Influence of fracture surface roughness on local flow pattern: visualization using a microfluidic field experiment
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PAPER
Influence of fracture surface roughness on local flow pattern: visualization using a microfluidic field experiment Pingye Guo 1,2
&
Meng Wang 1,2 & Kai Gao 1,2 & Manchao He 1,2 & Yanwei Wang 3
Received: 19 February 2020 / Accepted: 7 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract An understanding of the influence of fracture surface roughness on local flow patterns is critical for underground engineering and geological sciences. The flow pattern in a fracture is not only affected by the large-scale waviness of the fracture morphology, but also by the local small-scale roughness of the fracture surface, in particular the local flow pattern. The microfluidic field of flow in two fracture models with and without local small-scale roughness was investigated through a microscopic visualization hydraulic experiment. By quantitatively analyzing the velocity and vorticity in the two fracture models, the results indicate that the characteristics of the fracture microfluidic field are closely related to the local small-scale roughness. First, due to the effect of the local small-scale roughness, it is easier to generate and develop eddies in the original fractures that contain small-scale roughness. Meanwhile, the local small-scale roughness increases the velocity gradient in the vertical section of the fracture flow and further enhances the complexity of the fracture flow field. Moreover, although the small-scale roughness has little impact on the position of the maximum velocity, the area of eddies increases and the effective flow aperture is significantly reduced. Keywords Hydraulic testing . Tracer tests . Rough-wall fracture . Local flow pattern . Laboratory experiments/measurements
Introduction Most of rocks in nature contain a large number of complex fractures or pore networks, and the local geometry of these networks affects the seepage of the rock mass. Quantitatively analyzing and understanding the influence of the complexity of the fractures’ local geometry on fracture fluid flow are critical for underground engineering and geological sciences,
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10040-020-02210-1) contains supplementary material, which is available to authorized users. * Pingye Guo [email protected] 1
State Key Laboratory for Geo-Mechanics and Deep Underground Engineering, Beijing 100083, China
2
School of Mechanics and Civil Engineering, China University of Mining and Technology, Beijing 100083, China
3
China institute of Water Resources and Hydropower Research, Beijing 100038, China
such as schemes involving hydrothermal systems (Huang et al. 2019; Luo et al. 2017), water resources management (Folch et al. 2011; Jiang et al. 2014) and petroleum and gas resource exploitation (Singh and Cai 2018). In general, the fluid flow in rough-walled fractures is characterized by the three-dimensional Navier-Stokes (N-S) equations (Zimmerman and Bodvarsson 1996; Liu et al. 2016b). Unfortunately, due to the exi
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