Abstract
The mixing, migration, and degradation of pollutants in sewers are the main causes for pipeline corrosion and the increased pollution scope. The clarification of the turbulent mixing characteristics in pipelines is critical for finding the source of pollution in a timely fashion and inspecting pipelines’ damaged locations. In this paper, numerical simulations and experiments were conducted to investigate the turbulent mixing characteristics in pipelines by studying a T-junction system, of which four variables (main pipe diameter φ, cross-flow flux Q, mixing ratio δ, the incident angle of T-junctions θ) were considered. The coefficient of variation (COV) of the salt solution was selected as the evaluation index and effective mixing length (LEML) was defined for quantitative analysis. The numerical results were found to be in good agreement with the experimental results. The results reveal that the values of LEML rise as Q or φ increase and decrease with the increase of δ, where the influence of φ is much greater than Q and δ, and there is no obvious regularity between LEML and θ. By dimensional analysis and multivariate nonlinear regression analysis, a dimensionless relationship equation in harmony with the dimensional analysis was fitted, and a simplified equation with the average error of 4.01% was obtained on the basis of correlation analysis.
Highlights
Sewers as indispensable infrastructures in urban development, are located in all corners of the city, which undertake the sewage conveyance, water pollution control, flood control, storm drainage, and other significant functions
A massive amount of pollutants accumulated on the urban ground surface is washed into sewers and the receiving water of the city through the collapse point, resulting in pipeline corrosion and point source pollution which can be regarded as turbulent mixing
A CFD study of turbulent mixing in a T-junction system was performed comparing with the experimental results
Summary
Sewers as indispensable infrastructures in urban development, are located in all corners of the city, which undertake the sewage conveyance, water pollution control, flood control, storm drainage, and other significant functions. After the heavy rainfall flood, the sewers may be full at one place due to the large increase of flow. The mixing, migration, and degradation of pollutants in sewers are significant reasons for pipeline corrosion [1] and the expansion of the pollution scope [2,3], resulting in point source pollution. The study of turbulent mixing characteristics in sewers is critical for inspecting the pipeline damage and identifying sources of pollution, including the determination of a single source of pollution for a water supply network. Turbulent mixing in a T-junction system [4]
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