Mathematical Model to Predict the Permeability of Water Transport in Concrete Structure

OpenAIRE

Solomon Ndubuisi Eluozo

2013-01-01

Mathematical model to predict the permeability of water transport in concrete has been established, the model is to monitor the rate of water transport in concrete structure. The process of this water transport is based on the constituent in the mixture of concrete. Permeability established a relation on the influence of the micropores on the constituent that made of concrete, the method of concrete placement determine the rate of permeability deposition in concrete structure, permeability es...

Critical review: Radionuclide transport, sediment transport, and water quality mathematical modeling; and radionuclide adsorption/desorption mechanisms

Energy Technology Data Exchange (ETDEWEB)

Onishi, Y.; Serne, R.J.; Arnold, E.M.; Cowan, C.E.; Thompson, F.L. [Pacific Northwest Lab., Richland, WA (United States)

1981-01-01

This report describes the results of a detailed literature review of radionuclide transport models applicable to rivers, estuaries, coastal waters, the Great Lakes, and impoundments. Some representatives sediment transport and water quality models were also reviewed to evaluate if they can be readily adapted to radionuclide transport modeling. The review showed that most available transport models were developed for dissolved radionuclide in rivers. These models include the mechanisms of advection, dispersion, and radionuclide decay. Since the models do not include sediment and radionuclide interactions, they are best suited for simulating short-term radionuclide migration where: (1) radionuclides have small distribution coefficients; (2) sediment concentrations in receiving water bodies are very low. Only 5 of the reviewed models include full sediment and radionuclide interactions: CHMSED developed by Fields; FETRA SERATRA, and TODAM developed by Onishi et al, and a model developed by Shull and Gloyna. The 5 models are applicable to cases where: (1) the distribution coefficient is large; (2) sediment concentrations are high; or (3) long-term migration and accumulation are under consideration. The report also discusses radionuclide absorption/desorption distribution ratios and addresses adsorption/desorption mechanisms and their controlling processes for 25 elements under surface water conditions. These elements are: Am, Sb, C, Ce, Cm, Co, Cr, Cs, Eu, I, Fe, Mn, Np, P, Pu, Pm, Ra, Ru, Sr, Tc, Th, {sup 3}H, U, Zn and Zr.

Model for tritiated water transport in soil

International Nuclear Information System (INIS)

Galeriu, D.; Paunescu, N.

1999-01-01

Chemical forms of tritium released from nuclear facilities are mostly water (HTO) and hydrogen (HT, TT). Elemental tritium is inert in vegetation and superior animals, but the microorganisms from soil oxidize HT to HTO. After an atmospheric HT emission, in short time an equivalent quantity of HTO is re-emitted from soil. In the vicinity of a tritium source the spatial and temporary distribution of HTO is dependent on the chemical form of tritium releases. During routine tritium releases (continuously and constant releases), the local distribution of tritium reaches equilibrium, and specific activities of tritium in environmental compartments are almost equal. The situation is very different after an accidental emission. Having in view, harmful effects of tritium when it is incorporated into the body several models were developed for environmental tritium transport and dose assessment. The tritium transport into the soil is an important part of the environmental tritium behavior, but, unfortunately, in spite of the importance of this problem the corresponding modeling is unsatisfactory. The aim of this paper was the improvement of the TRICAIAP model, and the application of the model to BIOMOVS scenario. The BIOMOVS scenario predicts HTO concentrations in soil during 30 days, after one hour atmospheric HTO emission. The most important conclusions of the paper are: the principal carrier of tritium into the soil is water; the transfer processes are the reactions of water in soil and the diffusion due to concentration gradient; atmosphere-soil transport is dependent of surface characteristics (granulation, humidity, roughness, etc.); the conversion rate of HT to HTO is not well known and is dependent on active microorganism concentration in soil and on soil humidity. More experimental data are needed to decrease the uncertainty of transfer parameter, for the definition of the influence of vegetation, etc. (authors)

Modelling of the reactive transport of organic pollutants in ground water; Modellierung des reaktiven Transports organischer Schadstoffe im Grundwasser

Energy Technology Data Exchange (ETDEWEB)

Schaefer, W [Heidelberg Univ. (Germany). Inst. fuer Umweltphysik

1999-07-01

The book describes reactive transport of organic pollutants in ground water and its quantitative monitoring by means of numerical reaction transport models. A brief introduction dealing with the importance of and hazards to ground water and opportunities for making use of ground water models is followed by a more detailed chapter on organic pollutants in ground water. Here the focus is on organochlorine compounds and mineral oil products. Described are propagation mechanisms for these substances in the ground and, especially, their degradability in ground water. A separate chapter is dedicated to possibilities for cleaning up polluted ground water aquifers. The most important decontamination techniques are presented, with special emphasis on in-situ processes with hydraulic components. Moreover, this chapter discusses the self-cleaning capability of aquifers and the benefits of the application of models to ground water cleanup. In the fourth chapter the individual components of reaction transport models are indicated. Here it is, inter alia, differences in the formulation of reaction models as to their complexity, and coupling between suspended matter transport and reaction processes that are dealt with. This chapter ends with a comprehensive survey of literature regarding the application of suspended matter transport models to real ground water accidents. Chapter 5 consists of a description of the capability and principle of function of the reaction transport model TBC (transport biochemism/chemism). This model is used in the two described applications to the reactive transport of organic pollutants in ground water. (orig.) [German] Inhalt des vorliegenden Buches ist die Darstellung des reaktiven Transports organischer Schadstoffe im Grundwasser und dessen quantitative Erfassung mithilfe numerischer Reaktions-Transportmodelle. Auf eine kurze Einleitung zur Bedeutung und Gefaehrdung von Grundwasser und zu den Einsatzmoeglichkeiten von Grundwassermodellen folgt ein

Visualization of root water uptake: quantification of deuterated water transport in roots using neutron radiography and numerical modeling.

Science.gov (United States)

Zarebanadkouki, Mohsen; Kroener, Eva; Kaestner, Anders; Carminati, Andrea

2014-10-01

Our understanding of soil and plant water relations is limited by the lack of experimental methods to measure water fluxes in soil and plants. Here, we describe a new method to noninvasively quantify water fluxes in roots. To this end, neutron radiography was used to trace the transport of deuterated water (D2O) into roots. The results showed that (1) the radial transport of D2O from soil to the roots depended similarly on diffusive and convective transport and (2) the axial transport of D2O along the root xylem was largely dominated by convection. To quantify the convective fluxes from the radiographs, we introduced a convection-diffusion model to simulate the D2O transport in roots. The model takes into account different pathways of water across the root tissue, the endodermis as a layer with distinct transport properties, and the axial transport of D2O in the xylem. The diffusion coefficients of the root tissues were inversely estimated by simulating the experiments at night under the assumption that the convective fluxes were negligible. Inverse modeling of the experiment at day gave the profile of water fluxes into the roots. For a 24-d-old lupine (Lupinus albus) grown in a soil with uniform water content, root water uptake was higher in the proximal parts of lateral roots and decreased toward the distal parts. The method allows the quantification of the root properties and the regions of root water uptake along the root systems. © 2014 American Society of Plant Biologists. All Rights Reserved.

Modeling water flow and solute transport in unsaturated zone inside NSRAWD project

International Nuclear Information System (INIS)

Constantin, A.; Diaconu, D.; Bucur, C.; Genty, A.

2015-01-01

The NSRAWD project (2010-2013) - Numerical Simulations for Radioactive Waste Disposal was initiated under a collaboration agreement between the Institute for Nuclear Research and the French Alternative Energies and Atomic Energy Commission (CEA). The context of the project was favorable to combine the modeling activities with an experimental part in order to improve and validate the numerical models used so far to simulate water flow and solute transport at Saligny site, Romania. The numerical models developed in the project were refined and validated on new hydrological data gathered between 2010-2012 by a monitoring station existent on site which performs automatic determination of soil water content and matrix potential, as well as several climate parameters (wind, temperature and precipitations). Water flow and solute transport was modeled in transient conditions, by taking into consideration, as well as neglecting the evapotranspiration phenomenon, on the basis of a tracer test launched on site. The determination of dispersivities for solute transport was targeted from the solute plume. The paper presents the main results achieved in the NSRAWD project related to water flow and solute transport in the unsaturated area of the Saligny site. The results indicated satisfactory predictions for the simulation of water flow in the unsaturated area, in steady state and transient conditions. In the case of tracer transport modeling, dispersivity coefficients could not be finally well fitted for the data measured on site and in order to obtain a realistic preview over the values of these parameters, further investigations are recommended. The article is followed by the slides of the presentation

Pupils' Response to a Model for Water Transport.

