Flow structure, bed morphology, and contaminated sediment transport at the confluences of pipes with an angle 60°

The convergence of pipes within urban drainage networks introduces the accumulation of sediments and pollutants, significantly impacting operational efficiency and the water environment. Research focusing on the mean and turbulent structures within the shear layer, including parameters, such as the flow field, turbulent kinetic energy, and Reynolds shear stress, yields insight into flow dynamics. The study elucidates that the precise identification of the shear layer position is facilitated by specific values, with spiral flow manifesting under particular conditions, thereby mitigating sediment accumulation. Moreover, the study underscores the pivotal role of the confluence ratio in shaping the confluence bed and influencing sediment transport mechanisms. The temporal evolution of contaminated sediment transport demonstrates a migratory trend toward the downstream bar, signifying the attainment of a state of bed morphological equilibrium. This research imparts valuable insight for addressing sediment reduction in confluence pipes and enhancing overall drainage network efficiency.