Anti-typhoon Design And Hydrodynamic Performance Analysis Of The Large Deep-water Fish Cage

Deep-water fish cage is an important way of aquaculture.Compared with the traditional offshore fish cage,the large deep-water fish cage has a higher degree of intensification and a larger breeding density.It produces abundant oceanic food sources so that fish and other aquatic products grow fast with high quality.At the same time,the flow can take away the excrement of fish,thus it effectively reduces the fish diseases in the deep-water fish cage.These advantages inspire the development potential of the large deep-water fish cages and improve the economic benefits of aquaculture.Recently,more and more scholars and researchers have paid attention to this emerging marine strategic industry.Therefore,it is necessary to develop and explore the new types of the deep-water fish cage.In this thesis,two different deep-water fish cage configurations which are based on the traditional deep-water fish cages,are designed for the open area with less shelter in the sea and in satisfaction of the requirement of resisting the harsh environmental condition caused by typhoon.The hydrodynamic performance of prototype type and two anti-typhoon designed configurations of deep-water fish cages are studied and the rationality and feasibility of the anti-typhoon design scheme are verified.The main contents have shown as follows:1.Based on the traditional design of deep-water fish cage configuration,according to the wave grade,wind force grade,tropical cyclone level table,it determines the environmental conditions under typhoon.In order to meet the requirements of resisting typhoon in the sea,analyse the common damage forms of deep-water cages.Two different configurations of the anti-typhoon deep-water fish cages are designed,including bottom mooring type and middle floating ring type respectively.2.Based on the potential flow theory and the finite element method,a numerical model of a deep-water fish cage is established.In this thesis,the numerical simulation is performed under steady flow,and the calculated value of the remaining volume of the fish net is compared with the experiment results.The correctness and validity of the numerical fish net model are verfied,as well as the sensitivity analysis of the solidity ratio,velocity reduction factor and current velocity of the prototype deep-water fish cage is performed.3.Based on the computational research and verification of the numerical fish net model,the hydrodynamic performance of the prototype deep-water cage and the two proposed largescale deep-water fish cages are studied.It analyzes the influence of the change of incident angle,wave height and period on mooring force,motion response and volume loss with three different configurations.Compared with the prototype deep-water fish cage,the anti-typhoon design of fish cages which has a clear effect of anti-typhoon are analyzed.The results show that the numerical fish net calculation method verified in this thesis can simulate the deformation and volume loss of the deep-water fish cage.The two designed schemes for deep-water fish cages reflects better hydrodynamic performance than the prototype cages.On the premise of the mooring system meets the safety check,the cage volume and the survival space are maintained well.Compared with the middle floating ring type,the tension distribution of the bottom mooring type is more symmetrical and the displacement is lower,and the volume of the cage remains more complete.Therefore,the final anti-typhoon design determined in this thesis is a bottom mooring type deep-water fish cage.