Study On Numerical Simulation Of Dynamic Response Of Circular Aquaculture Cages In Constant Flow

With the decline of capture fisheries, aquaculture has played an important role in meeting the growing demand for seafood in China. Now cage culture is developed rapidly in China and has been the important marine industries. However, it's a high risk operation. The practice is vulnerable to natural hazards, such as strong tides, storms and typhoons. So, it's necessary to assess the behavior of a sea cage exposed to currents and waves in advance for the need of improving design and reliability of the structure. Cages consist of flexible nets, ropes and rigid frames. Generally, the experimental studies (sometimes combined with in-situ observations) and numerical predictions are employed to analyze the mechanical performance of such structure. Computer simulation as having many advantages, has been widely used in research into flexible structures with advances in computer technology. Therefore, the present study is focus on investigating the performance of cages using the numerical technique and developing suitable numerical tools.The lumped mass method is adopted to form the numerical model of the net. Each mesh bar is simulated by a linear bar element. The strand is supposed to be elastic and the relationship between tension and strain follows Hooke's law. All knots at which the elements are connected to other elements are supposed to be non-frictional rotatable links. According to the lumped mass method, for each element the lumped mass points are set at the two ends.The mass of each mesh bar is equally divided between the two ends of the element. Each knot mass is equal to half the mass of all mesh bars around it. As the elements have specified lengths, it's possible to calculate external forces exerted on them, such as hydrodynamic force, gravity force and buoyancy force. The external forces are also equally distributed to the two ends of the elements. Thus, the net can be modeled by a discretized model consisting of many point masses and elements without mass. Newton's second law of motion is applied to these points to obtain their expressions of motion. For simplification of calculation, the frames of the cage are assumed to be rigid bodies and their equations of motion are acquired from the...