Methodology for Wind/Wave Basin Testing of Floating Offshore Wind Turbines

Abstract

Scalemodel wave basin testing is often employed in the development and validation of largescale offshore vessels and structures by the oil and gas, military, and marine industries. A basinmodel test requires less time, resources, and risk than a fullscale test, while providing real and accurate data for numerical simulator validation. As the development of floating wind turbine technology progresses in order to capture the vast deepwater wind energy resource, it is clear that model testing will be essential for the economical and efficient advancement of this technology. However, the scale model testing of floating wind turbines requires accurate simulation of the wind and wave environments, structural flexibility, and wind turbine aerodynamics and thus requires a comprehensive scaling methodology. This paper presents a unified methodology for Froude scale model testing of floating wind turbines under combined wind and wave loading. First, an overview of the scaling relationships employed for the environment, floater, and wind turbine are presented. Afterward, a discussion is presented concerning suggested methods for manufacturing a highquality, lowturbulence Froude scale wind environment in a wave basin to facilitate simultaneous application of wind and waves to the model. Subsequently, the difficulties of scaling the highly Reynolds number–dependent wind turbine aerodynamics is presented in addition to methods for tailoring the turbine and wind characteristics to best emulate the fullscale condition. Lastly, the scaling methodology is demonstrated using results from 1/50thscale floating wind turbine testing performed at the Maritime Research Institute Netherlands (MARIN) Offshore Basin. The model test campaign investigated the response of the 126 m rotor diameter National Renewable Energy Lab (NREL) horizontal axis wind turbine atop three floating platforms: a tensionleg platform, a sparbuoy, and a semisubmersible. The results highlight the methodology's strengths and weaknesses for simulating fullscale global response of floating wind turbine systems.