多孔介质速度场和流量场分布

Velocity and flow field in porous media

流体在多孔介质中的宏观特性由介质本身的孔隙结构直接决定,速度场和流量场作为连接微观和宏观的桥梁显得尤为重要,但相关的研究相对较少。基于孔隙网络模型中的流动模拟,采用欧拉描述方法,系统统计了多孔介质中速度和流量的分布,分析了速度和流量的概率密度函数随孔隙结构的变化关系。研究表明:①随多孔介质无序性的增加,速度的分布范围急剧增加,流量的分布范围变化不大;②速度的概率密度函数随无序因子的减小依次表现为:高斯分布、指数分布、指数截断的幂律分布及幂律分布,流量的概率密度函数主要受孔隙非均质性的影响,表现为高斯分布和指数截断的幂律分布;③归一化流体速度的平均值受变异系数和配位数共同影响,且与配位数成乘幂关系,归一化流体流量的平均值不随配位数的变化而变化,但其随变异系数的增加而降低。

The macroscopic properties characterizing fluid transport in porous media are directly determined by the pore structure of the media itself. Velocity field and flow field,connecting microscopic and macroscopic theories,are particularly important,but few studies have been carried out. Based on the simulation of single-phase flow in pore network model,this paper systematically calculated the distribution of Eulerian velocity and flow in porous media,and analyzed the relationship between pore structure and the probability density function of velocity and flow. And the following research results were obtained. Firstly,with the increase of the disorder of porous media,the distribution range of velocity increases sharply,while that of flow rate does not change much.Secondly,as the disorder factor decreases,the probability density function of velocity satisfies the following distributions in turn:Gauss distribution,exponential distribution,power law with exponential cut-off distribution and power law distribution. The probability density function of the flow is mainly affected by the heterogeneity of porous media,which basically obeys Gauss distribution and power law with exponential cut-off distribution.Thirdly,the average value of the normalized fluid velocity(v*)is affected by both the coefficient of variation and the coordination number,and the relationship between v* and the coordination number obeys power law.The average value of normalized fluid flow(q*)does not change with coordination number,but decreases with the increase of the coefficient of variation.