给水管网的污染物入侵流量模型研究

发布时间：2018-08-30 19:42

【摘要】：当给水管网内发生负压时,埋地管道周围环境中含有污染物的地下水会通过管道上的破损口侵入管网内部,对饮用水造成污染。侵入管网的地下水的体积流量的估算对用户暴露风险的评估具有重要作用。目前在计算入侵流量时常用的孔口公式未能考虑管道周围土体的影响。本文针对负压驱动下侵入埋地管道破损口的地下水的流量估算问题,进行了实验研究与理论分析,重点考虑破损口周围土体对入侵流量的影响。第三章通过实验研究管道周围的多孔介质对孔口入侵流量的影响。由于含有污染物的地下水与普通的水具有相同的流动特性,所以本文实验均采用普通水进行。实验采用2种孔径,3种多孔介质,分别研究了小孔所处表面形式(平面／曲面)、小孔周围的多孔介质以及大雷诺数对入侵流量的影响。第四章考虑流速、孔径和多孔介质渗透性等多种因素的影响,实验研究了孔口水头损失和多孔介质水头损失。在第五章中,将多孔介质中的三维渗流与孔口入流相结合推导了污染物入侵流量改进模型。模型考虑管道物理边界的影响对透水区域进行修正,改进了已有模型中几何修正系数的取值方法,本模型中多孔介质水头损失部分的流量线性项系数降低了40%-60%,流量二次项系数降低了70%-80%。第六章进行了三维渗流条件下的圆孔入侵实验,验证入侵流量改进模型的准确性。通过对实验结果进行分析,可得主要结论如下：(1)小孔周围的多孔介质可以使小孔流量系数发生改变,且使入侵流量与孔径、多孔介质渗透性及流动雷诺数有关；(2)孔口流量系数根据雷诺数的不同呈现出分区的变化特点；(3)孔口流动雷诺数较大时,流量系数可能存在突变的现象,这是流线从孔壁的分离导致的；(4)入侵流量与管道内外的压力差、破损口的大小、土体的渗透性以及管道直径有关；(5)三维渗流实验结果证明本模型具有较高的准确性。本次研究主要针对稳定流动条件下的单个圆孔形破损口进行研究,并且没有考虑管道周围土颗粒的运动。后续研究可围绕管内压力瞬变的情况,管道的多种破损形式,管网中分布的多个破损口,破损口周围土颗粒的移动等问题展开。
[Abstract]:When the negative pressure occurs in the water supply network, the groundwater containing pollutants in the surrounding environment of the buried pipeline will invade the pipe network through the damaged opening of the pipeline, which will cause pollution to the drinking water. The estimation of groundwater volume flow is very important to the assessment of user exposure risk. At present, the commonly used method for calculating the invasion flow is the influence of soil around the pipeline. In this paper, an experimental study and theoretical analysis are carried out on the estimation of the underground water flow in the damaged outlet of a buried pipeline driven by negative pressure, with emphasis on the influence of the soil around the damaged opening on the intrusive discharge. In the third chapter, the influence of porous media around the pipeline on the flow rate of orifice intrusion is studied experimentally. Since the groundwater containing pollutants has the same flow characteristics as ordinary water, the experiments are carried out with ordinary water. In this paper, two kinds of pore size and three kinds of porous media were used to study the influence of the surface form (plane / surface) of the pore, the porous media around the pore and the large Reynolds number on the intrusion flow rate. In chapter 4, considering the influence of flow rate, pore diameter and permeability of porous media, the loss of orifice head and porous media head are studied experimentally. In the fifth chapter, the improved model of pollutant intrusion flow is derived by combining three-dimensional seepage and orifice flow in porous media. Considering the influence of the physical boundary of pipeline, the model modifies the permeable region, and improves the method of calculating the geometric correction coefficient in the existing model. In this model, the linear coefficient of flow in the head loss of porous media is reduced by 40 to 60, and the coefficient of the second term of flow is reduced by 70 to 80. In chapter 6, the experiment of circular hole intrusion under three-dimensional seepage condition is carried out to verify the accuracy of the improved intrusion flow model. Through the analysis of the experimental results, the following conclusions can be drawn: (1) the porous media around the pores can change the flow coefficient of the pores, and the intrusion flow rate is related to the pore diameter, the permeability of porous media and the flow Reynolds number; (2) the flow coefficient of the orifice presents the characteristic of zone change according to the Reynolds number, (3) when the Reynolds number of the orifice is larger, the flow coefficient may have a sudden change, which is caused by the separation of the flow line from the hole wall; (4) the intrusion flow rate is related to the pressure difference inside and outside the pipeline, the size of the damaged opening, the permeability of the soil and the diameter of the pipeline. (5) the experimental results of three-dimensional seepage show that the model has high accuracy. In this study, a single circular hole is studied under steady flow conditions, and the movement of soil particles around the pipe is not considered. Further studies can be carried out around the transient pressure in the pipe, the various damaged forms of the pipeline, the distribution of multiple damaged openings in the pipe network, and the movement of soil particles around the damaged opening.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU991.33

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