21,473,428 Works

A Serendipitous, Long-term Infiltration Experiment: Water and Radionuclide Circulation Beneath the CAMBRIC Trench at the Nevada Test Site.

Reed Maxwell, Andrew Tompson, Steven Carle, Mavrik Zavarin, Stefan Kollet & Reed Maxwell
Underground atomic weapons testing at the Nevada Test Site introduced numerous radionuclides that may be used to characterize subsurface hydrologic transport processes in arid climates. Beginning in 1975, groundwater adjacent to the CAMBRIC test, conducted beneath Frenchman Flat in 1965, was pumped steadily for 16 years to elicit experimental information on the migration of residual radioactivity through the saturated zone. Radionuclides in the pumping well effluent, including tritium, 36Cl, and 85Kr, were extensively monitored prior...

Numerical Evaluation of Multicomponent Cation Exchange Reactive Transport in Physically and Geochemically Heterogeneous Porous Media

Javier Samper, Changbing Yang & Javier Samper
Sophisticated deterministic numerical models have been developed during the last two decades for the analysis of multicomponent reactive solute transport. Most of these models account for spatial heterogeneity by parameter zonation. Most stochastic analyses of reactive transport in physically and geochemically heterogeneous porous media consider a single reactive species. Attempts have been made recently for the stochastic analysis of multicomponent reactive species which rely on simplifying assumptions. Given the lack of theoretical stochastic analyses of...

Derivative-Free Optimization Methods for Handling Fixed Costs in Optimal Groundwater Remediation Design

Thomas Hemker, Kathleen Fowler & Thomas Hemker
Groundwater remediation design problems are routine in water resource management. The starting point for such a design problem is to formulate an objective function that represents a measure of the manager's goal. For example, in plume migration control, we need to determine the cost to design a well field to alter the direction of groundwater flow and thereby control the destination of a contaminant. Constraints must be specified to ensure that the plume is captured,...

Derivative-Free Optimization Methods for Handling Fixed Costs in Optimal Groundwater Remediation Design

Thomas Hemker, Kathleen Fowler & Thomas Hemker
Groundwater remediation design problems are routine in water resource management. The starting point for such a design problem is to formulate an objective function that represents a measure of the manager's goal. For example, in plume migration control, we need to determine the cost to design a well field to alter the direction of groundwater flow and thereby control the destination of a contaminant. Constraints must be specified to ensure that the plume is captured,...

Simulating Effects of Non-Isothermal Flow on Reactive Transport of Radionuclides Originating From an Underground Nuclear Test

Steven Carle, Mavrik Zavarin, Andrew Tompson, Reed Maxwell, Gayle Pawloski & Steven Carle
In numerical simulation of radionuclide transport, a mechanistic reactive transport model can account for non-electrostatic surface complexation, ion exchange, and mineral dissolution/precipitation reactions. However, in radionuclide transport originating from an underground nuclear test, thermal effects must also be considered because heat accounts for the majority of energy released from the test. A large fraction of residual test heat is initially contained in a “puddle” of solidified melt glass and rubble containing much of the less-volatile...

3D Field-Scale Reactive Transport Modeling of In Situ Immobilization of Uranium in Structured Porous Media via Biostimulation

Yilin Fang, Timothy Scheibe, Eric Roden, Wiwat Kamolpornwijit, Scott Brooks & Yilin Fang
A two-month-long ethanol injection experiment was conducted to study the impacts of porous media structure (i.e., heterogeneity existing at multiple scales) on the effectiveness of metal/radionuclide bioremediation in a highly heterogeneous unconfined aquifer near Oak Ridge, TN, USA. We have constructed a 3D field-scale groundwater flow and multicomponent reactive transport model to simulate the experimental observations. The model incorporates a suite of abiotic reactions and microbially-mediated redox reactions for multiple terminal electron accepting processes (TEAPs)...

Smoothed particle hydrodynamics model for pore-scale flow, reactive transport and mineral precipitation.

Alexandre Tartakovsky, Timothy Scheibe, George Redden, Yilin Fang, Paul Meakin, Prasad Saripalli & Alexandre Tartakovsky
We have developed a pore-scale numerical reactive transport model, based on smoothed particle hydrodynamics (SPH), that incorporates heterogeneous precipitation/dissolution reactions. Lagrangian particle methods such as SPH have several advantages for modeling pore-scale flow and transport: i) in a Lagrangian framework there is no non-linear term in the momentum conservation equation, so that SPH allows accurate solution of momentum dominated flows; ii) complicated physical and chemical processes associated with realistic equations of state, changes in solid...

A Pore-Level Approach to Petrophysical Interpretation of Well Logging Measurements

Mikhail Gladkikh, Alberto Mezzatesta & Mikhail Gladkikh
An accurate description of water- or oil-bearing reservoirs and the assessment of reserves strongly depend on a robust determination of their petrophysical parameters, e.g., porosity, permeability and fluid distribution, reflecting fluid type, content, and mobility. Downhole measurements provide means to formation evaluation; however, they do not directly provide the petrophysical properties of interest. To interpret well logging data, a range of empirical models are usually employed. These empirical relationships, however, lack scientific basis and usually...

