More than 60 representatives of the international offshore wind industry gathered in[ds_preview] early November at the Offshore Wind Seminar, organized by the Maritime Research Institute Netherlands (Marin) and the Energy research Centre of the Netherlands (ECN). This seminar included a visit to unique model tests in the Marin facilities of breaking waves against an offshore wind turbine. This pilot series of model tests, with a special model of an offshore wind turbine with realistic flexibility, was completed today and confirmed that breaking waves can induced significant oscillations and accelerations in the turbine.
Marin has a lot of expertise in the field of wave impacts against ships and offshore structures. Dr. Bas Buchner, Vice President of Marin and one of the leader of its Renewable Energy Team (RENT): »Marin wants to contribute to the development of reliable offshore renewable energy with this expertise from the maritime industry. Breaking waves can occur quite often in the shallow water areas of fixed wind turbines. Considering the relatively flexible foundations and towers of offshore wind turbines, we realized that the impulsive loading of breaking waves might result in resonant vibrations of the structure. This can have significant effects on the loads in the tower and accelerations in the critical mechanical systems at nacelle level. But we did not want to state this as a problem without a confirmation, so we developed these pilot model tests within our own R&D.« For this purpose a special model was developed by Marin’s specialists in the field of hydrodynamic loading and structural response. The model material and set-up was chosen such that the model had the correct flexibility and natural periods, a technique recently developed to investigate the vibrations of ships in extreme waves.
