High-fidelity coupling framework for floating offshore wind turbine dynamics under turbulent wind loading and wave forcing

A novel, computationally efficient, high-fidelity two-way coupling framework for floating offshore wind turbines is presented. The framework couples a large-eddy simulation (LES) solver for atmospheric flow and wake dynamics ( DOFAS ) with a time-domain Cummins-based hydrodynamic–mooring solver ( OREGEN_X ), accounting for linear and non-linear wave forcing and six-degree-of-freedom platform motion. In the two-way coupling strategy only net aerodynamic rotor loads and platform kinematics are exchanged iteratively between the Eulerian flow module and Lagrangian rigid-body dynamics module implemented within a single framework. This avoids explicit resolution of the air–water interface and the use of multiphase in the CFD solver, while retaining the essential aero–hydro–mooring interactions. The framework is validated for the NREL 5 MW turbine mounted on the OC4 DeepCwind platform under uniform and fully developed turbulent inflow conditions combined with regular waves. Rotor loads and acceleration, platform motion are analysed with several grid resolutions using actuator disc (ADM) and actuator line (ALM) methods. The ADM yields predictions comparable to Blade Element Momentum Theory (BEMT) and to the ALM with relatively finer grids in terms of global turbine response, indicating its suitability for wind farm modelling. Adopting the ALM provides an improved representation of blade-scale loading, providing significantly lower thrust amplitudes under low-turbulence conditions compared with BEMT/ADM. The proposed framework provides a scalable and computationally efficient numerical approach for fully-coupled simulations of floating wind turbines under realistic environmental forcing, readily applicable for wind farm scale, offering a practical alternative to fully resolved multiphase CFD approaches that explicitly model the air–water interface at a high computational cost.