Numerical Simulation Of Three-dimensional Flow Field In Donglei Irrigation Distribution

The desilting funnel is a kind of hydraulic structure which uses the spiral flow to separate the water and sediment,and has the characteristics of high sand interception rate and low water consumption rate.Based on the background of the three parallel sand funnel in Donglei Yellow River Pumping area of Shaanxi Province,this paper studies the hydraulic characteristics of the flow field composition and three-dimensional velocity distribution in the interior of the funnel by using numerical simulation method,obtains comprehensive and detailed flow field structure information,and then analyzes the sand discharge mechanism of the sand funnel.This study is of great significance to the design and operation management of desilting funnel.First of all,the three-dimensional numerical model is verified by using the classical physical model test results of sand funnel.The results show that the calculated values are in good agreement with the experimental values,which shows the reliability and adaptability of the selected model.Then,according to the characteristics of three-dimensional flow and two-phase flow of water and gas,the large eddy model and VOF method are used to study the three kinds of sediment discharge funnel of Donglei pumping Yellow River.The finite volume method and simple algorithm are selected to solve the problem.Finally,the hydraulic characteristics of tangential,radial and axial velocity distribution in different discharge discharge discharge funnel are analyzed.The main conclusions are as follows:(1)Under various inlet flow conditions,the tangential velocity decreases along the radial direction in the region near the center and both sides of the funnel chamber,showing the characteristics of free vortex;but in other regions,the tangential velocity increases along the radial direction,showing the characteristics of forced vortex.(2)There is secondary flow on the side without suspended plate.The upper flow moves to the side wall of the funnel chamber,and the lower cone area flows to the center of the funnel.Among them,the secondary flow is the most obvious when the flow is Q1=20m3/s,Q2=15m3/s and Q3=10m3/s.(3)Compared with other schemes,when the flow rate is Q1=20m3/s,the vertical velocity along the radial direction is basically the same,and the direction is generally downward,which is conducive to sediment settlement.Under this flow rate,the water sediment separation effect of the desilting funnel is the most significant.(4)The main contribution of the flow characteristics of the desilting funnel to the separation of water and sediment is that the tangential velocity of the flow mainly maintains the spiral strength of the flow and avoids sediment deposition;the radial velocity mainly transports sediment to the bottom slope of the funnel;the axial velocity plays a role in promoting sediment deposition.This is the main reason why the desilting funnel can effectively separate water and sediment.