摘要
【目的】在同时考虑进水与池内水的污泥质量浓度差异和温度差异的条件下,对平流式二沉池内的异重流现象进行数值模拟,重点研究异重流对池内流场及污泥沉降规律的影响,为优化沉淀池结构设计及提高沉淀池工作效率提供理论支持。【方法】选取Mixture模型和RNGκ-ε2方程紊流模型,设初始时刻二沉池内水为清水,进水为含一定质量浓度污泥的污水,并通过设置池内水与进水的不同温差模拟夏季与冬季环境,利用模拟数据分析不同时刻各工况下异重流的演变规律。【结果】池内水与进水的单纯污泥质量浓度差异会产生下异重流,小温差低温水与夏季大温差低温水进入均会导致下异重流产生,温差增大,下异重流作用更为明显;高温水进入会同时产生上异重流与下异重流,冬季温差高温水进入时上异重流起主导作用,异重流产生的旋流作用明显,对沉淀池工作效率的影响很大。【结论】温差异重流与污泥质量浓度差异重流本质均为密度差异,低温水进入增强下异重流,高温水进入削弱下异重流,温度影响会消失,污泥质量浓度差异重流作用时间更长。
[Objective] The impact of gravity flow caused by differences of sludge concentrations and temperatures between influent and tank on stream and the sludge concentration distribution was studied. [Method] In the initial time,there was clean water in the tank and the inlet was sewage. The Mixture mod- el and RNG k-ε two-equation turbulence model were used to simulate different temperature cases in sum- mer and winter. The variation of gravity flow in different times and conditions was studied. [Result] The concentration difference and low-temperature water inflow produced gravity flow in the bottom in summer, while high-temperature water inflow produced the gravity flow both on the top and in the bottom in sum- mer and on the top only in winter. The gyrating current had significant influence on the work efficiency of the tank. [Conclusion] Both concentration and temperature differences were density differences. The low- temperature water inflow strengthened the gravity flow in the bottom while the high-temperature water in- flow weakened it. The impact of the temperature would disappear and the impact of concentration differ- ences would exist longer when high-temperature water inflow was used.
出处
《西北农林科技大学学报（自然科学版）》
CSCD
北大核心
2013年第9期221-228,共8页
Journal of Northwest A&F University(Natural Science Edition)
基金
陕西省重点学科建设专项
关键词
二沉池
异重流
数值模拟
rectangular sedimentation tanks
gravity flow
numerical simulation
