The Study Of The Flow Field In Triangular Grid Flocculation Tank By Numerical Simulation

By numerically simulating the flow field of the grid flocculation tank,the influence of the grid shape(square,triangle)and the size of the grid plate on the flow field was compared and analyzed.Triangles evolve from squares under the premise that the hole rate of the grid plate is unchanged.The first is to analyze and study the influence of the grid shape on the flow field of the grid flocculation tank.by comparing the square grid and the triangular grid flow field.Then change the grid size and block size of the triangular grid plate to study the effect of the geometric size change of the grid plate on the flow field.In the previous simulation study,through the comparison and verification of the numerical simulation flow field and the PIV measurement flow field,the RNG calculation model is more suitable as a simulation calculation model.The main conclusions are as follows:1.Starting from the grid flow rate of the center surface of the grid,the average turbulence kinetic energy of the flow field and the dispersion coefficient of the turbulent kinetic energy,the average dissipation and the effective action distance of the flow field turbulence,the square and the triangular grid flow field are compared,and it is found that the grid flow rate,turbulence kinetic energy and turbulent dissipation of the central surface of the grid of the square grid are greater than the triangular grid;The dispersion coefficient of turbulence kinetic energy of the triangular grid is less than that of the square grid,that is,the uniformity of the triangular grid is better than that of the square grid,which is more suitable for obtaining stable hydraulic conditions;The effective action distance of the triangular grid is less than that of the square grid,which can reduce the installation spacing of the grid plate and is more conducive to the rate of flocculation reaction.2.The influence of the grid size increases the convection field:(1)The grid flow rate of the center surface of the grid is reduced,and the speed is maximized when the grid size is 6mm,and then gradually attenuated,and the minimum is when the grid size is 12 mm.(2)The turbulence kinetic energy of the flow field is reduced,and the turbulence kinetic energy is maximized when the grid size is 6mm,and then gradually attenuated,and the minimum is when the grid size is 12mm;The uniformity of the flow field is gradually deteriorated in the grid size of 6mm,8mm,and 10 mm,but the grid size is sharply improved at 12 mm,and the optimization is much greater than the magnitude of the above variation.Therefore,if you need to obtain stable hydraulic conditions,the size of the grid should not be too small,and the grid size should be controlled at 12 mm.(3)Turbulence dissipation gradually decreases,turbulence dissipation is largest when the grid size is 6mm,and then gradually attenuated,and is minimized when the grid size is 12 mm.The difference in effective operating distance is small and negligible.3.The effect of the convection field increased by the block size:(1)The grating flow rate of the center surface of the grid increased,and the speed was minimized when the block size was 6mm,and then gradually increased,and the maximum was 12 mm when the blocking size was 12 mm.(2)The turbulence kinetic energy of the flow field increases,and the turbulence kinetic energy is the smallest when the block size is 6mm,and then gradually increases,and the maximum is when the block size is 12mm;The uniformity of the flow field is gradually improved in the block size of 6mm,8mm,and 10 mm,but there is a sharp difference in the12 mm grid,and the magnitude of the difference is much greater than the previous optimization.Therefore,if you need to obtain stable hydraulic conditions,the size of the block should not be too large,and the size of the block should be controlled at 10 mm.(3)Turbulence dissipation gradually increases,turbulence dissipation is the smallest when the block size is 6mm,and then gradually increases,and is the largest when the block size is 12 mm.The effective range change coincides with the change in turbulence dissipation and gradually increases,up to the maximum at 12 mm in block size.4.The influence of the increase in grid size and the increase in the grid size on the convection field:(1)The grid flow rate of the center surface of the grid increases,and the speed is minimized when the grid and grid size are 6mm,and then gradually increased,and the maximum is when the grid and grid size are both 12 mm.(2)The maximum turbulence kinetic energy of the flow field is maximum when the grid and block size are 6mm,and the average turbulence kinetic energy of the flow field is maximum when the grid and grid size are 12mm;The uniformity of the flow field is best when the grid and block size are both 6mm,and then gradually deteriorate,and the uniformity is the worst when the grid and grid size are both 12 mm.(3)Turbulence dissipation first increases,then decreases,and finally increases,showing oscillation fluctuations,the grid and block size are 8mm turbulence dissipation is the largest,and the grid and block size are 10 mm turbulence dissipation is the smallest;The effective action distance of turbulence dissipation is increasing,and the grid and grid sizes are the smallest when they are 6mm,and the grid and grid sizes are 12 mm.5.The influence of the increase in grid size and the decrease in the size of the block on the flow field:(1)The turbulence kinetic energy of the flow field is reduced,and the reduction is very large;In terms of the uniformity of the flow field,the oscillation fluctuations that become worse first and then better are presented,and the uniformity is the best when the grid size is 12 mm and the block size is 6 mm.That is,if stable hydraulic conditions are required,the size of the grid should not be too small,and the size of the block should not be too large.(2)Turbulence dissipation is greatly reduced,and turbulence dissipation is greatest when the grid size is the smallest and the block size is the largest;The change in the effective operating distance is consistent with the change in turbulence dissipation and also shows a decrease.