VELOCITY DEPENDENCE OF DISPERSION FOR TRANSPORT THROUGH A SINGLE FRACTURE OF VARIABLE ROUGHNESS
VELOCITY DEPENDENCE OF DISPERSION FOR TRANSPORT THROUGH A SINGLE FRACTURE OF VARIABLE ROUGHNESS
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DOI：
10.1029/93wr01407
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发表时间：
1993-10
影响因子：
5.4
通讯作者：
D. G. Dronfield;S. Silliman
中科院分区：
文献类型：
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作者：
D. G. Dronfield;S. Silliman
一些作者最近表示有兴趣在裂缝介质中的化学传输。这些努力中的大多数是基于裂缝内的分散系数和平均流体速度之间的线性关系。这一关系在所有应用中并不完全合理。对于本研究，假设（如作者在多孔介质中所建议的）弥散系数与速度的n次方成正比。此外，假设裂缝内的输送遵循经典的对流-弥散行为（例如，Fickian色散）。本研究的重点是一系列人工裂缝中的幂n值。特别地，利用实验装置来通过单个裂缝进行受控示踪剂实验。当裂缝由光滑的平行板组成时，实验结果表明，弥散系数与速度的平方成正比（与Taylor（1953）关于横向扩散主导的输运的早期工作一致）。随着裂缝粗糙度通过裂缝内堵塞的使用和/或沿着裂缝壁沿着增加表面粗糙度而增加，分散和速度之间的关系发生变化。对于每种裂缝粗糙度，结果遵循一般关系，其中分散度与速度的n次方成正比。然而，幂n强烈依赖于断裂粗糙度，对于光滑平行板取2.0的值，对于粗糙板则减小到约1.3的值。
Several authors have recently expressed interest in chemical transport within fractured media. The majority of these efforts have been based on a linear relationship between the dispersion coefficient and the average fluid velocity within the fracture. It is not apparent that this relationship is fully justified in all applications. For the present study, it is assumed (as suggested by authors working in porous media) that the dispersion coefficient is proportional to the velocity raised to a power, n. Further, it is assumed that transport within the fracture follows classic advection-dispersion behavior (e.g., Fickian dispersion). The present study focuses on the value of the power n in a series of artificial fractures. In particular, an experimental apparatus is utilized to run controlled tracer experiments through a single fracture. When the fracture consists of smooth parallel plates, the results from the experiments indicate that the dispersion coefficient is proportional to the velocity squared (consistent with the early work by Taylor (1953) for transport dominated by transverse diffusion). As the fracture roughness is increased through use of blockages within the fracture and/or addition of surface roughness along the fracture walls, the relationship between dispersion and velocity varied. For each fracture roughness, the results followed the general relationship in which dispersion is proportional to velocity raised to the power n. The power n, however, was strongly dependent on the fracture roughness, taking on a value of 2.0 for smooth parallel plates and decreasing to a value of approximately 1.3 for rough plates.