Research On Local Scour Of Pipeline Under The Action Of Water Current

Oil and gas pipelines are responsible for the transportation of petroleum and other energy resources in China.In recent years,with the rapid development of national economy,pipelines play an increasingly important role in the development of national economy.However,oil and gas pipelines usually need to pass through areas with poor environment.Under the action of water flow and other conditions,local scouring around pipelines is prone to form scouring pits near pipelines,and the burial depth of pipeline foundation is decreasing continuously,resulting in pipeline suspension,which may lead to pipeline damage,even loss of life and property,which is of public safety and social economy.There are great hidden dangers in development.Therefore,it is of great significance to study the flow field around the pipeline,the location of the scour pit and the depth of the scour pit.In this paper,physical model tests and computational fluid dynamics(CFD)are combined to simulate the flow field around the pipeline and the development of scour pits.The main contents of this paper are as follows:(1)Set up the test device,carry out physical model test,and get the distribution law of X-direction velocity on the vertical surface of the pipeline center line.(2)Based on the principle of computational fluid dynamics(CFD),a three-dimensional numerical model of local scour around pipeline is established by FLOW-3D,and the results of numerical calculation are compared with those of physical model test.The velocity characteristics,pressure characteristics,turbulent kinetic energy and bed shear response around pipeline are studied under different time,different velocity and different burial depth conditions.The force distribution is calculated numerically.It can be seen that the downward flow of the pipeline,the downward accelerated flow along the pipeline and the backwater in front of the pipeline can be well simulated.At the same time,it can be seen that the pressure difference between the front and the back of the pipeline is large.(3)Based on the principle of computational fluid dynamics,considering the interaction of water flow,pipeline and sediment particles,a three-dimensional numerical model of local scour around pipeline is established by FLOW-3 D software.The mechanism of local scour around pipeline is simulated and analyzed by numerical simulation.The formation process,shape and maximum depth of scour pit around pipeline are visually displayed,and the maximum depth of scour pit is realized.The dynamic visualization simulation of the whole process of local scour around the road is carried out,and the causes of the scour pit formation are analyzed theoretically.(4)Summarizing the research results of domestic and foreign scholars on pipeline local scouring,focusing on the analysis of the impact of five factors on pipeline scouring law,such as incoming flow velocity,particle size of sediment,initial water depth,pipeline diameter and pipeline burial depth.