154,692 Works

Black Silicon Solar Cells

Rasmus Schmidt Davidsen & Michael Stenbæk Schmidt
This project aims to optimize the solar cell by applying a new kind of material, black silicon, in order to optimize the absorption of the solar radiation. By changing the surface of the conventional solar cell absorption-material, silicon, on nanoscale, the absorption can possibly and hopefully be improved. If this is the case the next challenge in this project is to incorporate the material in a functioning solar cell, which can actually transform sunlight into...

Advantages of Nanostructured Surfaces

Kim Degn Jensen, Lisa Katharina Tschammer, Tanya Bakmand, Anders Kristensen & Peter Bøggild
The project is based on the 3-week course Nanolithography at DTU-Nanotech, where the overall competence goal has been the introduction and understanding of Nano-Imprint Lithography (NIL). NIL can basically be described as surface manipulation of polymer resists using stamps with nanosized features for various applications. A special focus of imprinted nanostructures has been made concerning applications where the technology has environmental impact, both in terms of energy consumption and pollution. Specific examples of the later...

Absorption Chilled Automobile Climate System

Anders Worning Slot, Claus Svend Simonsen, Morten Bjelbo Thomsen & Arne Jørgensen Egelund
In an average combustion engine automobile, more than half of the fuel energy released upon combustion, is lost through dissipated heat. By employing the principle of absorption cooling, our project aims to utilize this excess heat to provide the cooling needed for the car’s climate system. This would in turn increase the fuel efficiency of the average car with up to 10%, as the conventional cooling system in today’s cars is a compressor driven system,...

A VIRTUAL GREENTECH LABORATORY

Mads Tvillinggaard Bonde & Mogens Kilstrup
It is crucial for the development of tomorrows green technologies, to ensure a sufficient engineering work-force in the future. However, application for engineering educations is low. Here I present a virtual laboratory that aims to educate and inspire young people to study greentech engineering. Furthermore, the project aims to reduce the use of chemicals and lab-equipment through replacement of some experiments with in silico simulations. In the virtual laboratory genetic engineering can be applied to...

Support Vector Machines for delineation of geologic facies from poorly differentiated sedimentological data.

Alberto Guadagnini, Daniel M. Tartakovsky, Brendt E. Wohlberg & Daniel M. Tartakovsky
Our knowledge of the spatial distribution of the physical properties of geologic formations is often uncertain because of ubiquitous heterogeneity and the sparsity of data. While many studies consider the effects of incorporating various types of data (including transmissivity, electrical resistivity, hydraulic heads and/or travel times) on predicting flow and transport processes in heterogeneous systems, the uncertainty associated with the delineation of lithofacies and associated hydraulic conductivity and porosity from limited geological and geophysical data...

The Duke University Helicopter Observation Platform (HOP) for environmental studies

Ron I Avissar & Ron I Avissar
Duke University purchased a Bell 206B3 ("JetRanger") helicopter to perform various atmospheric in situ and remotely-sensed environmental observations. As compared to other aircraft, the helicopter has the unequaled flexibility and maneuverability to fly slowly and close to the ground. Furthermore, it can land and refuel at station, which allows performing long-term observations during field campaigns. It can also operate from a ship at sea. This presents significant advantages especially for the observations of aerosols, fluxes...

Sensitivity Analysis for the Numerical Simulation of the Transport of Contaminants

Estelle Marchand, Francois Clement & Estelle Marchand
The questions of safety and uncertainties are central to feasibility studies for an underground waste storage site. One of the important points to be considered is the problem of the evaluation of concentration uncertainties which are due to input parameter uncertainties. These concentration uncertainties can be obtained by probabilistic methods. These methods give good results and are relatively easy to implement, but they are expensive because they require a large number of simulations. The method...

Efficient and Accurate Simulation of Large General Reactive Multicomponent Transport Processes in Porous Media by Model-Preserving a priori and a posteriori Decoupling Techniques of Large General Reactive Multicomponent Transport Processes in Porous Media by Model-Preserving a priori and a posteriori Decoupling Techniques

Peter Knabner, Serge Kraeutle, Alexander Prechtel & Peter Knabner
Detailed modelling of reactive transport processes in the underground often requires the consideration of a wide range of reactive species. A prominent example is natural attenuation, that is the assessment and monitoring of microbially catalysed degradation processes of organic contaminants in the subsoil or aquifer with full geochemistry. Often the reactions exhibit a wide range of relaxation times, which advises to model those reactions being much faster than the time scale of the transport processes...

Efficient and Accurate Simulation of Large General Reactive Multicomponent Transport Processes in Porous Media by Model-Preserving a priori and a posteriori Decoupling Techniques of Large General Reactive Multicomponent Transport Processes in Porous Media by Model-Preserving a priori and a posteriori Decoupling Techniques

Peter Knabner, Serge Kraeutle, Alexander Prechtel & Peter Knabner
Detailed modelling of reactive transport processes in the underground often requires the consideration of a wide range of reactive species. A prominent example is natural attenuation, that is the assessment and monitoring of microbially catalysed degradation processes of organic contaminants in the subsoil or aquifer with full geochemistry. Often the reactions exhibit a wide range of relaxation times, which advises to model those reactions being much faster than the time scale of the transport processes...

