| Summary: | 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 <i>φ</i>, cross-flow flux <i>Q</i>, mixing ratio <i>δ</i>, the incident angle of T-junctions <i>θ</i>) were considered. The coefficient of variation (COV) of the salt solution was selected as the evaluation index and effective mixing length (<i>L<sub>EML</sub></i>) 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 <i>L<sub>EML</sub></i> rise as <i>Q</i> or <i>φ</i> increase and decrease with the increase of <i>δ</i>, where the influence of <i>φ</i> is much greater than <i>Q</i> and <i>δ</i>, and there is no obvious regularity between <i>L<sub>EML</sub></i> and <i>θ</i>. 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.
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