Dynamic Analysis On The Tension Leg Platform For Offshore Floating Wind Turbinethe

As the fossil energy consumption and environmental pollution,the renewable energy exploration and development is becoming more and more important for the countries' development strategy all over the world.The wind as one of the most value of green renewable energy,its development and utilization is from land to sea gradually.The platform of offshore wind turbine is indispensable for the offshore wind turbine system,which can guarantee the strength of the platform structure safety and prevent the platform resonance.It is extremely important meaning to the safe and stable operation for the offshore wind turbine.Basing on the tension leg platform of the NREL 5MW offshore wind turbine as the research object and using the finite element method,I have made a three-dimensional model of the platform structure and analysed the tension leg platform structure stress and vibration characteristic under the once-in-a-century extreme sea condition,the main work is as follows:1.Basing on the three dimensional potential flow theory and numerical simulation technology,I have calculated dynamic response for the tension leg platform floating wind turbine,six degrees of freedom movement response and hydrodynamic load for the floating wind turbine tension leg platform under the extreme sea condition.The results show the hydrodynamic load is mainly concentrated in the platform of surge,heave and pitch direction,the load in the other direction is relatively small,it can be negligible.At the same time,the dynamic response of the six degree of freedom of the platform is also focused on the surge,heave and pitch direction,when the wind,wave and current is 0°.2.Establishing the geometrical model by CAD software,I have studied the structure stress with the coupled action of dynamic load and aerodynamic load,under the wind,wave and current along the same direction and 0°,15°,30° and 45°under the extreme sea condition.The results show that the equivalent stress and maximum shear stress on the tension leg platform structure is increases with the increase of incident Angle;When the wind and wave is 0° and the current respectively in 15°,30°,45°,60°,75°,90°,105°,120°,135°,150°,165°,180°,The stress of the platform structure is changing with current incidence Angle increases first and then decreases,and when the current the 180°,the maximum equivalent stress and the maximum shear stress on the platform is minimum and the maximum equivalent stress is about 2 times of the maximum shear stress;Different wind,wave and current incidence Angle influence the platform structure stress seriously,so,it is important to choose the right wind turbine installation Angle to the platform's safety.3.The TLP of floating wind turbine is complicated thin-walled structure and platform prestress has significant effect on stiffness of structure.In order to ensure the accuracy of modal parameters,I must use prestress modal analysis method to anslys the frequency of the TLP.according to the extracted the former ten order modal vibration mode and natural frequency,I can conclude that ocean waves of low frequency and the six degrees of freedom of platform movement response is not able to lead the tension leg platform resonance response.