Numerical evaluation of diffusive and dispersive transport in periodic porous media

Alexandre Ern, Luc Dormieux, Pierre Tardif D'Hamonville & Pierre Tardif D'Hamonville
At the macroscopic scale, the transport of a fluid component in a porous medium is governed by advective, diffusive, and dispersive fluxes. The two latter fluxes are formulated using a diffusion tensor and a dispersion tensor. The actual value of these tensors depends on the pore geometry and on the magnitude of the advection velocity. Using the double scale expansion technique and provided the problem is homogeneizable, it is well-known that the the diffusion and...

Numerical evaluation of diffusive and dispersive transport in periodic porous media

Alexandre Ern, Luc Dormieux, Pierre Tardif D'Hamonville & Pierre Tardif D'Hamonville
At the macroscopic scale, the transport of a fluid component in a porous medium is governed by advective, diffusive, and dispersive fluxes. The two latter fluxes are formulated using a diffusion tensor and a dispersion tensor. The actual value of these tensors depends on the pore geometry and on the magnitude of the advection velocity. Using the double scale expansion technique and provided the problem is homogeneizable, it is well-known that the the diffusion and...

Modelling of two-phase flow in porous media including non-equilibrium capillary pressure effects

Cas Berentsen, Majid Hassanizadeh & Cas Berentsen
Two-phase flow models commonly use equilibrium capillary-pressure relations. However, in core-flow experiments the time needed to reach capillary equilibrium is already in the order of days. Some recently developed theories [1],[2] account for non-equilibrium capillary pressure at the (upscaled) macro-scale, by proposing that capillary pressure is a function of saturation rate. There is plenty of experimental evidence on the significance of non-equilibrium effects in unsaturated media. However, there are very few experiments dealing with two-phase...

Numerical Aspects of Density Driven Flow in Porous Media

Klaus Johannsen & Klaus Johannsen
The analysis as well as the numerical simulation of density driven flow in porous media is still a challenging task. Whereas thorough theoretical investigations are limited to special situations, the numerical treatment, especially of real-world problems, requires special numerical techniques. In this talk we focus on two aspects, which are relevant in this context. The first deals with the design of robust multigrid solvers for problems with high spatial anisotropies. In the second part, we...

Subsurface Characterization Using Geophysical and Geohydrological Data Fusion

Metin Ozbek, James Ross, George Pinder & Metin Ozbek
We are introducing a novel technology applicable to the robust interpretation of the spatial distribution of hydraulic conductivity in heterogenous formations. The evidence theory approach is based on a combination of directly measured hydrogeological and geophysical data together with expert opinion. The approach first utilizes fuzzy-set based approximate reasoning to quantify subjective expert opinion, especially when data are scarce, to create a fuzzy prior characterization of the hydraulic conductivity field. Subjective information includes, but is...

Sensitivity Analysis for the Numerical Simulation of the Transport of Contaminants

Estelle Marchand, Francois Clement & Estelle Marchand
The questions of safety and uncertainties are central to feasibility studies for an underground waste storage site. One of the important points to be considered is the problem of the evaluation of concentration uncertainties which are due to input parameter uncertainties. These concentration uncertainties can be obtained by probabilistic methods. These methods give good results and are relatively easy to implement, but they are expensive because they require a large number of simulations. The method...

Simultaneous heat and solute transport modeling of ground water with lattice Boltzmann methods

Kathleen Bardsley, Shadab Anwar, Michael Sukop & Michael Sukop
Recent advances in lattice Boltzmann modeling permit simulation of large-scale density-dependent ground water flow and heat/solute transport systems while retaining the advantages of ‘regular’ lattice Boltzmann methods, such as solute/heat transport at higher Reynolds numbers that can characterize flows in conduits. We model the simultaneous heat/solute problem described by Henry and Hilleke in 1972 as an extension of Henry’s classic 1964 seawater intrusion problem. We also demonstrate the method’s ‘dual domain’ modeling potential.

Simultaneous heat and solute transport modeling of ground water with lattice Boltzmann methods

Kathleen Bardsley, Shadab Anwar, Michael Sukop & Michael Sukop
Recent advances in lattice Boltzmann modeling permit simulation of large-scale density-dependent ground water flow and heat/solute transport systems while retaining the advantages of ‘regular’ lattice Boltzmann methods, such as solute/heat transport at higher Reynolds numbers that can characterize flows in conduits. We model the simultaneous heat/solute problem described by Henry and Hilleke in 1972 as an extension of Henry’s classic 1964 seawater intrusion problem. We also demonstrate the method’s ‘dual domain’ modeling potential.

