Structural analysis of aquaculture net cages in current

A method for structural analysis of aquaculture net cages has been developed and verified for a netting solidity of 0.23, water current velocities from 0.1 to 0.5 m/s and relatively large deformations (volume reduction up to 70%) by comparing the numerical results to tests in a flume tank. Strength analysis was performed using commercial explicit finite element software to calculate distribution of loads in the net cage due to current, weights and gravity. The net cage was modelled using truss elements that represented several parallel twines. Sub-elements allowed the trusses to buckle in compression, and only negligible compressive forces were seen in the numerical results. Resulting drag loads and cage volume were shown to be dependent on the net cage size and weight system. Drag loads increased almost proportional to the current velocity for velocities in the range of 0.2–0.5 m/s, while the cage volume was reduced proportional to the current velocity. The calculated forces in ropes and netting of full-size net cages were well below the design capacity for current velocities up to 0.5 m/s. However, netting seams in the bottom panel of the net cage were identified as a potential problem area as the forces could reach the design capacity.