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Über dieses Buch

Any numerical subsurface model is comprised of three components: a theoretical basis to translate our understanding phenomena into partial differential equations and boundary conditions, a numerical method to approximate these governing equations and implement the boundary conditions, and a computer implementation to generate a generic code for research as well as for practical applications. Computational Subsurface Hydrology: Reactions, Transport, and Fate is organized around these themes.
The fundamental processes occurring in subsurface media are rigorously integrated into governing equations using the Reynolds transport theorem and interactions of these processes with the surrounding media are sophisticatedly cast into various types of boundary conditions using physical reasoning. A variety of numerical methods to deal with reactive chemical transport are covered in Computational Subsurface Hydrology: Reactions, Transport, and Fate with a particular emphasis on the adaptive local grid refinement and peak capture using the Lagrangian-Eulerian approach. The topics on coupled fluid flows and reactive chemical transport are unique contributions of this book. They serve as a reference for research as well as for practical applications with a computer code that can be purchased from the author.
Four computer codes to simulate vertically integrated horizontal solute transport (LEMA), contaminant transport in moving phreatic aquifers in three dimensions (3DLEMA), solute transport in variably saturated flows in two dimensions (LEWASTE), and solute transport under variably saturated flows in three dimensions (3DLEWASTE) are covered. These four computer codes are designed for generic applications to both research and practical problems. They could be used to simulate most of the practical, real-world field problems.
Reactive chemical transport and its coupling with fluid flows are unique features in this book. Theories, numerical implementations, and example problems of coupled reactive transport and flows in variably saturated media are presented. A generic computer code, HYDROGEOCHEM 3.0, is developed. A total of eight example problems are used to illustrate the application of the computational model. These problems are intended to serve as examples for setting up a variety of simulations that one may encounter in research and field-site applications.
Computational Subsurface Hydrology: Reactions, Transport, and Fate offers practicing engineers and scientists a theoretical background, numerical methods, and computer codes for modeling contaminant transport in subsurface media. It also serves as a textbook for senior and graduate course on reactive chemical transport in subsurface media in disciplines such as civil and environmental engineering, agricultural engineering, geosciences, soil sciences, and chemical engineering.
Computational Subsurface Hydrology: Reactions, Transport, and Fate presents a systematic derivation of governing equations and boundary conditions of subsurface contaminant transport as well as reaction-based geochemical and biochemical processes. It discusses a variety of numerical methods for moving sharp-front problems, expounds detail procedures of constructing Lagrangian-Eulerian finite element methods, and describes precise implementation of computer codes as they are applied to subsurface contaminant transport and biogeochemical reactions.

Inhaltsverzeichnis

Frontmatter

1. Fundamental of the Subsurface System

Abstract
This book along with its companion book (Yeh, 1999) are concerned with the mathematical description and numerical modeling of subsurface media. It is about the subsurface media that control the movement of fluids (including water, nonaqueous liquids, and gas), the migration of chemicals, the transfer of heat, and the deformation of media. It is about the physical laws that describe the flux of fluid, heat, and chemicals, and the relationship between stress and strain. It is about the chemical reactions along with fluid flows. It is about the biological interaction within the flow and thermal domain and among chemical constituents. It is about numerical methods needed to conduct simulations of both fluid flows and advection-dominant transport. In short, the study of the subsurface system is the investigation of major processes occurring in the subsurface and the interplay of these processes with the media through which they occur. Understanding the mechanisms controlling the occurrence of these processes and their interplay is the ultimate goal of this book because it provides a method for the prediction of the occurrence of these processes in the media. To make this goal possible, accurate numerical methods to efficiently and accurately approximate mathematical descriptions are of ultimate importance. Extensive coverage of finite element methods used in fluid flows was provided in a companion book (Yeh, 1999). The hybrid Lagrangian-Eulerian approaches best suited to deal with advection-dominant transport are included in this book.
Gourt-Tsyh Yeh

2. Reactive Geochemical and Biochemical Transport

Abstract
This chapter covers the basis of biogeochemical modeling and its coupling with fluid flow and hydrologic transport. The basis of biogeochemical modeling is the principle of mole balance, the law of mass action, and rate laws. The basis of reactive biogeochemical transport is the conservation principle and flux laws. We begin the chapter by introducing a simple example of geochemical equilibrium (Section 2.1). Then we derive equations governing generalized geochemical equilibrium (Section 2.2), basic and parallel geochemical kinetics (Section 2.3), and mixed chemical equilibrium and kinetics (Section 2.4) from a reaction point of view. Following the derivation of geochemical processes, we deal with reactive chemical transport (Section 2.5), and transport and fate of chemicals and microbes (Section 2.6). Finally, a variety of strategies to model multicomponent-multispecies reactive transport is presented (Section 2.7).
Gourt-Tsyh Yeh

3. Numerical Methods for Advection-Dominant Transport

Abstract
The numerical solution of the transport equation, describing the fate of a passive scaler in a moving fluid, has been the object of intense research for the past few decades. So much interest concerning an apparently inoffensive (in many occasions it is even linear) equation may seem, at first sight, misplaced. However, there is a fundamental difficulty in the solution of the transport equation, which results from the fact that, while advection and dispersion are simultaneous processes, they promote mass transport very differently: in the case of advection, transport is along characteristic lines that follow the flow, while in the case of dispersion, it is both along and between characteristic lines. Mathematically, this means the need to treat simultaneously hyperbolic terms associated with advection and parabolic terms associated with dispersion terms, a problem that no numerical method has yet fully overcome. Prevailing approaches of solving the transport equations may be classified into three broad categories: Eulerian methods (EMs), Lagrangian methods (LMs), and EulerianLagrangian methods (ELMs).
Gourt-Tsyh Yeh

4. Finite-Element Modeling of One-Component Solute Transport

Abstract
This chapter presents four basic solute transport models. Four basic flow models were presented in the third chapter of a companion book (Yeh, 1999). Based on these eight basic models, many more complicated models could be constructed. Each transport and its corresponding flow model form a pair of transport and flow models. Each transport model can be used as a stand-alone model to simulate contaminant transport using known flow fields from either measurements or simulations by other flow models. It can also be used in tandem with its corresponding flow model to simulate contaminant transport with the flow model creating hydrological variables.
Gourt-Tsyh Yeh

5. Coupled Fluid Flow and Reactive Chemical Transport

Abstract
The couplings among fluid flows, advective and diffusive transport, and chemical reaction rates in fractured media or soils and changes in hydraulic properties due to precipitation and dissolution along fractures and rock matrix are important for many environmental management problems. Chemicals may undergo geochemical reactions and transformations, and the resultant speciation can enhance or hinder mobility. Some of these geochemical processes are fast and reversible, while others are slow in comparison with transport phenomena; many are dependent upon and cause changes in the pH and redox condition of the subsurface environment. Aqueous complexation, including acid-base reactions, tend to be rapid, while adsorption-desorption, precipitation-dissolution, and redox processes are often kinetic in nature, with system conditions far from equilibrium.
Gourt-Tsyh Yeh

Backmatter

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