栅条絮凝池内部流场及颗粒运动状态模拟分析

利用数值模拟方法对栅条絮凝池前段内部流场进行模拟分析，以涡旋速度梯度和湍动能作为综合评价指标，对其结构设计的合理性进行了验证。在流场中加入了11组不同粒径和有效密度的絮凝颗粒，每组在流场入口处随机释放98560个粒子，利用DPM模型对粒子运动轨迹进行追踪统计。结果表明:随着絮凝颗粒的增大，其有效密度呈相应下降趋势。絮凝颗粒直径为1~1000 μm，沉积率<10%，且在各竖井内沉积均匀，能够很好地满足絮凝要求。当颗粒粒径为1000~5000 μm时，沉积率呈急剧上升趋势，但在各竖井内沉积较为均匀。当颗粒粒径进一步增大至10000 μm时，大量粒子在第1段竖井内沉积，不利于排泥的均匀性。综合考虑沉积率和排泥均匀性，实际工程中应尽量避免出现1000 μm以上的大粒径絮凝体。

NUMERICAL SIMULATION AND ANALYSIS OF FLOW FIELD AND PARTICLE MOTION IN GRID FLOCCULATION TANK

Numerical simulation method was used to analyze the characteristics of the internal flow in the front section of the grid flocculation tank. With the vortex velocity gradient and turbulent kinetic energy as the evaluation index of flocculation, the paper verified the rationality of the structural design. In addition, 11 groups of particles with different sizes and effective densities were added to the flow field. Each group randomly released 98560 particles at the entrance of the flow field and their motion was tracked by the DPM model. It was noted that as the particle size increased, the effective density decreased accordingly. The research found that when the particle diameter changed from 1 μm to 1000 μm, the deposition rate was kept less than 10% and the deposition was uniform in each shaft, which could meet the flocculation requirements. When the particle diameter was 1000~5000 μm, the deposition rate increased sharply, but the deposition was uniformed in each shaft. However, when the particle diameter increased to 10000 μm, a large number of particles were deposited in the first shaft, which was not conducive to the uniformity of sludge discharge. So taking deposition rate and the uniformity of sludge discharge into consideration, such large size particles of more than 1000 μm should be avoided in actual engineering practice.