Coupled Dynamics Modelling of a Floating Wind Farm With Shared Mooring Lines

This work presents a coupling of numerical models to allow simulation of a farm of floating wind turbines in which some mooring lines are shared between platforms. This shared mooring approach has potential to reduce mooring costs for floating offshore wind farms, but introduces additional complexity in system behaviour and design considerations for which new simulation capabilities are needed. Multiple instances of the FAST floating wind turbine simulator are coupled modularly to the MoorDyn mooring system simulator to achieve a coupled simulation of a full shared-mooring floating wind farm. The model is demonstrated on a square-shaped four-turbine shared mooring farm configuration in the presence of irregular waves and turbulent winds. Results show reasonable behaviour of the platform motions, with surge displacements under wind and wave loading that reflect the complex restoring properties of the shared mooring arrangement. Varying phase relationships in the platforms’ motions arising from their spatial offsets in the sea state show that the shared mooring lines will see different excitation at either end. Fluctuations in the mooring line tensions bear out this fact, and also show the importance of line dynamics in these shared mooring arrangements. In particular, the shared mooring lines show a greater tendency for resonance due to the absence of seabed contact.