Science.gov (United States)

Johnstone, A. H.; Mahmoud, N. A.

1981-01-01

Described is a model, based on the physical sciences, designed to teach secondary students about water transport through the use of an animated film. Pupils (N=440) taught by this method developed a self-consistent, although reduced, picture and understanding of osmosis. (Author/DC)

Water-Level Data Analysis for the Saturated Zone Site-Scale Flow and Transport Model

International Nuclear Information System (INIS)

Tucci, P.

2001-01-01

This Analysis/Model Report (AMR) documents an updated analysis of water-level data performed to provide the saturated-zone, site-scale flow and transport model (CRWMS M and O 2000) with the configuration of the potentiometric surface, target water-level data, and hydraulic gradients for model calibration. The previous analysis was presented in ANL-NBS-HS-000034, Rev 00 ICN 01, Water-Level Data Analysis for the Saturated Zone Site-Scale Flow and Transport Model (USGS 2001). This analysis is designed to use updated water-level data as the basis for estimating water-level altitudes and the potentiometric surface in the SZ site-scale flow and transport model domain. The objectives of this revision are to develop computer files containing (1) water-level data within the model area (DTN: GS010908312332.002), (2) a table of known vertical head differences (DTN: GS0109083 12332.003), and (3) a potentiometric-surface map (DTN: GS010608312332.001) using an alternate concept from that presented in ANL-NBS-HS-000034, Rev 00 ICN 01 for the area north of Yucca Mountain. The updated water-level data include data obtained from the Nye County Early Warning Drilling Program (EWDP) and data from borehole USW WT-24. In addition to being utilized by the SZ site-scale flow and transport model, the water-level data and potentiometric-surface map contained within this report will be available to other government agencies and water users for ground-water management purposes. The potentiometric surface defines an upper boundary of the site-scale flow model, as well as provides information useful to estimation of the magnitude and direction of lateral ground-water flow within the flow system. Therefore, the analysis documented in this revision is important to SZ flow and transport calculations in support of total system performance assessment

Modeling UTLS water vapor: Transport/Chemistry interactions

International Nuclear Information System (INIS)

Gulstad, Line

2005-01-01

This thesis was initially meant to be a study on the impact on chemistry and climate from UTLS water vapor. However, the complexity of the UTLS water vapor and its recent changes turned out to be a challenge by it self. In the light of this, the overall motivation for the thesis became to study the processes controlling UTLS water vapor and its changes. Water vapor is the most important greenhouse gas, involved in important climate feedback loops. Thus, a good understanding of the chemical and dynamical behavior of water vapor in the atmosphere is crucial for understanding the climate changes in the last century. Additionally, parts of the work was motivated by the development of a coupled climate chemistry model based on the CAM3 model coupled with the Chemical Transport Model Oslo CTM2. The future work will be concentrated on the UTLS water vapor impact on chemistry and climate. We are currently studying long term trends in UTLS water vapor, focusing on identification of the different processes involved in the determination of such trends. The study is based on natural as well as anthropogenic climate forcings. The ongoing work on the development of a coupled climate chemistry model will continue within our group, in collaboration with Prof. Wei-Chyung Wang at the State University of New York, Albany. Valuable contacts with observational groups are established during the work on this thesis. These collaborations will be continued focusing on continuous model validation, as well as identification of trends and new features in UTLS water vapor, and other tracers in this region. (Author)

Some analytic diagnostic models for transport processes in estuarine and coastal waters

International Nuclear Information System (INIS)

Suarez Antola, R.

2001-03-01

Advection and dispersion processes in estuarine and coastal waters are briefly reviewed. Beginning from the basic macroscopic equations of transport for a substance diluted or suspended in the considered body of water,several levels of filtering in time and space are described and applied to obtain suitable diagnostic mathematical models both with scale effects and gaussian.The solutions of the aforementioned models,for initial distributions and boundary conditions with enough symmetry,are discussed, as well as their applications to a parameter characterization of the transport properties of the receiving body of water

Mathematical model of water transport in Bacon and alkaline matrix-type hydrogen-oxygen fuel cells

Science.gov (United States)

Prokopius, P. R.; Easter, R. W.

1972-01-01

Based on general mass continuity and diffusive transport equations, a mathematical model was developed that simulates the transport of water in Bacon and alkaline-matrix fuel cells. The derived model was validated by using it to analytically reproduce various Bacon and matrix-cell experimental water transport transients.

Improving activity transport models for water-cooled nuclear power reactors

Energy Technology Data Exchange (ETDEWEB)

Burrill, K.A

2001-08-01

Eight current models for describing radioactivity transport and radiation field growth around water-cooled nuclear power reactors have been reviewed and assessed. A frequent failing of the models is the arbitrary nature of the determination of the important processes. Nearly all modelers agree that the kinetics of deposition and release of both dissolved and particulate material must be described. Plant data must be used to guide the selection and development of suitable improved models, with a minimum of empirically-based rate constraints being used. Limiting case modelling based on experimental data is suggested as a way to simplify current models and remove their subjectivity. Improved models must consider the recent change to 'coordinated water chemistry' that appears to produce normal solubility behaviour for dissolved iron throughout the fuel cycle in PWRs, but retrograde solubility remains for dissolved nickel. Profiles are suggested for dissolved iron and nickel concentrations around the heat transport system in CANDU reactors, which operate nominally at constant chemistry, i.e., pH{sub T} constant with time, and which use carbon steel isothermal piping. These diagrams are modified for a CANDU reactor with stainless steel piping, in order to show the changes expected. The significance of these profiles for transport in PWRs is discussed for further model improvement. (author)

Osmotic water transport in aquaporins

DEFF Research Database (Denmark)

Zeuthen, Thomas; Alsterfjord, Magnus; Beitz, Eric

2013-01-01

Abstract  We test a novel, stochastic model of osmotic water transport in aquaporins. A solute molecule present at the pore mouth can either be reflected or permeate the pore. We assume that only reflected solute molecules induce osmotic transport of water through the pore, while permeating solute...... molecules give rise to no water transport. Accordingly, the rate of water transport is proportional to the reflection coefficient σ, while the solute permeability, P(S), is proportional to 1 - σ. The model was tested in aquaporins heterologously expressed in Xenopus oocytes. A variety of aquaporin channel...... sizes and geometries were obtained with the two aquaporins AQP1 and AQP9 and mutant versions of these. Osmotic water transport was generated by adding 20 mM of a range of different-sized osmolytes to the outer solution. The osmotic water permeability and the reflection coefficient were measured...

A High-Resolution Model of Water Mass Transformation and Transport in the Weddell Sea

Science.gov (United States)

Hazel, J.; Stewart, A.

2016-12-01

The ocean circulation around the Antarctic margins has a pronounced impact on the global ocean and climate system. One of these impacts includes closing the global meridional overturning circulation (MOC) via formation of dense Antarctic Bottom Water (AABW), which ventilates a large fraction of the subsurface ocean. AABW is also partially composed of modified Circumpolar Deep Water (CDW), a warm, mid-depth water mass whose transport towards the continent has the potential to induce rapid retreat of marine-terminating glaciers. Previous studies suggest that these water mass exchanges may be strongly influenced by high-frequency processes such as downslope gravity currents, tidal flows, and mesoscale/submesoscale eddy transport. However, evaluating the relative contributions of these processes to near-Antarctic water mass transports is hindered by the region's relatively small scales of motion and the logistical difficulties in taking measurements beneath sea ice.In this study we develop a regional model of the Weddell Sea, the largest established source of AABW. The model is forced by an annually-repeating atmospheric state constructed from the Antarctic Mesoscale Prediction System data and by annually-repeating lateral boundary conditions constructed from the Southern Ocean State Estimate. The model incorporates the full Filchner-Ronne cavity and simulates the thermodynamics and dynamics of sea ice. To analyze the role of high-frequency processes in the transport and transformation of water masses, we compute the model's overturning circulation, water mass transformations, and ice sheet basal melt at model horizontal grid resolutions ranging from 1/2 degree to 1/24 degree. We temporally decompose the high-resolution (1/24 degree) model circulation into components due to mean, eddy and tidal flows and discuss the geographical dependence of these processes and their impact on water mass transformation and transport.

Application of a soil and ground-water pollutant-transport model

International Nuclear Information System (INIS)

Reeves, M.; Duguid, J.O.

