海上单桩风机结构冰激振动响应分析

Ice-induced vibration response analysis of monopile offshore wind turbine

针对冰区海上单桩风机易发生冰激振动的问题,以NREL 5MW风机为对象,详细开展其在风-冰联合作用下的动力响应研究。基于叶素动量理论,考虑Prandtl叶尖损失修正和Grauert修正,利用MATLAB编程计算获得叶片空气动力载荷;基于Maattanen自激振动模型,采用APDL开发冰区风机自激振动分析程序;基于我国渤海某海域冰情参数,从时域和频域对不同风-冰角下的风机结构动力响应特征进行分析,确定冰激锁频振动的冰速区间,并给出风机结构的最大位移响应振幅、基础倾覆力矩以及结构等效应力分布,结果表明:低冰速和高冰速下,风机塔顶与基础环顶的振动特性不同,中冰速时均表现为稳态的简谐振动;在常遇和极端冰厚下,均发生一阶锁频振动,对应的锁频冰速范围分别为0.01~0.06m/s和0.03~0.09m/s;锁频时,风机塔顶动力响应显著,两种冰厚下塔顶最大振幅分别1.425m和1.454m,最大等效应力响应分别为146MPa和183MPa,基础结构面外弯矩响应分别为243MN和358MN。文中研究结论和结果可为相似冰区海域同类风机结构的设计与优化提供技术参考。

Aiming at the issue of ice-induced vibration for offshore monopile wind turbines(OWTs)located in ice-infested waters,the dynamic responses of the NREL 5 MW monopile OWT under the combined actions of ice and wind loads were studied in this work.The aerodynamic loading was computed using the MATLAB code developed based on the Blade Element Momentum(BEM)principle,considering the Prandtl’s tip loss factor and the Glauert correction.Based on the Maattanen self-excited model,APDL was employed to develop an ice-induced vibration analysis program.By using the ice data of one ice zone in the Bohai Sea,the dynamic responses of the OWT were calculated under different wind and ice load attack angles.The time and frequency domain analysis of the tower top and base displacements were carried out,the vibration characteristics were analyzed and the ice load frequency lock-in(FLI)scenarios were identified.Based on the simulation,the maximum vibration amplitude of the tower top and base displacement,the maximum overturning moment of the foundation as well as von Mises stress of the structure were provided.The results show that the dynamic responses of the tower and the substructure of the OWT are different under low and high ice velocities,but they are harmonic vibrations in the medium ice velocity.The frequency of the ice load was locked in the first modal of the structure under normal and extreme ice thicknesses.The ice velocity causing FLI ranges from 0.01 m/s to 0.06 m/s and from 0.03 m/s to 0.09 m/s under the normal ice condition and the extreme ice condition,respectively.The dynamic responses of the wind turbine were significant when the FLI happened.The maximum vibration amplitudes of the tower top under normal and extreme conditions were 1.42 m and 1.45 m,the maximum von Mises stress were 146 MPa and 183 MPa,and the overturning moments were 243 MN and 358 MN,respectively.The present study provides a reference for the design and optimization of the 5 MW OWT structure installed in similar ice-infested waters.