采用大涡PIV研究Taylor-Couette流及其对混凝过程的影响

Large eddy PIV study of Taylor-Couette flow and its influence on the coagulation process

采用大涡PIV方法对Taylor-Couette流场的湍动能及湍动能耗散率进行了估算,并利用数值模拟对其进行验证,结合絮凝实验,综合对比速度矢量、湍动能分布、湍动能耗散率分布及对应流场中混凝过程的絮体图像,探究了湍动能与湍动能耗散率对絮凝效能的影响.结果表明,大涡PIV法与数值模拟在雷诺数较高的情况下有较好的一致性,且雷诺数越大一致性越好.在Taylor-Couette涡流场中,随着雷诺数的增大,湍动能与湍动能耗散率数值不断增大,且在流场中的分布由规律有序到紊乱最终趋于各向均匀一致.而混凝过程中湍动能与湍动能耗散率的数值大小及其在流场中的空间分布情况,均对产生絮体的大小和浊度去除率有较大影响.

Turbulent kinetic energy and turbulence kinetic energy dissipation rate of Taylor-Couette flow were estimated using a large eddy PIV approach,and the results were verified by numerical simulation. The influence of the turbulent kinetic energy and its dissipation rate on the flocculation efficiency was studied through a comprehensive comparison of velocity vector,turbulent kinetic energy distribution,turbulence kinetic energy dissipation rate,and the flocs image in the corresponding flocculation flow field. The results estimated by the large eddy PIV approach are in good agreement with those obtained by the numerical simulation at high Reynolds numbers,and the higher the Reynolds number is,the more consistent between the results. In a Taylor-Couette vortex flow,the turbulent kinetic energy and its dissipation rate increase with the increase of Reynolds number,and their distribution in the flow changes from a regular state to a chaotic state and finally to a uniform state. In the process of coagulation,both the value and the spatial distribution of the turbulent kinetic energy and its dissipation rate in the flow field have a significant effect on the flocs size and the turbidity removal rate.