Two-dimensional Numerical Simulation Of Flow And Sediment Characteristics Of Continuous Curved Multi-rapid And Dangerous Rivers In The Upper Reaches Of The Yellow River

The multi-rapid in the lower reaches of the Changsheng Wharf is located in the Gansu Province in the upper reaches of the Yellow River and belongs to the continuous curved multi-rapid river.There are 4 rapids in the river section,which are the downstream rapid of Changsheng Wharf,the 1# rapid of Shuigouyuanzi,the 2# rapid of Shuigouyuanzi and the 3# rapid of Shuigouyuanzi,which are complex of the nature of the mid-flood rapids and the low-water shoal.Beach risk,emergency,shallow,narrow,dangerous and other obstacles.This paper takes the mathematical model as the main research method and the river model as the auxiliary.By constructing a two-dimensional mathematical model of water and sediment in the plane,the obstacle navigation characteristics,hydraulic characteristics and river channel erosion and siltation characteristics of the multi-rapid river channel in the downstream of Changsheng Wharf are calculated and analyzed.The main research results are:(1)Analyze the causes of the natural obstacles in the continuous improvement of the floodplain in the upper reaches of the Yellow River,the downstream of the Changsheng Wharf,and propose four different remediation schemes for the flow rate,specific drop,water depth and flow regime of the main channel of the river channel and the river channel.The calculation of the scouring and silting conditions and the comparative analysis show that the fourth scheme is the recommended scheme for the final remediation.(2)In the recommended scheme,the downstream beach section of Changsheng Wharf adopts dredging measures to meet the water depth requirement in the design of the trough after the rectification of the dry water flow channel;the 1# beach section of Shuigouyuanzi adopts the rectification measures such as cutting nozzle and filling trough to improve the flow pattern;The 2# beach section of the Shuigouyuanzi section of the river section adopts measures such as cutting nozzles,dredging,and construction of squat dams to adjust the flow velocity and specific drop under the flood flow,improve the flow pattern of the water flow,and reduce the erosion and siltation of the river channel;The section uses dredging and other remediation measures to improve the flow pattern.(3)The recommended scheme better solves the problem that the water depth in the main channel of the natural river channel is not satisfied with the navigation water depth and the disorder of the flow state in the partial position of the natural river channel under the low water flow rate;the flow rate ratio of the 2# beach section of the Shuigouyuanzi is under the middle flood flow The combination can not meet the water level indicators of the beach,so it can not meet the navigation problems such as navigation requirements,flow anomalies and river sediments;and the flow disorder and sedimentation in the main channel of Shuiyuanyuanzi 3# beach design.(4)Through the analysis of the obstruction factors and the remediation plan of the natural conditions of the continuous curved multi-strait dangerous channel in the upper reaches of the Yellow River,the main obstacle law of continuous curved section and the regulation law of facilitating navigation and improving the effect of river channel erosion and siltation are obtained.(5)With the help of the river model test,the recommended scheme is verified.The results show that the water depth in the design main channel meets the navigation requirements under the low water flow.The flood flow in the Shuigouyuan 2# beach meets the water level of the beach,and the Shuiyuanyuan 3# beach design master There is no sedimentation in the trough,and the flow in the channel is stable under different flow rates,which is conducive to the navigation of the ship.The physical model test verifies the rationality of the mathematical model calculation results.