Numerical investigation of the hydrodynamic behaviors of multiple net cages in waves

Large fish farms that include multiple-cages are becoming common in the aquaculture industry. Selecting an appropriate mooring structure and arrangement of cages is necessary to avoid fish cage and mooring grid system failures. A numerical model based on the lumped mass method and the principle of rigid body kinematics is developed to predict the hydrodynamic response of a fish cage and mooring grid system to regular waves. To validate the numerical model, a series of experiments is conducted. The numerical results of this model correspond with those obtained from experimental observations. Then, two cage arrangements are investigated, and the effect of the wave direction is analyzed. The results show that when the wave incident angle is 0°, the maximum tension forces on the anchor lines of the two cage arrangements are close to each other. There is not a significant difference between the effective fish cage volumes of the two cage arrangements. However, if one anchor line is broken, the two cage arrangements have different degrees of risk of having the cage structures swept away. When the propagation direction of the incident wave changes, the tension forces on the anchor lines also change due to different transfer load paths.

► An effective numerical model is developed to study the hydrodynamic behavior of multiple net cages in waves.
► A comparison between two cage arrangements is performed to offer data for the design of mooring cage design.
► The effect of wave directions on hydrodynamic behavior of multiple cages is analyzed, and the damage of a prototype mooring cage system is simulated.