A Fully Coupled Numerical Model for a Semi-Submersible Cage and Its Dynamic Response Characteristics under Regular Waves
With the development of aquaculture from near shore to offshore regions,new semi-submersible aquaculture cages with the ability to resist harsh sea conditions have been designed and manufactured successively,and it is of great engineering significance to study their hydrodynamic performance.Based on potential flow theory and Morison model,combining the 3D panel method and finite element method,the main frame-net-mooring fully coupled numerical model of a semi-submersible aquaculture cage has been established,and after validating the reliability of the numerical simulation,the hydrodynamic response and structural stress response of the cage under regular waves are analyzed,focusing on the relative motion of each part of the cage.The results show that the motion of the cage is composed of two parts:slow drift motion and wave frequency motion,and the slow drift motion will cause the offset of the equilibrium position.In the direction of wave propagation,the nodes at the same height in the frame hardly have relative motion,while the nodes at different heights have relative dislocation due to the rotating displacement and the bending deformation of the vertical beams.There is a large structural deformation in the center area of the side net,which leads to a large relative motion between the flexible net and the main frame.In addition,the influence of wave parameters and net solidities on the motion of the cage was analyzed.The research results can provide some certain references for the numerical simulation method for the semi-submersible cage.