水温对平流式二沉池运行影响的数值模拟  

Numerical simulation of the effect of water temperature on the behaviors of a rectangular secondary sediment tank

作　　者：施周[1] 涂朦朦 王涛[1] 施清华[1] 

机构地区：[1]湖南大学土木工程学院水工程与科学系,长沙410082

出　　处：《安全与环境学报》2015年第4期222-226,共5页Journal of Safety and Environment

基　　金："十二五"国家科技支撑计划项目(2012BAJ24B03)

摘　　要：借助改进的RNGκ-ε两方程湍流模型和简化的多相流混合模型,采用计算流体力学软件Fluent模拟某污水处理厂平流式二沉池在不同水温下的运行效果。通过对比Johnson对水库水温变化的实测数据验证了模型和模拟方法的可靠性。对平流式二沉池的模拟结果表明:不同水温条件下池内水流速度存在相似的分布,在池的下部和上部各存在一个回流区;池内水温降低会造成上部回流区域减小、出水固体颗粒质量浓度增大,从而导致二沉池的颗粒去除率降低;采取增大颗粒粒径、密度和在沉淀池出水口前加设挡板的措施均能有效降低出水固体颗粒质量浓度。This paper attempts to provide a numerical simulation model of the effects of water temperature on the behaviors of a rectangular secondary sediment tank（ RSST） by taking a sewage treatment plant as a case study sample. The afore-mentioned 3-D numerical simulation of the RSST＇s operation has been working with a software named Fluent. In proceeding with our simulation model,we have first of all managed to improve a RNG κ-ε two-equation model while simplifying the multiphase mixture model for the simulation purpose,with the functions between the temperature and the viscosity or temperature and density established based on the study of the model functions of MATLAB and added to the mathematic model by the user-defined function program. In order to validate the functions of the models,we have borrowed Johnson＇s experiment data obtained from the study of the temperature effect on a reservoir and employed the methods for simulating the effects of the temperature. We have thus found that the outcomes of the simulation are well in accord with the Johnson data,indicating that the reliability of the models and methods established in the paper. Furthermore,we have done the simulation activities to test the behaviors of the RSST with the water temperatures varying in a range between 5-25 ℃. The simulation results prove that the velocity distributions in the RSST obtained under different temperatures have the similar pattern. While the velocity of the water near the bottom of the tank turns out to be negative,it would turn to become positive in the middle of the tank,and finally turns out to be negative again on the top of the tank,for there are mainly only two recirculation zones at the bottom and the surface of the tank,respectively. We have also found that the increase of temperature tend to expand the volume of the recirculation zone at the top of the tank while decreasing the particle concentrations of the effluent. At the same time,since the change of temperature can directly affect the viscosity and density

关 键 词：环境工程学 数值模拟 平流式二沉池 水温影响 

分 类 号：X703[环境科学与工程—环境工程]