Numerical Simulation Of Flow And Erosion Of Multiphase Flow In Submarine Oil Pipelines

With the advancement of our country’s technology and the development of the offshore oil industry,our country’s offshore oil resources have also been continuously developed,and exploration also being carried out in the deeper sea.Submarine pipelines play an irreplaceable role in the production and transportation of crude oil.Due to the complexity of the submarine environment,submarine pipelines would rupture in the process of transporting crude oil.The oil leak into the ocean will pollute the marine environment and endanger the marine life.Therefore,studying the problems of multiphase flow in submarine oil pipelines and erosion and wear of pipelines could reduce the occurrence of marine environmental pollution incidents,and play a certain role in the protection and pollution prevention of marine environment.In this paper,computational fluid dynamics and fluid simulation technology are used to numerically simulate the oil-water sand multiphase flow in the pipeline and the erosion of particles on the pipeline.Firstly,simulated the flow field in the 90° elbow,studied the different factors which affect the erosion rate of pipe wall,and analyzed the trajectory of the particles in the 90° elbow.Then simulated and analyzed the multiphase flow field the particle trajectories in S-shaped pipeline,and the collision law between particles and the pipe wall is obtained.Finally,provided some suggestions about the protection of submarine pipelines.The main research findings are as follows:(1)For the 90° elbow,the central flow velocity of the inlet horizontal pipe is greater than the flow velocity near the pipe wall.Due to the centrifugal force in the elbow,the maximum velocity deviates to the outside of the elbow.And there is a secondary flow in the elbow,the direction is from the inside to the outside of elbow,then along both sides of the pipe wall to the inside.(2)Under three flow rate conditions,the particle diameter,pipe bending angle,and crude oil water content were changed to calculate the maximum erosion rate of the pipe wall.Calucate the life of pipe by calculating the maximum thickness loss of the pipe wall.It is found that when under the large flow rate,the change of the maximum erosion rate of the pipe wall is more obviously affected by these three factors.When other conditions remain unchanged except the particle diameter,the maximum erosion rate decreases with the increase of particle diameter,and the main erosion position is transferred from the inner side to both sides of the elbows;only changing the bending angle of the 90° elbow,the larger the bending angle,the higher the maximum erosion rate;only changing the water content of the crude oil,the maximum erosion rate increases as the water content of the crude oil increases.(3)Tracking the motion trajectory of particles which carried by the fluid into the pipeline at different locations in the 90° elbow under the conditions of low flow rate,high fluid viscosity and high flow rate and low viscosity,respectively.When the flow rate is low and the viscosity is high,the movement path of the particles affected by the secondary flow at the elbow moves inward along both sides of the pipe wall,so the main collision position is on both sides and inside of the elbow.When the flow rate is high and the viscosity is low,most of the particles will directly collide with the outside of the elbow.(4)Perform flow field and erosion rate analysis on S-shaped pipes,compared with the 90° elbow,each bent pipe part of S-shaped pipe has the secondary flow phenomenon,and the direction is the same as the elbow part of the 90° elbow.After tracking trajectory of the particles carried into the pipeline with the fluid at different positions under the two cases,it is found that the particle’s movement law in the S-shaped pipe is similar to that in the 90° elbow.It shows that the movement of particles in the pipelines is mainly affected by the fluid drag force and its own inertial force.When the fluid drag force is large,the main collision position occurs on both sides and the inner side of the elbow section,and when its own inertial force acts larger,the main collision position occurs on the outer arch of the elbow section.(5)In order to reduce the occurrence of incidents of pipeline rupture and oil leakage that pollutes the marine environment,in actual production,the parts that are prone to bend in the pipeline should be reinforced,and the factors affecting the erosion rate of the pipe wall should be controlled within a reasonable range.Calculate the life of the pipeline according to the actual working conditions,analyze the force of the particles in the pipeline,and check and replace the corresponding locations prone to erosion in time.