ISPH Simulation Research Of Sediment Erosion Around Submarine Pipelines

In recent years,the erosion of sediment around submarine pipelines has become a key challenge in ocean engineering and deep-sea oil and gas development,as well as transportation engineering.The local scour around pipelines has become an important research topic because scour pits caused by sediment erosion can lead to instability and rupture of submarine pipelines,which may affect the safety of oil and gas transportation,potentially leading to personal and property losses.Therefore,revealing the process of local scour and sediment transport around submarine pipelines is considered a key scientific problem in the field of marine research,and studying the characteristics of local scour and scour equilibrium depth around submarine pipelines has become a top priority for submarine pipeline engineering.These factors are critical to determining the quality of pipeline engineering design.Meanwhile,the incompressible smoothed particle hydrodynamic method(ISPH)is a numerical simulation method that has gained recognition among many scholars due to its advantage in handling complex free surfaces and water-sediment interfaces.Therefore,this study will use the ISPH method to conduct research on sediment erosion around submarine pipelines.The specific content includes three aspects:(1)The control equation of incompressible smooth particle hydrodynamics(ISPH)method and the solution process of SPS turbulence model are introduced.The space average format and two-step projection method solution theory of the discrete N-S equation under the ISPH framework are expounded.The discrete formats of viscosity term,shear stress term and modified format pressure Poisson’s equation in the N-S equation are derived respectively.The sediment and water two-phase flow model The coupling process between the SPS turbulence model and the developed CWP-TWP-CSS sediment incipient erosion model.(2)Establish a flow field motion model and sediment erosion model around the pipeline under the action of fixed bed unidirectional flow,reproduce the flow field and sediment motion process in physical model experiments,and compare the numerical results of erosion pit morphology under different cross-sectional flow velocities and clearance ratios with experimental data.It is found that the numerical calculation results are in good agreement with experimental data,thus verifying the accuracy and applicability of the numerical model in this paper.(3)The numerical model of sediment scouring around the submarine Oil pipeline in twodimensional one-way flow is established,and the scouring process around the pipeline is studied under different working conditions,namely,different pipe diameters,different gap ratios,and different flow velocities;Discuss and analyze the numerical simulation results,and study the impact of different operating conditions on the depth and development process of pipeline erosion.When the pipeline diameter and inflow velocity remain unchanged,the maximum scouring depth first increases and then decreases as the gap ratio increases;When the diameter and gap ratio of the pipeline remain unchanged,the maximum scouring depth also increases with the increase of incoming flow velocity;When the inflow velocity and clearance ratio remain constant,the maximum scouring depth gradually decreases with the increase of pipeline diameter.Analyze the vortex structure before and after pipeline erosion and the development process of vortices around the pipeline,and further study the mutual influence between the development of erosion pits and vortex motion.(4)Through the detailed processing and analysis of the numerical simulation results of the scouring process around the pipeline,combined with the existing experimental data and numerical simulation research laws,this paper expounds several ways to prevent the scouring near the pipeline,provides a theoretical basis for the stability design of submarine pipelines in the engineering community,summarizes the scouring protection methods around the submarine Oil pipeline,and designs the protection devices for submarine pipelines.