Dynamic response of a shallow-draft floating wind turbine concept: experiments and modelling

This paper considers the dynamic response of a novel lightweight FOWT concept being developed by T-Omega Wind Ltd, that is able to float over even steep high waves, and be economical in deep water. The study aims to understand the response to waves during marine operations (installation, or maintenance) as part of optimizing its design. For this purpose real-time 6 degrees-of-freedom (6 DOF) simulations are computed for the system under operational and extreme sea wave scenarios in the state-of-the-art Multiphysics Marine Simulator at the National Decommissioning Centre (NDC). RAOs for heave and pitch displacements are evaluated across varying wave heights and periods of excitation to identify system behaviour including resonant frequencies. The model is calibrated by adjusting system damping parameters for each wave frequency to match experimental tests on a 1:60 scaled prototype at the Kelvin Hydrodynamics Laboratory, resulting in an ad hoc damping expression to produce appropriate system dynamic behaviour for “High” and “Low” Sea States. The study concludes by identifying ranges of wave parameters that limit peak motions, proposes analytical expressions for RAO responses and provides damping parameters that validate the Marine Simulator as a suitable tool to predict FOWT dynamic responses with reduced computation time.