This paper is concerned with the hydrodynamic response of a novel offshore fish farm that combines a floating spar wind turbine and a fish cage (named as COSPAR for brevity). The open net steel cage is octagonal in shape with a partially porous wave fence at its top end to attenuate wave energy for a calm fish farming environment as well as to keep predators out. The deep draught spar is made from concrete for its bottom half and from steel for its top half. The spar carries a control unit and a 1[Formula: see text]MW wind turbine that provides the required power to operate the offshore salmon fish farm. The COSPAR fish cage has four catenary chains as mooring lines attached to mid length of the spar (outside the fish cage) so as to mitigate tension force in the mooring lines and to reduce the benthic footprint. ANSYS Design Modeler and Aqwa are used to perform the hydrodynamic response analysis of free-floating condition of COSPAR in the frequency domain and coupled analysis involving COSPAR and the mooring lines in the frequency domain and time domain. Environmental conditions, representing 5-year, 20-year and 50-year wave return periods with a constant current flow at an exposed fish farming site in Storm Bay of Tasmania, Australia, are adopted for the analyses. A comparison study is made against having a floating fish cage only (i.e. without the bottom half concrete of the spar) with four catenary chains attached to side vertical columns of the cage so that the fish cage behaves like a semi-submersible cage. Based on the comparison study, the COSPAR fish cage shows enhanced hydrodynamic responses in the following respects: (1) more stable motion responses in heave and pitch against wave and current forces, (2) less susceptible to the viscous damping when it is assumed by a linearized drag force of Morison elements in the frequency domain and (3) reduction of tension forces in the mooring lines. Interestingly, the pitch motion response of COSPAR fish cage in the frequency domain is in close agreement with the time domain result due to its greater pitching stiffness that reduces nonlinear effects from viscous drag and mooring interaction.

中文翻译：

---

近海养鱼场组合式Spar风力发电机和鱼笼水动力响应分析

本文关注一种新型近海养鱼场的水动力响应，该养鱼场结合了浮动式翼梁风力涡轮机和鱼笼（简称为 COSPAR）。开放式钢网笼呈八角形，其顶端有一个部分多孔的波浪栅栏，可减弱波浪能量，营造平静的养鱼环境，并防止捕食者进入。深吃水翼梁的下半部分由混凝土制成，上半部分由钢制成。晶石带有一个控制单元和一个 1[公式：见正文]MW 风力涡轮机，可提供运营近海鲑鱼养殖场所需的电力。COSPAR 鱼笼有 4 条悬链作为系泊线，连接到翼梁的中间长度（鱼笼外），以减轻系泊线上的张力并减少底栖足迹。ANSYS Design Modeler和Aqwa用于频域COSPAR自由漂浮状态的水动力响应分析，以及频域和时域COSPAR与系泊线的耦合分析。环境条件，代表 5 年、20 年和 50 年的波浪回归期，在澳大利亚塔斯马尼亚州风暴湾的一个裸露鱼类养殖场具有恒定的电流流动，用于分析。一项比较研究是针对仅具有一个浮动鱼笼（即没有梁的下半部分混凝土），四个悬链链连接到笼子的侧面垂直柱上，这样鱼笼就可以像半潜式笼子一样工作。根据比较研究，COSPAR 鱼笼在以下方面表现出增强的水动力响应：(1) 对波浪力和水流力的升沉和俯仰运动响应更稳定，(2) 当在频域中由 Morison 元件的线性化阻力假设时，粘性阻尼不易受到粘性阻尼的影响，以及 (3) 张力减小在系泊线上。有趣的是，COSPAR 鱼笼在频域中的俯仰运动响应与时域结果非常一致，因为它具有更大的俯仰刚度，从而减少了粘性阻力和系泊相互作用的非线性效应。