Nonlinear hydrodynamics of floating offshore wind turbines: A review

Floating offshore wind turbine (FOWT) is a highly sophisticated system that involves multiphysical dynamics that includes hydrodynamics, aerodynamics, structural dynamics, servo dynamics, and mooring dynamics. Hydrodynamics is one of the most critical aspects directly related to the stabilization and safety of FOWTs. As the turbine capacity keeps growing and the target depth of the water becomes deeper, the nonlinear hydrodynamic effect becomes more significant, especially under extreme conditions that occur more frequently in recent years. In this paper, theoretical challenges and state-of-the-art research progress regarding the nonlinear hydrodynamic problems related to FOWTs and their stationkeeping systems are introduced from both numerical and physical point of view. Nonlinear wave characteristics and nonlinear hydrodynamics of wave–structure interactions are addressed with different theories ranging from linear, weakly nonlinear to fully nonlinear. A number of nonlinear phenomenon such as low-frequency resonance, transient impacts, hydroelastic coupling, current effects and shallow water effect are discussed. Theoretical inconsistency due to large horizontal motions and challenges in accounting for the viscous drag loads in the state-of-the-art engineering tools are addressed. Future perspectives are finally brought up.