Early Development of Karst Systems: 2. Turbulent Flow

Howard, A. D.; Groves, Christopher G.

doi:10.1029/94wr01964

Cited by 87 publications

(63 citation statements)

References 18 publications

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“…In contrast, the role of predesign is less clear for preferential flow in soils and in karstified aquifers. In particular, the formation of conduit patterns in karst has been addressed by several modeling studies (e.g., Groves and Howard, 1994;Howard and Groves, 1995;Siemers and Dreybrodt, 1998;Braun, 1999, 2000;Liedl et al, 2003;Dreybrodt et al, 2005;Kaufmann et al, 2010;Gabrovšek and Dreybrodt, 2011;Hubinger and Birk, 2011), pioneered by early work of Kiraly (1979). Although there may be some predesign, too, it is generally believed that the solution of material by the flow causes a strong tendency towards self-organization of the flow pattern.…”

Section: Introductionmentioning

confidence: 99%

Transferring the concept of minimum energy dissipation from river networks to subsurface flow patterns

Hergarten

Winkler

Birk

2014

Hydrol. Earth Syst. Sci.

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Abstract. Principles of optimality provide an interesting alternative to modeling hydrological processes in detail on small scales and have received growing interest in the last years. Inspired by the more than 20 years old concept of minimum energy dissipation in river networks, we present a corresponding theory for subsurface flow in order to obtain a better understanding of preferential flow patterns in the subsurface. The concept describes flow patterns which are optimal in the sense of minimizing the total energy dissipation at a given recharge under the constraint of a given total porosity. Results are illustrated using two examples: two-dimensional flow towards a spring with a radial symmetric distribution of the porosity and dendritic flow patterns. The latter are found to be similar to river networks in their structure and, as a main result, the model predicts a power-law distribution of the spring discharges. In combination with two data sets from the Austrian Alps, this result is used for validating the model. Both data sets reveal power-law-distributed spring discharges with similar scaling exponents. These are, however, slightly larger than the exponent predicted by the model. As a further result, the distributions of the residence times strongly differ between homogeneous porous media and optimized flow patterns, while the mean residence times are similar in both cases.

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Section: Introductionmentioning

confidence: 99%

Transferring the concept of minimum energy dissipation from river networks to subsurface flow patterns

Hergarten

Winkler

Birk

2014

Hydrol. Earth Syst. Sci.

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“…Their results indicate that the selective enlargement of fracture flow passages may be strongly influenced by their initial sizes. Groves and Howard [1994b] and Howard and Groves [1995] then developed numerical models for fracture dissolution in limestone for laminar and turbulent flow. Their results show that for laminar flow, passage enlargement taking place early in the conduit network development is highly selective, while the transition to turbulent flow often results in more general passage enlargement.…”

Section: Introductionmentioning

confidence: 99%

Precipitation and dissolution of reactive solutes in fractures

Dijk¹,

Berkowitz²

1998

Water Resources Research

107

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Abstract. The precipitation and dissolution of reactive solutes, transported under the action of fully developed laminar flow in saturated fractures, is analyzed assuming an irreversible first-order kinetic surface reaction for one component. Equations describing solute transport, precipitation and dissolution, and the evolution of fracture aperture were approximated and solved using combined analytical and numerical techniques; dimensionless transport parameters incorporated into the solutions were estimated from data available in the literature. Fractures with initially flat, linearly constricted, and sinusoidal apertures were investigated. The initial fracture geometry and the solute saturation content of the inflowing fluid have a profound effect on the reaction processes. The results show that the evolution of the solute transport and fracture geometry can be adequately described by the Damk6hler and P6clet numbers. Two extreme transport regimes were identified: relatively uniform evolution of fracture apertures and nonuniform evolution of fracture apertures restricted to the inlet region of fractures. In the case of precipitation with half-life times of the order of seconds to years and with fluid residence times of the order of minutes to days, the time for a fracture to close completely is of the order of days to millions of years. This is consistent with the order of magnitude of hydrogeological timescales. In the model the process of dissolution is the inverse of precipitation, although the combined solute transport and reaction processes are irreversible. These results and the applied dimensionless analysis can be used as a basis for the development of more complex models of reactive solute transport, precipitation, and dissolution in saturated fractured media. IntroductionThe transport of contaminants through fractured geological media has received considerable attention in recent years. While many studies have analyzed the transport of conservative solutes in discrete fracture networks, relatively little attention has been devoted to the analysis of the transport of reactive solutes. Even less work has been devoted to the influence of reactive solutes on the physical and chemical properties of the fracture networks and the surrounding porous matrix. This is in part due to the highly complex interaction between the mass transport mechanisms and the changing properties of a fractured porous medium.Precipitation and dissolution can significantly modify the physical and chemical properties of fractured media. Physical changes of fracture aperture, tortuosity, and thus effective mass diffusivities and permeabilities are coupled to the subsequent fluid flow and solute transport and the precipitation and dissolution reactions. Chemical changes of the fractures, such as sorption and reaction capacities, also have a significant effect on solute transport. As such, a variety of closure patterns can be observed in the field, which range from fully filled (mineralized) fractures to those with pockets or irregul...

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“…The extension of the single conduit concept into a twodimensional, rectangular network of interconnected conduits has been studied by several authors. Groves and Howard [1994b] and Howard and Groves [1995] modeled the evolution of a conduit network under laminar and turbulent flow conditions with discrete recharge and discharge locations given by fixed hydraulic heads. Their results show a highly selective enlargement of conduits under laminar conditions, which characterize the early phase of karst aquifer evolution, resulting in single passages.…”

Section: Introductionmentioning

confidence: 99%

Karst Aquifer evolution in fractured, porous rocks

Kaufmann¹,

Braun²

2000

Water Resources Research

126

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Abstract. The evolution of flow in a fractured, porous karst aquifer is studied by means of the finite element method on a two-dimensional mesh of irregularly spaced nodal points. Flow within the karst aquifer is driven by surface recharge from the entire region, simulating a precipitation pattern, and is directed toward an entrenched river as a base level. During the early phase of karstification both the permeable rock matrix, modeled as triangular elements, and fractures within the rock matrix, modeled as linear elements, carry the flow. As the fractures are enlarged with time by chemical dissolution within the system calcite-carbon dioxide-water, flow becomes more confined to the fractures. This selective enlargement of fractures increases the fracture conductivity by several orders of magnitude during the early phase of karstification. Thus flow characteristics change from more homogeneous, pore-controlled flow to strongly heterogeneous, fracture-controlled flow. We study several scenarios for pure limestone aquifers, mixed sandstone-limestone aquifers, and various surface recharge conditions as well as the effect of faulting on the aquifer evolution. Our results are sensitive to initial fracture width, faulting of the region, and recharge rate.

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Early Development of Karst Systems: 2. Turbulent Flow

Cited by 87 publications

References 18 publications

Transferring the concept of minimum energy dissipation from river networks to subsurface flow patterns

Transferring the concept of minimum energy dissipation from river networks to subsurface flow patterns

Precipitation and dissolution of reactive solutes in fractures

Karst Aquifer evolution in fractured, porous rocks

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