During the course of the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project, which focused on the validation of numerical methods through comparison against tank test data, the authors created a numerical FAST model of the 1:50-scale DeepCwind semisubmersible system that was tested at the Maritime Research Institute Netherlands ocean basin in 2013. This paper discusses several model calibration studies that were conducted to identify model adjustments that improve the agreement between the numerical simulations and the experimental test data. These calibration studies cover wind-field-specific parameters (coherence, turbulence), hydrodynamic and aerodynamic modeling approaches, as well as rotor model (blade-pitch and blade-mass imbalances) and tower model (structural tower damping coefficient) adjustments. These calibration studies were conducted based on relatively simple calibration load cases (wave only/wind only). The agreement between the final FAST model and experimental measurements is then assessed based on more- complex combined wind and wave validation cases.
In 2013, a 1:50-scale model of the DeepCwind semisubmersible floating offshore wind turbine was tested at the Maritime Research Institute Netherlands (MARIN) ocean basin under the direction of the University of Maine. The data from this test campaign was then used in 2015/2016 within the framework of Phase II of the International Energy Agency (IEA) Wind Task 30 Project, also known as OC5 (Offshore Code Comparison Collaboration, Continued, with Correlation). The National Renewable Energy Laboratory (NREL), both led and participated in the OC5 project, which included conducting a series of model calibration studies to improve the match between their numerical model and the wave tank test data. Several of these studies and their key findings are presented in this paper. The authors modeled the DeepCwind system using NREL's open-source wind turbine simulation software FAST version 8 (NREL, 2015).
The key properties of the numerical and the physical model as tested in the wave tank are summarized below.