The Use of a Real-gas Potential Approach in a Multi-component Simulator for Highly Fractured Reservoirs

Duane Smith, W. Neal Sams, Joseph Wilder & Duane Smith
Dual-porosity simulators are ubiquitously used for fractured reservoirs. However, explicit-fracture simulators may be able to increase the accuracy and reliability of simulations for highly fractured reservoirs, because they can directly use descriptions (i.e., lengths, orientations, and apertures) of fractures as obtained from well logs (especially, fmi), out crop analyses, and other geological data. Al- Hussainy et al developed the real gas potential primarily for use in gas-well testing analyses and in single-phase simulators for a...

Estimation of path-average precipitation using a 27 GHz microwave link

Hidde Leijnse, Remko Uijlenhoet, Han Stricker, Alexis Berne & Hidde Leijnse
Between May and July 1999 we operated a 27 GHz microwave link over a 5 km path between the towns of Rhenen and Wageningen in the Netherlands. The instrument, which was built at Eindhoven University of Technology, measures the power arriving at the receiving antenna with a sampling frequency of 18 Hz. During dry weather conditions, it can be used as a microwave scintillometer, i.e. the (turbulent) fluxes of sensible and latent heat can be...

Data assimilation in a flood modelling system using the ensemble Kalman filter

Henrik Madsen, Johan Hartnack, Jacob Tornfeldt Sørensen & Henrik Madsen
Data assimilation in a combined 1D-2D numerical flood modelling system is considered. The model is based on a dynamic linking between existing and well- established 1D and a 2D numerical modelling systems enhanced with new features which are targeted specifically towards modelling of floods. This combination ensures a maximum of flexibility by allowing modelling some areas in 2D detail (floodplain), while other areas can be modelled in 1D (river network). For this combined modelling system...

Macro-scale models for Cesium transport in sandy-clayed porous media

Sébastien Cadalen, Michel Quintard & Sébastien Cadalen
This paper discusses the type of macro-scale or Darcy-scale model suitable for modelling Cesium transport in sandy-clayed soil. While the motivation for the study comes from the context of nuclear risk control, this study may be viewed in the more general framework of surface contaminations with reactive solute transport. The adopted strategy consists in looking at an idealized soil composed of Fontainebleau sand with a few percents of fine particules of Illite du Puy. This...

An Integrated Media, Integrated Processes Watershed Model – WASH123D: Part 4 – A characteristics-based finite element method for 2-D overland flow

GUOBIAO HUANG, Gour-Tsyh Yeh & GUOBIAO HUANG
The Method of Characteristics (MOC) in the context of finite element method was applied to the complete 2-D shallow water equations for 2-D overland flow. For two- dimensional overland flow, finite element or finite volume methods are more flexible in dealing with complex boundary. Recently, finite volume methods have been very popular in numerical solution of the shallow water equations. Some have pointed out that finite volume methods for 2-D flow are fundamentally one-dimensional (normal...

An Integrated Media, Integrated Processes Watershed Model – WASH123D: Part 2 – Simulating surface water flows with different water wave models

GUOBIAO HUANG, Gour-Tsyh Yeh & GUOBIAO HUANG
The complete Saint Venant equations/2-D shallow water equations (dynamic wave equations) and the kinematic wave or diffusion wave approximations were implemented for 1-D channel network flow and 2-D overland flow in a watershed model, WASH123D. Careful choice of numerical methods is needed even for the simple kinematic wave model. Motha and Wigham (1995) reported numerical oscillation in Galerkin finite element of kinematic wave overland flow. Since the kinematic wave equation is of pure advection, the...

Limitations to Upscaling of Groundwater Flow Models dominated by Surface Water Interaction

Peter Vermeulen & Peter Vermeulen
Different upscaling methods for groundwater flow models are investigated. A suit of different upscaling methods is applied to several synthetic cases with structured and unstructured porous media. Although each of the methods applies best to one of the synthetic cases, no performance differences is formed if the methods were applied to a real 3D-case. Furthermore, we focus on boundary conditions such as Dirichlet, Neumann and Cauchy conditions, that characterize the interaction of groundwater with e.g....

Model-reduced Variational Data Assimilation in Groundwater Modeling

Peter Vermeulen, Arnold Heemink & Peter Vermeulen
This paper describes a new approach to variational data assimilation that with a comparable computational efficiency does not require implementation of the adjoint of the tangent linear approximation of the original model. In classical variational data assimilation, the adjoint implementation is used to efficiently compute the gradient of the criterion to be minimized. Our approach is based on model reduction. Using an ensemble of forward model simulations, the leading EOFs are determined to define a...

