Analysis Of Three-dimensional Flow Field Of Grid Flocculation Tank Based On FLUENT

With the continuous improvement of water supply technology,water quality standards become more stringent,coupled with the characteristics of spatial water resources distribution,result in different parts of the water supply process is not the same.In the water treatment process,flocculation is a very important part of it directly affects the use of pharmaceuticals,follow-up precipitation process load,thus affecting the water quality.For a long time,many researchers have done a lot of research on the mechanism and process of flocculation of water treatment,so that it has been developed rapidly.From the practical point of view,the flocculation process not only is affected by the temperature,PH,alkalinity and other factors,and flocculation process will be affected by the particles in the collision,aggregation,crushing process.The flocculation process is not only affected by the addition of flocculants,but also by the hydraulic conditions provided by the structures.The action of the flocculation hydraulic condition is determined by the turbulence characteristics of the flow and the structural conditions of the structure.The grid flocculation tank is widely used in the water supply process in the southwest,and there are many blind spots in the design of the flocculation tank.Therefore,the grid flocculation tank is selected as the research object.Compared with other forms,the flocculation tank flocculation collision effect is good,the formation of floc density is good,flocculation time is short,no need to consume too much power,etc.,can provide good hydrodynamic conditions.Firstly,based on the common design experience and the requirements of the size and flow rate,the influence of the size of the structure on the flow field distribution in a single shaft is discussed.According to the optimized size requirements,the experiment pilot test device is designed,and the results of the numerical simulation are verified by the vortex and velocity contrast observed in the experiment.The influence of the size of the structure on the flow field distribution in a single shaft shows that the distance(h2)of the outlet to the bottom bar should be greater than 400-600 mm and the influence of the distance on the flow field distribution is less than the distance from the inlet to the first floor(h1)On the distribution of flow field.H1 value range should be between 600 ~ 800 mm.At the same time,the number of grid layers has a great influence on the physical quantity(such as velocity,turbulent kinetic energy,turbulent kinetic energy dissipation rate,velocity gradient,etc.)of the whole shaft space.The more layers,turbulent kinetic energy,turbulent kinetic energy dissipation rate The distribution of the average k and turbulent energy dissipation in the shaft is greater,and the higher the proportion of the small water vortex formed near the front and rear of the bar and the local recirculation zone,The better the effect of the collision.Through the comparative study of widths of 800,900,1000,1100,1200,1300,1400 and 1500 mm,it is found that the optimal width to depth ratio is near 0.29.It is found that when the cross section is funnel shape,the velocity gradient in the shaft is the largest and the turbulent kinetic energy is also the largest,and the vortex-affected area near the bar is found in the case of rectangle,diamond,circle and funnel.The largest,can provide better hydraulic conditions.It is recommended that in the actual project,the shape of the front spoiler can be set to funnel shape,the middle is set to rectangular or diamond,the last paragraph does not set the spoiler components,which can reduce the volume of the pool.In this paper,the typical silo in the first,middle and last stages of the grid flocculation tank is taken as the object of study.The corresponding size distribution is based on the structural optimization of this paper.On this basis,The display technology shows the formation of water traces and vortices in the grid(grill)flocculation tank,and verifies the distribution and size of the vortices in the flow field in the flocculation tank.At the same time,the simulated hydraulic retention time was verified by the conductivity meter.