Dynamic Analysis Of Deep-sea Mining Flexible Pipe Under The Action Of Internal And External Flow

In the deep sea far away from the coast,an environment full of all kinds of complexity,the deep-sea mining system needs to transport the poly-metallic marine minerals to the mining ships on the sea surface safely and orderly.In order to guarantee the efficient,continuous,and systematic work of deep-sea mining,the fluid-solid coupling mechanical behaviors of the flexible pipes of the deep-sea mining and lifting system should be studied.The main content and conclusion of this essay are described in the following:1)The basic theories of the fluid-solid coupling mechanics is elaborated.Based on the solid-fluid control equation,its boundary conditions equation,and the force conditions of the flexible pipes,the axial vibration equation and the transverse vibration equation of the flexible pipe representative elemental volume under the co-action of the fluid and solid,and the transition matrix are derived.2)Based on the multi-rigid-body discrete element method and using the virtual prototype simulation technology,a model of the 1200 m full flexible pipe lifting system is established.In continuous buoyancy configuration,considering the laying length,the buoyancy size,and the horizontal distance between collector and the mining ship,the configuration and the mechanical characteristics of flexible pipe lifting system are analyzed under the ocean current action.Results show that when the buoyancy configuration length is between 190m and 210m,the buoyancy size between 1.0G and 1.1G(G is the net weight of the 250m flexible pipe in water),and the horizontal distance of the collector and the mining ship between 260m and 300m,better space configuration and mechanical state can be obtained.3)At present,it is very difficult to analyze the fluid-solid coupling of the long scale full flexible pipe lifting system with full size.According to the fact that the vibration of flexible pipe far away from the collector would decrease sharply,only a small part of flexible pipe near the collector has been studied.Based on the fluid-solid coupling theory and using the finite element method,the wet mode and the displacement time-history curve of flexible pipe were obtained respectively according to the three initial configurations from the above.The results show that the flexible pipe would swing periodically under the action of fluid-solid coupling and the amplitude and the period of flexible pipe would reduce along with the increase of the horizontal distance between the collector and the mining ship.