Hydrodynamical Responses of a Novel Spar-Type Floating Offshore Wind Turbine: Experiments and Modelling

The development of new concepts of floating wind turbines has experienced a rapid increase in recent years to harvest deep water offshore wind resources, leading to designs capable of with standing different sea conditions. This study focuses on modelling a novel spar-type floating wind turbine, specifically designed to facilitate assembly and deployment from shallow ports. The Ultra Marine Spar design allows horizontal assembly and tow-out from shallow ports, then tilts to the vertical operational position at the offshore deployment site through ballasting of a lower tank prior to seabed mooring. A1:100 scaled prototype is tested in the wave tank at Kelvin Hydrodynamics Lab (KHL), and subsequent detailed modelling studies are performed in the Marine Simulator at the UK National Decommissioning Centre (NDC) to predict system hydrodynamics, which serve as a basis for future turbine deployment feasibility studies. A 6-DOF fluid-structure interaction model of the Ultra Marine turbine is implemented in the Marine Simulator to perform real-time multi-physics simulations of system hydrodynamic responses. The full-scale model is validated against model scale experimental RAOs for horizontal tow out and vertical operation across regular “Low” to “Moderate” Sea States, while varying wave incident angles, showing good agreement. The system dynamics topology is evaluated using time histories, Poincaré sections, and phase planes. Further experiments and simulations are conducted under irregular waves modeling survival Sea States for which computed exceedance curves, derived from platform time histories, indicate that maximum angular and vertical response probabilities remain within safe operational limits.