Research On Hydrodynamic Characteristics Of Floating Wind Turbine Mooring System In 40m Water Depth

Wind energy is the most popular clean energy source among renewable energy sources in recent years,and wind power is also the most promising renewable energy technology at present.Wind power generation has the conditions for large-scale development and commercialization and is gradually developing offshore.Offshore wind power has the advantages of low pollution,high wind speed,no land resources,and long duration compared with onshore wind power,but the characteristics of China’s coastal shelf are that the water depth increases slowly with the increase of offshore distance.Therefore,it is necessary to study the hydrodynamic characteristics of the floating wind turbine mooring system that can adapt to the water depth conditions in China and resist the harsh wind and wave flow conditions.This dissertation uses numerical simulation methods to study floating fans.Based on the theory of multi body dynamics,a finite element coupled model of the entire system of floating fans is established.According to Wilson-θ And New Mark-β Numerical methods for solving nonlinear problems in coupled models.In order to verify the accuracy of the numerical simulation method for the coupled model of floating turbine,aerodynamic analysis is carried out at 200 m water depth to verify the decay period of the platform and the static restoring force of the mooring,and the RAO,additional mass and radiation damping of the platform are calculated at 40 m water depth to provide the basis for the following coupling calculation.In addition,the kinematic response and tension values of the floating wind turbine under the combined effect of turbulent wind,irregular waves and wind and waves are simulated,and the statistical values and time history curves are compared with the experimental results and FAST simulation results to ensure the credibility of the numerical tool for the coupled model simulation.The mooring system was initially designed according to specifications and empirical formulas for a 40 m water depth in China to adapt to the conditions of small water depths and to withstand severe wind and wave currents,and the mooring system was analyzed for its hydrodynamic characteristics and safety checks under hazardous sea conditions of one in 100 years.The OC4-Deep Cwind semi-submersible platform and the NREL 5MW wind turbine were used as the research objects to compare the advantages and disadvantages of the two mooring methods of traditional tensioning and suspension line on the motion control and positioning ability of the floating wind turbine according to the specific sea environment,and to select the mooring method more suitable for the small water depth conditions.In order to significantly change the overall dynamic characteristics of the floating system,while taking into account the safety and cost of the system,this dissertation uses a combination of buoy,clump weight and mooring line to optimize the mooring system of the floating wind turbine.Parameter sensitivity analysis is performed using the control variable method for both individual and combined use of accessories to study the effect of the same parameters on the dynamic response of the floating turbine in different forms of use and the effect.The optimized mooring system was checked for accidental limit states,mainly in the form of buoy and clump weight used alone and in combination,and the mooring system without accessories was used as a reference to study the cable breakage response of floating wind turbines under different forms of accessory use and to determine the effect of mooring accessories on the cable breakage response of floating wind turbines.The partial safety factor method is used to verify the safety of the floating turbine after the breakage,and the safety factors of the different forms of accessories used under the two failure levels of the breakage are analyzed to verify their safety performance and resistance to more severe sea conditions.This dissertation provides some theoretical support and reference for the future design of floating turbines adapted to China’s water depth conditions.