Study On Dynamic Characteristics Of Long Distance Transport Pipeline In Deep Sea Mining

With the development and utilization of deep-sea mineral resources,the safety of deep-sea mining transportation system has been widely concerned,which is related to the further development of deep-sea mineral resources exploitation.The deep sea mining system is located in a complex Marine environment,which is affected externally by wave,ocean current and wind loads,and internally by liquid slurry action on the pipe wall,resulting in continuous nonlinear fluid-solid coupling,which ultimately leads to the failure and fatigue failure of the transport system.Therefore,in view of the complex fluid-solid coupling dynamic characteristics of long distance vertical transport pipeline in deep-sea mining system during operation,the following work is focused on:(1)The establishment of a connection between warehouse deep sea transport system calculation model,based on the three dimensional potential flow theory,the additional quality standard and separation variable method is deduced with a concentrated mass at the end(warehouse)among the pipeline of fluid-solid coupling vibration equation,the equation is solved by Matlab software,the calculated results are compared with the simulation validation,the analysis results show that the theoretical calculation results and the numerical simulation results are basically identical.(2)In view of the process of deep-sea mining system layout and recovery and the changes of mining pipe lengths at different depths,the influence of pipeline length on structural vibration characteristics is emphatically studied.It is found that the natural frequency of the conveying pipe decreases gradually with the increase of the pipe length,with an obvious drop,and the vibration mode is mainly bent vibration.(3)In view of the intermediate positions in the process of pulp conveying process by light condition to full load condition,the different working conditions with different size in the middle of the warehouse,the outer wall of pipeline erosion by water and slurry attached on the inner wall of the pipeline,pipe wall thickness changes caused by such factors,deepen the middle quality,size and wall thickness of pipeline vibration characteristics influence,it is concluded that tube natural frequency as the intermediate warehouse among quality,warehouse and volume decreases with the increase of wall thickness.(4)For the connection mode between the transport pipeline and the mining ship,the differences between the natural frequencies and modes of vibration of different constrained pipelines are compared.By comparing the modal analysis results of the three constraints,the natural frequencies and amplitudes of the elastic constrained pipelines are the largest,and the modes of vibration are the simplest.Among all the factors,the variation of pipe length has the greatest influence on the natural frequency of pipelines.Therefore,pipe length can be considered as the main influencing factor in the analysis of fluid-solid coupled vibration characteristics in the design of deep-sea mining transportation system.(5)For deep-sea mining system in long distance pipeline in the vertical drain the mechanical properties of role at the same time,focus on the external fluid(four,six levels of sea state)and internal pulp(velocity and density)of the displacement and the influence of the equivalent stress of pipeline found pipelines maximum lateral displacement and the maximum equivalent stress are as outflow,the flow velocity and flow increases with increasing density.