分层式潜流人工湿地水力学特性数值模拟与分析

Numerical simulation and analysis of hydraulic characteristics of layered subsurface flow constructed wetland

人工湿地水力学特征对其污染物去除过程有重要影响。采用计算流体力学软件FLUENT中的多孔介质模型对分层式潜流人工湿地内部的流场进行模拟,并分析了不同进出口位置对湿地水力学行为的影响。模拟结果表明,分层式潜流人工湿地基质层内部速度分布的差异较大,水流多从进口端的左半部汇入下部砾石层以大于3.69×10-4m/s的速度出流,形成快速出流通道,而出口端的右上部水流速度小于2.58×10-5m/s,出现滞留现象,整个湿地系统的水力效率未得到充分发挥;进水口位于基质层以下使得系统的水力效率进一步下降,而出水口位于基质层中上部则在一定程度上提高了右半部基质层的利用率,降低了下部快速流道的速度,整个系统的水力效率也有所提高。因此,建议将进水口置于湿地基质表层,而将出水口置于基质层的中上部。

Hydraulic characteristics of constructed wetland have a significant effect on the pollutant removal process.Flow field of a subsurface flow constructed wetland with layered medium was simulated by the model of porous media in FLUENT,a computational fluid dynamic software.Also the influence of inlet and outlet position on hydraulic behavior was analyzed.The results of simulation showed that： most of the fluid flowed into the gravel layer from the left part near the inlet and flow out with a velocity of larger than 3.69×10^-4m/s forming a ＂fast-speed effluent path＂.While fluid in the upper right area flowed with a velocity less than 2.58×10^-5m/s causing stagnant.The hydraulic efficiency of the system was not used sufficiently.Putting the inlet below medium surface reduced the hydraulic efficiency of the system further.While putting the outlet at the middle-up of the medium improved utilization of medium in right part to a certain extent and reduced the flow rate in the ＂fast-speed effluent path＂ thus improved the hydraulic efficiency of the whole system.Consequently,putting inlet at the surface of medium and putting outlet at the middle-upper part of the medium is advised.