Cross-Scale Performance Assessment of a 10 MW Floating Offshore Wind Turbine via CFD, Openfast, and Model-Scale Experiments

This paper presents a cross-scale performance assessment of a 10 MW semi-submersible floating offshore wind turbine (FOWT) using a combination of model-scale experiments, high-fidelity Computational Fluid Dynamics (CFD) simulations, and OpenFAST simulations. Model tests were conducted in an ocean basin at a scale ratio of 1:60 to investigate turbine aerodynamic performance and six-degree-of-freedom (6DOF) platform motions under floating conditions. Numerical simulations were performed using fully coupled CFD and OpenFAST models to evaluate turbine performance at both model and full scales. Comparisons at model scale show that both CFD and OpenFAST capture the main trends of turbine thrust and torque observed in the experiments, providing confidence in their ability to represent the dominant aerodynamic performance of the fixed-bottom FOWT. Full-scale simulations were subsequently carried out using CFD and OpenFAST, and the results were assessed alongside scaled-up model test data to examine scale-dependent performance behaviour. The results indicate that turbine thrust exhibits broadly consistent behaviour across model-scale experiments and full-scale numerical simulations. The predicted full-scale platform motions show reasonable agreement with the model test results. In contrast, significant discrepancies are observed in the predicted turbine torque at full scale. These differences are shown to be systematic rather than incidental and are primarily attributed to Reynolds number effects and scale-dependent aerodynamic characteristics, which are not fully captured through direct scaling according to Froude number similarity. The findings highlight that, while commonly used experimental and numerical approaches are effective for assessing global loads and motions, caution is required when interpreting power-related performance metrics across scales.