风湍流强度对Spar型海上浮式风机极端响应的影响

Effect of wind turbulence intensity on extreme response of spar-type floating wind turbine

评估极端环境条件下的动态响应对于海洋结构物的结构设计非常重要。通常所采用的传统完全长期分析法虽然精确却十分耗时,而环境等值线法因其高效性和高准确性被逐步用于分析海洋结构物的极端响应。该方法以环境变量的联合概率密度函数为基础,获取所求重现期所对应的环境等值线,进而基于此等值线预报结构物的长期极端响应。然而在此前该方法的应用中,通常只考虑风速,有义波高与谱峰周期的影响,并未严格考虑风的实际湍流强度的影响。为了接近更真实的风况,本文将湍流强度视为环境变量,用概率方法将其纳入环境等值线法中,并研究湍流强度对Spar型浮式风机极端响应的影响。通过对Spar型浮式风机50年一遇极端响应预报值的对比发现,变化的湍流强度使环境等值线法对风机塔底的力与力矩极端响应预报值变小,平台纵摇角与锚链的力变大。

Evaluation of the dynamic responses of offshore structures under extreme environmental conditions is important for the structural design.The traditional full long-term analysis(FLTA)method is accurate but time-consuming,the environmental contour method(ECM)is proposed as an efficient and accurate method for predicting the extreme response of marine structures.This method is based on the joint probability density distribution of environmental variables to obtain the environmental contour corresponding to the required return period.And the long-term extreme response of the structure is predicted based on the obtained contours.In the existing application of this method,only the wind speed,the significant wave height and the spectrum peak period are generally considered,while the effect of the turbulence intensity is ignored.For a more realistic consideration of the wind conditions,this paper considers the turbulence intensity as an environmental variable,incorporates it into the environmental contour method based on probability method,and studies its effect on the extreme response of the Spar-type floating wind turbine.By comparing the predicted extreme responses with 50-yr return period,it is found that the analysis with varying turbulence intensity predicted a smaller value of the extreme response of the tower bottom force and moment,and a higher pitch angle of the platform and the mooring force than the analysis with constant turbulence intensity.