Research On Response And Optimization Of Offshore Floating Fan In Extreme Sea Conditions

Accelerating the development of wind power,especially offshore wind power,has become an important guarantee for promoting China's social energy transformation and realizing the great rejuvenation of the Chinese nation.The development of offshore wind power depends on the research on the basic performance of wind turbines designed for specific offshore environments.It is of great significance to carry out hydrodynamic research on the foundation of floating wind turbines for the development of offshore high-power wind power with a water depth of more than 50 meters.Therefore,studying the hydrodynamic characteristics of the offshore floating wind turbine foundation and its mooring structure in the marine dynamic environment,especially under the action of extreme waves,will have important scientific significance and practical value for the construction of offshore wind farms.To this end,this article first refers to the specific parameters of the International Electrotechnical Commission on OC4-Deep Cwind and the specific information of the NREL 5MW semi-submersible floating fan foundation proposed by the American Renewable Energy Laboratory for structural model construction.Based on the three-dimensional potential flow theory of hydrodynamics,this paper uses Matlab and ANSYS-AQWA to carry out hydrodynamic analysis and research on the fan platform to obtain the hydrodynamic coefficients such as RAO,additional mass and radiation damping of the fan platform in different environments.Finally,the construction of the hydrodynamic numerical model of the fan platform was completed.Secondly,in order to further consider the safety performance of floating wind turbines under the action of extreme waves,this paper is based on a special extreme wave-the theory of generating freak wave,using Matlab to construct a numerical model of generating freak wave,and through AQWA-Drift module imports its waveheight time-history curve for time domain analysis.Considering that the heave response of the floating fan has a serious impact on the power generation performance of the fan,the article specifically compares the heave response of the floating fan under the action of regular wave,ordinary random wave and freak wave.The results show that the heave displacement,velocity and acceleration of the system change dramatically at the moment of the freak wave.This paper also explores the influence of the foundation column on the heave motion of the floating fan by changing the shape of the foundation column,the radius of the bottom surface and void ratio.The results show that when the area of the bottom surface of the foundation column remains unchanged,the shape of the bottom surface has a relatively small effect on the response of the heave motion of the floating fan;the smaller the radius of the bottom surface of the foundation column,the smaller the response of the heave motion of the floating fan;The greater the void ratio,the better the suppression of the heave motion of the floating fan.Finally,in order to consider the actual operating environment of the actual offshore wind turbine,the joint effect of wind and wave flow on the floating wind turbine and the coupling between the mooring system and the floating wind turbine are developed to solve the fan's motion response and mooring cable tension.Due to the large horizontal offset of the wind turbine,the mooring system is optimized by adjusting the length of the mooring line and increasing the number of mooring lines.On this basis,considering the motion response of the floating fan and the change of cable tension under the scenario of mooring breakage and extreme sea conditions.The research work and analysis results of this paper can provide corresponding scientific basis for the preliminary design of floating fans in the East China Sea and South China Sea with large water depth.