Observation and simulation of non‐Darcian flow transients in fractured rock

Köhl, Thomas; Evans, Keith F.; Hopkirk, R.J.; Jung, Reinhard; Rybach, Ladislaus

doi:10.1029/96wr03495

Cited by 128 publications

(80 citation statements)

References 10 publications

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“…Kosakowski and Berkowitz [150] established numerical models with a wide variability of fracture intersection geometry and studied the streamline distributions as well as the validity of Darcy's law, by solving the NS equations using the available FEATFLOW package [151]. Their results indicate that the nonlinear inertial effects are significant for Re = 1∼100, which is the range that often exists in the karst systems [17] and/or in the vicinity of wells during pump tests [18]. As introduced in the previous Sections 3.3 and 3.4, Liu et al [40] estimated the influence of number of fracture intersections on the basis of a series of simple and complex DFNs.…”

Section: Effect Of Fracture Intersectionmentioning

confidence: 99%

“…The fluid flow in rock fractures and/or fracture networks is commonly assumed to obey the cubic law, in which the flow rate is linearly proportional to the pressure drop [10][11][12][13][14][15][16]. However, in the karst systems and/or in the vicinity of wells during pump tests, when the flow rate/velocity is large, fluid flow enters the nonlinear flow regime and flow rate is nonlinearly correlated with pressure drop [14,[17][18][19][20]. In such case, using the cubic law to calculate fluid flow will overestimate the conductivity of rock fractures and/or fracture networks [21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Effect Of Fracture Intersectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Jiang

2017

Geofluids

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“…Different from conduits, the flow regime prevailing between rough-walled surfaces does not immediately switch from Darcy flow to turbulent flow as velocity is increased or vice versa (Kohl et al, 1997), but transitional regimes can be distinguished.…”

Section: Cherubini Et Al: Bench Scale Laboratory Tests To Analyzementioning

confidence: 99%

Bench scale laboratory tests to analyze non-linear flow in fractured media

Cherubini

Giasi

Pastore

2012

Hydrol. Earth Syst. Sci.

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Abstract. The knowledge of flow phenomena in fractured rocks is very important for groundwater resources management in hydrogeological engineering.A critical emerging issue for fractured aquifers is the validity of the Darcian-type "local cubic law", which assumes a linear relationship between flow rate and pressure gradient to accurately describe flow patterns.Experimental data obtained under controlled conditions such as in a laboratory increase our understanding of the fundamental physics of fracture flow and allow us to investigate the presence of non-linear flow inside fractures that generates a substantial deviation from Darcy's law.In this study the presence of non-linear flow in a fractured rock formation has been analyzed at bench scale in laboratory tests. The effects of non-linearity in flow have been investigated by analyzing hydraulic tests on an artificially created fractured rock sample of parallelepiped (0.60 × 0.40 × 0.8 m) shape.The volumes of water passing through different paths across the fractured sample for various hydraulic head differences have been measured, and the results of the experiments have been reported as specific flow rate vs. head gradient. The experimental results closely match the Forchheimer equation and describe a strong inertial regime. The results of the test have been interpreted by means of numerical simulations. For each pair of ports, several steady-state simulations have been carried out varying the hydraulic head difference between the inlet and outlet ports. The estimated linear and non-linear Forchheimer coefficients have been correlated to each other and respectively to the tortuosity of the flow paths.A correlation among the linear and non-linear Forchheimer coefficients is evident. Moreover, a tortuosity factor that influences flow dynamics has been determined.

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“…Interested readers can see Kohl et al (1997) and Sudicky et al (1995) for reviews of these studies. A model is required to simulate not only the laminar and turbulent flow, but also the transitional flow.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Pumping Tests in Multilayer Wells with Non‐Darcian Flow in the Wellbore

Chen¹,

Jiao²

1999

Groundwater

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An important feature of pumping in a multilayer system is the dynamic interaction between the aquifers via non-Darcian vertical flow within the wellbore. An equivalent hydraulic conductivity (EHC) approach is used to include this transient interaction as a special leakage through the confining layer in the flow system. Different flow regimes (laminar and turbulent flows, and the transition range) are involved in a multilayer pumping test where the relation between the hydraulic gradient and flow velocity is complicated. The change of flow regimes is accommodated by varying the content ofEHC as a function of the friction factor. For a particular well, the relation between friction factor and Reynolds number is unique and is obtained by interpolating Nikuradse's experimental results. A quasi-three-dimensional Galerkin finite-element method is used to integrate the vertical one-dimensional flow in the wellbore and confining layers and the two-dimensional flow in the aquifers. This approach makes it possible to couple the aquifer and wellbore flows of different flow regimes and to solve them in a single numerical framework based on the same linear relation between gradient and velocity. A carefully designed pumping test in a multilayer aquifer system near Beihai City, Guangxi Autonomous Region, China, is used to demonstrate the performance of the approach.

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Observation and simulation of non‐Darcian flow transients in fractured rock

Cited by 128 publications

References 10 publications

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

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

Bench scale laboratory tests to analyze non-linear flow in fractured media

Numerical Simulation of Pumping Tests in Multilayer Wells with Non‐Darcian Flow in the Wellbore

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