Three-Dimensional Numerical Investigation on Velocity Field and Mixing Characteristics at Channel Junctions
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Abstract
Channel confluence is an important component in river systems. The flow dynamics and mixing processes associated with such geometry are highly three-dimensional and complicated. In this study, a commercial software, ANSYS CFX, was employed to investigate the flow structures and mixing characteristics at channel confluences using steady-state three-dimensional numerical method. The results indicated that the flow converging could not produce rapid mixing within the confluence or immediately downstream because of locally confined secondary current. However, with the secondary current growing downstream, the mixing rate was accelerated. Transverse mixing coefficients were determined for channel junctions with different confluent angles and discharge ratios using the generalized method of moments. This research provided the insight view on the curvature-induced secondary circulation at channel confluence and proposed the corresponding mixing rate.