异波折板流场模拟分析与结构优化

Simulation analysis of flow field and structure optimization of asynchronous folded plates

基于FLUENT技术,以连续方程、Navier-Stokes方程及k-epsilon湍流方程作为流动基本控制方程,对异波折板絮凝反应流场进行了数值模拟,并通过网格独立性检验,保证了模拟结果的真实性.以流场速度分布、紊动动能、有效能耗作为评价标准,根据数值模拟提出了不同絮凝段的最优折板单元组合.结果表明,夹角90°的短折板适宜于絮凝前段,而夹角120°的长折板更适宜于后续絮凝段.在此基础上建议对絮凝前段的折板单元进行结构优化,在每个折板单元中心增设菱形扰流板,用以增强折板内流场紊动动能,提高有效能耗相对比例.优化后折板内的流场面积平均紊动动能可由2.75×10-3m2·s-2提高到3.83×10-3m2·s-2;面积平均有效能耗可由4.70×10-3m2·s-3提高到7.74×10-3m2·s-3.该优化将有利于营造更优越的水力条件从而提高絮凝效率.

Based on FLUENT technology,the numerical simulation of flow field of asynchronous folded-plate flocculation reactor was performed by using continuity equation,Navier-Stokes equations and k-epsilon turbulence equations as the basic fluid control equations,and the reliability of simulation results was confirmed through the test of grid independency.The optimum geometric structures of folded-plate units of different flocculation stages were determined,taking the distributions of flow velocity,turbulent kinetic energy and turbulent dissipation rate as evaluation standards.It turned out that short folded plates with 90° included angle are more applicable to the preceding flocculation stage,while long folded plates with 120° included angle are more applicable to the subsequent flocculation stage.On that basis,appropriate suggestion that rhombic spoilers should be added in the centre of each folded-plate unit was proposed,which contributed to intensifying turbulent kinetic energy and enhancing the ratio of turbulent dissipation rate in the flow field of folded-plate flocculation units,thus the structure of units of the preceding flocculation stage was optimized.Area-weighted average turbulent kinetic energy raise from 2.75×10^-3 m^2 · s^-2 to 3.83×10^-3m^2 · s^-2and area-weighted average turbulent dissipation rate raise from 4.70×10-3m^2 · s^-3to 7.74×10^-3m^2 · s^-3respectively after the optimization.This structure optimization will lead more to favorable hydrodynamic conditions and improve flocculation efficiency.