Numerical Experiments Involving Solute Transport in Heterogeneous Media PDF Download

Author: Thomas Ralph Pratt
Publisher:
ISBN:
Category : Aquifers
Languages : en
Pages : 382

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Author: Michel Bechtold
Publisher: Forschungszentrum Jülich
ISBN: 3893367950
Category :
Languages : en
Pages : 161

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Author: Stephanie J. Harrington
Publisher:
ISBN:
Category : Mass transfer
Languages : en
Pages : 246

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Book Description
The conventional advection-dispersion equation cannot adequately describe all processes driving solute transport in heterogeneous systems. This dissertation focuses on the individual influences of both chemical (Chapter 2) and physical processes (Chapters 3 and 4) which affect solute transport. In Chapter 2 we analyzed uranium transport in natural sediment using the chemical multirate mass transfer model available within the STAMMT-L software. This model was used due to many uncertainties of the overall mass transfer influences, which were generalized into a distribution of first-order rate coe cients. Results indicated that the multirate model was adequate for the available experimental data, but the results were not definitive due to incomplete mass recovery information. A second experimental system was constructed in order to provide a well-characterized system for analysis. It consisted of 203 low conductivity (K[subscript im] = 0.011 cm/min) spherical inclusions within a high conductivity (K[subscript m] = 4.66 cm/min) matrix material, creating a highly heterogeneous binary system with a conductivity ratio of 1/424. Three flow rates were used to provide complete mass recovery curves. Results were initially analyzed using a multirate spherical diffusion model available within the STAMMT-L software (Chapter 3). This worked well for the fast and medium flow rate experiments, while its representation of the slow flow rate experiment proved inadequate. An analysis of the time scales for mass transport indicated that the diffusive time through the inclusions was competing with advection through the matrix as the dominant mass transport mechanism. Subsequent modeling was performed by direct numerical simulation using the commercially available STAR-CCM+ software (Chapter 4). Results showed inconsistencies with its ability to adequately describe the system when compared with the multirate model results. This dissertation provides insight into the importance of gathering complete mass recovery data, obtaining detailed measurements to describe the system, as well as analysis of results from multirate solute transport processes in order to obtain an improved understanding of their influences on overall mass transport behavior.

Author: Tian-Chyi Jim Yeh
Publisher: Cambridge University Press
ISBN: 1316511189
Category : Science
Languages : en
Pages : 365

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Book Description
This book provides a unified and comprehensive overview of physical explanations of the stochastic concepts of solute transport processes, important scaling issues, and practical tools for the analysis of solute transport.

Author: Andrew Francis Burke Tompson
Publisher:
ISBN:
Category : Porous materials
Languages : en
Pages : 114

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Author: A. F. B. Tompson
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Wei Zhang
Publisher:
ISBN:
Category : Civil engineering
Languages : en
Pages :

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Civil Engineering

Author: Roy Haggerty
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
Understanding and predicting mass transfer coupled with solute transport in permeable media is central to several energy-related programs at the US Department of Energy (e.g., CO{sub 2} sequestration, nuclear waste disposal, hydrocarbon extraction, and groundwater remediation). Mass transfer is the set of processes that control movement of a chemical between mobile (advection-dominated) domains and immobile (diffusion- or sorption-dominated) domains within a permeable medium. Consequences of mass transfer on solute transport are numerous and may include (1) increased sequestration time within geologic formations; (2) reduction in average solute transport velocity by as much as several orders of magnitude; (3) long ''tails'' in concentration histories during removal of a solute from a permeable medium; (4) poor predictions of solute behavior over long time scales; and (5) changes in reaction rates due to mass transfer influences on pore-scale mixing of solutes. Our work produced four principle contributions: (1) the first comprehensive visualization of solute transport and mass transfer in heterogeneous porous media; (2) the beginnings of a theoretical framework that encompasses both macrodispersion and mass transfer within a single set of equations; (3) experimental and analytical tools necessary for understanding mixing and aqueous reaction in heterogeneous, granular porous media; (4) a clear experimental demonstration that reactive transport is often not accurately described by a simple coupling of the convection-dispersion equation with chemical reaction equations. The work shows that solute transport in heterogeneous media can be divided into 3 regimes--macrodispersion, advective mass transfer, and diffusive mass transfer--and that these regimes can be predicted quantitatively in binary media. We successfully predicted mass transfer in each of these regimes and verified the prediction by completing quantitative visualization experiments in each of the regimes, the first such experiments that show mass transfer in porous media in great detail. Experimental and theoretical work in media with pore-scale heterogeneity showed the temporal scale-dependency of mass transfer. Extension of the work into reactive transport, where mass transfer is very important to mixing, suggests a number of promising research directions for constructing better models of reactive transport and provides the experimental tools to develop and test these models. In particular, it is important to determine how the different solute spreading mechanisms in heterogeneous conductivity fields affect the rate and spatial pattern of chemical reaction. The project was conducted collaboratively between Oregon State University, Sandia National Laboratories, and the Massachusetts Institute of Technology. While each institution is submitting a copy of this final report for administrative purposes, the report is the largely the same since the project was a joint effort. This final report will outline the results of work completed and summarize publications and presentations. Manuscripts published or in press are attached, and subsequent publications will follow once published.

Author: Don Kulasiri
Publisher: Springer
ISBN: 9783642431142
Category : Science
Languages : en
Pages : 0

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Book Description
The advection-dispersion equation that is used to model the solute transport in a porous medium is based on the premise that the fluctuating components of the flow velocity, hence the fluxes, due to a porous matrix can be assumed to obey a relationship similar to Fick’s law. This introduces phenomenological coefficients which are dependent on the scale of the experiments. This book presents an approach, based on sound theories of stochastic calculus and differential equations, which removes this basic premise. This leads to a multiscale theory with scale independent coefficients. This book illustrates this outcome with available data at different scales, from experimental laboratory scales to regional scales.

Author: William Taylor
Publisher:
ISBN: 9781632403872
Category : Science
Languages : en
Pages : 0

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Book Description
This research-based book provides a mathematical approach based on stochastic calculus which describes state-of-the-art information regarding porous media science and engineering - prediction of dispersivity from covariance of hydraulic conductivity (velocity). The complication is of great significance for tracer examination, for improved recovery by injection of miscible gases, etc. The book elucidates a generalized mathematical model and efficient numerical methodologies that may greatly affect the stochastic porous media hydrodynamics. It begins with a descriptive basic analysis of the complication of scale dependence of the dispersion coefficient in porous media. Furthermore, relevant topics of stochastic calculus which would be helpful in modeling are discussed subsequently. An in-depth elaborative discussion regarding the development of a generalized stochastic solute transport model for any provided velocity covariance without conferring to fickian expectations from laboratory scale to field scale is also illustrated in this book. The mathematical approaches described in this book will serve as useful solutions for several other complications associated with chemical dispersion in porous media.