Experiments On Flow Character And Sediment Movement Under Symmetrical ("Y") Planform Confluence

River channel confluence form important morphological elements of every riversystem, being points at which rapid changes in flow,sediment discharge andhydraulic geometry must be accommodated. According to Plane intersection form,confluence can be divided into two parts,asymmetrical planform confluence&symmetrical (“Y”) planform confluence. Currently, by the way of natural measuredresources、model type、mathematical model, scholars have a better understanding ofasymmetrical planform confluence. while the research of symmetrical (“Y”)planform confluence is lacked.In this paper,flume experimental studies wereconducted to observe the Water and sediment movement under the30°symmetrical(“Y”) planform confluence. In this,we can have a better understanding of the rulesof flow structure&sand movement of “Y” confluence,which can providetheoretical and technical support to channel regulation、the water department andThe environmental protection department.Firstly, the paper makes an anlysis of the3D hydrodynamic characteristics ofconfluences, meanwhile,the paper analyses the influence of discharge ratio to Spiralflow structure, then describes turbulence characteristics of confluence and theinfluence of discharge ratio&water height to turbulence intensity. Lastly, the paperconsiders the influence of discharge ratio to water power axis. The general characterof symmetrical (“Y”) planform confluence is the double circulation in crosssection, the whole water movement is a to face spiral flow, At any discharge ratio,vertical; longitudinal turbulence reach maximum in cross-section. With the waterdepth changing, it has a grate influence on the turbulence of tributary side.to waterpower axis, it has a great effect on the position of river junction. With the dischargeratio increasing, the position of river junction goes downstream.In the end,the paper does research into the punch in bed at discharge ratio of0.34、0.5、0.7.