Hydrodynamic Behavior Of Deep-water Net Cage With The Frame Anchor System

In order to relieve the pressure of marine capture fisheries and implement the strategy of sustainable development of marine fisheries, deep-water cage industry has been developed rapidly in the coastal areas of our country recently. Net cage aquaculture of scale, intensification and industrialization has become an important direction of aquaculture development. Compared with net cage used in sheltered area, the net cage in open sea will resist more severe wave loading. For this reason, the deep-water cage is required to withstand severe conditions such as strong winds, currents and storms. The safety of cage system should be ensured, and then the loss of fishermen could be minimized. During the design of deep-water cage, the research on the mooring system design and hydrodynamic behaviors of cage under mooring system should be put in a significant place. The doctoral dissertation has been financially supported by the National 863 High Technology Project and National Natural Science Foundation Project.The contents are mainly composed of seven parts. The first part is a general introduction to the research background, the development and prospects of deep-water cage at home and abroad. The second part is about the design of physical model method. In the third part, according to the result analysis of model experiment about four-point mooring, under-water grid mooring net cage, the reasonal suggestion has been proposed on mooring types and direction of incident wave-current. The fourth part of the dissertation presents the design of six types of grid mooring net cage, the flow velocities in front of the net cage, behind the net cage and inside the net cage are measured. With the analyses of the data, flow-resistance effect of cage net is studied, which is a result of flow field for numerical simulation investigation afterwards. The basic method of numerical simulation investigation of net cage is presented in the fifth part. And in the sixth part, with the combination of the numerical simulation method and the model experiment, the hydrodynamic behavior of single under-water gird mooring net cage under the influence of current, wave and combined wave-current are studied. Based on the study, the effect of the submerged depth of net cage grid and direction of incident combined wave-current on hydrodynamic behavior of net cage is analyzed. In the seventh part, a model of under-water grid mooring net cage is designed, which is the combination of two net cages, to analyze the hydrodynamic behavior under the influence of current, wave and combined wave-current with the combination of the numerical simulation method and the model experiment, and compares the hydrodynamic behaviors between the double net cags and single net cage on same conditions.At last, the achievements of the study are summarized and the prospects of the study of hydrodynamic behavior of deep-water grid mooring net cage are also discussed.