3D Numerical Simulation Of Hydraulic Characteristics In Confluence Between Main Stream And Tributary

By the flow blended with each other and the direction of the water potential changed, the confluence of the natural river waters affects the safety of shipping and sediment transported, flood discharged and dirt transferred. As a result, the hydraulic characteristics of the natural river confluence research are very necessary. This article uses commercial fluent software which is widely used and mature, establishes the three-dimensional mathematical model, and studies the hydraulic characteristics of the confluence waters which is on the basis of the previous research. The research results are as follows:[1] By the created three-dimensional model, calculating and analyzing of project examples of the intersection rive sections of the Jialing River and the Yangtze River:mainly research the spiral flow in different cross-confluence ratio. By the increase of the discharge ratio the mixing area of convergence which is in the downstream section of the confluence, the water level in the main stream continuously reduced, the tributary water level is rising.According to the interception of the downstream section spiral flow, we can see that the confluence obviously appears positive and negative spiral intersecting helical FIG. Negative center keep moving to the tributaries, and the positive center closer toward the direction of the mainstream.With the convergence ratio increased, the positive helicity gradually decreases, negative helicity first decreases and then increases[2] According to the past studies have shown that the impact of the hydraulic characteristics of the main flow and the tributaries confluence is mainly due to the interchange angle, the intersection flow ratio, interchanges inflow height difference and the water height of the confluence downstream and Froude number of the main stream and tributary. As a result of this generalized model mainly research in three different flows external conditions, different flow rate, different intersection angles, different confluence height, to establish generalize model for "Y style" symmetric confluence and asymmetric confluence of two confluence way. Calculating and comparing, get to the relative hydraulic characteristics.[3] In the generalized model, in the case of a certain amount of the total flow, for the impact of convergence ratio are discussed below when the main stream and the tributaries flow gap is large,the "Y style" spiral flow of the confluence is that the large flow part will form a larger spiral flow which is at the confluence close to the smaller one flow.The other side of the spiral flow would be closer to the flow side of a small which is oppressed by the stream.The whole section will be leaded by the large flow side of the spiral flow; when the main stream and the tributaries flow is fair, the downstream of the confluence would converge two sizable double helix structure.[4] In different inflow height for asymmetric generalized model,at the inflow elevation and the separation zone which is formed in the tributary side are influenced for each other, When the separation zone coincident with the inflow elevation,can enlarge the inflow energy of the tributaries, a larger energy positive spiral flow is formed in the bottom of the bottom surface.When the separation zone is moved downstream, and will be offset by the inflow elevation,and format a negative spiral flow which is at the opposite side of the positive spiral flow.