Influence of surface roughness on nonlinear flow behaviors in 3D self-affine rough fractures: Lattice Boltzmann simulations

Wang, Min; Chen, Yi‐Feng; Guo, Wanwu; Jia, Zhou; Zhou, Chi

doi:10.1016/j.advwatres.2016.08.006

Cited by 233 publications

(118 citation statements)

References 81 publications

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“…The main flow channel becomes narrow due to the expansion of the eddy domain. Several previous works [28][29][30][31][32] showed similar results for the growth of eddies due to the increasing Reynolds number. At high Reynolds number (Re=170), it can be seen clearly that the eddy-controlled domain occupies a large portion of the fracture.…”

Section: Flow Field and Eddies Formationsupporting

confidence: 63%

Pore-Scale Modeling of Mixing-Induced Reaction Transport through a Single Self-Affine Fracture

et al. 2018

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This pore-scale modeling study in single self-affine fractures showed that the heterogeneous flow field had a significant influence on the mixing-induced reaction transport. We generated the single self-affine fracture by the successive random additions (SRA) technique. The pore-scale model was developed by coupling the Navier-Stoke equation (NSE) and advection-diffusion equation with reaction (ADER). Eddies were captured in the self-affine fracture due to the increasing Reynolds number and the sudden expansion of aperture. The flux-weighted breakthrough curves (BTCs) of reaction product showed the typical non-Fickian characteristics (i.e., "early arrival" and "heavy tail"). It was found that the reactant was involved in eddies and then reacted inside the eddy-controlled domain. Consequently, eddies played a significant role in delaying the mass exchange process between the eddycontrolled domain and the main flow channel, which resulted in the "heavy tail" in BTCs. As the Reynolds number increased, the breakthrough time increased while the concentration peaks of BTCs decreased. Furthermore, the dilution index presenting the exponential of the Shannon entropy of a concentration probability distribution was used to quantify the degree of reactant mixing. The results showed that the quantification of dilution for nonreaction transport was in good agreement with the outcomes of mixing-induced reaction transport. The high Reynolds number and Peclet number had a negative influence on the mixing process at the early time whereas they led to the enhanced mixing process at the late time.

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Section: Flow Field and Eddies Formationsupporting

confidence: 63%

Pore-Scale Modeling of Mixing-Induced Reaction Transport through a Single Self-Affine Fracture

et al. 2018

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“…The previous works have shown that the fracture surface roughness, especially the secondary roughness, plays a significant role on the nonlinear flow properties of rock fractures, because the eddy flow occurs due to the surface roughness [79]. Wang et al [124] established a series of 3D self-affine rock fractures using the successive random additions (SPA) method, in which the geometry of fracture surface is fractal [125,126]. The fractal dimension ( 3 ) is incorporated to characterize fracture surface roughness, which is correlated with the Hurst exponent (H) as D 3 = 3 − [127][128][129][130][131].…”

Section: Effect Of Fracture Surface Roughnessmentioning

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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“…When assessing the fluid flow through a single rock fracture, the Reynolds number (Re), which is defined as the ratio of inertial forces to viscous forces, is typically used to quantify the onset of nonlinear flow. As noted above, the variations of normalized transmissivity ( / 0 ) versus Re can be determined by extending the linear Darcy law with = /(−∇ ) [23,25,34,43],…”

Section: Test Results and Discussionmentioning

confidence: 99%

“…Some empirical expressions were proposed to describe the nonlinear flow in fractures, and Forchheimer's law is the most extensively used approach where the pressure gradient is a quadratic function of the flow rate, written as [32][33][34] …”

Section: Governing Equations Of Fluid Flow In Fracturesmentioning

confidence: 99%

Experimental Study on Stress-Dependent Nonlinear Flow Behavior and Normalized Transmissivity of Real Rock Fracture Networks

et al. 2018

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The mechanism and quantitative descriptions of nonlinear fluid flow through rock fractures are difficult issues of high concern in underground engineering fields. In order to study the effects of fracture geometry and loading conditions on nonlinear flow properties and normalized transmissivity through fracture networks, stress-dependent fluid flow tests were conducted on real rock fracture networks with different number of intersections (1, 4, 7, and 12) and subjected to various applied boundary loads (7, 14, 21, 28, and 35 kN). For all cases, the inlet hydraulic pressures ranged from 0 to 0.6 MPa. The test results show that Forchheimer's law provides an excellent description of the nonlinear fluid flow in fracture networks. The linear coefficient and nonlinear coefficient in Forchheimer's law = + 2 generally decrease with the number of intersections but increase with the boundary load. The relationships between and can be well fitted with a power function. A nonlinear effect factor = 2 /( + 2 ) was used to quantitatively characterize the nonlinear behaviors of fluid flow through fracture networks. By defining a critical value of = 10%, the critical hydraulic gradient was calculated. The critical hydraulic gradient decreases with the number of intersections due to richer flowing paths but increases with the boundary load due to fracture closure. The transmissivity of fracture networks decreases with the hydraulic gradient, and the variation process can be estimated using an exponential function. A mathematical expression / 0 = 1 − exp(− −0.45 ) for decreased normalized transmissivity / 0 against the hydraulic gradient was established. When the hydraulic gradient is small, / 0 holds a constant value of 1.0. With increasing hydraulic gradient, the reduction rate of / 0 first increases and then decreases. The equivalent permeability of fracture networks decreases with the applied boundary load, and permeability changes at low load levels are more sensitive.

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Influence of surface roughness on nonlinear flow behaviors in 3D self-affine rough fractures: Lattice Boltzmann simulations

Cited by 233 publications

References 81 publications

Pore-Scale Modeling of Mixing-Induced Reaction Transport through a Single Self-Affine Fracture

Pore-Scale Modeling of Mixing-Induced Reaction Transport through a Single Self-Affine Fracture

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

Experimental Study on Stress-Dependent Nonlinear Flow Behavior and Normalized Transmissivity of Real Rock Fracture Networks

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