Study On Prevention And Control Of Algal Residue Deposition In Long Distance Water Transport Project

The unbalanced distribution of water resources in time and space in China makes it inevitable to carry out inter basin water transfer projects.However,with the increase of the operation period away from the water conveyance project,the problem of siltation of sediment or algal remains in the river channel is gradually highlighted,especially near some rarely used diversion and outlet gates along the water conveyance project.In order to alleviate this engineering problem,this paper selects the area near Shahe Tui Sluice as the research object to explore the prevention and control of algal residue deposition in long-distance water transfer projects from two perspectives:(1)When the water is divided in side channels,the scour effect of different shunt ratio on the sediment deposition in side channels is studied;(2)When the side channel does not divide water,the arc diversion wing wall is built near the bifurcation of the main channel and the side channel.The Angle of the arc diversion wing wall is set as:Six different angles of-10°,-5°,0°,5°,10°,15°were simulated,and there was no diversion wing wall.The incoming flow was simulated according to two conditions:the general incoming flow was 280m~3/s and the designed incoming flow was 320m~3/s.A total of 14 groups of experiments were simulated.The main research contents and results are as follows:(1)When there is water distribution in the side channels of the water transmission project,14 groups of working conditions are selected for simulation from the perspectives of different flow from the main channel,the same flow from the main channel,different diverting amount and the same diverting amount.The changes of the volume fraction of algae residue at the bottom of the side channel were observed during the calculation period of 1500s,4000s and 7500s,respectively.(2)When the side channel does not divide water,the arc diversion wing wall is placed near the bifurcated inlet formed by the intersection of the main channel and the side channel.The influence of the different angles of the arc diversion wing wall before and after the installation of the diversion wing wall on the velocity in the area of the installation wing wall is explored from two perspectives.(3)Through the different diversion ratio of side channels and the construction of arc-shaped diversion wing wall,the separation and non-separation of side channels in long-distance water transmission projects were studied respectively.The results showed that increasing the separation ratio and the amount of water divided in side channels had obvious effect on the prevention and control of sediment deposition in side channels;In the numerical simulation,the scour rate decreases with the increase of calculation time.After the diversion wing wall is installed,the velocity change around the area is greatly affected,and the velocity is obviously increased.When the flow rate of the main canal is280m~3/s,the maximum flow rate increases from the initial 0.94m/s to 1.44m/s.When the flow rate is 320m~3/s,the maximum velocity increases from 1.12m/s to 1.7m/s.Through the analysis of flow velocity,it can be concluded that the Angle of diversion wing wall at-10°,-5°,0°and 5°can prevent and control algae growth and residue deposition near the branching point.When the Angle of the diversion wing wall is 10°or 15°,the downstream velocity of the main channel will be reduced and the normal operation of the project will be affected.