Surface wave scattering by multiple flexible fishing cage system

TL;DR

This paper models and analyzes the wave scattering and hydrodynamic forces on a multiple flexible fishing cage system using linear wave theory, Fourier-Bessel series, and Darcy's law, revealing how cage arrangement and membrane tension influence wave damping.

Contribution

It introduces a novel combined analytical approach for wave scattering by flexible cage systems, incorporating porous effects and mooring, which advances understanding of their hydrodynamic behavior.

Findings

Wave damping is significantly affected by cage arrangement and membrane tension.

The cage system can serve as an effective breakwater based on far-field scattering results.

Hydrodynamic forces and power dissipation vary with wave and cage parameters.

Abstract

A study of the wave dynamics around a multiple fishing cage system is carried out under the assumption of the linear water wave theory and small-amplitude wave response. The Fourier--Bessel series expansion of the velocity potential is derived for regions enclosed under the open-water and cage systems and in the immediate vicinity. Further, the scattering between the cages is accounted for by employing Graf's addition theorem. The porous flexible cage system is modelled using Darcy's law and the three-dimensional membrane equation. The edges of the cages are moored along its circumferences to balance its position in the deep sea. The unknown coefficients in the potentials are obtained by employing the matched eigenfunction method in conjunction with the least-squares approximation method. In addition, the far-field scattering coefficients for the entire system are obtained by expanding the Bessel and Hankel functions in the plane wave representation form. Numerical results such as the hydrodynamic forces, scattering coefficients, and power dissipation are investigated for various cage and wave parameters. The wave loading on the cage system can be significantly damped by the spatial arrangement, membrane tension, and porous-effect parameter. Moreover, the far-field results suggest that the cage system can also be used as a breakwater.