This paper deals with a new combined concept consisting of an oscillating water column (OWC) device and an offshore wind turbine for the multi-purpose utilization of offshore renewable energy resources. The wind turbine is supported by a monopile foundation, and the attached OWC is coaxial with the foundation. Within the chamber, the exterior shell of the OWC and the monopile foundation are connected by four vertical stiffening plates. Correspondingly, the whole chamber is divided into four equivalent fan-shaped sub-chambers. A higher-order boundary element method is then adopted to model the wave interaction with the combined system. Numerical models based on two different approaches, namely ‘Direct’ and ‘Indirect’, are both developed in this study. In addition, a self-adaptive Gauss integration method is developed to treat the nearly singular integration that occurs when the field and source points are very close to each other. A detailed numerical analysis is then conducted for the case of an OWC integrated into a NREL 5 MW wind turbine in both regular and irregular sea states. Numerical results illustrate that a significant energy extraction efficiency is attained when remarkable piston-like fluid motion is induced within each sub-chamber, and the wave power absorption by the OWC is not restricted by wave direction. The air compressibility makes a negative effect on the wave power absorption especially when the wave frequency is less than the resonance frequency of the piston-mode motion of the fluid in the chamber. In addition, the wave forces on the OWC and the monopile can balance each other at specific wave conditions, leading to a nearly zero net wave force on the whole system. The results also illustrate that by using an optimal turbine parameter, the wave power production by the OWC can be an important supplement to the combined system in operational sea states.

本文讨论了一种新的组合概念，包括一个振荡水柱（OWC）设备和一个海上风力涡轮机，用于海上可再生能源的多用途利用。风力涡轮机由单桩基础支撑，连接的OWC与基础同轴。在室内，OWC的外壳和单桩基础通过四个垂直加强板连接。相应地，整个腔室被分成四个等效的扇形子腔室。然后采用高阶边界元方法来模拟波与组合系统的相互作用。这项研究基于两种不同的方法，即“直接”和“间接”，建立了数值模型。此外，开发了一种自适应高斯积分方法来处理当场和源点彼此非常接近时发生的几乎奇异的积分。然后，针对在规则和不规则海况下将OWC集成到NREL 5 MW风力发电机中的情况进行了详细的数值分析。数值结果表明，当在每个子腔室内引起明显的活塞状流体运动时，可获得显着的能量提取效率，并且OWC吸收的波功率不受波方向的限制。空气可压缩性对波功率吸收产生负面影响，尤其是当波频率小于腔室内流体的活塞模式运动的共振频率时。此外，在特定的波浪条件下，OWC和单桩上的波浪力可以彼此平衡，从而导致整个系统上的净波浪力几乎为零。结果还表明，通过使用最佳涡轮机参数，OWC产生的波功率可以作为在海上运行状态下组合系统的重要补充。