| The gradual exhausting of mineral resources in land store becomes an important motive which promotes more and more powerful research on ocean mining. It is main research topic of the deep ocean mining that efficiently collecting and transporting system of poly-metallic nodule from the sea floor to surface mining vessel is needed under complicated influence of the ocean environment, in the meantime which has high reliability and commercial applied value. The collector-pipe mining system as a typical commercial mining system for deep ocean poly-metallic nodule is extensively accepted by the nations currently. From the 70's in 20 centuries, many technology research and ocean experiments on such mining system had been carried out by many international research organizations or some nations. Collector-pipe lift mining system is also adopted in Chinese 1000m sea trial project of mining system for deep ocean poly-metallic nodule, which is a long multibody pipeline system consists of lifting steel pipe, pump, buffer station, flexible hose, etc.During the ocean mining process, lifting pipeline system bears complex coupled external loads such as hydrodynamic loads of ocean environment, and is also affected by the motions of surface mining vessel and submarine collector. Therefore, the kinematic and dynamic responses of lifting pipeline system are very complex not only in the launch and retrieval operation process but also in towing mining process. Numerical simulation on space configuration and dynamic characteristic of lifting pipeline system in linkage operations for deep ocean mining was carried out by geometric nonlinear finite element method (FEM) in this thesis, as a part of national project of deep ocean technology research & development. The main contents are as follows:1. There are couple effects of mechanics on each part of the multibody lifting pipeline in deep ocean mining. According to total system design and operating plan of lifting pipe system for 1000m sea trial project, the modeling methods of multibody lifting pipeline system were studied in this thesis, based on the structure characteristic, connection modes, operation condition. Especially, the flexible hose is an important part of lifting pipeline; its modeling method influences the calculation efficiency and precision of integral pipeline analysis of deep ocean mining process greatly. A modeling method of element couple was put forward based on space beam model of finite element model to simulate the macrostructure characteristic of flexible hose, which tensile rigidity was large and bending stiffness was small relatively. The integral system model of multibody pipeline system was established, which consists of lifting steel pipe, flexible hose, buffer station, pump, etc. A kind of mechanics model of the integral lifting pipeline was achieved for the dynamic analysis of the launch, retrieval and towing process in deep ocean mining. 2. In FEM model of lifting pipeline, the following external loads are considered: gravity, buoyancy, hydrodynamic forces, internal and external fluid pressures, torsional moment and axial force induced by pump working, friction induced by interal flow, concentrated suspension buoyancy on the flexible hose, etc. For the dynamic analysis of working motion of lifting pipeline, the motion loads of collector and ship, and the pipeline's motion loads during the launch and retrieval operation, are also considered. The pipeline's hydrodynamic force induced by ocean wave and current is the main environment loads of lifting pipeline. It belongs to the hydrodynamic problem of pipe or cylinder with small diameter in ocean engineering. The calculation method of pipeline's hydrodynamic force was described based on the Morison's equation in this thesis. To evaluate the drag coefficients of lifting pipe with some adjunctive pipes used in 1000m sea trial, the hydrodynamic experiments had been done in the large low-noise circulation tank. The experimental methods and results of the drag coefficients were given.3. There are several important approaches of nonlinear finite element method to solve geometric nonlinear problem of spatial pipe & beam structures, which includes deformation process with large displacements and finite rotations, such as Total Largrangian (TL) formulation, Updated Largrangian (UL) formulation and Corotation (CR) formulation. Comparing the advantages of these approaches, the principle of Corotation formulation introduced by Rankin was described. The Corotation formulation was adopted to solve nonlinear problems of lifting pipeline.4. In order to obtain the basic parameters of lifting pipeline system for the dynamic analysis of launch and retrieval operation and towing mining, the configuration of lifting pipeline in space was analyzed by static analysis method based on multibody pipeline FEM model. Among many influencing factors of flexible hose configuration, the concentrated suspension buoyancy on hose affects its configuration greatly. Based on combinational analysis of configuration in space, action force on collector and deflection angle of flexible hose bottom, optimized arrangement of concentrated suspension buoyancy on hose was presented, including buoyancy value, arrangement proportion and suspension position of buoyancy balls.5. During the launch and retrieval operation, the configuration, shape and mechanical characteristic of lifting pipeline system transform quickly and greatly. The exploratory research of numerical simulation for launch and retrieval towing process was carried out in this thesis. According to the dynamic analysis of pipeline for launch operation process affter collector landing the sea floor, the initial FEM model for transient dynamic analysis was established. The pipeline shape and dynamic characteristic during launch and retrieval process under various motions parameters were analyzed by transient dynamic method. The research indicates: lower velocity of pipeline's launch improves the dynamic characteristic of flexible hose; the flexible hose is easily piled and enwind at some launch operation mode, and the advice to avoid such situation was offered; the numerical simulation of pipeline's retrieval is the inverse process of launch operation approximately, kinematics and dynamics characteristic of retrieval is comparable with that of launch.6. Based on the FEM model of integral lifting pipeline, transient dynamic characteristic of various linkage motions and 3 typical towing mining modes under continuous tracks was analyzed. Considering the combination effects of steady loads, transient loads and simple periodic motion, the dynamic response of pipeline in time domain was calculated, such as displacement, action force, stress, etc. The results of dynamic analysis indicate: the deflection angle of steel pipe and lateral deflecting of buffer increase with augmentation of towing velocity, as well as the deformation of hose's saddle shape; when towing velocity is less than 0.5m/s, the towing track of buffer is coincided with the setting route of ship on the whole and the following ability of pipeline system is also kept well.7. The launch length of flexible hose will be determined according to the water depth in sea trial, and the distance between buffer and sea floor varies with terrain changing. Therefore, safety domain for collector's motions was designed, in which the buffer was the center of coordinate system. The launch length of flexible hose and the distance between buffer and sea floor are discretized in range. Based on the analysis by FEM, the real-time inquiry table of safety domain for collector's motions was established for real-time monitor system in ocean mining.8. An experimental model in towing water tank with the similar characters of pipeline system in 1000m sea trial was designed to verify the FEM modeling method. And the FEM model of experiment system was established by modeling methods introduced by this thesis. Measuring records of typical hydrodynamic experiment and anhydrous experiment were obtained. The simulation results of pipe stress were coincided with the experimental results by comparison.Conclusions of research in this thesis provided basic characteristic parameters and theory reference for the design of mining system and operation planning of 1000m sea trial. And its methods can also provide references for mechanics research of long pipeline system in ocean engineering.
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