1975-01-01

A general two-dimensional model was developed for simulation of saturated-unsaturated transport of radionuclides in ground water. This model is being applied to the transport of radionuclides from waste-disposal sites, where field investigations are currently under way to obtain the necessary parameters. A zero-order simulation of a waste-disposal trench is presented. Estimated values of the soil properties have been used since very limited experimental information is available at the present time. However, as more measured values become available from field studies, the simulation will be updated. The end product of this research will be a reliable computer model useful both in predicting future transport of radionuclides from buried waste and in examining control measures if they are shown to be necessary. (U.S.)

Hydrogeochemical transport modeling of 24 years of Rhine water infiltration in the dunes of the Amsterdam Water Supply.

NARCIS (Netherlands)

van Breukelen, B.M.; Appelo, C.A.J.; Olsthoorn, T.N.

1998-01-01

Water quality changes were modelled along a flowpath in a plume of artificially recharged, pretreated Rhine water in the dunes of the Amsterdam Water Supply, after 24 years of infiltration. The hydrogeochemical transport model PHREEQC was extended with dispersion/diffusion and kinetics for selected

A Mathematical Model of Solute Coupled Water Transport in Toad Intestine Incorporating Recirculation of the Actively Transported Solute

DEFF Research Database (Denmark)

Larsen, Erik Hviid; Sørensen, Jakob Balslev; Sørensen, Jens Nørkær

2000-01-01

those of tight junction and interspace basement membrane by convection-diffusion. With solute permeability of paracellular pathway large relative to paracellular water flow, the paracellular flux ratio of the solute (influx/outflux) is small (2-4) in agreement with experiments. The virtual solute......A mathematical model of an absorbing leaky epithelium is developed for analysis of solute coupled water transport. The non-charged driving solute diffuses into cells and is pumped from cells into the lateral intercellular space (lis). All membranes contain water channels with the solute passing...... increases with hydraulic conductance of the pathway carrying water from mucosal solution into lis. Uphill water transport is accomplished, but with high hydraulic conductance of cell membranes strength of transport is obscured by water flow through cells. Anomalous solvent drag occurs when back flux...

Hydrological model for the transport of radioisotope in surface water

International Nuclear Information System (INIS)

Adoboah, E.K.

2011-01-01

The use of radioisotopes has gained grounds in Ghana as a result of the numerous benefits that could be derived from it. In Ghana, radioisotope materials are used for various purposes in a number of institutions. However, improper disposal of the waste poses threat to the environment. To evaluate the environmental impact of radioisotope pollution, mathematical models play a major role in predicting the pollution level in any medium. This study is concerned with the hydrological model for the transport of radioactive material in the river. The model was composed by employing partial differential equations, describing relevant physical processes evolution (water level, velocities and dissolved substances concentrations) that occurs in water bodies. The mass conservation and momentum laws, state equation and state transport equations are equation system basis. The explicit central difference scheme in space and a forward difference method in time were used for the evaluation of the generalized transport equation, the Advection-Dispersion Equation. A Matlab code was developed to predict the concentration of the radioactive contaminant at any particular time along the river and in a reservoir. The model was able to simulate accurately the various levels of radionuclide concentration changes in the flowing rivers as the flows are augmented by tributary inflows. (au)

Computational simulation of water transport in PEM fuel cells using an improved membrane model

International Nuclear Information System (INIS)

Cao, J.; Djilali, N.

2000-01-01

Computational models and simulation tools can provide valuable insight and guidance for design, performance optimization, and cost reduction of fuel cells. In proton-exchange membrane fuel cells it is particularly important to maintain appropriate water content and temperature in the electrolyte membrane. In this paper we describe a mathematical model for the membrane that takes into account the diffusion of water, the pressure variation, and the electro-osmotic drag in the membrane. Applying conservation laws for water and current and using an empirical relationship between electro-osmotic drag and water content, we obtain a transport equation for water molar concentration and derive a new equation for the electric potential that accounts for variable water content and is more accurate than the conventionally employed Laplace's equation does. The model is coupled with a computational fluid dynamics model for diffusive transport in the electrodes and convective transport in the reactant flow channels. Simulations for a two-dimensional cell are performed over nominal current densities ranging form i=0.1 A/cm≅ to 1.2 A/cm≅. The impact and importance of temperature and pressure non-uniformity, and of two-dimensionality are assessed and discussed. (author)

Water-transporting proteins

DEFF Research Database (Denmark)

Zeuthen, Thomas

2010-01-01

. In the K(+)/Cl(-) and the Na(+)/K(+)/2Cl(-) cotransporters, water is entirely cotransported, while water transport in glucose uniporters and Na(+)-coupled transporters of nutrients and neurotransmitters takes place by both osmosis and cotransport. The molecular mechanism behind cotransport of water...... transport. Epithelial water transport is energized by the movements of ions, but how the coupling takes place is uncertain. All epithelia can transport water uphill against an osmotic gradient, which is hard to explain by simple osmosis. Furthermore, genetic removal of aquaporins has not given support...... to osmosis as the exclusive mode of transport. Water cotransport can explain the coupling between ion and water transport, a major fraction of transepithelial water transport and uphill water transport. Aquaporins enhance water transport by utilizing osmotic gradients and cause the osmolarity...

Numerical modeling of coupled water flow and heat transport in soil and snow

Science.gov (United States)

Thijs J. Kelleners; Jeremy Koonce; Rose Shillito; Jelle Dijkema; Markus Berli; Michael H. Young; John M. Frank; William Massman

2016-01-01

A one-dimensional vertical numerical model for coupled water flow and heat transport in soil and snow was modified to include all three phases of water: vapor, liquid, and ice. The top boundary condition in the model is driven by incoming precipitation and the surface energy balance. The model was applied to three different terrestrial systems: A warm desert bare...

Analysis of coupled proton and water transport in a PEM fuel cell using the binary friction membrane model

International Nuclear Information System (INIS)

Carnes, B.; Djilali, N.

2006-01-01

Transport of liquid water within a polymer electrolyte membrane (PEM) is critical to the operation of a PEM fuel cell, due to the strong dependence of the membrane transport coefficients on water content. In addition, enhanced predictive abilities are particularly significant in the context of passive air breathing fuel cell designs where lower water contents will prevail in the membrane. We investigate and analyze the numerical predictions of a recently proposed rational model for transport of protons and water in a PEM, when compared to a widely used empirical model. While the performance is similar for a saturated membrane, for PEMs with low water content, the difference in computed current density and membrane water crossover can be substantial. The effects of coupling partially saturated gas diffusion electrodes (GDLs) with the membrane are studied in both a 1D and 2D context. In addition, a simplified 1D analytical membrane water transport model is validated against the complete 1D model predictions. Our numerical results predict a higher current density and more uniform membrane hydration using a dry cathode instead of a dry anode, and illustrate that the strongest 2D effects are for water vapor transport

Field-scale water flow and solute transport : SWAP model concepts, parameter estimation and case studies = [Waterstroming en transport van opgeloste stoffen op veldschaal

NARCIS (Netherlands)

Dam, van J.C.

2000-01-01

Water flow and solute transport in top soils are important elements in many environmental studies. The agro- and ecohydrological model SWAP (Soil-Water-Plant-Atmosphere) has been developed to simulate simultaneously water flow, solute transport, heat flow and crop growth at field scale

Unsaturated water flow and tracer transport modeling with Alliances

Energy Technology Data Exchange (ETDEWEB)

Constantin, Alina, E-mail: alina.constantin@nuclear.ro [Institute for Nuclear Research, Campului Str, No. 1, PO Box 78, Postal Code 115400 Mioveni, Arges County (Romania); Genty, Alain, E-mail: alain.genty@cea.fr [CEA Saclay, DM2S/SFME/LSE, Gif-sur-Yvette 91191 cedex (France); Diaconu, Daniela; Bucur, Crina [Institute for Nuclear Research, Campului Str, No. 1, PO Box 78, Postal Code 115400 Mioveni, Arges County (Romania)

