Research On Dynamic Response And Tower Foundation Structure Strength Of Semi-submersible Wind Turbine Based On Wind-wave Coupling

Floating wind turbines are affected by wind and wave loads at the same time during operation,and wind and waves are always changing.In the face of complex and variable wind and wave loads,the movement of the floating wind turbine system will be greatly affected;while wind turbines At the same time,the movement of the floating wind turbine will have a reaction to the wave load and wind load.Therefore,it is necessary to consider the floating wind turbine as a coupled overall system to study its dynamic response;part of the structure of the floating wind turbine is affected by the wind load,and the floating foundation is affected by the wave load The tower foundation is the key position connecting the upper structure and the floating foundation,so it is necessary to conduct strength check and fatigue analysis of the tower foundation structure.In this thesis,combining OC4 and Wind Float semi-submersible floating wind turbine basic structure type,improved design OC4-Wind Float semi-submersible floating wind turbine.The wind turbine has a lower construction cost than the OC4 semi-submersible wind turbine and better stability than the Wind Float semi-submersible wind turbine.First,in accordance with the "Guide for Building and Classing-Floating Offshore Wind Turbine Installations ",Then use the SIMA module of the DNV classification society SESAM finite element software to conduct wind-wave coupling analysis on the OC4 semi-submersible floating wind turbine finite element model,and compare the natural period results with the literature test results.On the basis of consistent results,Carry out OC4-Wind Float semi-submersible floating wind turbine wind and wave coupling numerical simulation analysis,conduct time domain dynamic response research of different types of floating types;then use ANSYS software to establish OC4-Wind Float semi-submersible floating wind turbine integral tower base and partial flange structure finite element Model and perform overall and local strength analysis and strength verification;finally,the linear fatigue cumulative damage theory is used to analyze and verify the fatigue life of the local flange structure.The main conclusions of this thesis are as follows:(1)OC4-Wind Float and OC4 semi-submersible floating wind turbines are basically the same as the natural periods of vertical and horizontal oscillations and bowing,while the natural periods of rolling and pitching and heaving are different;for extreme and operating conditions,in swaying,swaying and bowing The displacement response amplitudes of OC4-Wind Float and OC4 semi-submersible wind turbines are relatively similar;there is a certain difference in the motion response amplitudes of roll,pitch and heave.(2)The Von-Mises stress concentration point of the OC4-Wind Float semi-submersible floating wind turbine tower base structure is located at the connection between the bolt and the upper flange when the wind turbine is shut down under extreme conditions and the wind turbine is normally generating power under operating conditions.The maximum Von-Mises stress is the maximum Von-Mises stress under extreme conditions.It is 283MPa;under operating conditions,it is 197 MPa,which meets the strength requirements of relevant specifications.(3)When the wind turbine is shut down under extreme conditions and the wind turbine is normally generating power under operating conditions,the Von-Mises stress concentration point of the flange structure of the OC4-Wind Float semi-submersible wind turbine is on the upper surface of the nut and the upper flange plate;the largest part under extreme conditions The maximum Von-Mises stress of the flange structure is 302 MPa,and it is 211 MPa under operating conditions,which meets the strength requirements of relevant specifications.(4)The pre-tightening force can effectively reduce the top deformation of the OC4-Wind Float semi-submersible wind turbine under the axial tension of the local flange structure.The longitudinal bending moment has a greater influence on the Von-Mises stress of the local flange structure.As the force increases,the position of the maximum Von-Mises stress concentration point of the bolt also changes.When the pre-tightening force is 0%,the stress concentration point of the bolt is at the nut,and when the pre-tightening force is100%,the stress concentration point of the bolt is at the nut position.(5)The fatigue life of the partial flange structure of the OC4-Wind Float semi-submersible wind turbine tower base is 21.21 years,and the fatigue strength requirements of the relevant specifications are met.