Establishing a fully coupled CFD analysis tool for floating offshore wind turbines

- A CFD tool based on OpenFOAM is developed for FOWT applications.
- Relative body motion is handled by a sliding mesh technique.
- Coupling effects between the floating platform and the wind turbine are analysed.
- Flow field near FOWT and pressure distribution along turbine blades are presented.

An accurate study of a floating offshore wind turbine (FOWT) system requires interdisciplinary knowledge about wind turbine aerodynamics, floating platform hydrodynamics and mooring line dynamics, as well as interaction between these discipline areas. Computational Fluid Dynamics (CFD) provides a new means of analysing a fully coupled fluid-structure interaction (FSI) system in a detailed manner. In this paper, a numerical tool based on the open source CFD toolbox OpenFOAM for application to FOWTs will be described. Various benchmark cases are first modelled to demonstrate the capability of the tool. The OC4 DeepCWind semi-submersible FOWT model is then investigated under different operating conditions.With this tool, the effects of the dynamic motions of the floating platform on the wind turbine aerodynamic performance and the impact of the wind turbine aerodynamics on the behaviour of the floating platform and on the mooring system responses are examined. The present results provide quantitative information of three-dimensional FSI that may complement related experimental studies. In addition, CFD modelling enables the detailed quantitative analysis of the wind turbine flow field, the pressure distribution along blades and their effects on the wind turbine aerodynamics and the hydrodynamics of the floating structure, which is difficult to carry out experimentally.