Rearch On Flow Characteristics Of Deposition And Diffusion Law Of Point Source Pollution In Drainage Pipeline

There are a lot of hydrodynamic problems in the drainage pipeline system,including not only the flow characteristics themselves,but also the flow capacity of the silted pipeline and the diffusion law of point source pollution.In this paper,the method of combining laboratory tests and numerical calculation was used to study,which gave full play to the characteristics of experimental research and numerical calculation.On the basis of a large number of literature reviews,taking the specific engineering problems as the starting point,this paper made a detailed discussion on the flow characteristics of drainage pipes by using the results of experimental research and numerical calculation.In this paper,62 groups of working conditions with different deposition and different flow rate in the pipelines were studied by means of experiment and numerical simulation.The results show that the water depth of each measuring point is approximately the same,and the over current can be regarded as uniform flow.The pipeline fullness increases with the increase of flow rate,and the pipeline fullness increases with the increase of pipeline siltation.The shear stress on the pipe wall increases with the increase of the flow rate,and the maximum shear stress appear at the center of the deposition at the bottom of the pipeline for the pipeline with deposition,and the larger shear stress formed by deposition causes the erosion of the pipeline.The formula for capacity loss is established to calculate quantitatively the capacity loss of pipeline under different siltation degrees.Through analyzing the capacity loss of pipeline under different working conditions,it can be seen that the increase in siltation reduces the capacity of pipeline.Under the same siltation degree,the increase in the inner diameter of the pipeline increases the flow capacity of the pipeline.When the siltation is 0.4 and the maximum design fullness is 0.55,the loss of the flow capacity reaches the maximum value of 82%,which provides ideas and suggestions for the qualitative and quantitative evaluation of the silted drainage pipeline in the project.Secondly,this paper used numerical simulation as the main means and combined with experimental verification to analyze the diffusion process of point source pollution,and studied the flow,pipe diameter and water pollution ratio(pollution amount / water volume)as variables to set a total of 36 working conditions.Combined with the characteristics of pollution phase distribution of the cross section and vertical section of the pipeline,the diffusion process of pollutants was discussed.Comparison of pollutant diffusion under different flows,different pipe diameters and different water pollution ratios shows that the higher water pollution ratio,the higher mixing diffusion efficiency,and the lower mixing diffusion efficiency corresponding to the larger pipe diameter and flow rate,that is to say,the longer pipe length is required to achieve the mixing uniformity.Selected the evaluation index of mixing uniformity of water and sewage in the pipeline section to calculate the diffusion degree of pollutants in each working condition quantitatively,and then used the dimensional analysis method to get the formula of mixing diffusion uniformity length according to the calculation results,which can predict the diffusion situation in different working conditions.By means of experimental research and numerical simulation,the flow capacity of gravity flow silting pipeline and point source pollution diffusion law of pressure flow were studied in this paper,which provide theoretical guidance for practical engineering,and promote the further development of the method of combining experimental research and numerical simulation in the study of drainage system.