Traditional coastal aquaculture becomes less and less attractive due to its environmental impact on the surrounding marine habitat. Offshore aquaculture cages are considered as a promising alternative today. The new environment implies larger loads on the structures and higher risk of fish loss due to the influence of strong current and extreme waves. Alternative design choices adapted from ocean engineering, like semi-submerged or floating rigid structures, are considered in order to cope with the expected loads. At the same time, the design process requires more advanced tools to account for the non-linear fluid-structure interaction involving rigid and flexible structures as well as complex free surfaces.This paper presents a complete numerical framework for analysing the interaction of Offshore aquaculture cages and waves using Computational Fluid Dynamics (CFD). The structural dynamics of nets and mooring lines as well as the motion of the rigid floating cage structure are considered. The presence of the net is considered in the momentum equations of the fluid using a forcing term based on Lagrangian-Eulerian coupling and the hydrodynamic loads on the net. The proposed framework is suitable for simulating nets of arbitrary geometry and under large motion with fluids including complex free surfaces.The numerical model is validated against existing measurements for loads and responses of floating structures with and without nets in waves and current. Afterwards, the dynamics of a typical offshore aquaculture structure is investigated in details.

A Cfd Approach for Modelling the Fluid-Structure Interaction of Offshore Aquaculture Cages and Waves

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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