Research On Influence Of Embankment Line Optimization On Hydraulic Characteristics Of Confluence Zone

In the natural river channel,there are often intersecting flow,and the complex hydraulic phenomena are generated in the intersection of the river,such as higher water level,separation zone and spiral flow.The separation zone narrows the flow section,which leads to the large difference in velocity between the left and right banks.Sediment deposition and pollutants retention will appear in the low velocity area near the intersection,and the high velocity far from the intersection will seriously affect shipping safety and limit the development of the shipping industry,it has important theoretical and practical significance for the study and optimization of the separation zone.In this paper,GAMBIT is used to perform two-dimensional modeling of the tributary into the mainstream at 60°angle,FLUENT is used to perform numerical simulations under seven convergence ratios of the original embankment line and the optimized embankment line.The hydraulic characteristics of the intersecting flow are researched at different confluence ratios,the effects of the embankment line optimization are analyzed,and the degree of improvement is evaluated.The main conclusions are as follows:(1)The size L*,B*of the separation zone increases as the convergence ratio RQ increases for 60° intersection flow.(2)The rectification schemes of the two optimized embankments of ellipse and parabola are analyzed and compared from the flow field,velocity and flow axis.Finally,the ellipse scheme is chosen as the optimal solution.After elliptical optimization,the size of the separation zone can be effectively reduced,and the reflow phenomenon is significantly improved.(3)The high velocity gradient regions of the intersecting water flow are mainly distributed in the branch flow area.After optimization of the embankment line,the cross-section velocity gradient can be reduced by about 50%.(4)The pulsation along the water flow direction is stronger at longer distances and has a wide range of action.But the pulsation along the groove width is very sharp only near the intersection.After optimizing the embankment line,the turbulence intensity can be effectively reduced,and the longitudinal turbulence intensity is optimized slightly higher.(5)As the convergence ratio RQ increases,the lateral motion intensity of the intersecting flow increases,and the flow is more concentrated;the optimization of the embankment line can significantly reduce the lateral motion intensity,but will not reduce the size of its effect area.