Hydrodynamic Analysis Of Ship And Deep-Sea Cage Mooring System

With the improvement of people’s living standards,seafood is more and more needed.However,there is little room for further growth of offshore aquaculture due to environmental degradation caused by overexploitation.The deep sea where has relatively stable temperature and suitable water quality for fish growth,and has not been developed on a large scale.Thus great development potential is contained in the deep sea.For the needs of green development,far-reaching mariculture has become a research hotspot.However,the deep-sea environment is complex and changeable,and the safety of deep-sea aquaculture facilities is seriously threatened by severe natural conditions.In addition,the deep sea is far from the coast and lack of supply,that means it is difficult for a single cage to achieve sustainable development.In view of the typical marine environment in the South China Sea,the hydrodynamic response of the aquaculture ship,the cage and their coupling mooring systems are analyzed in this paper The main contents of the paper are as followed:（1）The aquaculture ship model is established and meshed,and the hydrodynamic parameters of the ship under unit regular waves are obtained through frequency domain analysis,which mainly include amplitude response operator RAO,additional mass,damping coefficient,first-order wave force and second-order wave force.（2）The dynamic response of the moored aquaculture ship is simulated.The motion of the ship and the stress of the mooring line under different sea conditions are obtained by time domain analysis.Different mooring cases are analyzed and compared.The results show that when the mooring lines are connected on the seabed,the tension of each mooring line is small,and the ship has a large range of motion,which is conducive to the breeding operation.（3）The dynamic response of the moored gravity cage is analyzed.Deformation and displacement of the cage,tension of mooring lines under different sea conditions are studied,and the safety factor of mooring line is checked.The results show that with the increase of the harshness of the marine environment,the cage deformation is aggravated,the drift radius is increased,and the tension of each mooring line is also increased.The drift radius of the cage in the 180° current flow increases slightly compared with the 90°current flow.（4）The dynamic response of the aquaculture ship coupled the cage mooring system is analyzed The dynamic time domain analysis is carried out for the two cases of the cage moored at the connection point and the stern,and the hull motion response,the mooring cable tension and the cage motion are obtained.The results show that compared with moored at the connection point,when the cage is moored at the stern,the motion amplitude of the hull is decreased,the drift radius of the cage is increased,and the tension of the mooring line is increased.