2013-12-15

Highlights: • Simulation of water flow and solute transport at Saligny site, Romania was done. • Computation was based on the available experimental data with Alliances platform. • Very good results were obtained for the saturation profile in steady state. • Close fit to experimental data for saturation profile at 3 m in transient state. • Large dispersivity coefficients were fitted to match tracer experiment. - Abstract: Understanding water flow and solute transport in porous media is of central importance in predicting the radionuclide fate in the geological environment, a topic of interest for the performance and safety assessment studies for nuclear waste disposal. However, it is not easy to predict transport properties in real systems because they are geologically heterogeneous from the pore scale upwards. This paper addresses the simulation of water flow and solute transport in the unsaturated zone of the Saligny site, the potential location for the Romanian low and intermediate level waste (LILW) disposal. Computation was based on the current available experimental data for this zone and was performed within Alliances, a software platform initially jointly developed by French organizations CEA, ANDRA and EDF. The output of the model developed was compared with the measured values in terms of saturation profile of the soil for water movement, in both steady and transient state. Very good results were obtained for the saturation profile in steady state and a close fit of the simulation over experimental data for the water saturation profile at a depth of 3 m in transient state. In order to obtain information regarding the solute migration in depth and the solute lateral dispersion, a tracer test was launched on site and dispersivity coefficients of the solute were fitted in order to match the experimental concentration determined on samples from different locations of the site. Results much close to the experiment were obtained for a longitudinal

Stable isotope reactive transport modeling in water-rock interactions during CO2 injection

Science.gov (United States)

Hidalgo, Juan J.; Lagneau, Vincent; Agrinier, Pierre

2010-05-01

Stable isotopes can be of great usefulness in the characterization and monitoring of CO2 sequestration sites. Stable isotopes can be used to track the migration of the CO2 plume and identify leakage sources. Moreover, they provide unique information about the chemical reactions that take place on the CO2-water-rock system. However, there is a lack of appropriate tools that help modelers to incorporate stable isotope information into the flow and transport models used in CO2 sequestration problems. In this work, we present a numerical tool for modeling the transport of stable isotopes in groundwater reactive systems. The code is an extension of the groundwater single-phase flow and reactive transport code HYTEC [2]. HYTEC's transport module was modified to include element isotopes as separate species. This way, it is able to track isotope composition of the system by computing the mixing between the background water and the injected solution accounting for the dependency of diffusion on the isotope mass. The chemical module and database have been expanded to included isotopic exchange with minerals and the isotope fractionation associated with chemical reactions and mineral dissolution or precipitation. The performance of the code is illustrated through a series of column synthetic models. The code is also used to model the aqueous phase CO2 injection test carried out at the Lamont-Doherty Earth Observatory site (Palisades, New York, USA) [1]. References [1] N. Assayag, J. Matter, M. Ader, D. Goldberg, and P. Agrinier. Water-rock interactions during a CO2 injection field-test: Implications on host rock dissolution and alteration effects. Chemical Geology, 265(1-2):227-235, July 2009. [2] Jan van der Lee, Laurent De Windt, Vincent Lagneau, and Patrick Goblet. Module-oriented modeling of reactive transport with HYTEC. Computers & Geosciences, 29(3):265-275, April 2003.

Predictive capabilities of a two-dimensional model in the ground water transport of radionuclides

International Nuclear Information System (INIS)

Gureghian, A.B.; Beskid, N.J.; Marmer, G.J.

1978-01-01

The discharge of low-level radioactive waste into tailings ponds is a potential source of ground water contamination. The estimation of the radiological hazards related to the ground water transport of radionuclides from tailings retention systems depends on reasonably accurate estimates of the movement of both water and solute. A two-dimensional mathematical model having predictive capability for ground water flow and solute transport has been developed. The flow equation has been solved under steady-state conditions and the mass transport equation under transient conditions. The simultaneous solution of both equations is achieved through the finite element technique using isoparametric elements, based on the Galerkin formulation. However, in contrast to the flow equation solution, the weighting functions used in the solution of the mass transport equation have a non-symmetric form. The predictive capability of the model is demonstrated using an idealized case based on analyses of field data obtained from the sites of operating uranium mills. The pH of the solution, which regulates the variation of the distribution coefficient (K/sub d/) in a particular site, appears to be the most important factor in the assessment of the rate of migration of the elements considered herein

A computerized coal-water slurry transportation model

Energy Technology Data Exchange (ETDEWEB)

Ljubicic, B.R.; Trostad, B. [Univ. of North Dakota, Grand Forks, ND (United States); Bukurov, Z.; Cvijanovic, P. [Univ. of Novi Sad (Yugoslavia)

1995-12-01

Coal-water fuel (CWF) technology has been developed to the point where full-scale commercialization is just a matter of gaining sufficient market confidence in the price stability of alternate fossil fuels. In order to generalize alternative fuel cost estimates for the desired combinations of processing and/or transportation, a great deal of flexibility is required owing to the understood lack of precision in many of the newly emerging coal technologies. Previously, decisions regarding the sequential and spatial arrangement of the various process steps were made strictly on the basis of experience, simplified analysis, and intuition. Over the last decade, computer modeling has progressed from empirically based correlation to that of intricate mechanistic analysis. Nomograms, charts, tables, and many simple rules of thumb have been made obsolete by the availability of complex computer models. Given the ability to view results graphically in real or near real time, the engineer can immediately verify, from a practical standpoint, whether the initial assumptions and inputs were indeed valid. If the feasibility of a project is being determined in the context of a lack of specific data, the ability to provide a dynamic software-based solution is crucial. Furthermore, the resulting model can be used to establish preliminary operating procedures, test control logic, and train plant/process operators. Presented in this paper is a computerized model capable of estimating the delivered cost of CWF. The model uses coal-specific values, process and transport requirements, terrain factors, and input costs to determine the final operating configuration, bill of materials, and, ultimately, the capital, operating, and unit costs.

Modeling of Dense Water Production and Salt Transport from Alaskan Coastal Polynyas

Science.gov (United States)

Signorini, Sergio R.; Cavalieri, Donald J.

2000-01-01

The main significance of this paper is that a realistic, three-dimensional, high-resolution primitive equation model has been developed to study the effects of dense water formation in Arctic coastal polynyas. The model includes realistic ambient stratification, realistic bottom topography, and is forced by time-variant surface heat flux, surface salt flux, and time-dependent coastal flow. The salt and heat fluxes, and the surface ice drift, are derived from satellite observations (SSM/I and NSCAT sensors). The model is used to study the stratification, salt transport, and circulation in the vicinity of Barrow Canyon during the 1996/97 winter season. The coastal flow (Alaska coastal current), which is an extension of the Bering Sea throughflow, is formulated in the model using the wind-transport regression. The results show that for the 1996/97 winter the northeastward coastal current exports 13% to 26% of the salt produced by coastal polynyas upstream of Barrow Canyon in 20 to 30 days. The salt export occurs more rapidly during less persistent polynyas. The inclusion of ice-water stress in the model makes the coastal current slightly weaker and much wider due to the combined effects of surface drag and offshore Ekman transport.

Modeling particle transport and discoloration risk in drinking water distribution networks

Directory of Open Access Journals (Sweden)

J. van Summeren

2017-10-01

Full Text Available Discoloration of drinking water is a worldwide phenomenon caused by accumulation and subsequent remobilization of particulate matter in drinking water distribution systems (DWDSs. It contributes a substantial fraction of customer complaints to water utilities. Accurate discoloration risk predictions could improve system operation by allowing for more effective programs on cleaning and prevention actions and field measurements, but are challenged by incomplete understanding on the origins and properties of particles and a complex and not fully understood interplay of processes in distribution networks. In this paper, we assess and describe relevant hydraulic processes that govern particle transport in turbulent pipe flow, including gravitational settling, bed-load transport, and particle entrainment into suspension. We assess which transport mechanisms are dominant for a range of bulk flow velocities, particle diameters, and particle mass densities, which includes common conditions for DWDSs in the Netherlands, the UK, and Australia. Our analysis shows that the theoretically predicted particle settling velocity and threshold shear stresses for incipient particle motion are in the same range as, but more variable than, previous estimates from lab experiments, field measurements, and modeling. The presented material will be used in the future development of a numerical modeling tool to determine and predict the spatial distribution of particulate material and discoloration risk in DWDSs. Our approach is aimed at understanding specific causalities and processes, which can complement data-driven approaches.

Leaf water stable isotopes and water transport outside the xylem.

Science.gov (United States)

Barbour, M M; Farquhar, G D; Buckley, T N

2017-06-01

How water moves through leaves, and where the phase change from liquid to vapour occurs within leaves, remain largely mysterious. Some time ago, we suggested that the stable isotope composition of leaf water may contain information on transport pathways beyond the xylem, through differences in the development of gradients in enrichment within the various pathways. Subsequent testing of this suggestion provided ambiguous results and even questioned the existence of gradients in enrichment within the mesophyll. In this review, we bring together recent theoretical developments in understanding leaf water transport pathways and stable isotope theory to map a path for future work into understanding pathways of water transport and leaf water stable isotope composition. We emphasize the need for a spatially, anatomically and isotopically explicit model of leaf water transport. © 2016 John Wiley & Sons Ltd.

