Research on the three-dimensional flow field distribution law of underwater pipelines under different flow rates

Abstract Due to the numerous water systems in the southwestern region of China, oil pipelines usually need to cross rivers. Underwater pipelines are exposed to long-term erosion from riverbed sediment, strong river water erosion, and corrosive environments, facing extremely high leakage risks. This experiment adopts an indoor water tank test and simulates underwater pipelines with circular organic glass tubes. Three different flow conditions are set up, namely 14L/s, 25L/s, and 39L/s. The research results indicate that: 1) When underwater pipelines generate flow around, vortices show a characteristic of alternating up and down generation, and the width of the wake vortices is basically maintained within the range of 1.2-1.5 times the pipe diameter; 2) There are significant distribution differences in the vertical flow velocity and turbulence intensity of underwater pipelines, and the greater the flow rate, the more obvious the differences. The flow velocity in the middle layer is the smallest, and the turbulence intensity is the largest; 3) By drawing the force diagram of the underwater pipeline, it can be seen that the net horizontal thrust increases the fastest, while the dynamic buoyancy increases the slowest.