The Characteristic Analysis Of Flow And Channel Evolution In Meandering Streams In Baotou Section Of The Yellow River

In recent years,the problems and the limitations of current research about the sandy river,combined with the actual situations of the curve in Baotou section of the Yellow River,which analyzes the flow characteristics of the river bend and the silt transport characteristics,then combine with the two characters and research how the channel scouring and silting move.The main contents of the study include the flow characteristics of the bend river,the sedimentation and start of sediment,the variation of sediment concentration and the analysis of the related factors.The results show that:(1)Bend flow characteristics:The bending section of the concave and convex velocity is significantly smaller than the center line velocity,entrance and exit section of the curve of velocity distribution near the shore and the center line velocity difference.Each section near the concave and convex two perpendicular longitudinal velocity distribution change on the same level and at the centerline velocity distribution along the depth increases and the velocity distribution is relatively slow,and the lower velocity is greater than the upper velocity variation amplitude.The velocity distribution in different period of ice flow,Under the ice sheet condition,the flow velocity in different depths of water meets different logarithmic distributions.(2)Riverbed morphology analysis:At present the overall shape curve section at the convex concave bank,deposition phenomenon;in the period of ice bed configuration change;frozen period after the break-up period appeared in the top bend shoal.(3)Sediment characteristics analysis:Through the analysis of different sampling periods of incipient velocity and the observed velocity comparison found that in most cases the flow velocity is greater than the starting speed the velocity of flow,which means that suspended displacement,on the other hand,the flow velocity is less than the starting speed,which means that the suspended sediment is not easy to move,causing the riverbed to deposit.(4)Variation of sediment concentration:Generally,there is a trend of decreasing firstly then show the increase and decrease,that is,in the sampling section,the river bed shows the trend of deposition erosion deposition.The minimum period of ice concentration,sediment concentration increased gradually after the break-up.The sediment concentration in the basin and the trend of change of sediment carrying capacity is basically the same,with the change of season showed an increase,then showed decrease,at last show an increase,which has a greater relationship with the size and capacity of the flow changes.