Experimental study on flow velocity and mooring loads for multiple net cages in steady current

•Laboratory experiments are conducted with a fish farm containing 1 up to 8 net pens.•Both flow velocity and mooring loads for different multi-cage configurations are analyzed.•The experimental results provide the basis for the optimum design of a fish farm. To enable the optimum design and evaluation of fish farm and mooring performance in the energetic open ocean, a series of physical model experiments were conducted to investigate the hydrodynamic characteristics of a large fish farm containing 1 up to 8 net pens with the model scale of 1:40. In the physical model experiments, the main mooring line tension and flow-velocity magnitude were measured when current flowed through the multiple net cages. According to the experimental data, the upstream anchor lines of the cage will endure most of the current load acting on the multi-cage system. When the net cages are arranged in double columns, the tension force in the upstream anchor lines increases with increasing number of net cage. But this phenomenon is not obvious when the net cages are arranged in single column. There exists obvious flow-velocity reduction inside net cages of the multi-cage configurations; however, there is no statistical difference in flow velocity over varied configurations with different number of net cage. The appropriate multi-cage system in engineering practices should be determined through considering both the mooring line force and the flow-velocity distribution.