Vibration Characteristics Analysis And Optimization Design Of Submarine Pipelines

Submarine pipeline is a very important offshore oil transportation and pipeline system consists of internal flow field,pipeline,outflow field and pipeline attachment,whose structure is susceptible to crude oil pulsation,ocean currents,shock vibration and other external incentives to produce vibration.When it comes to severe cases,the pipeline will rupture leading to oil leakage.Consequently,it is of great significance for security and economics in marine industry to both analyze the vibration characteristics of the undersea pipeline and control in reduction vibration,as well as optimizing designs on the grounds for its vibration characteristics.Currently,scholars at home and abroad have made extensive researches on the problem of pipe flow solid coupling vibration,mainly using one-way coupling and two-way coupling methods,which are more complex and not easy to converge and the additional quality method also only takes the additional quality of the pipe into consideration.Nonetheless,the acoustic solid coupling fully considers the additional quality of the fluid,additional damping and flow-solid coupling.I mainly make three aspects in research as followings on the foundation of the acoustic solid coupling algorithm,which concentrates on researching the influence of two internal and external flow fields on the vibration characteristics of the pipeline.Firstly,the vibration theory and numerical calculation method of submarine pipelines are analyzed and introduced,which emphatically analyze and deduce the acoustic-solid coupling algorithm.A test platform is built to conduct modal experiments on the free empty pipe,the liquid filled pipeline and the underwater liquid filled pipeline Moreover,establishing finite models on the liquid filled pipeline and underwater liquid filled pipeline on the basic of the ANSYS acoustic module Sounds solid coupling algorithm.According to the sound and solid coupling algorithm 's calculation,liquid pipeline inherent frequency difference between the experimental testing result and the value is within 1.78%.Similarly,the underwater liquid pipeline inherent frequency difference between the experimental testing result and the value is within 3.01%,which prove that analyze the coupling vibration characteristics on liquid filled pipeline and the underwater filled liquid pipeline(internal and external double flow field)is feasible on the foundation of sound andsolid coupling algorithm.Secondly,two conclusions can be drawn from comparable results on the basic of acoustic solid coupling algorithm to model the realistic undersea pipeline,which respectively studies the impact of seawater on pipelines,the impact of crude oil on them as well as the influence of from both of them together on pipelines.First,sea water and crude oil on the natural frequency of the pipeline has the function of attenuation,and in comparison with only considering sea water and crude oil,sea water and crude oil two fluid media together,the natural frequency of pipeline decay is more obvious;analogously,the reduction of the amplitude of the pipe solid mode pattern is more obvious by this above method.Finally,the influence of pipeline support structure and pipe support stiffness on the vibration characteristics of pipe is studied,and it is found that the support structure will reduce the natural frequency of the pipe,and the increase of pipe support stiffness can improve the stability of the pipe.This paper also analyzes the vibration reduction control and optimization design of the pipeline system,and the addition of a rubber damping layer to the pipe support structure can effectively suppress the pipe vibration,and the parameter optimization of pipe wall thickness and support stiffness can also effectively reduce the vibration amplitude of the pipe.