Experimental study of flow characteristics in non-mated rock fractures considering 3D definition of fracture surfaces

Guan, Rong; Hou, Di; Yang, Jie; Cheng, Long; Zhou, Chuangbing

doi:10.1016/j.enggeo.2017.02.005

Cited by 56 publications

(20 citation statements)

References 53 publications

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“…They speculated that plastic deformation or brittle damage of the of surface asperities could be responsible for the initial increase in critical Reynolds numbers with increased confining pressure due to a reduction in surface roughness. A similar increase in critical Reynolds numbers at increasing but moderate confining pressures was observed by Rong et al (2017). Also unexpected are the results reported by Chen et al (2019) obtained in sandstone fractures, showing that the critical Reynolds number decreases with increasing hydraulic aperture.…”

Section: Introductionsupporting

confidence: 86%

The Effect of Fracture Roughness on the Onset of Nonlinear Flow

Cunningham

Auradou

Shojaei-Zadeh

et al. 2020

Water Resources Research

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In fractures where surface fluctuations are large compared to their aperture (narrow fractures), the flow is forced to move in tortuous paths that produce additional viscous friction and are subject to inertia effects. We consider the relation between the magnitude of surface roughness and the onset of inertial effects in the pressure driving the flow through a single open fracture. We performed experiments systematically varying the average aperture of the open fracture and covering a wide range of Reynolds numbers. For each aperture, we analyze the data in terms of the Forchheimer equation and show that the critical Reynolds number, defined as the Reynolds number at which inertial effects contribute 10% of the total pressure losses, is highly correlated with the roughness of the surface. In particular, we show that significant inertial effects appear earlier as the relative importance of surface roughness increases. Finally, we present results showing that the magnitude of the deviations in the pressure field compared to a linear profile, taken at different points in the fracture along the flow direction, is directly related to the relative surface roughness of the fracture.

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Section: Introductionsupporting

confidence: 86%

The Effect of Fracture Roughness on the Onset of Nonlinear Flow

Cunningham

Auradou

Shojaei-Zadeh

et al. 2020

Water Resources Research

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“…In the previous works, it is assumed that the critical Reynolds number (Re ) is the Re that corresponds to = 0.1 [93,[95][96][97]. Besides the dimensionless Re that is used for characterizing the transition from linear to nonlinear flow regimes, the dimensionless Forchheimer number ( 0 ) is another widely accepted parameter, which is defined as the ratio of nonlinear to linear pressure losses, written as [20,92,98] …”

Section: Cubicmentioning

confidence: 99%

A Review of Critical Conditions for the Onset of Nonlinear Fluid Flow in Rock Fractures

Jiang

2017

Geofluids

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Selecting appropriate governing equations for fluid flow in fractured rock masses is of special importance for estimating the permeability of rock fracture networks. When the flow velocity is small, the flow is in the linear regime and obeys the cubic law, whereas when the flow velocity is large, the flow is in the nonlinear regime and should be simulated by solving the complex NavierStokes equations. The critical conditions such as critical Reynolds number and critical hydraulic gradient are commonly defined in the previous works to quantify the onset of nonlinear fluid flow. This study reviews the simplifications of governing equations from the Navier-Stokes equations, Stokes equation, and Reynold equation to the cubic law and reviews the evolutions of critical Reynolds number and critical hydraulic gradient for fluid flow in rock fractures and fracture networks, considering the influences of shear displacement, normal stress and/or confining pressure, fracture surface roughness, aperture, and number of intersections. This review provides a reference for the engineers and hydrogeologists especially the beginners to thoroughly understand the nonlinear flow regimes/mechanisms within complex fractured rock masses.

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“…Izbash's equation describes the relationship between the fluid flow velocity and the hydraulic gradient is given a theoretical background arriving from a drag model. The exponent in Izbash's equation [25,26] has been obtained over a wide range of Reynolds' numbers.…”

Section: Relation Between Flow Within Smooth Fracture and Crackmentioning

confidence: 99%

Non-Darcy Flow Experiments of Water Seepage through Rough-Walled Rock Fractures

Niu

Yuan

et al. 2018

Geofluids

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The knowledge of flow phenomena in fractured rocks is very important for groundwater-resources management in hydrogeological engineering. The most commonly used tool to approximate the non-Darcy behavior of the flow velocity is the well-known Forchheimer equation, deploying the "inertial" coefficient that can be estimated experimentally. Unfortunately, the factor of roughness is imperfectly considered in the literature. In order to do this, we designed and manufactured a seepage apparatus that can provide different roughness and aperture in the test; the rough fracture surface is established combining JRC and 3D printing technology. A series of hydraulic tests covering various flows were performed. Experimental data suggest that Forchheimer coefficients are to some extent affected by roughness and aperture. At last, favorable semiempirical Forchheimer equation which can consider fracture aperture and roughness was firstly derived. It is believed that such studies will be quite useful in identifying the limits of applicability of the well-known "cubic law," in further improving theoretical/numerical models associated with fluid flow through a rough fracture.

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Experimental study of flow characteristics in non-mated rock fractures considering 3D definition of fracture surfaces

Cited by 56 publications

References 53 publications

The Effect of Fracture Roughness on the Onset of Nonlinear Flow

The Effect of Fracture Roughness on the Onset of Nonlinear Flow

A Review of Critical Conditions for the Onset of Nonlinear Fluid Flow in Rock Fractures

Non-Darcy Flow Experiments of Water Seepage through Rough-Walled Rock Fractures

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