Study On Inlet Flow Pattern And Optimization Measures Of Exihe Flood Drainage New Station

Sluice-pump combination is an arrangement form that organically combines pumping stations and sluices.This arrangement has been widely used in plain river network areas due to its small footprint,low investment cost,convenient operation and management.Different from the separate arrangement of traditional pumping stations and sluices,the combined sluice-pump project has a compact structure.When the pumping station or sluice operate independently,the direction of the water flow will form an angle with the river bed,resulting in a deflection,which will complicate the flow of the project,produce backflow,vortex,siltation,scouring and other undesirable phenomena.These phenomena not only reduce the pumping efficiency of pumping station or the discharge capacity of sluice,and even threaten the safe and stable operation of the project.Therefore,analyzing the influent flow pattern and optimizing the influent conditions are of great significance to the efficient and stable operation of the combined sluice-pump project.The Exihe flood drainage new station adopts an arrangement form of sluice-pump combination,consists of four pump units and two controlling gates.In this paper,we take this project as the research object,use UG modeling software and Fluent calculation software to carry out numerical calculation and analysis of the influent flow pattern of the project.Numerical simulation results show that when the pumping station is operating independently,the project will present a side-direction influent flow state,large-scale backflows and vortices will appearing not only in the right side of the pumping station’s forebay,but also in the intake pool.This phenomenon directly affects the water intake conditions of the flow channel,and is unfavorable to the safe and stable operation of the pump units.In order to improve the poor flow pattern during operation of the pumping station of this project,we propose different optimization measures on the basis of the original design plan,including changing the length of the diversion wall,setting the bottom sill and diversion piers.Through comparative analysis,we found that:First,suitable diversion wall’s length can effectively improve the flow velocity uniformity of the inlet section of the flow channel,but the improvement of backflows and vortices in the forebay is limited.Second,the setting of the bottom sill has a certain effect on improving the flow pattern of the forebay,it can effectively make the backflow limited in front of the bottom sill.However,affected by the direction of the influent flow,the swirling water flow behind the sill are inconsistent on the left and right sides,and the bottom water flow is deflected.It reduces the uniformity of flow velocity at the inlet section of the flow channel.Third,the diversion pier can effectively eliminate the backflow and vortice in the forebay and improve the flow velocity uniformity of the inlet section of the flow channel.The length of the diversion pier has a greater impact on the rectification effect.Too long or too short will both reduce the rectification effect.We found that the arrangement of 4 diversion piers with a length of 17m in the forebay of the project can achieve a better rectification effect.On this basis,we combined with the hydraulic model test to compare and analyze the typical calculation schemes of the numerical simulation.The model test results of the influent flow pattern are in good agreement with the numerical simulation results.At the same time,the model test also shows that setting diversion piers in the forebay can effectively improve the flow pattern and obtain a satisfactory rectification effect.The study results of this paper can provide improvement suggestions and measures for the engineering design of the Exihe flood drainage new station,which is of great significance to ensure the safe,efficient and stable operation of the project.Moreover,it can also provide a certain reference value for the design or retrofit of similar combined sluice-pump project.