Macroscopic dispersion in porous media: The controlling factors
Macroscopic dispersion in porous media: The controlling factors
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多孔介质中的宏观分散：控制因素
DOI：
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发表时间：
1977
期刊：
影响因子：
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通讯作者：
F. Schwartz
中科院分区：
文献类型：
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作者：
F. Schwartz
应用模拟技术来分析地下水系统的传质，最重要的限制之一是难以描述自然系统的色散特性。虽然存在大量的实验室尺度实验数据，但从区域系统中获得的少数测量结果表明，由大尺度多孔介质非理想性产生的色散更为重要。本文模拟了均匀非均质多孔介质在一维流动条件下的宏观分散效应。用于详细分析的理想介质包括高渗透率介质中的低渗透率包裹体。当包裹体在区域内排列不均匀时，无法定义介质的唯一色散值，色散随空间的变化而变化。分散的大小是由包裹体和其余介质之间的水力传导性对比、包裹体的数量和聚集模式控制的。一般情况下，随着电导率对比度的降低和介质结构的规整化，色散会降低。用随机分析来估计介质的色散是可能的。假设的多孔介质具有与某些实际介质相似的特性，将产生一系列色散值。该技术的基本数据将是对多孔介质聚集模式和介质内电导率对比的详细统计分析。
One of the most important limitations to the application of modeling techniques for the analysis of mass transfer in groundwater systems is the difficulty in characterizing the dispersive character of natural systems. Although large quantities of experimental data exist for laboratory scale experiments, the handful of measurements which have been obtained from regional systems suggest that dispersion produced by large-scale porous medium nonidealities is considerably more important. In this paper the effects of macroscopic dispersion are simulated for uniform heterogeneous porous media under conditions of one- dimensional flow. The idealized media considered for detailed analysis consist of low permeability inclusions within a higher-permeability medium. When the inclusions are not arranged rather homogeneously within the region, a unique dispersivity value for the medium cannot be defined, and dispersivity changes as a function of space. The magnitude of dispersion is controlled by the contrast in hydraulic conductivity between the inclusions and the remainder of the medium, the number of inclusions, and the mode of aggregation. Generally, dispersivity is found to decrease as the conductivity contrast decreases and the structure of the medium is regularized. It will be possible to estimate the dispersivity of a medium by using stochastic analysis. Hypothetical porous media with characteristics similar to those of some actual medium will yield a range of dispersivity values. The basic data for this technique will be detailed statistical analysis of the mode of porous medium aggregation and the conductivity contrasts within the medium.