A fully nonlinear wave model to account for breaking wave impact loads on offshore wind turbines

This paper presents a numerical model capable of simulating offshore wind turbines exposed to extreme loading conditions. External condition-based extreme responses are reproduced by coupling a fully nonlinear wave kinematic solver with a hydro-aero-elastic simulator. The transient nonlinear free surface problem of water waves is formulated assuming the potential theory and a higher-order boundary element method (HOBEM) is used to discretize Laplace’s equation. For temporal evolution a second-order Taylor series expansion is implemented. The code is successfully adopted to simulate overturning plunging breakers, which give rise to dangerous impact loads when they break against wind turbine substructures. Emphasis is also placed on the development of a global simulation framework that aims at embedding the wave simulator into a more general stochastic environment. Indeed, first a linear irregular sea is generated by a spectral approach, then only on critical sub-domains, where wave impacts are expected, the fully nonlinear solver is invoked for a more refined simulation. This permits to systematically account for dangerous effects on the structural response (which would be missed by adopting linear or weakly nonlinear wave theories alone) without penalizing the computational effort.     

张力腿基础刚度对大跨浮式悬索桥风-浪动力响应的影响

采用张力腿基础的大跨度浮式桥梁是一种新型跨海桥梁体系,由于张力腿结构横向刚度弱,风-浪作用下结构响应受基础设计的影响大。该文构建了浮式桥梁风-浪荷载计算及结构运动响应有限元分析方法,以某采用张力腿基础的浮式悬索桥为对象,分析了张力腿基础淹没深度、张力腿拉索倾角等设计参数对张力腿基础横、竖向刚度以及风-浪作用下浮桥动力响应的影响。结果表明,风荷载对浮桥主梁的动力响应起主导性作用;通过增加张力腿基础的淹没深度增大结构的竖向刚度,能直接有效地减少大跨浮桥的动力响应;调整张力腿拉索倾角为75°～80°时可以有效降低结构的横、竖向运动响应,过小的倾角虽然可以提供较大的横向刚度,但会增大主梁的运动响应。因此,张力腿基础刚度是大跨浮式桥梁结构动力响应的控制性因素,应对基础设计参数开展重点研究。