| More and more fish resources are needed in the market with inshore water pollution and fish disease being severe on coastal zones. So, growing fish offshore will be an inevitable trend. However, Open Ocean Aquaculture has to withstand a high energy environment such as strong waves, currents and storms. Thus, to study dynamic response for net cage under the wave action is very important and necessary.In the paper, the numerical model of the net cage was built based on finite element method using the pipe element, and a series of physical model test was conducted to validate the numerical model. Then the study of dynamic response for fish cage and metal cage net under the wave action was conducted. The results are important for design of fish cage system and optimizing structure.The paper includes the following sections.The first chapter is a preface, including the purpose and background of the study and main types of open ocean cages. Then the progress in the net cage study and content of the paper is also given.In the second chapter, the basic theory of finite element and dynamic response is introduced. The pipe element is used to simulate the float collar and the link element is used to simulate the mooring line. Finally, the numerical model of the float collar and the mooring line under the wave action was established.In the third chapter, a series of physical model test was conducted to validate the numerical model. The physical model test on motion of float collar was conducted to validate the motion and force, and the physical model test on stretching of the ring specimen was conducted to validate the deformation.In the fourth chapter, the numerical simulation was performed to analyze the dynamic response for the float collar under wave action. Finally, the stress, deformation and tension under different wave incident directions or those after breakage of mooring line were obtained.In the fifth chapter, four models with different amount of clamps, four models with different bending rigidity of clamps, four models with different bending rigidity of float collar and five models with different tensile stiffness of mooring line are calculated Then the results are used to design fish cage system and optimizing structure.In the sixth chapter, the numerical model of metal cage net under wave action was established. The dynamic response for metal cage net with diamond mesh and square mesh were both discussed. After that, the paper discussed the influence of rigidity, wave height and wave period.At the end of the dissertation, the achievements are summarized, and the prospects of Open Ocean Aquaculture are also given. |
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