Hydrodynamic performance of a monopile offshore wind turbine in extreme wave groups

Dynamic responses of offshore wind turbines, particularly under extreme wave excitations, are crucial to structural design. Extreme waves, e.g. breaking waves, are random processes, which induce uncertainty in the estimation of dynamic responses. This type of uncertainty has been accommodated through a safety of factor which is conservative and thus leads to cost inflation. To reduce the cost and enable economically viable development of offshore wind, it is essential to understand the dynamic process of offshore wind turbines under extreme wave excitation scenarios. However, it is challenging to predict these dynamic responses through numerical simulations, due to the nonlinearity and randomness in such a complex process. To overcome these challenges, this study conducted a series of physical model testing to better capture the extreme wave induced loads on a monopile, which are then served as input for numerical modelling. Through this hybrid model, different vibration mechanisms are revealed, which shed lights on further cost reduction in the design of offshore wind turbines.