Abstract
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.
Highlights
The harnessing of wind energy as a clean and renewable energy source has undergone rapid growth over the last decade
The aerodynamics of the National Renewable Energy Laboratory (NREL) 5-MW fixed wind turbine is firstly studied in full scale without the floating platform and will be used for later comparison with the data of a floating wind turbine
The modelling tool is established via an open source framework OpenFOAM with our further developments on a numerical wave tank module and a static mooring line analysis module
Summary
The harnessing of wind energy as a clean and renewable energy source has undergone rapid growth over the last decade. By comparing CFD results obtained from STAR-CCMþ with those from other tools, such as unsteady Blade Element Momentum (UBEM), FAST with BEM and Generalized Dynamic Wake (GDW), it was found that good agreement was achieved for all cases at small oscillation amplitudes, large discrepancies occurred when the oscillation amplitude increased to 4 This was explained in their work via pointing out the limitations of the simplified methods used in modelling the dynamic interaction between wind turbine and wake, which was induced by the platform motion. We will present a numerical modelling tool based on the open source CFD framework OpenFOAM [34] for fully coupled dynamic analysis of floating offshore wind turbine systems under combined wind-wave excitation.
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Published Version
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