栅条絮凝池过水孔洞位置对絮凝水力条件的影响研究

通过改变栅条絮凝池中过水孔洞位置,利用数值模拟的方法对池体内部的流场流态特性进行分析研究,以涡旋速度梯度G0、湍动能k和湍动能耗散率ε作为絮凝评价指标,探讨过水孔洞的位置对絮凝水力条件的影响。经过分析,可知在絮凝过程的前段、中段和末段,过水孔洞依次抬高的设置能够优化絮凝的水力条件,获得更好的絮凝效果。     

往复式隔板絮凝池内部流场数值模拟分析

通过对往复式隔板絮凝池的内部流场进行数值模拟,计算得到絮凝池内水流速度（v）、湍动能（k）及湍动耗散率（ε）的空间变化,并根据絮凝动力学机理详细分析了絮凝过程中v、k及ε对絮凝效果的影响。结果表明：模拟计算得到的v、k和ε可以较为准确地判断絮凝过程中的水力条件变化,同时为絮凝池的设计和运行提供一定的指导。     

网格絮凝池结构参数对流场影响的数值模拟

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。     

横向流栅条絮凝在水厂挖潜改造中的应用

广东南海九江自来水公司将水厂的往复式隔板絮凝池改造为横向流栅条絮凝池,大大改善了絮凝效果,使产水量由19200m(3)/d提高到33600m(3)/d,出水水质也明显改善.木文介绍了横向流栅条絮凝池的设计计算及实测结果.     

基于计算流体力学的往复式隔板絮凝池流场模拟分析

应用计算流体力学软件FLUENT对往复式隔板絮凝池进行了流场数值模拟分析.通过分析发现,池内的水流变化模拟特征与实际情况相吻合,能够较真实地反映流场内部微观的变化情况,从水力学的角度分析了流场对絮凝效果的影响.同时也可为工程设计人员的设计方案优化提供参考.     

往复隔板絮凝池涡漩流场的研究与探讨

往复隔板絮凝池不同边壁形状水流结构对混凝沉淀效果有影响,但由于往复隔板絮凝池廊道狭窄、絮凝池拐弯水流结构复杂,致使整个流场的量测十分困难.应用粒子图像测速技术,建立了研究往复隔板絮凝池水流结构的室内测试系统.对往复隔板絮凝池拐弯处水流涡漩运动进行了研究,使用量测系统软件,对不同方案下水流涡漩运动进行了分析,并对混凝沉淀效果进行了比较.     

往复隔板絮凝池边壁形状对絮凝反应的影响研究

通过往复隔板絮凝池混凝反应的模型试验 ,对不同边壁条件下的絮凝效果进行了分析比较 ,可知边壁的形状对改善水流结构起着显著的作用。将絮凝池拐角及隔板端面设计为圆弧形 ,可保持所要求的紊流能耗和最佳水力条件 ,为老水厂改造提供了一条有效途径。     

基于FLUENT的折板絮凝池三维涡旋水流数值模拟

折板絮凝池复杂的涡旋流场对絮凝效果具有重大影响,借助大型流体软件FLUENT,采用κ-ε方程对不同角度的折板絮凝池内涡旋水流进行了数值模拟,比较不同折板絮凝池内水流流态和压力状态,结果表明90°异波折板与90°同波波折板组合对提高絮凝效果最为有利,这为折板絮凝池的工程设计提供了重要的参考价值.     

机械搅拌澄清池导流室直径对絮凝条件的影响

絮凝是水处理工艺中的重要环节,从水力条件方面优化絮凝工艺有利于提升水处理构筑物的处理效果。本文基于计算流体动力学(CFD)数值模拟对机械搅拌澄清池内部流场和流态的特性进行分析,以涡旋速度梯度G_0、湍动能耗散率ε作为絮凝评价指标,针对八种不同规模的机械搅拌澄清池,研究导流室直径变化对絮凝效果的影响,给出了对应的最优导流室直径,得出八种规模的机械搅拌澄清池清水区液面负荷为3.4～3.6 m~3/(m~2·h),比室外给水设计规范中机械搅拌澄清池清水区的液面负荷的取值范围小。可为实际工程设计提供一定的参考。     

回转式隔板絮凝池提效改造设计

为提高生产效益,解决回转式隔板絮凝池药耗较高、絮凝效果不理想的问题,将回转式隔板絮凝池改造为折板絮凝池,并利用原中央进水管为排泥管设置排泥区,减少改造工程量,缩减工程建设时间。改造后沉淀池出水浊度小于3NTU,药耗降低21%。     

低温低浊水絮凝工艺的数值模拟与响应面优化试验研究

为探究微涡流絮凝工艺处理低温低浊水时,絮凝区流场流态的变化以及水中浊度、CODMn、UV254的最优去除效果,采用CFD数值模拟探究不同流量(絮凝时间)下絮凝区流场流态,确定最佳絮凝时间;应用响应面中Box-Behnken的中心组合设计方法,研究了流量、混凝剂投加量与涡流反应器投配比及其交互作用对微涡流絮凝工艺去除浊度...     