MODFLOW/MT3DMS-Based Simulation of Variable-Density Groundwater Flow with Simultaneous Heat and Solute Transport

Danny Thorne, Christian Langevin, Michael Sukop & Christian Langevin
SEAWAT is a finite-difference computer code, based on MODFLOW and MT3DMS, designed to simulate coupled variable-density groundwater flow and solute transport. This paper describes a new version of SEAWAT, which adds the ability to simultaneously model energy and solute transport. This is necessary for simulating the transport of heat and salinity in coastal aquifers for example. This work extends the equation of state for fluid density to vary as a function of temperature and/or solute...

Multidomain Modeling for the Simulation of Flow and Transport in a Neighborhood of an Underground Nuclear Waste Repository

Amel Sboui, Francois Clement, Jerome Jaffre, Michel Kern, Vincent Martin, Jean Roberts & Amel Sboui
In this presentation we are concerned with the problem of developing a numerical simulator for modeling flow and contaminant transport in the vicinity of an underground nuclear waste repository for use in performance assessment. Clearly reasonably accurate and reliable simulators are needed, but as performance assessment requires many simulations, it is also important that the simulators be very efficient. The simulations under consideration necessarily involve large scale calculations both in space and in time, and...

CO2-PENS: A CO2 Sequestration Systems Model Supporting Risk-Based Decisions

Philip Stauffer, Hari Viswanathan, George Guthrie, Rajesh Pawar & Philip Stauffer
The Zero Emissions Research and Technology (ZERT) project at the Los Alamos National Laboratory is studying the injection of CO2 into geologic repositories. We are formulating the problem as science based decision framework that can address issues of risk, cost, and technical requirements at all stages of the sequestration process. The framework is implemented in a sys tem model that is capable of performing stochastic simulations to address uncertainty in different geologic sequestration sc enarios,...

Perspective from the Comet: Modeling water and gas species under variable gravity

Stuart Stothoff & Stuart Stothoff
NASA is developing life-support technology for manned missions, using plants to provide supplemental food and improve air quality. It is a challenge to design a medium that allows oxygen and carbon dioxide to exchange between plant roots and cabin atmosphere, while simultaneously supplying roots with water, without significant gravitational body forces to move water around. As a precursor to medium design, a simulator was developed with the intention of characterizing plant uptake, water redistribution, and...

A novel method to couple well bore flow to reservoir flow to understand the impact of a well bore failure during CO2 sequestration operation

Rajesh Pawar, George Zyvoloski & Rajesh Pawar
One of the major concerns of geologic sequestration is consequences of a failed well bore and subsequent release of CO2. The release can be slow or catastrophic depending on the mode of well bore failure. It is important to predict the release characteristics of a failed well bore in order to develop monitoring plans, to understand potential impact and to develop strategies to mitigate the leak. In order to understand the total amount of CO2...

Pore-scale modelling of dynamic capillary pressure: the role of fluid viscosities and length scale

Twan Gielen, Majid Hassanizadeh, Helge H.K. Dahle, Michael Celia & Twan Gielen
Traditional theories of multiphase flow rely on capillary pressure and saturation relationships that are measured under equilibrium conditions. To incorporate transient behaviour, new multiphase flow theories have been proposed. These include an extended capillary pressure-saturation relationship that is valid under dynamic conditions. In this relationship, the difference between the two fluid pressures is called dynamic capillary pressure, and is assumed to be a function of saturation and its time rate of change. The dependency is...

Turbulent transport mechanics within and above tall canopies on gentle hills

Gabriel Katul, Davide Poggi & Gabriel Katul
Progress on many practical problems in eco-hydrology and eco-hydraulics are now requiring fundamental understanding of how topography modulates the basic properties of turbulence. In particular, how hilly terrain alters the ejection-sweep cycle, which is the main coherent transporting motion, remains a problem that received surprisingly little theoretical and experimental attention. Here, we investigate how boundary conditions, including canopy and gentle topography, alter the properties of the ejection-sweep cycle and whether it is possible to quantify...

Multi-scale model inter-comparisons of CO2 and H2O exchange rates in inhomogeneous canopies

Gabriel Katul, Mario Siqueira & Gabriel Katul
Models for the exchange of CO2 and H2O between the atmosphere and terrestrial ecosystems are needed for assessing the effects of anthropogenic CO2 emissions on atmospheric concentration of CO2. To date, no single model captures the entire spectrum of variability of the processes affecting CO2 and H2O transfer and storage within terrestrial ecosystems; rather, a modular approach is adopted in which the forcing and response variables are coupled over an inherent or assumed time scale...

Registration Year

  • 2011
    154,692

Resource Types

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    103,598
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    13,926
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    33
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    7
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Affiliations

  • French National Centre for Scientific Research
    38
  • Duke University
    21
  • University of British Columbia
    20
  • The University of Texas at Austin
    16
  • Centre for Ecology & Hydrology
    13
  • UK Centre for Ecology & Hydrology
    13
  • University of Montpellier
    10
  • University of Sheffield
    10
  • University of Cambridge
    9
  • Indiana University
    9