Effects of wave forces on knotless polyethylene and chain-link wire netting panels for marine aquaculture cages

Abstract

The growth of offshore marine aquaculture requires improvements in the engineering and materials used for cage netting in order to better withstand wave forces. To clarify the hydrodynamic characteristics of knotless polyethylene (PE) and chain-link wire netting panels in non-uniform currents, we measured the wave forces acting on netting panels with varying solidity ratios and other parameters under regular wave conditions in a wave tank. The drag and added mass coefficients (CD, CM) were obtained using the Morison equation, and the behavioral trends in CD and CM for the netting panels were determined based on the Reynolds number (Re) and the Keulegan-Carpenter (KC) number. The experimentally derived coefficients were then incorporated into numerical simulations with the same conditions, and then were used to model the dynamic behavior of the netting panels. The normal CD of PE netting was similar to that in a uniform current and was positively associated with the solidity ratio, decreasing as Re increased. When the KC number was > 30, the normal CM of both the PE and chain-link wire netting remained unchanged, averaging 4.3 and 2.8, respectively. Large differences in displacement were observed for varying values of CD, suggesting that the effects of marine fouling should be considered during the design stage. Overall, these results provide a basis for further research toward a comprehensive hydrodynamic model for netting panels that can inform improved engineering for modern aquaculture.