Analysis of the Impacts of Geometric Factors on Hydraulic Characteristics and Pollutant Transport at Asymmetric River Confluences

Asymmetrical river confluence zones play a critical role in water quality protection and remediation. This study develops a three-dimensional numerical model to simulate the hydraulic characteristics and contaminant dispersion processes within river channels. The results indicate that variations in the two geometric factors—the confluence angle and elevation difference—can produce a range of effects. Under the combined influence of these factors, the trajectory line at the pollutant-mixing interface follows a “logarithmic” growth pattern. As indicated by the inhomogeneity index, an increase in the junction angle and elevation difference significantly accelerates the mixing rate of pollutants and enhances dispersion. These insights suggest that, in cases with large confluence angles and significant elevation variations, intense mixing of water flow facilitates the rapid transport and extensive dispersion of pollutants, which may help reduce localized pollution loads. These findings are crucial for developing effective water environment management strategies.