Dynamic Response Analysis of IEA 15 MW FOWT Under Extreme Focused Wave–Wind Conditions Based on Multi-Region Coupled Method

This study employs a multi-region coupled method to investigate the motion responses and aerodynamic load variations of the IEA 15 MW semi-submersible floating wind turbine (FOWT) under extreme focused wave conditions. The methodology employs the self-developed MRFoam solver within OpenFOAM to integrate aerodynamic and hydrodynamic analyses. The computational framework combines an incompressible viscous flow model with kOmegaSST turbulence closure and an actuator line representation of turbine blades. Extreme wave conditions are generated using NewWave theory, with systematic variations in wave height and wind speed to evaluate coupled effects. Results demonstrate that platform heave responds predominantly to wave excitation, showing minimal wind sensitivity. Turbine thrust maintains consistent mean values across wave conditions but exhibits wind-speed-dependent fluctuations. Mooring dynamics correlate strongly with surge motions, showing amplified tension variations from wave-induced platform displacements, though mean tensions remain stable under uniform wind regardless of wave magnitude.