Characteristics Of Carrying Sediment By Density Currents And Determination Of Reasonable Location Of Sediment Releasing Outlet、Sand Suction Mouth In Stratified Reservoir

Many scholars have done a lot of research about reservoir sediment concentration distribution and the use of the characteristics of density flow sand flushing. But the study about sediment concentration distribution and density flow desilting characteristics and sand under the environment of the reservoir water temperature stratification reservoir had little amount.In this paper, the hierarchical model was used to start a series of layered reservoir density flow pilot study and determinate change process with time and characteristics of different vertical location in the reservoir sediment concentration vertical distribution.This model was based on natural water temperature stratification reservoir. And related parameters is inflow discharge of 0.08 to 0.64 m3 / h, inflow and sediment concentration of 1.25 to 7.5 g/L and sediment particle size of 0.01 mm,0.05 mm. To the fixed condition,the position for appropriate river mouth should be where outlet section of maximum concentration and sediment concentration was defined no less than 10%(≥10% Cmax). Analysis shows that the appropriate location of the reservoir bottom sediment trapping by is defined as the bottom of the biggest precipitation location model. The pilot tests results show that the stratified condition of temperature gradient in temperature jump layer is about 41-48℃/m, all of inflow discharge,sediment concentration and particle size have influence on the vertical distribution of sediment concentration. With the inflow discharge and sediment concentration increased, and vertical distribution of sediment concentration curve by inverse curve(increase with the increase of the elevation of concentration in) transition to parabola and straight line in two parts and(parabola opening downward, linear part by concentration does not change along with the elevation of the transition to concentration decrease with the increase of elevation) transition to only in the form of a straight line(decrease with the increase of elevation. Along with the increase of inflow discharge and sediment concentration,sediment delivery center of mouth water depth range and depth increase, and suitable sediment concentration of drain increases. With the increase of particle size, model maximum turbidity would become smaller, and the minimum elevation of suitable river mouth will rise, of which range decreases. So did the sediment of model at the bottom. There was little relationship between suitable location and concentration,flow and particle size. The appropriate location basically stable in section 0.3,and effective trapping sediment precipitation amount was more than 30%. According to the above situation,it is concluded that we can set reasonable reservoir drain position. The setting of suction device in the bottom of the reservoir sediment deposition quantity biggest place can maximize the discharge and desilting within the reservoir, reduce reservoir sedimentation rate, extend the service life of the reservoir and increase the economic benefits of the reservoir.