Modelling transport of water and solutes in future wetlands in Forsmark

Energy Technology Data Exchange (ETDEWEB)

Vikstroem, Maria; Gustafsson, Lars-Goeran [DHI Water and Environment AB, Vaexjoe (Sweden)

2006-03-15

The Forsmark area consists of a number of natural wetlands. As a part of the evaluation of wetlands in the safety assessment for the area, possible future wetlands are being studied with respect to hydrology and transport mechanisms. A sensitivity analyses is performed to point out the governing parameters for the wetland hydraulics. The analysis of future wetlands is carried out using the hydrological model system Mike SHE. Mike SHE has been used to describe the near-surface hydrology for a regional model area in Forsmark. Three types of areas have been chosen. Today's lake Bolundfjaerden is because of its shallow depth likely to develop into a mire in the future. As it is situated in the downstream part of the regional model area, the runoff to the lake from upstream surface water system is significant. Lake Eckarfjaerden is situated in the upstream part of the catchment at a higher altitude and with a smaller inflow. Lake Puttan is situated above a planned layout of the repository and has a potential to receive discharges from a repository. It also lies in the downstream part of a large discharge area. The topography of the future mires is assumed to be flat, up to today's mean water level in each lake. To transport the surface runoff through the wetland, streams or water courses are assumed to form within the peat. The analyses of future wetlands in the Forsmark area show that the hydraulic conditions that exists today will somewhat alter as the peat is formed. For Bolundsfjaerden, where there during present conditions are weak discharge areas, a recharge area has formed during the summer. This can be explained by the amount of surface water that forms on the surface which increases the head elevation in the upper soil layers. The same holds for Eckarfjaerden, while Puttan after the peat has developed still is a discharge area due to its naturally strong discharge position close to the sea. Different vegetation and development stages for the peat have

Modelling transport of water and solutes in future wetlands in Forsmark

International Nuclear Information System (INIS)

Vikstroem, Maria; Gustafsson, Lars-Goeran

2006-03-01

The Forsmark area consists of a number of natural wetlands. As a part of the evaluation of wetlands in the safety assessment for the area, possible future wetlands are being studied with respect to hydrology and transport mechanisms. A sensitivity analyses is performed to point out the governing parameters for the wetland hydraulics. The analysis of future wetlands is carried out using the hydrological model system Mike SHE. Mike SHE has been used to describe the near-surface hydrology for a regional model area in Forsmark. Three types of areas have been chosen. Today's lake Bolundfjaerden is because of its shallow depth likely to develop into a mire in the future. As it is situated in the downstream part of the regional model area, the runoff to the lake from upstream surface water system is significant. Lake Eckarfjaerden is situated in the upstream part of the catchment at a higher altitude and with a smaller inflow. Lake Puttan is situated above a planned layout of the repository and has a potential to receive discharges from a repository. It also lies in the downstream part of a large discharge area. The topography of the future mires is assumed to be flat, up to today's mean water level in each lake. To transport the surface runoff through the wetland, streams or water courses are assumed to form within the peat. The analyses of future wetlands in the Forsmark area show that the hydraulic conditions that exists today will somewhat alter as the peat is formed. For Bolundsfjaerden, where there during present conditions are weak discharge areas, a recharge area has formed during the summer. This can be explained by the amount of surface water that forms on the surface which increases the head elevation in the upper soil layers. The same holds for Eckarfjaerden, while Puttan after the peat has developed still is a discharge area due to its naturally strong discharge position close to the sea. Different vegetation and development stages for the peat have been

Modelling of Transport of Radioactive Substances in the Primary Circuit of Water Cooled Reactors

International Nuclear Information System (INIS)

2012-03-01

Since the beginning of the development of water cooled nuclear power reactors, it has been known that the materials in contact with the water release some of their corrosion products into the water. As a consequence, some of the corrosion products are neutron-activated while in the reactor core and then create a gamma radiation field when deposited outside the core. These radiation fields are hazardous to the inspection, maintenance and operating staff in the power plant and therefore must be minimized. Many methods have been developed to control these radiation fields, such as the proper selection of materials and surface finishing technologies at the design stage, operating and shutdown water chemistry optimization, and the application of different decontamination methods. The need to understand the causes of this radioactivity transport has resulted in many mathematical models to describe the transport, irradiation and deposition of the radioactive corrosion products out of the core. Early models were empirical descriptions of the transport, irradiation and deposition steps, and these models allowed analytical solution of the resulting differential equations. As the mechanisms responsible for radioactivity transport gradually became better understood, more precise models of the mechanisms were made. Computer codes to solve the equations describing these models are necessary. Accurate codes are invaluable design tools for carrying out cost-benefit analysis during materials selection, for estimating shielding thicknesses and for evaluating water chemistry specifications, for example. Such codes are also useful in operating plants to predict radiation fields at specific locations where shielding may be required during a maintenance shutdown, for example, when control of radiation dose to staff is essential. To complement the previous work of the International Atomic Energy Agency (IAEA) to improve the mechanistic understanding of radioactivity transport, a

Modeling Coupled Water and Heat Transport in the Root Zone of Winter Wheat under Non-Isothermal Conditions

Directory of Open Access Journals (Sweden)

Rong Ren

2017-04-01

Full Text Available Temperature is an integral part of soil quality in terms of moisture content; coupling between water and heat can render a soil fertile, and plays a role in water conservation. Although it is widely recognized that both water and heat transport are fundamental factors in the quantification of soil mass and energy balance, their computation is still limited in most models or practical applications in the root zone under non-isothermal conditions. This research was conducted to: (a implement a fully coupled mathematical model that contains the full coupled process of soil water and heat transport with plants focused on the influence of temperature gradient on soil water redistribution and on the influence of change in soil water movement on soil heat flux transport; (b verify the mathematical model with detailed field monitoring data; and (c analyze the accuracy of the model. Results show the high accuracy of the model in predicting the actual changes in soil water content and temperature as a function of time and soil depth. Moreover, the model can accurately reflect changes in soil moisture and heat transfer in different periods. With only a few empirical parameters, the proposed model will serve as guide in the field of surface irrigation.

Modeling ground water flow and radioactive transport in a fractured aquifer

International Nuclear Information System (INIS)

Pohll, G.; Hassan, A.E.; Chapman, J.B.; Papelis, C.; Andricevic, R.

1999-01-01

Three-dimensional numerical modeling is used to characterize ground water flow and contaminant transport at the Shoal nuclear test site in north-central Nevada. The fractured rock aquifer at the site is modeled using an equivalent porous medium approach. Field data are used to characterize the fracture system into classes: large, medium, and no/small fracture zones. Hydraulic conductivities are assigned based on discrete interval measurements. Contaminants from the Shoal test are assumed to all be located within the cavity. Several challenging issues are addressed in this study. Radionuclides are apportioned between surface deposits and volume deposits in nuclear melt glass, based on their volatility and previous observations. Surface-deposited radionuclides are released hydraulically after equilibration of the cavity with the surrounding ground water system, and as a function of ground water flow through the higher-porosity cavity into the low-porosity surrounding aquifer. Processes that are modeled include the release functions, retardation, radioactive decay, prompt injection, and in growth of daughter products. Prompt injection of radionuclides away from the cavity is found to increase the arrival of mass at the control plane but is not found to significantly impact calculated concentrations due to increased spreading. Behavior of the other radionuclides is affected by the slow chemical release and retardation behavior. The transport calculations are sensitive to many flow and transport parameters. Most important are the heterogeneity of the flow field and effective porosity. The effect of porosity in radioactive decay is crucial and has not been adequately addressed in the literature. For reactive solutes, retardation and the glass dissolution rate are also critical

Modeling the effects of different irrigation water salinity on soil water movement, uptake and multicomponent solute transport

Science.gov (United States)

Lekakis, E. H.; Antonopoulos, V. Z.

