The subject of this study is the verification and the validation of existing numerical codes for floating offshore wind turbine structures using wave tank model tests as part of the INNWIND.EU project. A model of the OC4-DeepCwind semisubmersible platform, together with a Froude-scaled rotor model, is tested in a combined wind-and-wave basin. The simulation environment comprises a multibody approach with hydrodynamic and aerodynamic loads and mooring line forces. The focus of this paper is the validation of the hydrodynamics of a modified model hull shape, which compensates for the excess mass of the nacelle. The results show that the simulation model agrees well with the experiment.
At offshore sites with higher water depths, the use of floating structures is more reasonable than the use of large fixed-bottom structures such as monopiles, tripods, and jackets as described by James and Costa Ros (2015) and Beiter et al. (2016). A floating wind turbine experiences many different loading conditions. Floater motion with six degrees of freedom (6DOF) as well as aerodynamic and hydrodynamic loads have to be considered. At this point, few floating wind turbine prototypes have been built, e.g., the Fukushima FORWARD project, which was started in 2013.
To increase the reliability of wind turbines for floating applications, validated simulation codes are needed to predict the forces on the system structure and their dynamic responses for combined stochastic wave and wind loadings (Müller et al., 2016). Although several verification tests have been done by Robertson et al. (2013), Huijs et al. (2014), and Müller et al. (2014), for example, the validation of coupled simulation of floating wind turbines is still part of current research.
This work is associated with task 4.2 of the INNWIND.EU project as part of its model test campaign at LHEEA, École Centrale de Nantes (ECN), France, in 2014. INNWIND.EU, with its 27 European partners, aims to improve the design of beyond-state-of-the-art 10–20 MW offshore wind turbines, including hardware demonstration. A scaled 10 MW model of the OC4-DeepCwind semisubmersible was built at the University of Stuttgart, together with a Froude-scaled wind turbine with low Reynolds rotor blades, developed by the Politecnico di Milano.
