The confluence phenomenon is fairly common in the natural river[1-2]. In the confluence regions, two
mutual mixing streams lead to unique hydraulic behavior such as flow field changing, spiral flow, convex
water surface, local flow stagnation, and so on. In the confluence region the flows mutual mix so
violently as to lose energy very greatly, so the original equilibrium state of mainstream and tributary is
broken, which weaken highly sediments and pollutants transport, impact water ecological environment
and seriously reduce river flood discharge capacity. Therefore the confluence problem has been a focus of
attention of water conservancy, shipping, flood control and environmental protection department.
Since Taylor firstly put up with the confluence problem of rectangle open channel in 1944, the
hydraulic behavior at the confluence is already studied detailed based on theoretical analysis and sketch
model experiment at home and abroad[3~5], but the study on hydraulic behavior of natural river
confluence is not sufficient. The confluence of Yangtze River and Jialing River is the aquatic gate of two
river shipping in Changing, where the flow is so complicated and varied as to seriously endanger shipping
safety. The hydraulic behavior of the confluence of Yangtze River and Jailing River is researched in
detail by numerical simulation in this paper.arge and negative correlation to the discharge ratio.