Research On Overall Hydrodynamic Performance Of Deep Sea Mining System

The abundant metal minerals on the ocean floor will become a major source of mineral resources in the future,and the key technologies and equipment for the development and utilization of ocean floor resources will become a hot spot in the frontier research field of marine engineering.Nowadays,the deep sea mining system with lifting pipe has been recognized as the most promising mining scheme.The pipeline lifting deep sea mining system mainly includes a surface support vessel,a long-distance vertical transportation lifting pipeline,an underwater TMS,a conveying hose,and a subsea mining robot.At present,there are few related researches on the overall hydrodynamic performance of deep-sea mining systems,and no comprehensive system model test research has been carried out.The thesis is based on the national key research and development plan project "Deep-sea Polymetallic Nodule Mining Test Project",which integrates the three-dimensional potential flow theory,computational fluid dynamics method,and flexible pipeline centralized mass method to establish a complete deep-sea mining system value from the surface to the bottom.The calculation model has carried out the analysis of the hydrodynamic performance of the deep sea mining system in place and in the state of deployment,and calculated for other different operating states existing in the operation of the deep sea mining system.A model test has been completely simulated in the test pool of SKLOE of Shanghai Jiao Tong University.Combining numerical calculations with experiments,the loads and motions of key positions in deep sea mining systems under complex marine environment conditions are analyzed,and the relationship between the structural responses is analyzed.The thesis research reached the following conclusions:The deep sea mining system could work normally in level 5 sea condition and the deployment could be conducted in level 4 sea condition when the angle of surface vessel and wave is between 180 degree to 135 degree;Von mises stress and the collision probability of lifting pipe and moon pool will increase when the angle of surface vessel and wave is between 135 degree to 90 degree.In the deployment conditions,Von mises stress at the bottom connection position of lifting pipe are relatively large in the initial stage of the deployment;due to less restrictions,the mining vessel will have a offset.During the movement of the mining vessel,Hose and lifting cables connected to it may become entangled;The passive heave compensation device can reduce the load and vertical displacement at the top position,but it is mainly effective when vessel is heading the wave;the universal joint structure can significantly reduce shear force of the structure in the transverse wave.The movement of the mining vessel has a certain effect on the load and configuration of the hose,and the route of mining vessel need to be considered cautiously;When the surface vessel is facing the wave,the heave motion has a significant effect on the axial load of the lifting pipe.Depending on the direction of the wave,roll and pitch will have some effect on the axial tension.