Assessing Global Performance of 15 and 22 MW Floating Wind Semi-Submersible (FWSS) Platforms Through Cyber-Physical Modelling and Simulation

Abstract The objective of the paper is to present the global performance of large (15 MW or more) Floating Wind Semi-Submersible (FWSS) platforms under combined wind, waves and current loads. FWSS platform is an in-house semi-submersible design with three side columns on pontoons and one center column incorporating enhanced stability with outrigger pontoons, low draft, and large airgap. The paper discusses the efficient use of cyber-physical model tests to arrive at reliable results to demonstrate a scalable FWSS design as the turbine size becomes larger. The assessment is derived from model tests involving real-time coupling of physical and numerical simulation, termed cyber-physical testing. In this approach, the aerodynamic loads on the turbine/rotor are computed numerically in real-time while the hydrodynamic loads on the floater and mooring lines are simulated physically, forming closed-loop feedback. Since the aerodynamic loads are obtained numerically, different sizes of reference turbines can be considered, while keeping the same physical floater throughout the model test since the floaters of both turbine sizes are geometrically scaled. Both operational (1 year return period) and survival scenarios (50-year return period) are tested. The global performance of the FWSS platforms supporting the turbines is assessed and compared. Results are presented in terms of rigid body motion, acceleration and mooring line tension loads. Preliminary analysis suggests that for the operational scenarios, the influence of wind load on the turbine is significant and can affect the overall dynamics of the FWSS platform, while for the survival scenarios involving idling or parked turbines, the dynamics of the platform are mainly dominated by the hydrodynamic loads on the floater. Insights in terms of scaling behavior of the performance of the FWSS platforms are derived. The paper also demonstrates the possible benefit on coupled wind-wave model test using cyber-physical methodology.