竖流式沉淀池流体力学模拟

发布时间：2018-06-26 23:55

本文选题：沉淀池 + 数值模拟　；参考：《太原科技大学》2015年硕士论文

【摘要】：沉淀池是水处理中重要的构筑物,其固液分离的效果直接影响着处理系统对固体悬浮颗粒物的去除效率。但是沉淀池中流态变化多样,不仅有自身湍流作用的影响,沉淀颗粒的密度、粒径、粘度等也会对它的运行造成影响。沉淀池固液两相流的数值模拟是研究沉淀池水力特性及沉降特性的重要方法,对沉淀池的优化设计有重要的参考价值。本文通过实验确定了固体颗粒的密度、固体颗粒粒度分布;建立了沉淀池内固体絮凝团的沉降速度模型,其沉降速度与浓度的关系符合Vesilind沉降速度模型,并通过数值拟合技术得到能够反映特定物料的沉降速度模型。固体沉降过程中液体粘度随固体浓度的变化而变化,粘度的变化将会对液体的流动状态产生很大的影响,同时,对固体的沉降性能和压缩性能产生影响。本文通过流变学实验,确定了不同固体浓度时液体的粘度,为沉淀池CFD分析提供了可靠的参数。根据上述实验,将CFD两相流k-Epsilon湍流模型、欧拉多相流模型和沉降速度及粘度进行耦合,实现了固体的沉降及粘度变化。以实验室小型竖流沉淀池为研究对象,采用计算流体力学分析软件ANSYS CFX对其进行数值计算。模拟并分析了沉淀池内流场与固体浓度的分布。选取合适的测定断面,通过实验测定,取得实验数据,并与模拟结果进行比较。模拟结果与实验数据基本吻合,证明所建立的数学模型能够反映沉淀池的实际运行状态,可为沉淀池的设计提供理论依据。
[Abstract]:Sedimentation tank is an important structure in water treatment. The effect of solid-liquid separation directly affects the removal efficiency of solid suspended particulates in the treatment system. However, the flow state in the sedimentation tank is varied, which has not only the effect of its own turbulence, but also the density, particle size and viscosity of the precipitate particles. The numerical simulation of solid-liquid two-phase flow in sedimentation tank is an important method to study the hydraulic characteristics and settlement characteristics of sedimentation tank, which has important reference value for the optimum design of sedimentation tank. In this paper, the density and particle size distribution of solid particles are determined by experiments, and the settling velocity model of solid flocculation in sedimentation tank is established. The relationship between settling velocity and concentration is in accord with Vesilind settling velocity model. The settlement velocity model which can reflect the specific material is obtained by numerical fitting technique. In the process of solid settlement, the viscosity of liquid varies with the concentration of solid, and the change of viscosity will have a great influence on the flow state of liquid, at the same time, on the settling performance and compressibility of solid. In this paper, the viscosity of liquid with different solid concentration is determined by rheological experiment, which provides reliable parameters for CFD analysis of sedimentation tank. According to the above experiments, the k-Epsilon turbulence model and the Euler multiphase flow model of CFD two-phase flow are coupled with the settling velocity and viscosity to realize the settlement and viscosity changes of solids. In this paper, a small vertical flow sedimentation tank in laboratory is studied. The numerical calculation is carried out by using CFX software ANSYS. The distribution of flow field and solid concentration in the sedimentation tank was simulated and analyzed. The experimental data were obtained by selecting the appropriate section and comparing with the simulation results. The simulation results are in good agreement with the experimental data. It is proved that the established mathematical model can reflect the actual operating state of the sedimentation tank and provide a theoretical basis for the design of the sedimentation tank.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

【相似文献】