Abstract This paper presents a complete numerical framework for modelling open ocean aquaculture structures in waves and current using Computational Fluid Dynamics (CFD). A structural dynamics model is incorporated to account for the motions and deformations of the net. It is based on the lumped mass method, a non-linear material law and implicit time step advancing. The presence of the porous net is considered in the momentum equations of the fluid using a forcing term based on Lagrangian-Eulerian coupling and the acting forces on the net. The proposed framework is suitable for simulating the interaction of nets of arbitrary geometry and under large motion with fluids including complex free surfaces. This is in contrast to existing models which either neglect important non-linearities, the physical interaction with the fluid or are limited to certain net geometries. In addition, the fluid-structure interaction of floating objects with mooring lines, nets and fluid is accounted for in the model. A new floating algorithm is presented for the interaction of the fluid and the rigid structure. It is based on a continuous direct forcing immersed boundary method and a level set representation of the object in the Eulerian fluid domain. This effectively avoids computationally expensive reconstruction processes of existing approaches and enables the application to large three-dimensional structures. The complete numerical framework is first validated against existing measurements for forces on rigid and flexible nets, net deformations and moored-floating structures with and without a net in waves. Then, a semi-submersible and a mobile floating open ocean aquaculture structure are investigated, and the possibilities of the numerical approach are highlighted.

中文翻译：

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用于模拟粘性流体中开阔海洋水产养殖结构动力学的数值框架

摘要 本文提出了一个完整的数值框架，用于使用计算流体动力学 (CFD) 模拟波浪和洋流中的开阔海洋水产养殖结构。结合了结构动力学模型来解释网的运动和变形。它基于集中质量法、非线性材料定律和隐式时间步长。使用基于拉格朗日-欧拉耦合的力项和网络上的作用力，在流体的动量方程中考虑了多孔网络的存在。所提出的框架适用于模拟任意几何形状的网络与包括复杂自由表面在内的流体的大运动下的相互作用。这与忽略重要非线性的现有模型形成对比，与流体的物理相互作用或仅限于某些净几何形状。此外，模型中还考虑了漂浮物体与系泊绳、网和流体的流固耦合。针对流体与刚性结构的相互作用，提出了一种新的浮动算法。它基于连续直接强迫浸入边界方法和欧拉流体域中对象的水平集表示。这有效地避免了现有方法的计算成本高昂的重建过程，并能够应用于大型三维结构。完整的数值框架首先针对刚性和柔性网上的力、网变形和带和不带网在波浪中的系泊浮动结构的现有测量进行验证。然后，