Numerical Simulation Of Flows Around Pipe And Local Scour

Subsea pipelines are one of the major modes of ocean oil and gas transport. Nearly ten thousand kilometers pipelines have been buried in Bohai Sea,East China Sea and South China Sea. The pipelines protection plays an important role in oil and gas resource exploitation and ocean environment protection. The local scour around the pipelines could cause the pipe hanging and might finally lead to have breakages. Therefore, the study on the flow around the pipeline and local scour mechanism becomes more and more important in the marine resources development.This paper, based on FLUENT model, simulated the 2-D flow around the pipeline, and compared the simulation results with the experimental results collected in the flume of Harbor and Coastal Engineering department, SJTU. Firstly, the velocity was computed according with the experimental conditions, then the numerical flow around the pipeline was compared with the physical results and the influence of pipeline location was analyzed.The pipeline surface and the bed shear stresses at different inlet velocities and different gap-ratios were simulated in this paper. The results showed that there was a pressure gap between two sides of the pipeline and the place where the scour most easily happened was illustrated.On the base of the flow around the pipeline, the hydraulic gradient under the pipeline was calculated supposing the bed was alluvial. The result evidenced that seepage was one of the main factors causing the scour. Finally, the mechanism of pipeline local scour was discussed and the process was summarized.