Design Of Water And Sediment Diversion In The Yellow River-to-Baiyangdian Water Transfer Project

The Yellow River-to-Baiyangdian Water Transfer Project is a major water conservancy project for the optimal allocation of water resources in North China,and since the opening of the water supply,the problem of sediment deposition in settling basins and channels has long affected the normal operation of the project.In view of this,this study proposes a new sediment disposal scheme for the Yellow River-to-Baiyangdian Water Transfer Project,which is divided into four modules: “sediment extraction-sediment distribution-sediment transport-water supply”,which can realize the rapid disposal of sediment,improve the operation efficiency of the project,and ensure the guarantee rate of water supply.Among them,the integrated technology for water and sediment diversion in the sediment distribution module is the focus and difficulty of this schem.This study combines the physical model test with numerical simulation to design a sediment sedimentation and distribution device suitable for the settling basins in the lower reaches of the Yellow River.The contents and conclusions of the study are as follows:(1)In this study,a water and sediment diversion scheme based on four modules of“sediment extraction-sediment distribution-sediment transport-water supply” is proposed,the operation mode of the original settling basin is changed,the application mode of the settling basin is changed from double to single,and a sediment fine sand separation plant is built on the other settling basin,under the condition of maintaining the normal operation of the original single settling basin,the pumped high sand content water flow is transported to the sediment fine sediment separation plant by a dredger,sediment screening is carried out by sedimentation centrifugal method,the selected sediment source is transported to market and the clean water is supplied to the graded water users.(2)Based on the sedimentation centrifugation method and Stokes formula,the sediment sedimentation and distribution device was established,the operating parameters of the device were changed,and 36 sets of tests were carried out by the control single variable method.The results showed that the mass distribution rate of coarse sediment was 75.86% when the sediment separation bucket was highly separated,and the effect was the most significant;the mass distribution rate of fine sand when the blade rotation frequency is separated is 60.91%,and the effect is more obvious;the working state of the water body only has obvious changes to the effect of fine sediment separation,and the mass distribution rate can reach 62.03%;the sedimentation centrifugation radius has an effect on the overall sediment separation effect.(3)The Fluent software was used to establish a three-dimensional digital simulation model,study the motion law of sediment particles in the device,further optimize the design of the device,and find the optimal working conditions and key technical parameters.A total of 432 sets of working conditions were simulated,and the following patterns were found:(1)Between the working areas of the device,fine sediment and a small amount of medium sediment make a longitudinal spiral movement;(2)Most of the coarse sediment and medium sediment do radial diffusion movement,and start rotating centrifugal descent when the centrifugal radius is large to a certain range;(3)Most of the fine sediment is concentrated near the central axis of the device for rotational descent.Based on the physical model test and numerical simulation of the sediment sedimentation and distribution device,the optimal working conditions are as follows: the height of the sediment separation cylinder is 1.20 m,the blade rotation frequency is 5.50 Hz,the working is in the hydrostatic state,and the rotation frequency of agitated blade is 5.50 Hz.(4)Sediment disposal plan of the Yellow River-to-Baiyangdian Water Transfer Project in this study ensures the normal operation of the project,ensures the safety of water supply,promotes the agricultural development of coastal irrigation areas,maximizes the utilization rate of sediment resources,and provides technical support for the irrigation and sediment dredging projects of the Yellow River.Guide the new direction of sediment disposal and application development in the Yellow River,fill the gap of efficient and high-quality utilization of sediment in the Yellow River,and play a positive role in the ecological belt and high-quality development of the Yellow River.