2015-11-01

Simulation models can be important tools for analyzing and managing irrigation, soil salinization or crop production problems. In this study a mathematical model that describes the water movement and mass transport of individual ions (Ca2+, Mg2+ and Na+) and overall soil salinity by means of the soil solution electrical conductivity, is used. The mass transport equations of Ca2+, Mg2+ and Na+ have been incorporated as part of the integrated model WANISIM and the soil salinity was computed as the sum of individual ions. The model was calibrated and validated against field data, collected during a three year experiment in plots of maize, irrigated with three different irrigation water qualities, at Thessaloniki area in Northern Greece. The model was also used to evaluate salinization and sodification hazards by the use of irrigation water with increasing electrical conductivity of 0.8, 3.2 and 6.4 dS m-1, while maintaining a ratio of Ca2+:Mg2+:Na+ equal to 3:3:2. The qualitative and quantitative procedures for results evaluation showed that there was good agreement between the simulated and measured values of the water content, overall salinity and the concentration of individual soluble cations, at two soil layers (0-35 and 35-75 cm). Nutrient uptake was also taken into account. Locally available irrigation water (ECiw = 0.8 dS m-1) did not cause soil salinization or sodification. On the other hand, irrigation water with ECiw equal to 3.2 and 6.4 dS m-1 caused severe soil salinization, but not sodification. The rainfall water during the winter seasons was not sufficient to leach salts below the soil profile of 110 cm. The modified version of model WANISIM is able to predict the effects of irrigation with saline waters on soil and plant growth and it is suitable for irrigation management in areas with scarce and low quality water resources.

Heat and Water Transport in Soils and Across the Soil-Atmosphere Interface: Comparison of Model Concepts

DEFF Research Database (Denmark)

Vanderborght, Jan; Smits, Kathleen; Mosthaf, Klaus

Evaporation from the soil surface represents a water flow and transport process in a porous medium that is coupled with free air flow and with heat fluxes in the system. We give an overview of different model concepts that are used to describe this process. These range from non-isothermal two......-phase flow two-component transport in the porous medium that is coupled with one-phase flow two-component transport in the free air to isothermal water flow in the porous with upper boundary conditions defined by a potential evaporation flux when available energy and transfer to the free air flow...... models were found. The effect of vapor flow in the porous medium on cumulative evaporation could be evaluated using the desorptivity, Sevap, which represents a weighted average of liquid and vapor diffusivity over the range of soil water contents between the soil surface water content and the initial...

Modeling of water flow and solute transport in unsaturated heterogeneous fields

International Nuclear Information System (INIS)

Bresler, E.; Dagan, G.

1982-01-01

A comprehensive model which considers dispersive solute transport, nonsteady moisture flow regimes and complex boundary conditions is described. The main assumptions are: vertical flow; spatial variability which is associated with the saturated hydraulic conductivity K/sub s/ occurs in the horizontal plane, but is constant in the profile, and has a lognormal probability distribution function (PDF); deterministic recharge and solute concentration are applied during infiltration; the soil is at uniform water content and salt concentration prior to infiltration. The problem is to solve, for arbitrary K/sub s/, the Richards' equation of flow simultaneously with the diffusion-convection equation for salt transport, with the boundary and initial conditions appropriate to infiltration-redistribution. Once this is achieved, the expectation and variance of various quantities of interest (solute concentration, moisture content) are obtained by using the statistical averaging procedure and the given PDF of K/sub s/. Since the solution of Richards' equation for the infiltration-redistribution cycle is extremely difficult (for a given K/sub s/), an approxiate solution is derived by using the concept of piston flow type wetting fronts. Similarly, accurate numerical solutions are used as input for the same statistical averaging procedure. The stochastic model is applied to two spatially variable soils by using both accurate numerical solutions and the simplified water and salt transport models. A comparison between the results shows that the approximate simplified models lead to quite accurate values of the expectations and variances of the flow variables for the entire field. It is suggested that in spatially variable fields, stochastic modeling represents the actual flow phenomena realistically, and provides the main statistical moments by using simplified flow models which can be used with confidence in applications

Eddy transport of water vapor in the Martian atmosphere

Science.gov (United States)

Murphy, J. R.; Haberle, Robert M.

1993-01-01

Viking orbiter measurements of the Martian atmosphere suggest that the residual north polar water-ice cap is the primary source of atmospheric water vapor, which appears at successively lower northern latitudes as the summer season progresses. Zonally symmetric studies of water vapor transport indicate that the zonal mean meridional circulation is incapable of transporting from north polar regions to low latitudes the quantity of water vapor observed. This result has been interpreted as implying the presence of nonpolar sources of water. Another possibility is the ability of atmospheric wave motions, which are not accounted for in a zonally symmetric framework, to efficiently accomplish the transport from a north polar source to the entirety of the Northern Hemisphere. The ability or inability of the full range of atmospheric motions to accomplish this transport has important implications regarding the questions of water sources and sinks on Mars: if the full spectrum of atmospheric motions proves to be incapable of accomplishing the transport, it strengthens arguments in favor of additional water sources. Preliminary results from a three dimensional atmospheric dynamical/water vapor transport numerical model are presented. The model accounts for the physics of a subliming water-ice cap, but does not yet incorporate recondensation of this sublimed water. Transport of vapor away from this water-ice cap in this three dimensional framework is compared with previously obtained zonally symmetric (two dimensional) results to quantify effects of water vapor transport by atmospheric eddies.

Management-oriented sensitivity analysis for pesticide transport in watershed-scale water quality modeling using SWAT.

Science.gov (United States)

Luo, Yuzhou; Zhang, Minghua

2009-12-01

The Soil and Water Assessment Tool (SWAT) was calibrated for hydrology conditions in an agricultural watershed of Orestimba Creek, California, and applied to simulate fate and transport of two organophosphate pesticides chlorpyrifos and diazinon. The model showed capability in evaluating pesticide fate and transport processes in agricultural fields and instream network. Management-oriented sensitivity analysis was conducted by applied stochastic SWAT simulations for pesticide distribution. Results of sensitivity analysis identified the governing processes in pesticide outputs as surface runoff, soil erosion, and sedimentation in the study area. By incorporating sensitive parameters in pesticide transport simulation, effects of structural best management practices (BMPs) in improving surface water quality were demonstrated by SWAT modeling. This study also recommends conservation practices designed to reduce field yield and in-stream transport capacity of sediment, such as filter strip, grassed waterway, crop residue management, and tailwater pond to be implemented in the Orestimba Creek watershed.

Modeling the transport of hydrogen in the primary coolant of pressurized heavy water reactors

International Nuclear Information System (INIS)

Subramanian, H.; Velmurugan, S.; Narasimhan, S.V.; Jain, A.K.; Dash, S.C.

2008-01-01

Heavy water (D 2 O) is used in primary heat transport systems of PHWRs. To suppress the radiolysis of heavy water and to control oxygen, hydrogen is added at regular intervals to the primary heat transport system. The added hydrogen finds it way to the heavy water storage tank after passing through the bleed condenser. Owing to the different temperatures and two phase region present in these systems, hydrogen gets redistributed. It is important to know the concentration of dissolved hydrogen in these regions in order to ensure a steady state dissolved hydrogen concentration in the primary system. Different power stations report variations in the frequency and quantity of hydrogen added to achieve the prescribed steady state level. This paper makes an attempt to account for the inventory of hydrogen and model its transport in PHT system. (author)

Review of ground-water flow and transport models in the unsaturated zone

Energy Technology Data Exchange (ETDEWEB)

Oster, C.A.

1982-11-01

Models of partially saturated flow and transport in porous media have application in the analysis of existing as well as future low-level radioactive waste facilities located above the water table. An extensive literature search along with telephone and mail correspondence with recognized leading experts in the field, was conducted to identify computer models suitable for studies of low-level radioactive waste facilities located in the unsaturated zone. Fifty-five existing models were identified as potentially useful. Ten of these models were selected for further examination. This report contains a statement of the ground-water flow-contaminant transport problem, a discussion of those methods used to reduce the physical problem to a computer model, a brief discussion about the data requirements of these models. The procedure used to select the ten codes for further discussion is given, along with a list of these models. Finally, the Appendices contain the data about the fifty-five codes examined. Specifically Appendix D contains the detailed discussion of each of the ten selected codes. Included in each discussion are such items which a potential user requires in determining whether the code is suitable for his applications. Appendix E contains brief summary information about each of the fifty-five codes. Included in the summaries are identification data, authors, pertinent references, and model type.

Review of ground-water flow and transport models in the unsaturated zone

International Nuclear Information System (INIS)

Oster, C.A.

