平流二次沉淀池中温差对异重流影响的数值模拟

Numerical Simulation of the Effect of Temperature Difference on Gravity Flow in Rectangular Secondary Setting Tanks

由于进水与池内水的浓度差异及不同季节进水与池内水的温度差异,会在沉淀池内产生异重流现象,会对池内的流态产生影响。以城市污水处理厂中平流二次沉淀池为研究对象,针对池内的异重流现象应用数值模拟的方法,选取RNG k-ε双方程模型和两相流混合模型作为计算的数学模型,对平流式二沉池池内单纯由浓度差引起的异重流,进一步引入温度差,进行了流动的二维数值模拟。研究了温差对平流二沉池中异重流的影响。结果表明,温差产生的影响随温差类型及温差大小的不同而改变,低温水流入产生下异重流效应,高温水流入产生上异重流效应;温差越大,影响越明显;随着温度达到平衡,温差的影响渐趋消失。

The concentration difference between influent water and tanks＇ water, or the different inlet temperature in different seasons would produce gravity flow phenomena in the sedimentation tanks. In this paper, gravity flow effeeted by temperature difference in rectangular secondary settling tanks is studied by numerical simulation. In aspect of mathematical model, the RNG k-e two-equation turbulence model and the Mixture model are selected as the simulation secondary setting tank mathematical model, and the tem- perature differences are further introduced into the density flow caused by the simple concentration differ- enees in the rectangular secondary setting tanks to carry out the flowing Z-D numerical simulation. The effect of temperature differences upon the density flow in the rectangular secondary setting tanks is studied ~ The results show that the effects of temperature difference changes with the types and size of the temper- ature difference, and that low-temperature inflow would produce the gravity flow in the substrate, while high-temperature inflow produces the gravity flow on the top. Accordingly, the greater is the temperature difference, the more obvious the influence will be, and the effect of temperature difference will gradually disappear with the temperature reaching balance.