The Numerical Simulation Study Of Mechanical Stirring Clarifier Tank

It is necessary to study the numerical simulation of mechanical stirring clarifier from the hydraulic conditions,because flocculation is an important part of the water treatment process,and the flocculation effect is affected by hydraulic conditions.In this paper,mechanical stirring clarifiers with eight different treatment scales were selected as the research object,based on the CFD numerical simulation method,the internal flow field of mechanical stirring clarifier was simulated.The average turbulent energy dissipation rate?,turbulence kinetic energy k and vortex velocity gradient G₀ of the agitated flocculation zone were used as indexes to analyze the impact of the diameter of diversion chamber,the height of the water outlet window,the position of water outlet window,the width of reflow seam,the disturbance of spoiler and the size and number of stirring paddle on flocculation hydraulic conditions in flocculation area.The results were showed:1.The diameter of diversion chamber has affect on the flocculation effect of flocculation zone.The range of liquid surface load corresponding to optimal diameter of the diversion chamber is 3.4³.6 m³/（m².h）,which reduces the range of liquid surface load（2.9³.6）m³/（m².h）of the mechanical agitation clarifier in the code for design of outdoor water supply engineering（GB50013-2006）.2.The outlet velocity corresponding to the optimal outlet height of the mechanical stirring clarifier is 0.05⁰.075m/s.3.The flocculation effect is the best when the distance between the outlet of the second flocculation chamber and the bottom plate is 1.4m.4.The optimal width of the reflow slit obtained by the simulation is greater than that calculated according to the design flow rate.5.When the paddle area is increased by 25%,the increase in the width of paddle mainly affects the radial turbulence intensity of the top of the first flocculation chamber;The turbulence intensity of the area around the stirring paddle of the first flocculation chamber can be enhanced through increasing the number of stirring paddles;The axial disturbance range of the agitator to the first flocculation chamber can be extended through increasing the length of the agitator;The effect of the spoiler in the skirt on the first flocculation chamber is relatively small.The simulation results can be used as reference for the design and operation of the mechanical stirring clarifier.