Numerical simulation analysis of flow field and dredging characteristics of pipeline self-cleaning

To alleviate sediment deposition in urban drainage pipelines, a hydraulic self-cleaning structure for pipelines was designed, incorporating a gate and flume.Numerical simulation methods were conducted to analyze the hydraulic characteristics of the dredging process under different slopes and initial inflow levels. The results show that at the initial stage of dredging, the flume shear stress and vertical mean velocity at the inlet of the pipeline can reach 16 and 1.55 times those at the end of the process, respectively. As the flushing wave moves to the end of the pipeline, the maximum flume shear stress and the maximum vertical mean velocity at the inlet of the pipeline can reach 5 and 2 times those at the end of the pipeline, indicating a stronger dredging effect in the upstream section. During dredging, the maximum shear stress of the flow in the flume and the maximum vertical mean velocity can reach 104 and 1.45 times those on the platform, respectively, indicating that the dredging efficiency in the flume is significantly superior to that on the platform.Specifically, the increased slope of the pipeline and higher initial inflow levels result in greater flushing wave shear stress and vertical mean velocity, with maximum recorded values of 156 Pa and 3.6 m/s, respectively, reflecting a better pipeline cleaning effect. During dredging, the flushing wave velocity and shear stress generated are significantly higher than the theoretical uplift flow velocity and critical shear stress of the sediment, which proves that the dredging effect of the hydraulic self-cleaning structure is good.