Wind-wave Coupling Experimental Research On Semi-submersible Offshore Floating Wind Turbine

Compared with onshore and nearshore shallow water areas,offshore wind resources have the advantages of more stability,abundant,and excellent quality.However,the inland wind turbine is not suitable for the water depth of more than 30 m,so the research on the floating wind turbine suitable for the deep sea has become the future research directions and development trend.Floating wind turbine is a complex structure,mainly including floating carrier and wind turbine.In the complex marine environment,it is subjected to the combined action of wind load and wave load,resulting in a complex motion response.The study of its motion characteristics involves issues such as aerodynamics,hydrodynamics and multi-body dynamics.This is also the focus and difficulty of the current research on floating wind turbines.In this paper,a semi-submersible platform is selected as the basis of the floating wind turbine,coupled with the 5MW wind turbine developed by the National Renewable Energy Laboratory(NREL)and semi-tensioned mooring system.Through the method of model test and numerical simulation,it is studied that the hydrodynamic performance under the coupled wind and wave conditions.Among them,the test adopted a 1:40 scale model.Through free attenuation,wind load and regular wave or irregular wave tests,these are obtained the inherent properties of the platform and the motion response under different environmental loads.Secondly,Open FAST was used for numerical calculation by real-scale model.The results show that motion responses of FOWT mainly show at natural frequencies and wave frequencies under the wind-wave coupling load.Wave load mainly affects the motion response of the system at wave frequencies,while wind load mainly affects at low frequencies.Finally,the numerical results can better reflect the law of response under frequency,but the numerical results are smaller than the experimental results.In order to make full use of the ocean space and improve economic benefits,a coupling system that integrates comprehensive utilization of renewable energy and aquaculture was proposed,and It is mainly based on a semi-submersible floating wind turbine system,integrated with wave energy conversion devices and aquaculture cages.The scale model was tested under the coupling of wind and waves to analyze the influence of floats and aquaculture cages on platform movement and mooring tension response.The test results show that the floats increases the wave force received by the platform,which increases the platform’s motion response and mooring tension.The cage can provide a certain damping force to reduce the platform’s motion amplitude.The research results of this paper are of great significance for exploring the performance of floating wind turbines coupling with the comprehensive utilization of renewable energy and aquaculture in the deep sea.