Characteristic Analysis Of Flow Field Of Folded-plate Flocculation Based On Technology Of FLUENT&PIV

Folded-plate flocculation has been an efficient flocculation process on the basis of baffled flocculation,and it has been a frequently-used flocculation process in water treatment in the past40years.Contact and collision among flocculation particles are energized through complicated fluid dynamic effects that repetitious folded-plate scaling or turning produces in the folded-plate flocculation,therefore,flocculation efficiency is increased and flocculation reaction time is shortened.There are substantive magazines to report qualitative flocculation mechanism,but which is scarcely reported through quantitative analysis of flow field included the folded plate.In order to quantitatively analyse the characteristic of flow field in the floded plate,and further detect flocculation mechanism,the paper will determine the optimum hydraulic condition of flocculation through the experiments of synchronous folded-plate flocculation in the different working conditions.Then,the typical flow field of velocity distribution is detected,with PIV measuring flow field included the folded plate,in the corresponding working conditions.Finally,the distribution of velocity,turbulenct kinetic energy and turbluent dissipation rate are computed,with FLUENT performing numerical simulation for the folded-plate flocculator model in the same boundary conditions.Actual measurement and numerical simulation are compared under the corresponding conditions to achieve the purpose of mutual test and guiding adjustment and improvement of simulation methods. According to the previous research experiences,the paper will confirm turbulenct kinetic energy and turbluent dissipation rate as the index measuring flocculation reaction rate.Grid independence is tested to numerical simulation,to ensure the accuracy of analysis in energy.Based on the previous research results,the result of flocculation experiment,PIVmeasurement and FLUENT numerical simulation,the paper comes to conclusion as follows:Lin the flow regime of turbulence, vorticity variation with time can reflect effects of the change of velocity gradient in flow field including big vortex,and can also reflect effects of viscous dissipation in flow field including tiny vortex;it synthesizes effects of dynamic and turbluence;therefore,vorticity variation with time can reflect the comprehensive effects turbulent flow field works.2.under folded-plate import flow for300L/h(folded-plate import velocity for0.0113m/s), flocculation effect is best, that is the best hydraulic conditions.3.area-weighted average velocity is growing,with folded-plate import flow rising. Centrifugal effect of flow is enhanced,and flow velocity is increasing in the impact zone in folded-plate units,faster than the other flow field.High-velocity flow of continuous S is saw in folded-plate gallery,and prolate vortexs grow in other flow field. 4.under the best hydraulic conditions of flocculation, area-weighted average velocity is0.321m/s in the first flocculation section, it is0.256m/s in the second section,and it is0.200m/s in the third section,which agree mainly with the velocity intervals given for each section in the current Design Rules of Outdoor Water Supply(GB50013-2006), which has verified the availability of the rules and the accuracy of the experiment.5.turbulent kinetic energy of the center flow field is higher than that of the zone near by folded plate.High-energy zone of turbulent kinetic energy and impact zone coincide.Turbulent dissipation rate of flow field near by the folded plate is obviously higher than that of the center flow field,and its high-energy zone lies near by the folded plate of impact zone6.based on the experimental model, to get the best flocculation effect,the attenuation rate of turbulent kinetic energy should keep at about25.8%and about13.5%, the attenuation rate of turbulent dissipation rate should keep at about35.5%and about66.1%.