网格絮凝池结构参数对流场影响的数值模拟

Numerical simulation of the effect of the structure parameters on the flow field in grid flocculation tank

针对网格絮凝池首层栅条位置及宽深比规范化的研究空白,运用FLUENT软件,采用标准k-ε湍流模型模拟了进口到首层栅条距离(h1)及宽深比对网格絮凝池流场变化的影响。首先对CFD模型进行了试验验证,计算得二者平均水力停留时间误差在3.03%,说明数值模型具有良好的可靠性。CFD模拟结果表明,h1在400~800mm范围内变化时,流场的死水区域较小,速度分布较为均匀,能够为絮体颗粒进行聚集和碰撞提供良好的水力条件;单个竖井宽深比在0.29左右时,流场的涡旋速度梯度G'值在26 s-1左右,有利于形成大量密实的絮体,且不易产生破碎现象。该研究可在一定程度上为网格絮凝池的结构设计提供相应的理论依据。

The research on the normalization of the position and width-to-depth ratio of the grid flocculation tank top layer grid is blank.Using the FLUENT software,the standard k-ε turbulence model was employed to simulate the effects of inlet-to-first grid layer distance（h1） and width-to-depth ratio on the flow field in the grid flocculation tank.The CFD model was first verified by experiments,which showed that the average residence time distribution error was 3.03%,indicating that the numerical model was reliable.The CFD simulation shows that,when h1 ranges between 400 and 800 mm,the dead zone in the flow field was small and the velocity distribution was relatively uniform,which provided good hydraulic conditions for floc particles to aggregate and collide.When the width-to-depth ratio of single tank was about 0.29,the vortex velocity gradient G＇ was about 26 s-1,which is conducive to the formation of lots of dense flocs,and the crushing phenomenon is not easy to occur.This research provides a theoretical basis to some extent for the structure design in a grid flocculation tank.