Numerical Study On The Impact Of Submarine Mudflow On Pipelines

Submarine oil and gas pipelines are important lifelines for oil and gas transportation in the deep sea.As a carrier for transporting oil and gas from inshore platforms to land,they are widely used in offshore oil and gas engineering due to their good continuity,large transport volume,and easy management.Due to the long-distance transport of submarine pipelines,the rough terrain experienced by the seabed changes greatly,and submarine pipelines easily form partial suspension spans.The seabed beneath the submarine pipelines is under the influence of various mechanisms,even under extremely gentle gradients.Landslides may also occur.The mud flow/turbidity flow generated by the submarine landslide impacts the suspended pipeline and affects the stability and safety of the operation of the submarine pipeline.Therefore,it is necessary to study the impact of mud flow/turbidity flow generated by submarine landslides on submarine pipelines.Using Fluent,the most widely used computational fluid dynamics software,as a platform,the characteristics of muddy flow and turbidity flow are distinguished from ordinary seawater.The power-law model and Herschel-Bulkley model are used to describe the fast-sliding mud flow.Then establish the two-dimensional and three-dimensional models to describe impact process of the non-Newtonian fluid.Comparing with previous scale test results,it shows that the two-dimensional model when using Power-law rheology simulates the rationality of mud flow impact on pipelines.A sensitivity analysis was performed on the relevant parameters of the rheological formulae fitted by the predecessors.The force characteristics of the suspended flow generated by the mudslide impacted by the submarine landslide are calculated and analyzed.The changing rule of the target weight such as drag coefficient and lift coefficient of the pipeline when the mud flow impacts the pipeline is analyzed.Based on the law of mud flow impinging on the force acting on the pipeline,the characteristics of the debris flow,mud flow and turbidity flow developed by the submarine landslide body are used to perform the impact action of mud flow,turbidity current and normal seawater on the pipeline.A comparative study was conducted to discuss the influence of mud flow on the impact of pipelines with different rheological parameters under different clay contents.Under typical sea conditions,the differences in mud flow,turbidity flow,and normal seawater impact on pipeline's provide guidance for pipeline safety analysis in the project.