Unsaturated flow modeling in high-level nuclear waste repository

Alain GENTY, Gilles BERNARD-MICHEL & Alain GENTY
In the context of high-level nuclear waste repository safety calculations, the modeling of desaturation and saturation processes in low permeable porous media is of first importance. Indeed these processes are strongly coupled with mechanics, inducing host rock confinement properties changes. They also control corrosion and the other geochemical processes responsible for waste canister failure. Above all, desaturation and saturation time scales of the repository components determine the physicochemical behavior of the repository by trapping or...

CO2 storage through mineral trapping in geothermal reservoirs

Michael Kuehn, Katrin Vosbeck, Martin Back, Christoph Clauser, Helge Stanjek, Stefan Peiffer & Michael Kuehn
Costs for carbon dioxide sequestration into deep saline aquifers can be transformed into a benefit when combined with ecologically desirable geothermal heat or power production. The produced energy can be used and marketed. Aim is a scientifically and technically feasible new technology to achieve a safe and economically attractive long-term storage of CO2 trapped in minerals. We develop, study, and evaluate a novel approach not only to sequester CO2 by physical trapping within a reservoir,...

Chemistry-Transport coupling : Implicit schemes keeping a code coupling approach

Raphaèle Herbin, Philippe Montarnal, Nicolas Bouillard & Nicolas Bouillard
This work is linked with the field of reactive transport simulations in the context of reactive waste storage in deep geological disposals. Indeed, the evolution of the different materials and the species migration are deeply influenced by chemical, hydraulic and transport interactions. For these modeling issues it is necessary to deal with numerical codes involving combined effect of transport and multiple geochemical species within groundwater flow. Currently, many of the codes use a sequential iterative...

Modeling of solute transport in a heterogeneous porous medium with a random source using stochastic finite element method

Abhijit Chaudhuri, Sekhar Muddu & Abhijit Chaudhuri
Most of the probabilistic studies in solute transport literature are focused on predicting the concentration uncertainty due to the heterogeneity of the governing flow and transport parameters. The randomness in the source condition can also be a major source of uncertainty in the concentration field. Some of the studies have also looked into this aspect and analysed the effect of random source condition while considering the system to be deterministic. For a deterministic system the...

Adaptive Lattice Boltzmann simulations of free-surface flows

Jonas Toelke, Manfred Krafczyk & Jonas Toelke
Recently Lattice-Boltzmann (LB) methods have matured as complementary models and simulation approaches for solving complex flow problems in engineering. In our work we extend an existing laminar free surface LB model recently developed by Koerner et al. by a Large Eddy model to describe turbulent flows and validate our model by threedimensional computations of a rigid body impact on a shoreline and the resulting wave generation. The results are compared to experimental and numerical data...

Investigating pore scale configurations of two immiscible fluids via Level Set Method

Masa Prodanovic, Steven L. Bryant & Masa Prodanovic
The study of pore level displacement of immiscible fluids has scientific appeal as well as a plethora of engineering applications, notably in oil reservoir engineering and in environmental problems in the shallow subsurface. Pore network models have been used for numerical simulation of fluid displacement over relevant physical volume sizes. An accurate description of the mechanics of 3D displacement could significantly improve the predictions from network models of capillary pressure - saturation curves, interfacial areas...

Sensitivity of Pore-Scale Flow and Dispersion to Properties of Random Bead Packs

Robert Maier, Mark Schure, Joe Seymour & Robert Maier
Comparisons between pore-scale simulations and physical experiments are complicated by the difficulty of reproducing the geometry of the experimental porous medium. For example, obtaining the coordinates of the beads in experimental bead packings is difficult, so pore-scale simulations typically develop geometry with some type of sphere-packing algorithm. Simulated and experimental geometries may have similar porosity but otherwise no direct correspondence. Flow and dispersion are affected by resulting differences in packing density, random packing variations, mild...

Sensitivity of Pore-Scale Flow and Dispersion to Properties of Random Bead Packs

Robert Maier, Mark Schure, Joe Seymour & Robert Maier
Comparisons between pore-scale simulations and physical experiments are complicated by the difficulty of reproducing the geometry of the experimental porous medium. For example, obtaining the coordinates of the beads in experimental bead packings is difficult, so pore-scale simulations typically develop geometry with some type of sphere-packing algorithm. Simulated and experimental geometries may have similar porosity but otherwise no direct correspondence. Flow and dispersion are affected by resulting differences in packing density, random packing variations, mild...

Defining macro-scale pressure from the micro-scale

Helge K. Dahle, S. Majid Hassanizadeh, Jan M. Nordbotten, Michael A. Celia & Jan M. Nordbotten
Micro-scale models have proven to be powerful theoretical tools in groundwater flow and transport modelling. In addition to being useful in estimating traditional parameters, such as (relative) permeability and capillary pressure functions, micro- scale models have recently provided insight into complex multi-phase flow phenomena, such as the so-called dynamic capillary pressure, and are central in investigating theoretical developments in multi-phase flow modelling. To transfer the results of a micro-scale model to larger scales, a proper...

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