Numerical Investigations on the Influence of Stiffness of Floating Collar and Net Cage on the Hydrodynamic Response of a Quadrate Aquaculture Structure in Waves

Abstract A method of investigating the hydrodynamic characteristics and deformation of a quadrate gravity fish farm is presented in this paper, which focus on two components: net cage and floating collar. First, lumped mass model and screen model are adopted to simulate the net structure and calculate the hydrodynamic force acting on the net; the discrete-module-beam (DMB) method is applied to analyze the hydroelastic response of the floating collar. And convergence analysis is conducted to determine a reasonable grid division form of the net cage and the floating collar. Then, drag forces of the rigid and flexible circular cylindrical net cage are investigated and show a good agreement with the experimental data, which verifies the accuracy of this numerical simulation method. Given the simplification of the calculation, the explicit coupling method was used to couple the net cage and the floating collar. Finally, the numerical model is used to study three combination forms of the fish farm in waves, which are flexible net cage with elastic floating collar, flexible net cage with rigid floating collar and rigid net cage with elastic floating collar. And calculation results show that the rigidity or elasticity of the floating collar and the rigidity and flexibility of the net has some influence on the motion amplitude and the mooring loads of the fish farm.