1982-11-01

Models of partially saturated flow and transport in porous media have application in the analysis of existing as well as future low-level radioactive waste facilities located above the water table. An extensive literature search along with telephone and mail correspondence with recognized leading experts in the field, was conducted to identify computer models suitable for studies of low-level radioactive waste facilities located in the unsaturated zone. Fifty-five existing models were identified as potentially useful. Ten of these models were selected for further examination. This report contains a statement of the ground-water flow-contaminant transport problem, a discussion of those methods used to reduce the physical problem to a computer model, a brief discussion about the data requirements of these models. The procedure used to select the ten codes for further discussion is given, along with a list of these models. Finally, the Appendices contain the data about the fifty-five codes examined. Specifically Appendix D contains the detailed discussion of each of the ten selected codes. Included in each discussion are such items which a potential user requires in determining whether the code is suitable for his applications. Appendix E contains brief summary information about each of the fifty-five codes. Included in the summaries are identification data, authors, pertinent references, and model type

Inelastic cross-sections for electron transport in liquid water: a comparison of dielectric models

International Nuclear Information System (INIS)

Emfietzoglou, D.

2003-01-01

Various methodologies for constructing inelastic cross-sections for low-energy (<10 keV) electron transport in liquid water are presented and compared. They are all based on an optical-data model which provides the dependence on energy loss, and a dispersion algorithm which incorporates the momentum-transfer dependence. A Drude dielectric model was used to analytically represent the optical data. Various dispersion schemes were examined: the Bethe approximation, the δ-oscillator models of Ashley and Liljequist, and two forms of Ritchie's extended-Drude model. They all have been used in Monte-Carlo (MC) codes for analog electron transport in the condensed phase. Results in the form of differential and total inelastic cross-sections are presented. Where possible, comparisons with results of other studies are made. It was found that, despite the application of general constraints (e.g. sum rules), the optical model has a notable influence on the single-collision energy loss spectrum. In addition, both the shape and peak position of the total and differential cross-section distributions depend strongly on the dispersion model adopted. The work is particularly relevant to the development of event-by-event MC transport codes for liquid water, as well as, to the calculations of stopping-powers below the range of applicability of Bethe's formula

Management-oriented sensitivity analysis for pesticide transport in watershed-scale water quality modeling using SWAT

International Nuclear Information System (INIS)

Luo Yuzhou; Zhang Minghua

2009-01-01

The Soil and Water Assessment Tool (SWAT) was calibrated for hydrology conditions in an agricultural watershed of Orestimba Creek, California, and applied to simulate fate and transport of two organophosphate pesticides chlorpyrifos and diazinon. The model showed capability in evaluating pesticide fate and transport processes in agricultural fields and instream network. Management-oriented sensitivity analysis was conducted by applied stochastic SWAT simulations for pesticide distribution. Results of sensitivity analysis identified the governing processes in pesticide outputs as surface runoff, soil erosion, and sedimentation in the study area. By incorporating sensitive parameters in pesticide transport simulation, effects of structural best management practices (BMPs) in improving surface water quality were demonstrated by SWAT modeling. This study also recommends conservation practices designed to reduce field yield and in-stream transport capacity of sediment, such as filter strip, grassed waterway, crop residue management, and tailwater pond to be implemented in the Orestimba Creek watershed. - Selected structural BMPs are recommended for reducing loads of OP pesticides.

Management-oriented sensitivity analysis for pesticide transport in watershed-scale water quality modeling using SWAT

Energy Technology Data Exchange (ETDEWEB)

Luo Yuzhou [University of California, Davis, CA 95616 (United States); Wenzhou Medical College, Wenzhou 325035 (China); Zhang Minghua, E-mail: mhzhang@ucdavis.ed [University of California, Davis, CA 95616 (United States); Wenzhou Medical College, Wenzhou 325035 (China)

2009-12-15

The Soil and Water Assessment Tool (SWAT) was calibrated for hydrology conditions in an agricultural watershed of Orestimba Creek, California, and applied to simulate fate and transport of two organophosphate pesticides chlorpyrifos and diazinon. The model showed capability in evaluating pesticide fate and transport processes in agricultural fields and instream network. Management-oriented sensitivity analysis was conducted by applied stochastic SWAT simulations for pesticide distribution. Results of sensitivity analysis identified the governing processes in pesticide outputs as surface runoff, soil erosion, and sedimentation in the study area. By incorporating sensitive parameters in pesticide transport simulation, effects of structural best management practices (BMPs) in improving surface water quality were demonstrated by SWAT modeling. This study also recommends conservation practices designed to reduce field yield and in-stream transport capacity of sediment, such as filter strip, grassed waterway, crop residue management, and tailwater pond to be implemented in the Orestimba Creek watershed. - Selected structural BMPs are recommended for reducing loads of OP pesticides.

A New Scheme for Considering Soil Water-Heat Transport Coupling Based on Community Land Model: Model Description and Preliminary Validation

Science.gov (United States)

Wang, Chenghai; Yang, Kai

2018-04-01

Land surface models (LSMs) have developed significantly over the past few decades, with the result that most LSMs can generally reproduce the characteristics of the land surface. However, LSMs fail to reproduce some details of soil water and heat transport during seasonal transition periods because they neglect the effects of interactions between water movement and heat transfer in the soil. Such effects are critical for a complete understanding of water-heat transport within a soil thermohydraulic regime. In this study, a fully coupled water-heat transport scheme (FCS) is incorporated into the Community Land Model (version 4.5) to replaces its original isothermal scheme, which is more complete in theory. Observational data from five sites are used to validate the performance of the FCS. The simulation results at both single-point and global scale show that the FCS improved the simulation of soil moisture and temperature. FCS better reproduced the characteristics of drier and colder surface layers in arid regions by considering the diffusion of soil water vapor, which is a nonnegligible process in soil, especially for soil surface layers, while its effects in cold regions are generally inverse. It also accounted for the sensible heat fluxes caused by liquid water flow, which can contribute to heat transfer in both surface and deep layers. The FCS affects the estimation of surface sensible heat (SH) and latent heat (LH) and provides the details of soil heat and water transportation, which benefits to understand the inner physical process of soil water-heat migration.

Radionuclide Transport Models Under Ambient Conditions

International Nuclear Information System (INIS)

Moridis, G.; Hu, Q.

2000-01-01

The purpose of this Analysis/Model Report (AMR) is to evaluate (by means of 2-D semianalytical and 3-D numerical models) the transport of radioactive solutes and colloids in the unsaturated zone (UZ) under ambient conditions from the potential repository horizon to the water table at Yucca Mountain (YM), Nevada. This is in accordance with the ''AMR Development Plan U0060, Radionuclide Transport Models Under Ambient Conditions'' (CRWMS M and O 1999a). This AMR supports the UZ Flow and Transport Process Model Report (PMR). This AMR documents the UZ Radionuclide Transport Model (RTM). This model considers: the transport of radionuclides through fractured tuffs; the effects of changes in the intensity and configuration of fracturing from hydrogeologic unit to unit; colloid transport; physical and retardation processes and the effects of perched water. In this AMR they document the capabilities of the UZ RTM, which can describe flow (saturated and/or unsaturated) and transport, and accounts for (a) advection, (b) molecular diffusion, (c) hydrodynamic dispersion (with full 3-D tensorial representation), (d) kinetic or equilibrium physical and/or chemical sorption (linear, Langmuir, Freundlich or combined), (e) first-order linear chemical reaction, (f) radioactive decay and tracking of daughters, (g) colloid filtration (equilibrium, kinetic or combined), and (h) colloid-assisted solute transport. Simulations of transport of radioactive solutes and colloids (incorporating the processes described above) from the repository horizon to the water table are performed to support model development and support studies for Performance Assessment (PA). The input files for these simulations include transport parameters obtained from other AMRs (i.e., CRWMS M and O 1999d, e, f, g, h; 2000a, b, c, d). When not available, the parameter values used are obtained from the literature. The results of the simulations are used to evaluate the transport of radioactive solutes and colloids, and

Anthropogenic contamination of a phreatic drinking water winning: 3-dimensional reactive transport modelling

NARCIS (Netherlands)

Griffioen, J.|info:eu-repo/dai/nl/091129265; van der Grift, B.|info:eu-repo/dai/nl/373433484; Maas, D.; van den Brink, C.|info:eu-repo/dai/nl/187443416; Zaadnoordijk, J. W.

2003-01-01

Groundwater is contaminated at the regional scale by agricultural activities and atmospheric deposition. A 3-D transport model was set-up for a phreatic drinking water winning, where the groundwater composition was monitored accurately. The winning is situated at an area with unconsolidated

A proposed strategy for the validation of ground-water flow and solute transport models

International Nuclear Information System (INIS)

Davis, P.A.; Goodrich, M.T.

