Study On Characteristic Of Water And Sediment In The Circulations Region Of Twin-groyne In Mountainous Channels

As one of the main building of river regulation,the spur dike is ofen layouted in the river in various forms.Meeting the requirements for the economic development and river stability in the mountainous channel,compared with single spur dikes,the arrangement form for twin-groyne can take advantages better to regulation effect better.But the three-dimensional turbulent characteristics in the circulations region of twin-groyne are more complex than single spur dikes,having a certain degree of influence on river form and navigable conditions.Therefore,studying on characteristic of water and sediment in the circulations region of twin-groyne in mountainous channels has an important significance.In the thesis,based on the channel construction projects in the Xuyu reach of upper reaches of the Yangtze River,relying on the ministry on science and technology project ”the upper Yangtze river waterway regulation mechanism and prevention of buildings water destruction monitoring technology”,analyzing with investigation and statistics the damage situation of the rapids remediation buildings,we carry out the fixed bed current model tests on the twin-groyne,realizing the exploratory analysis of characteristic of water and sediment in the circulations region of twin-groyne in mountainous channels.In the thesis,combining theoretical analysis and the method of experiment,we collect dates of flow velocity around the twin-groyne by using ADV,and calculate turbulent intensity and energy around the twin-groyne.Through drawing planar velocity figures,the general flow field is divided into the main flow region and the circulation region.Making further analysis,in the horizontal direction,the circulation region is divided into the negative-velocity region and the positive-velocity region,in the longitudinal direction,it is divided into the circulation-increased region and circulation-decreased region.By studying the influence of dam length and groynespacing on dividing the circulation regions,we find that the longer length of the bend-ended twin-groyne,the bigger area of the circulation region of the bend-ended twin-groyne,and the longer length of the re-circulation;the shorter length of the groynespacing,the bigger area of the circulation region of the bend-ended twin-groyne,and the longer length of the re-circulation.According to distribution curves of the the turbulence velocity,the turbulenceintensity and the turbulence energy in different circulation regions,we find turbulence intensity in circulation region is larger than the main flow region,the range of the longitudinal turbulence intensity is the widest to obtaining the fitting formula for the relative longitudinal turbulence intensity of it is derived.On the basis of some assumptions,based on the K equation,we study that the formula for the sediment-carrying capacity of the downstream water flow in the lower reaches of the bend-ended twin-groyne is derived,considering the conservation law of flow volume.