Numerical Simulation of the Three-Dimensional Sloshing and Internal Free Surface Oscillation Control in a Closed Fish Cage Using the Particle Method

An ambitious aim of aqua culturists is to mitigate the impact of aquaculture on the marine environment, in order to achieve an environmentally sustainable marine aquaculture system. In terms of the ecological preservation of the marine aquaculture environment, closed fish cages have attracted more and more attention. In this study, a simulation of the closed fish cage tank sloshing using the three-dimensional particle method is introduced. First, the accuracy validation of the sloshing of a rectangular tank was done through comparison with the results from the previous experiments. Then, we investigated the three-dimensional sloshing characteristics of free water inside a cylindrical closed fish cage. In the numerical simulation, the inhibitory effects of the horizontal plate and netting panel on free water sloshing were also examined, respectively. It was found that the run-up height of the internal free water surface was more obvious when the external excitation period was equal to the natural period of the first mode. It was observed that the resonance point shifted to the low-frequency side when the horizontal plate was placed. Regarding the flow velocity distribution, it was found that when the horizontal plate was installed, the movement of the fluid was mainly limited to the vicinity of the water surface and the bottom of the cage, and most of the fluid did not move much from the depth of the water where the horizontal plate was placed. In addition, it was observed that under the condition of placing the net panels in the closed fish cage, the run-up height of the free water was also significantly reduced. In the future, we will explore the influence of water inflow and outflow on the flow velocity distribution inside the fish cage.