Motion of a multi-unit wind-tracing floating offshore wind turbine (FOWT) to combined wave–current and wind is obtained in the frequency-domain. The linear diffraction wave theory with a Green function for small current speeds and the blade-element momentum method are used for the hydrodynamic and aerodynamic analysis, respectively. A finite-element method is coupled with the hydrodynamic and aerodynamic equations to obtain the elastic responses of the FOWT to the environmental loads. The wind-tracing FOWT consists of three 5 MW wind turbines installed at the corners of an equilateral triangular platform. The platform is connected to the seabed through a turret-bearing mooring system, allowing the structure to rotate and face the dominant wind direction; hence, the multi-unit FOWT is called the wind-tracing FOWT. In this study, rigid-body responses of the wind-tracing FOWT to waves and wind are compared with those to combined wave, current, and wind loads for several current speeds and various wave heading angles. For a chosen current speed and wave heading angle, hydro- and aeroelastic responses of the wind-tracing FOWT to combined waves, current, and wind are obtained and compared with those of the rigid structure. Discussion is provided on the effect of the wave–current interaction on the motion and elastic responses of the wind-tracing FOWT. The numerical results show that under the rated wind speed, the motion of the wind-tracing FOWT is mainly governed by the wave-induced hydrodynamic forces and moments and the presence of current results in larger elastic motion of the FOWT to the environmental loads.

中文翻译：

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多机组浮动海上风力发电机对波浪、海流和风载荷的动态响应

在频域中获得多单元追风浮式海上风力发电机 (FOWT) 结合波流和风的运动。小电流速度下具有格林函数的线性衍射波理论和叶片单元动量法分别用于流体动力学和空气动力学分析。有限元方法与流体动力学和空气动力学方程相结合，以获得 FOWT 对环境载荷的弹性响应。追风FOWT由安装在等边三角形平台角上的三台5兆瓦风力涡轮机组成。该平台通过转塔轴承系泊系统与海底连接，允许结构旋转并面向主导风向；因此，多单元FOWT被称为追风FOWT。在本研究中，将追风 FOWT 对波浪和风的刚体响应与多种海流速度和不同波向角下的组合波浪、水流和风载荷的响应进行了比较。对于选定的水流速度和波浪航向角，获得了追风 FOWT 对波浪、水流和风组合的水力和气动弹性响应，并将其与刚性结构的响应进行比较。讨论了波流相互作用对追风 FOWT 运动和弹性响应的影响。数值结果表明，在额定风速下，追风FOWT的运动主要受波浪引起的水动力和力矩的影响，而海流的存在导致FOWT对环境载荷产生较大的弹性运动。