高渗透性多孔介质室内弥散实验的拖尾效应及模拟研究

发布时间：2018-06-20 10:55

本文选题：室内弥散实验 + 高渗透性　；参考：《中国矿业大学》2017年硕士论文

【摘要】：本文开展了高渗透性多孔介质的溶质运移实验,并基于实验数据进行了穿透曲线的拖尾分析及数值模拟研究。实验选取0.125mm~0.3mm、0.3mm~0.5mm以及0.5mm~0.7mm三种粒径范围的河砂作为介质,并且每种介质分别进行了5种不同流速的弥散实验,本文共进行了15组实验,实验结果以C-t图的形式给出。此外,通过使用传统的对流-弥散方程和基于Riemann-Liouville分数阶导数形式的时间分数阶对流-弥散方程对每条穿透曲线进行了拟合,根据拟合结果,分析了拖尾的成因,并对拖尾进行了模拟研究,具体结论如下:1)对各实验砂柱的渗透系数与有效孔隙度进行了测量,测定结果为:介质粒径0.125mm~0.3mm砂柱的平均渗透系数为48.73m/d,有效孔隙度为0.284;介质粒径0.3mm~0.5mm砂柱的平均渗透系数为37.73m/d,有效孔隙度为0.258;介质粒径0.5mm~0.7mm砂柱的平均渗透系数为54.33m/d,有效孔隙度为0.298。根据测定结果,实验砂柱的平均渗透系数最小值达到了37.73m/d,属于高渗透性多孔介质。此外,通过对每个砂柱分段测量的结果可知,每个砂柱的各段渗透系数差别基本不大,可以视为相对均质介质。2)对于实验获得的穿透曲线,本文首先使用了传统的对流-弥散方程进行拟合,得到了各实验条件下的弥散度和有效孔隙度,并且,同一砂柱、同一取样口的弥散度和有效孔隙度基本都在一定范围内,但拟合得出的有效孔隙度要大于实测孔隙度。3)根据传统对流-弥散方程对穿透曲线的拟合效果图可以看出大部分穿透曲线出现了拖尾现象,对于拖尾的产生,从本文实验条件出发得出了:拖尾受多孔介质的均质性影响,其均质性越差,越容易产生拖尾现象;此外,关于流速对拖尾的影响,从实验结果来看,二者之间没有明确的关系。4)基于传统的对流-弥散方程对穿透曲线进行拟合时,出现了拖尾现象,为了处理该问题,本文引入了基于Riemann-Liouville分数阶导数的时间分数阶对流-弥散方程,对实测的C-t曲线进行拟合。根据拟合效果图可以看出时间分数阶对流-弥散方程可以较好的解决拖尾问题。
[Abstract]:In this paper, solute migration experiments of highly permeable porous media are carried out, and the trailing analysis and numerical simulation of the penetration curve are carried out based on the experimental data. Three kinds of river sand of 0.125 mm ~ 0.3mm ~ 0.3mm ~ 0.3mm ~ 0.3mm and 0.5mm~0.7mm were chosen as media, and five different velocity dispersion experiments were carried out in each medium. In this paper, 15 groups of experiments were carried out, and the results were given in the form of C-t diagram. In addition, each penetrating curve is fitted by using the traditional convection-dispersion equation and the time fractional convection-dispersion equation based on Riemann-Liouville fractional derivative. According to the fitting results, the causes of trailing are analyzed. The trailing tail is simulated. The specific conclusions are as follows: 1) the permeability coefficient and effective porosity of each experimental sand column are measured. The results show that the average permeability coefficient and effective porosity of 0.125mm~0.3mm sand column are 48.73 m / d, 0.284 m / d, 37.73 m / d and 0.258 m / d, respectively, and the average permeability coefficient and effective porosity of 0.5mm~0.7mm sand column are 54.33 m / d and 0.298 m / d, respectively. According to the measured results, the minimum average permeability coefficient of the experimental sand column is 37.73 m / d, which is a highly permeable porous medium. In addition, according to the results of sectional measurement of each sand column, it can be seen that the permeability coefficient of each sand column is not much different and can be regarded as a relative homogenous medium. 2) the penetration curve obtained by the experiment can be regarded as a relative homogeneous medium. In this paper, the traditional convection-dispersion equation is used for fitting, and the dispersion and effective porosity of each experimental condition are obtained. Moreover, the dispersion and effective porosity of the same sand column and the same sampling port are basically within a certain range. But the effective porosity obtained by fitting is larger than the measured porosity. 3) according to the fitting effect of the traditional convection-dispersion equation to the penetration curve, it can be seen that the trailing phenomenon appears in most of the penetrating curves, and the trailing phenomenon occurs for the trailing curve. From the experimental conditions in this paper, it is concluded that the tail is affected by the homogeneity of porous media, the worse the homogeneity is, the easier it is to produce the trailing phenomenon. In addition, as for the effect of the velocity of velocity on the trailing tail, the experimental results show that, There is no clear relationship between the two. 4) in order to deal with this problem, trailing phenomenon occurs when the penetrating curve is fitted based on the traditional convection-dispersion equation. In this paper, the time-fractional convection-dispersion equation based on Riemann-Liouville fractional derivative is introduced, and the measured C-t curve is fitted. According to the fitting effect diagram, it can be seen that the time fractional convection-dispersion equation can solve the trailing problem well.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P641

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