利用快速微型计算机断层扫描直接比较饱和与非饱和多孔介质中的溶质迁移

IF 2.7 3区 工程技术 Q3 ENGINEERING, CHEMICAL
Stefanie Van Offenwert, Veerle Cnudde, Sharon Ellman, Tom Bultreys
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引用次数: 0

摘要

非饱和条件下的溶质迁移在各种应用和自然环境中都很重要,例如地下水在软弱地带的流动。与饱和条件下的迁移相比,非饱和溶质迁移的孔隙尺度速度变化较大,因此非饱和溶质迁移研究显示出复杂的特征(如非费克迁移)。然而,由于对孔隙尺度的直接三维观测非常有限,人们对孔隙尺度的物理过程仍不完全了解。本研究通过在烧结玻璃和 Bentheimer 砂岩样本中进行示踪剂注入实验,直接确定了单相和两相溶质迁移的特征。这些实验通过基于实验室的快速微型计算机断层扫描进行连续扫描成像。利用基于孔隙的瞬态浓度场确定示踪剂到达每个孔隙的时间和填充持续时间,从而确定网络尺度的流速和传输特性。我们确定了重要的弥散度量(标量耗散率和填充持续时间),并指出在非饱和实验中,孔隙尺度流速范围很大,存在停滞和流动孔隙。此外,我们首次在三维实验数据上量化了停滞孔隙和流动孔隙之间的传质系数。我们还根据间隙速度和孔隙速度直接计算了迂回度。结果发现,与饱和条件相比,非饱和条件下的曲折度要高出 13%。我们的结果表明,孔隙尺度结构的异质性增加了饱和与非饱和溶质传输之间的差异。因此,这项研究为非饱和多孔介质中溶解物质的孔隙尺度扩散和混合提供了进一步的见解。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Direct Pore-Scale Comparison of Solute Transport in Saturated and Unsaturated Porous Media Using Fast Micro-Computed Tomography

Direct Pore-Scale Comparison of Solute Transport in Saturated and Unsaturated Porous Media Using Fast Micro-Computed Tomography

Direct Pore-Scale Comparison of Solute Transport in Saturated and Unsaturated Porous Media Using Fast Micro-Computed Tomography

Solute transport in unsaturated conditions is important in various applications and natural environments, such as groundwater flow in the vadose zone. Studies of unsaturated solute transport show complex characteristics (e.g. non-Fickian transport) due to larger variations in the pore-scale velocities compared to transport in saturated conditions. However, the physical processes at the pore scale are still not completely understood because direct three-dimensional observations at the pore scale are very limited. In this study, single-phase and two-phase solute transport was directly characterized by performing tracer injection experiments in a sintered glass and Bentheimer sandstone sample. These experiments were imaged by continuous scanning with fast laboratory-based micro-computed tomography. The network-scale flow velocities and transport properties were characterized by using the pore-based transient concentration fields to determine the tracer’s arrival time and filling duration in every pore. Important measures for dispersion (the scalar dissipation rate and filling duration) were determined and indicated a wide range in pore-scale velocities and the existence of stagnant and flowing pores for the unsaturated experiments. Furthermore, we performed the first quantification of the mass transfer coefficient between stagnant and flowing pores on three-dimensional experimental data. We also calculated the tortuosity directly from the interstitial velocity and the pore-based velocity. This was found to be 13% higher in unsaturated conditions compared to saturated conditions. Our results indicate that pore-scale structural heterogeneity increases the differences between saturated and unsaturated solute transport. This study thus provides further insight into pore-scale spreading and mixing of dissolved substances in unsaturated porous media.

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来源期刊
Transport in Porous Media
Transport in Porous Media 工程技术-工程:化工
CiteScore
5.30
自引率
7.40%
发文量
155
审稿时长
4.2 months
期刊介绍: -Publishes original research on physical, chemical, and biological aspects of transport in porous media- Papers on porous media research may originate in various areas of physics, chemistry, biology, natural or materials science, and engineering (chemical, civil, agricultural, petroleum, environmental, electrical, and mechanical engineering)- Emphasizes theory, (numerical) modelling, laboratory work, and non-routine applications- Publishes work of a fundamental nature, of interest to a wide readership, that provides novel insight into porous media processes- Expanded in 2007 from 12 to 15 issues per year. Transport in Porous Media publishes original research on physical and chemical aspects of transport phenomena in rigid and deformable porous media. These phenomena, occurring in single and multiphase flow in porous domains, can be governed by extensive quantities such as mass of a fluid phase, mass of component of a phase, momentum, or energy. Moreover, porous medium deformations can be induced by the transport phenomena, by chemical and electro-chemical activities such as swelling, or by external loading through forces and displacements. These porous media phenomena may be studied by researchers from various areas of physics, chemistry, biology, natural or materials science, and engineering (chemical, civil, agricultural, petroleum, environmental, electrical, and mechanical engineering).
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