Effect of simplification of aerodynamics on the motion of floating offshore wind turbines

While floating offshore wind turbines (FOTWs) are gathering an increasing interest for renewable energy production, there is still a limited associated design experience. Furthermore, the design of these objects is complicated by their novelty and their inherent complex multi-disciplinary nature. From the point of view of offshore seakeeping assessment, with focus on motions and mooring system design, such complexity can become problematic particularly at early design stages. It is therefore useful to assess the possibility of introducing some simplifications to reduce the amount of required data for early design assessment and to enlarge the set of simulation tools which can be potentially used for such purpose. This study deals, in particular, with the effects of simplification of the aerodynamic modelling. Motions and quasi-static mooring loads of a FOWT in irregular waves and gusty wind are compared using three different approaches for the modelling of the wind turbine aerodynamics. Results from the analysis indicate that an intermediate simplification of the rotor aerodynamics, which takes into account only the rotor thrust and allows modelling the system as a single rigid body, could be still sufficient for the early design stage.