Applying a 3-D image measurement technique exploring the deformation of net cage under wave–current interaction

Abstract

This study was conducted to calculate and analyze the net-cage volume of Submergible single-cage and double-cage systems affected by currents, waves, waves in cocurrent flow, and waves in countercurrent flow by using a 3-D imaging system to develop a more accurate method for estimating net-cage deformations. The results indicate that currents impose a significantly greater impact on net-cage deformation than waves do. The nets achieved maximal deformation when the trough passes through the net cages, and waves in concurrent flow caused greater deformation compared with waves in countercurrent flow. Test results for the double-cage system indicate that the upstream net cage provided a shielding effect to the downstream net cage, alleviating the net-cage deformation of the downstream cage. Under the test conditions of the present study, the shielding effect reduced the net-cage deformation resulting from waves by 50%. An analysis of the mooring rope tension revealed that the mooring rope tension was greater under waves in cocurrent conditions than under waves in countercurrent conditions. The double-cage system consumed more energy and generated lower maximum mooring rope tension than the single-cage system did. The submersible net cage simultaneously reduced the net-cage deformation and mooring rope tension, with the lowest mooring rope tension observed under wave–current interactions. Future researchers can adopt the proposed technique for measuring the 3-D deformation of net cages affected by waves and currents and use the results of the present study to verify relevant numerical models.