Measurements of the sediment flocculation characteristics in the Three Gorges Reservoir,Yangtze River

The flocculation of fine sediments in the Three Gorges Reservoir (TGR) was confirmed in previous studies, but the flocculation characteristics have yet to be fully clarified. In this study, field measurements were conducted in the TGR to investigate the sediment flocculation characteristics. First, the instantaneous flow velocity and sediment concentration were measured through Acoustic Doppler velocimeter and sediment sampling. Then, the effective settling velocity was calculated based on the sediment diffusion theory to deduce the floc size and flocculation degree. Finally, the influences of particle size, flow velocity, and sediment concentration on flocculation were analyzed. Results showed that flocculation occurred in more than half of the sediments in the TGR, and the maximum flocculation degree was between 10 and 30. Flocculation weakened as particle diameter increased, with the critical particle size being approximately 0.018 mm, meaning that flocculation was unlikely to occur when the particle size exceeded the critical value. As the flow velocity increased, the flocculation degree first increased and then decreased, with the critical flow velocity being approximately 0.7 m/s, but the critical flow velocity increased with an increase in sediment concentration and tended to be a constant. The flocculation degree also increased with increasing sediment concentration and tended to be constant when the sediment concentration exceeded approximately 0.5 kg/m³. The results provide new information on the flocculation characteristics of the TGR and should be useful for understanding and simulating fine sediment transport in the TGR.     

AN IMPROVED ALGORITHM FOR DPIV CORRELATION ANALYSIS

In a Digital Particle Image Velocimetry (DPIV) system, the correlation of digital images is normally used to acquire the displacement information of particles and give estimates of the flow field. The accuracy and robustness of the correlation algorithm directly affect the validity of the analysis result. In this article, an improved algorithm for the correlation analysis was proposed which could be used to optimize the selection/determination of the correlation window, analysis area and search path. This algorithm not only reduces largely the amount of calculation, but also improves effectively the accuracy and reliability of the correlation analysis. The algorithm was demonstrated to be accurate and efficient in the measurement of the velocity field in a flocculation pool.     

A new design of flocculation tank: the Turbomix applied to weighted flocculation.

As far as flocculation is concerned, the agglomeration of suspended particles into flocs is highly linked to the hydraulic behaviour of the agitation. The Turbomix is a special design of mixing tank; its design was developed to better control the flow during the flocculation stage. It enables a significant decrease in footprint of the process. The combination of the Turbomix and ballasted flocculation has been studied during pilot trials in terms of treatment efficiency. Its controlled hydraulic behaviour explains the efficiency of the process as proved by CFD investigation.     

水库疏浚底泥絮凝沉降室内试验研究

泥浆絮凝沉降效率是影响湖库疏浚工程进度的重要因素。为探索不同絮凝剂(有机、无机)对疏浚泥浆絮凝沉降效率的影响,以通济桥水库疏浚底泥为研究对象,通过室内试验先分析1种有机絮凝剂(PAM)和5种无机絮凝剂(PAC,FeCl₃,Na₂CO₃,Na₂SiO₃·9H₂O,KAl(SO₄)₂·12H₂O)单独作用下疏浚泥浆的絮凝沉降效果及上清液水质的优劣情况,然后对有机、无机絮凝剂进行优化组合试验,确定絮凝沉降效果和上清液水质最优的设计配比方案。试验结果表明:①PAM可以有效促进疏浚泥浆土颗粒的絮凝沉降,但对上清液的去浊率较低;CO₃^2-可以促进细颗粒絮凝结合成大颗粒,提高颗粒的沉降速率;Fe³⁺,Al³⁺具有改善上清液浊度的作用,但对促进泥浆絮凝沉降效果有限。②每1 000 mL疏浚泥浆中采用10 mL PAM+2 g PAC+2 g Na₂CO₃的有机-无机絮凝剂组合为最佳方案,既能快速促进疏浚泥浆的絮凝沉降,又能有效降低上清液的浊度。试验成果可为类似疏浚工程中选择絮凝剂最佳配比方案提供参考。     

黄河水磁化混凝处理试验研究

利用自制磁化装置,分别考察了磁感应强度、磁化时间和加药量对磁化混凝效果的影响,并对磁化水、非磁化水的加药量和污泥体积进行了对照试验.结果表明:当磁感应强度为51.6 mT、加药量为0.06 g、磁化时间为6 min时,磁化混凝能产生较好的效果;与非磁化水相比,磁化水可以在投加更少混凝剂的情况下,达到更好的出水水质;磁化水产生的污泥体积明显小于非磁化水,且污泥结构更密实、沉降速度更快.     

黏性泥沙絮凝研究现状与进展

黏性泥沙絮凝机理研究对河口、水库、航道淤积治理及水环境保护具有重要意义.总结了泥沙絮凝研究中数值模拟、现场观测、室内试验等手段的试验装置和方法,阐述了紊动剪切率、盐度、悬沙浓度、有机质等因素作用下的泥沙絮凝研究成果.分析认为,在三维絮团结构观测、高浓度水体絮凝试验装置、多因素影响的泥沙絮凝,以及水流紊动与絮团特性对应关...     

HYDRODYNAMICS OF FRACTAL FLOCS DURING SETTLING

The settling and hydrodynamic properties of 3-D fractal flocs in quiescent water are investigated with a numerical model based on the Lattice Boltzmann Method (LBM), with considering the settling velocity, hydrodynamic drag force and infra-floc flow. The comparisons of floc settling velocities and effective densities indicate that the numerical results present good agreements with observations in field and at laboratory. The results show that the drag force FD increases with the floc size df according to the relationship FD∝df3. Moreover, the intra-floc flow field and movement of the pore water provide a better understanding of the intra-floc flow from the microscopic viewpoint. The results also indicate that the lattice Boltzmann method is a promising approach to reveal the mechanisms of the flocculation in aquatic environments.