二阶波浪力对15MW漂浮式风力机动态响应影响研究

Effects of second-order hydrodynamics on the dynamic responses of a semisubmersible-type 15 MW wind turbine

为研究二阶波浪力对15 MW漂浮式风力机动态响应的影响程度,文章以IEA 15 MW风力机和VolturnUS-S平台为研究对象,通过WAMIT计算了平台和频及差频二阶传递函数,采用OpenFAST计算了常规运行工况和极端停机工况下,忽略及考虑二阶波浪力时的平台运动和塔基弯矩。计算结果表明:在运行工况下,平台运动主要受到气动载荷影响,但忽略二阶波浪力将导致塔基面内弯矩最大值偏大9.3%;二阶波浪力对极端停机工况下的平台运动具有显著影响,其可增大纵摇固有频率对应幅值达147.8%;忽略二阶波浪力,也会导致塔基面外弯矩最大值和标准差计算结果偏低10%以上,说明塔架结构强度校核及疲劳分析均应考虑二阶波浪力。

In order to investigate the effects of second-order hydrodynamics on dynamic responses of a 15 MW FOWT,the IEA 15 MW wind turbine and VolturnUS-S semisubmersible platform are employed for the case study.The sum-and difference-frequency quadratic transfer function matrices of the platform are obtained using WAMIT.OpenFAST is used to examine the platform motions and tower-base loads of the FOWT under normal operational and extreme conditions with and without considering the second-order hydrodynamics.The results indicate that platform motions are dominated by the aerodynamic loads under the operational condition.However,the tower-base in-plane bending moment is overestimated by 9.3%without the contribution of secondorder hydrodynamics.It is found that the second-order hydrodynamics has significant effects on the platform motions under the extreme condition.The amplitude corresponding to the pitch frequency is increased by 147.8%when considering the second-order hydrodynamics.In addition,the maximum and standard deviation of the tower-based out-of-plane bending moment are underestimated by over 10%.This has confirmed that the second-order hydrodynamics must be considered in the structural strength and fatigue analysis tower.