The Research On Flow Regime Influence On Islands Group Downstream The Xinmingtan At The Watercoures Of Huaihe River To Yangtze River

The middle section of the remediation project of the Watercoures of Huaihe River to Yangtze River in Jiangsu Province,from Gaoyou Lake to Shaobo Lake,has a total length of 57.6km.Gaoyou Lake,Xinmin islands,Shaobo Lake,lakes and beaches are in series,beach acquisitive is staggered,water is disorder,flood discharge is serious.According to observation of the water level in the past ten years,the water level rises nearly half a meter,and the water flow decreased by 2000 m3/s in the same water level,which is far below the standard of original design.To find out the reason,which is directly related to the island beaches,fish barricade,fishing nets and other obstacles in the Watercoures connecting Huaihe River with Yangtze River.The obstacles reduce the flood barrier section,which dramatically makes the flood discharge capacity lower,and causes the great effect on the regulation and management of flood discharge.In order to recover the ability of design of the Watercoures of Huaihe River to Yangtze River,it is necessary to fix the problems of the obstacles in the river.Flow pattern analysis carried out based on the CFX software for 3 improvement schemes under several conditions,before and after the renovation.Then model tests method is applied to verify the relatively optimal schemes.In the physical model test,the water level and flow regime test data of different time flow conditions were analyzed before and after the renovation of Xinmin islands.It provides references for the river regulation of the Xinmin islands,and is of great significance for promoting the sustainable development and utilization of rivers and lakes.The main results of the study are as follows:1?The flow at the exit of the original cut beach in the lower reaches of Xinmintan became smooth,after some of the small islands were cut off in the Xinmintan Houtan archipelago.The deflection angle of the water flow is reduced,and the flow velocity is increased,the low speed area and easy deposition area is reduced.2?Islands in natural flood discharge channel have an effect on the primary smooth discharge,the influence is greater when the flow rate is small.The water level difference between before and after avulsion,is obvious when the flow rate is small.The larger the flow,the smaller the water level difference.