Net Deformation and Cage Volumes in Towed Gravity Fish Cages

Abstract The deformations of the nets and cage volumes of gravity cages are investigated through experimental and numerical methods. The gravity cage model is towed in calm water as well as in regular waves. Pressure sensors are used to measure the depths at different points on the cage net. These depths are successfully measured in calm water and long waves. A numerical model is developed using ANSYS/APDL to compute the cage deformation. The results from the numerical model align well with the experimental results. Furthermore, cage volumes are calculated using a numerical method. Notably, the cage volume decreases as flow velocity increases. Increasing the bottom weight can help counteract the reduction in cage volume. Furthermore, the cage volume reduces more substantially in short waves, while that in long waves approaches the values observed in uniform flow. Finally, the limitations of the experiment are discussed, and suggestions for further enhancements are provided.