Turbulent and Laminar Flow in Karst Conduits Under Unsteady Flow Conditions: Interpretation of Pumping Tests by Discrete Conduit‐Continuum Modeling

Giese, Markus; Reimann, Thomas; Bailly-Comte, Vincent; Maréchal, Jean-Christophe; Sauter, Martin; Geyer, Tobias

doi:10.1002/2017wr020658

Cited by 48 publications

(38 citation statements)

References 46 publications

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“…This local dimensionless number is defined below. Equations (28), (29) and (43) open a series of questions about the definition of Bejan number. In particular, Bejan number presents the characteristics of being considered a difference of two dimensionless energy states that defines uniquely the energy in a point of a system, whatever is the sum of the energy components that constitute it.…”

Section: Consideration On Bejan Number and The Defined Bejan Dimensiomentioning

confidence: 99%

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A new dimensionless approach to general fluid dynamics problems that accounts both the first and the second law of thermodynamics

Trancossi¹,

Páscoa²

2018

MMEP

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Fluid dynamic systems are usually optimised through the equation of conservation of energy according to the first law of thermodynamics. In the aeronautic sector, many authors are claiming the insufficiency of this approach and are developing studies and models with the aim of coupling the analyses according to the first and the second law of thermodynamics. Second law analysis of internal fluid dynamics has not been studied with the same attention. Just heat exchangers and heat dissipation by electronic circuits are mostly considered. This paper focuses on the analysis of general internal fluid flow problem and recognizes initially it according to the first law of thermodynamics. The energy equation for a control volume is given in integral form along with a discussion on the concepts of total energy, heat and work. The dissipative terms, which need to be minimised to increase the system efficiency, are deeply analysed leading to a new dimensionless formulation of the equation of conservation of energy. It is based on Bejan number, according to the formulation by Bhattacharjee and Grosshandler. This formulation has been directly connected to second law analysis concerning both entropy generation and exergy dissipation making a step toward a future unification of the two alternative formulations of Bejan number which have been historically developed. The ambition of this research is far from providing a definitive solution. Otherwise, it aims to both raise problems and stimulate a discussion. Bejan number has been actually used in the definition of diffusive phenomena, such as convection and diffusion through porous media. Is it reasonable to enlarge its domain to the much larger domain of general fluid dynamics? If this extension will be evaluated possible, what are the potential implications for the future of scientific research? Can be the ambiguity between Hagen number and Bejan number be resolved? Can be the ambiguity between the diffusive definition and the entropy generation definition of Bejan number be solved? Can it be possible to state the equivalence between the two alternative formulations? Is it possible to define fluid dynamic and diffusive problems according to a unified vision in the domain of thermodynamics? What are the implications concerning analysis and optimisation of fluid dynamics phenomena by new equations that couples first and the second law of thermodynamics? Could it have the role of producing an effective unification of a larger multidisciplinary domain?

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Section: Consideration On Bejan Number and The Defined Bejan Dimensiomentioning

confidence: 99%

“…Internal flow Scientific literature reports two different formulations. One is the Colebrook, and White friction factor [27][28][29] has been formulated in equation 44:…”

Section: Nature Of Fluid Dynamic Lossesmentioning

confidence: 99%

A new dimensionless approach to general fluid dynamics problems that accounts both the first and the second law of thermodynamics

Trancossi¹,

Páscoa²

2018

MMEP

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“…These geomorphologic heterogeneities lead to variable pathways and velocities that are highly variable in space and time. For that reason, karst aquifers have always posed a challenge in the characterization of karst hydrological processes for quantification of their present and future water storages (Goldscheider and Drew 2007).…”

Section: Introductionmentioning

confidence: 99%

“…The most popular among them is the 10 application of methods to analyze signals of artificial and natural tracers at the karst springs (Hartmann et al 2014). Artificial tracers have been used to investigate the actual flow paths and flow times through karst systems (Mudarra et al 2014;Goldscheider et al 2008), while natural tracers, for instance, water isotopes, were used to understand the transit times and dispersion of water entering at the entire recharge of karst systems (Maloszewski et al 2002). Continuous monitoring of karst spring hydrographs and the hydrochemical signal have shown to reveal important information about the subsurface structure 15 and dynamics of karst aquifers (Mudarra and Andreo 2011).…”

Section: Introductionmentioning

confidence: 99%

A soil moisture monitoring network to characterize karstic recharge and evapotranspiration at five representative sites across the globe

