the experiments at HR Wallingford’s physical laboratory test facilities as part of the Foundation Response to Scour Protection research project.
All monopile founded wind turbine structures vibrate to some degree during operation, with the frequency of resonant vibration determined by the monopile, tower, nacelle and blade dimensions and interactions of the foundation with the soil. The design process addresses this system behaviour, and yields optimised installation depths for each monopile installation.
Erosion around the foundation caused by seabed scour changes the exposed length of the monopile at the seabed, and can alter the frequency at which the system resonates. If the turbine structure begins to vibrate excessively, it needs to be shut down, leading to revenue loss and potentially considerable remediation costs.
The physical modelling tests are being carried out in HR Wallingford’s Fast Flow Facility which can hold a million litres of water and generate waves up to 1m high and flows of over 2m/second.
Prof Richard Whitehouse, Chief Technical Director, Sediment Dynamics, at HR Wallingford, said: “We are using our Fast Flow Facility to test the response of a monopile foundation employing different scour protection measures including rock protection and tyre filled nets. We have designed the local and global scour scenarios for the project with a fully mobile sediment bed model and worked closely with Oxford University to deliver world class experiments on the interaction between scour and structural response.”
E.ON said that by conducting this research, the company is aiming to quantify the contribution of scour and scour protection measures in structural terms to inform proactive management of the operational fleet and designs on future projects.