扬水曝气器类型对分层水库藻类控制效果的影响

为优选扬水曝气器的类型以更经济有效地原位控藻,建立了基于Fluent软件的水库水动力与水质数值模拟方法,在不同温度梯度和水深条件下,预测了淹没式和非淹没式扬水曝气器对分层水库中藻类控制的效果. 以金盆水库扬水曝气水质改善工程为案例,对扬水曝气器外围流场和藻类混合迁移过程进行数值模拟. 结果显示,垂向流速和藻密度的模拟结果与实测数据吻合较好. 在典型的扬水曝气器运行条件下,水深分别为77.25、87.25和97.25 m时,淹没式和非淹没式扬水曝气器的外围流场均以顺时针环流为特征；淹没式扬水曝气器的环流发展较远,表层藻密度分别被削减了86.8%、88.2%、90.6%；扬水曝气器类型对藻密度削减率的影响不大. 采用淹没式扬水曝气器时,77.25、87.25和97.25 m水深下核心控藻区占整个流场区域的比例分别为39.71%、41.14%和42.73%,分别比非淹没式的高14.81%、8.95%和2.69%；藻类完全混合的时间分别为10、12和14 d,分别比非淹没式的少8、7和6 d. 不同季节和水深条件下的模拟结果表明,采用淹没式扬水曝气器,核心控藻区域较大,藻类混合较快. 

Comparison of Water-Lifting Aerator Type for Algae Inhibition in Stratified Reservoirs

To choose the proper type of water-lifting aerator for more effective in situ algae inhibition, a numerical simulation method based on Fluent software was developed for hydrodynamics and water quality of reservoirs. The effectiveness of algae inhibition using submerged and non-submerged water-lifting aerators was predicted under various conditions of temperature gradient and water depth. Taking the water quality improvement using water-lifting aeration technique in Jinpen reservoir as a study case, the flow field and process of mixing of algae were numerically simulated. The simulated results of vertical velocity and algae concentration agreed well with the field data. Under typical operational conditions of a water-lifting aerator, when the water depths were 77.25,7.25 and 97.25 m, the flow outside any water-lifting aerator was characterized as one large clockwise circulation under stable state. However, the circulated flow was developed further for the submerged case. The algae with an initial average concentration in the surface area was finally reduced by 86.8%, 88.2% and 90.6% respectively, and this was not sensitive to the type of water-lifting aerator. The percentages of the core algae inhibition zone to the whole flow domain were 39.71%, 41.14% and 42.73% for the submerged cases respectively, which were 14.81%, 8.95% and 2.69% larger than those for the non-submerged cases. The periods required for complete mixing of algae were 10,2 and 14 d for the submerged cases respectively, which were 8,7 and 6 d shorter than those for the non-submerged cases respectively. Simulated results of different temperature gradients and water depths showed the core algae inhibition zones were larger, and the mixing of algae was quicker, for the submerged case.