Berthelin¹,

Rinderer²,

Andreo³

et al. 2019

Preprint

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Abstract. Karst systems that are characterized by a high subsurface heterogeneity are posing a challenge to study their complex recharge processes. Experimental methods to study karst processes mostly focus on characterizing the entire aquifer. Despite their important role for recharge processes, the limited focus has been given on studies of the soil and epikarst and most available research has been performed at sites of similar latitudes. In our study, we describe a new monitoring concept that allows the improvement of soil and epikarst processes understanding by covering different karst systems with different land cover at different climate regions. First, we describe the site selection and the experimental setup. Then we describe the five individual sites and their soil profiles. We also present some preliminary data and highlight the potential of the data for future research aimed at answering the relevant research questions: (1) How do the soil and epikarst heterogeneities influence water flow and storage processes in the karst vadose zone? (2) What is the impact of the land cover type on karstic groundwater recharge and evapotranspiration? (3) What is the impact of climate on karstic groundwater recharge and evapotranspiration? In order to answer these questions, we monitor soil moisture, which controls the partitioning of rainfall into infiltration, soil water storage, evapotranspiration, and groundwater recharge processes. We installed a soil moisture-monitoring network at five different climate regions: in Puerto Rico (tropical), Spain (Mediterranean), the United Kingdom (humid oceanic), Germany (humid mountainous), and Australia (dry semi-arid). At each of the five sites, we defined two 20 m × 20 m plots to install soil moisture probes under different land use types (forest and grassland). At each plot, 15 soil moisture profiles were installed with probes at different depths from the top soil to the epikarst (over 400 soil moisture probes were installed). Our first results show that the monitoring network provides new insights into the soil moisture dynamics of the five study sites and that significant differences prevail among forest and grassland sites. Some profiles are characterized by sequential reactions of soil moisture, i.e., the uppermost probe reacts first and the lowest probe reacts last, while at other profiles, we find non-sequential reactions that we interpret to result from preferential flow processes. While the former favours storage in the soil providing water for evapotranspiration, the latter can be seen as an indicator for the initiation of fast and preferential recharge into the karst system. Covering the spatiotemporal variability of these processes through a large number of installed probes, our monitoring network will allow to develop a new conceptual understanding of evapotranspiration and groundwater recharge processes in karst regions across different climate regions and land use types, and provide the base for quantitative assessment with physically-based modelling approaches in the future.

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“…The coupling between two domains is established via a first-order exchange term governed by the conduit-matrix head difference [9] or by assuming continuous heads [10]. The first DC model was presented by Király [11], and example applications of DC models include [9,10,[12][13][14][15][16][17][18][19][20], among others. The most popular and widely used DC model is the conduit flow process (CFP) model [21] integrated into MODFLOW-2005 [22].…”

Section: Introductionmentioning

confidence: 99%

Groundwater Flow Modeling in Karst Aquifers: Coupling 3D Matrix and 1D Conduit Flow via Control Volume Isogeometric Analysis—Experimental Verification with a 3D Physical Model

Malenica

Gotovac

Kamber

et al. 2018

Water

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A novel numerical model for groundwater flow in karst aquifers is presented. A discrete-continuum (hybrid) approach, in which a three-dimensional matrix flow is coupled with a one-dimensional conduit flow, was used. The laminar flow in the karst matrix is described by a variably saturated flow equation to account for important hydrodynamic effects in both the saturated and unsaturated zones. Turbulent conduit flow for both free surface and pressurized flow conditions was captured via the noninertia wave equation, whereas the coupling of two flow domains was established through an exchange term proportional to head differences. The novel numerical approach based on Fup basis functions and control-volume formulation enabled us to obtain smooth and locally conservative numerical solutions. Due to its similarity to the isogeometric analysis concept (IGA), we labeled it as control-volume isogeometric analysis (CV-IGA). Since realistic verification of the karst flow models is an extremely difficult task, the particular contribution of this work is the construction of a specially designed 3D physical model ( dimensions: 5.66 × 2.95 × 2.00 m) in order to verify the developed numerical model under controlled laboratory conditions. Heterogeneous porous material was used to simulate the karst matrix, and perforated pipes were used as karst conduits. The model was able to capture many flow characteristics, such as the interaction between the matrix and conduit, rainfall infiltration through the unsaturated zone, direct recharge through sinkholes, and both free surface and pressurized flow in conduits. Two different flow experiments are presented, and comparison with numerical results confirmed the validity of the developed karst flow model under complex laboratory conditions.

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Turbulent and Laminar Flow in Karst Conduits Under Unsteady Flow Conditions: Interpretation of Pumping Tests by Discrete Conduit‐Continuum Modeling

Cited by 48 publications

References 46 publications

A new dimensionless approach to general fluid dynamics problems that accounts both the first and the second law of thermodynamics

A new dimensionless approach to general fluid dynamics problems that accounts both the first and the second law of thermodynamics

A soil moisture monitoring network to characterize karstic recharge and evapotranspiration at five representative sites across the globe

Groundwater Flow Modeling in Karst Aquifers: Coupling 3D Matrix and 1D Conduit Flow via Control Volume Isogeometric Analysis—Experimental Verification with a 3D Physical Model

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