14 established the coupled dynamic model of deep-water flexible pipeline, carried out the hydrodynamic analysis of pipe laying vessel by using AQWA software, and completed the numerical simulation of flexible pipeline by using OrcaFlex software, and analyzed the factors affecting the dynamic characteristics of the pipeline. The results showed that there is a significant connection between the dynamic responses of pipelines and the pipe laying vessel motions. The model was solved by Newmark method and verified with OrcaFlex software. 13 proposed a coupled time-domain numerical model of pipelines and pipe-laying vessel motions. For the vessel-pipe coupling system in the deep sea, Zan et al. With the increase of the length of the pipeline, the nonlinear effect and damping effect of pipeline gradually increase, the top tension of pipeline gradually increases, and the coupling effect between mining vessel and pipeline becomes more obvious. So, a complex coupling dynamic response system is formed between the pipe and the vessel. At the same time, the vibration of the lifting pipe in turn affects the vessel motion. On the other hand, the pump sets and the buffer also increase the stability of the lifting pipe 10.ĭue to the motion of the mining vessel, the lifting pipe is prone to longitudinal vibration, transverse vibration and torsional vibration 11, and in this process, a large dynamic load is added to the lifting system 12.
In this system, the lifting pipe must be equipped with pump sets for lifting the mineral resources to the vessel, and with a buffer to regulate the density of the ore-fluid mixture. The system typically consists of surface mining vessel, lifting pipe, lifting pump sets, buffer, lifting hose and subsea collector 6, 8, 9. Among them, the pipeline transportation mining system is recognized as the most practical deep-sea mining system, and it is also the only deep-sea mining system that has been verified by deep-sea experiments 7. Since 1970s, many research groups from the United States, Canada, China, France, Germany, Russia, Japan and India have studied the core technology of deep sea mining 5, 6. In order to extract these minerals from the deep sea bed, there are usually three methods, namely, seabed mechanical transportation, air lift system with ejector and hydraulic lift system with pump station 4. Marine solid mineral resources, such as the most common iron-manganese nodules, are usually found in the 4000–7000 m deep sea 3. At present, the proven potential deep-sea mineral resources include polymetallic nodules, cobalt-rich crusts, and polymetallic sulfides, among which deep-sea manganese nodules and cobalt-rich iron-manganese crusts are abundant 2. The research results of this paper are of great significance to the safety design of deep-sea mining lifting system and the planning of deep-sea operation activities.ĭeep sea contains a lot of resources, which can meet the needs of mankind for a long time in the future 1.
The coupling simulation results show that the coupling effect has a significant effect on the time domain dynamic response of the lifting pipe, but has little effect on the average effective tension and longitudinal amplitude along the pipe length. There is a very good agreement in RAO between the experiments and simulations. The response amplitude operator (RAO) is used to compare the measured and simulations dynamic response of the mining vessel. Therefore, this paper uses time-domain coupled numerical model as the research object, considering ocean current, surface wave, pipe dynamics and vessel-pipe contact mechanics, to study the dynamic behavior of the lifting pipe and mining vessel during the process of deep-sea mining using AQWA and OrcaFlex softwares. The characteristics of coupled motion model have not been fully considered in the existing research. In deep-sea mining, the coupling dynamic response between the mining vessel and the lifting pipe is a significant problem, which directly affects the structural design of the lifting system and the safety of field operation.
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