Numerical simulation study on hydraulic behavior at the confluence of Yangtze River and Jialing River

The confluence phenomenon is fairly common in the natural river. The research on the complicated and distinctive hydraulic behavior of confluence is of great practical and theoretic significance. The finite element model of Yangtze River and Jialing River is established based on two-dimensional depth-averaged surface-water flow and the hydraulic behavior at the confluence is investigated. The analysis shows that discharge ratio of mainstream to its confluent tributary is a crucial factor which dominates location of junction point, junction line and width of backflow zone near the lower reaches of confluence, the bigger is discharge ratio, the closer junction point is to shazui at Chaotianmen, the nearer junction line is on the side of Jialing River, and the smaller of width of backflow is. The water surface slope of the upper confluence depends on water level lifting up each other, when discharge ratio minish, the water surface slope of Yangtze River decreases, while the gradient of Jialing River increases. The water surface slope in the flow mixing region is direct proportional to Yangtze River's discharge and negative correlation to the discharge ratio.