1991-01-01

Ground-water flow and transport models can be thought of as a combination of conceptual and mathematical models and the data that characterize a given system. The judgment of the validity or invalidity of a model depends both on the adequacy of the data and the model structure (i.e., the conceptual and mathematical model). This report proposes a validation strategy for testing both components independently. The strategy is based on the philosophy that a model cannot be proven valid, only invalid or not invalid. In addition, the authors believe that a model should not be judged in absence of its intended purpose. Hence, a flow and transport model may be invalid for one purpose but not invalid for another. 9 refs

Modified finite element transport model, FETRA, for sediment and radionuclide migration in open coastal waters

International Nuclear Information System (INIS)

Onishi, Y.; Arnold, E.M.; Mayer, D.W.

1979-08-01

The finite element model, FETRA, simulates transport of sediment and radionuclides (and other contaminants, such as heavy metals, pesticides, and other toxic substances) in surface water bodies. The model is an unsteady, two-dimensional (longitudinal and lateral) model which consists of the following three submodels coupled to include sediment-contaminant interactions: (1) sediment transport submodel, (2) dissolved contaminant transport submodel, and (3) particulate contaminant (contaminant adsorbed by sediment) transport submodel. Under the current phase of the study, FETRA was modified to include sediment-wave interaction in order to extend the applicability of the model to coastal zones and large lakes (e.g., the Great Lakes) where wave actions can be one of the dominant mechanisms to transport sediment and toxic contaminant. FETRA was further modified to handle both linear and quadratic approximations to velocity and depth distributions in order to be compatible with various finite element hydrodynamic models (e.g., RMA II and CAFE) which supply hydrodynamic input data to FETRA. The next step is to apply FETRA to coastal zones to simulate transport of sediment and radionuclides with their interactions in order to test and verify the model under marine and large lacustrine environments

Sediment transport modelling in a distributed physically based hydrological catchment model

Directory of Open Access Journals (Sweden)

M. Konz

2011-09-01

Full Text Available Bedload sediment transport and erosion processes in channels are important components of water induced natural hazards in alpine environments. A raster based distributed hydrological model, TOPKAPI, has been further developed to support continuous simulations of river bed erosion and deposition processes. The hydrological model simulates all relevant components of the water cycle and non-linear reservoir methods are applied for water fluxes in the soil, on the ground surface and in the channel. The sediment transport simulations are performed on a sub-grid level, which allows for a better discretization of the channel geometry, whereas water fluxes are calculated on the grid level in order to be CPU efficient. Several transport equations as well as the effects of an armour layer on the transport threshold discharge are considered. Flow resistance due to macro roughness is also considered. The advantage of this approach is the integrated simulation of the entire basin runoff response combined with hillslope-channel coupled erosion and transport simulation. The comparison with the modelling tool SETRAC demonstrates the reliability of the modelling concept. The devised technique is very fast and of comparable accuracy to the more specialised sediment transport model SETRAC.

Water and solute transport across the peritoneal membrane.

Science.gov (United States)

Morelle, Johann; Devuyst, Olivier

2015-09-01

We review the molecular mechanisms of peritoneal transport and discuss how a better understanding of these mechanisms is relevant for dialysis therapy. Peritoneal dialysis involves diffusion and osmosis through the highly vascularized peritoneal membrane. Computer simulations, expression studies and functional analyses in Aqp1 knockout mice demonstrated the critical role of the water channel aquaporin-1 (AQP1) in water removal during peritoneal dialysis. Pharmacologic regulation of AQP1, either through increased expression or gating, is associated with increased water transport in rodent models of peritoneal dialysis. Water transport is impaired during acute peritonitis, despite unchanged expression of AQP1, resulting from the increased microvascular area that dissipates the osmotic gradient across the membrane. In long-term peritoneal dialysis patients, the fibrotic interstitium also impairs water transport, resulting in ultrafiltration failure. Recent data suggest that stroke and drug intoxications might benefit from peritoneal dialysis and could represent novel applications of peritoneal transport in the future. A better understanding of the regulation of osmotic water transport across the peritoneum offers novel insights into the role of water channels in microvascular endothelia, the functional importance of structural changes in the peritoneal interstitium and the transport of water and solutes across biological membranes in general.

Some analytic diagnostic models for transport processes in estuarine and coastal waters; Algunos modelos analiticos de diagnostico para procesos de transporte en estuarios y aguas costeras

Energy Technology Data Exchange (ETDEWEB)

Suarez Antola, R [Industry Energy and Mining Ministry, National Direction of Nuclear Technology, Montevideo (Uruguay)

2001-03-01

Advection and dispersion processes in estuarine and coastal waters are briefly reviewed. Beginning from the basic macroscopic equations of transport for a substance diluted or suspended in the considered body of water,several levels of filtering in time and space are described and applied to obtain suitable diagnostic mathematical models both with scale effects and gaussian.The solutions of the aforementioned models,for initial distributions and boundary conditions with enough symmetry,are discussed, as well as their applications to a parameter characterization of the transport properties of the receiving body of water.

Water-Level Data Analysis for the Saturated Zone Site-Scale Flow and Transport Model

International Nuclear Information System (INIS)

K. Rehfeldt

2004-01-01

This report is an updated analysis of water-level data performed to provide the ''Saturated Zone Site-Scale Flow Model'' (BSC 2004 [DIRS 170037]) (referred to as the saturated zone (SZ) site-scale flow model or site-scale SZ flow model in this report) with the configuration of the potentiometric surface, target water-level data, and hydraulic gradients for calibration of groundwater flow models. This report also contains an expanded discussion of uncertainty in the potentiometric-surface map. The analysis of the potentiometric data presented in Revision 00 of this report (USGS 2001 [DIRS 154625]) provides the configuration of the potentiometric surface, target heads, and hydraulic gradients for the calibration of the SZ site-scale flow model (BSC 2004 [DIRS 170037]). Revision 01 of this report (USGS 2004 [DIRS 168473]) used updated water-level data for selected wells through the year 2000 as the basis for estimating water-level altitudes and the potentiometric surface in the SZ site-scale flow and transport model domain based on an alternative interpretation of perched water conditions. That revision developed computer files containing: Water-level data within the model area (DTN: GS010908312332.002); A table of known vertical head differences (DTN: GS010908312332.003); and A potentiometric-surface map (DTN: GS010608312332.001) using an alternative concept from that presented by USGS (2001 [DIRS 154625]) for the area north of Yucca Mountain. The updated water-level data presented in USGS (2004 [DIRS 168473]) include data obtained from the Nye County Early Warning Drilling Program (EWDP) Phases I and II and data from Borehole USW WT-24. This document is based on Revision 01 (USGS 2004 [DIRS 168473]) and expands the discussion of uncertainty in the potentiometric-surface map. This uncertainty assessment includes an analysis of the impact of more recent water-level data and the impact of adding data from the EWDP Phases III and IV wells. In addition to being utilized

Water and sediment transport modeling of a large temporary river basin in Greece.

Science.gov (United States)

Gamvroudis, C; Nikolaidis, N P; Tzoraki, O; Papadoulakis, V; Karalemas, N

2015-03-01

The objective of this research was to study the spatial distribution of runoff and sediment transport in a large Mediterranean watershed (Evrotas River Basin) consisting of temporary flow tributaries and high mountain areas and springs by focusing on the collection and use of a variety of data to constrain the model parameters and characterize hydrologic and geophysical processes at various scales. Both monthly and daily discharge data (2004-2011) and monthly sediment concentration data (2010-2011) from an extended monitoring network of 8 sites were used to calibrate and validate the Soil and Water Assessment Tool (SWAT) model. In addition flow desiccation maps showing wet and dry aquatic states obtained during a dry year were used to calibrate the simulation of low flows. Annual measurements of sediment accumulation in two reaches were used to further calibrate the sediment simulation. Model simulation of hydrology and sediment transport was in good agreement with field observations as indicated by a variety of statistical measures used to evaluate the goodness of fit. A water balance was constructed using a 12 year long (2000-2011) simulation. The average precipitation of the basin for this period was estimated to be 903 mm yr(-1). The actual evapotranspiration was 46.9% (424 mm yr(-1)), and the total water yield was 13.4% (121 mm yr(-1)). The remaining 33.4% (302 mm yr(-1)) was the amount of water that was lost through the deep groundwater of Taygetos and Parnonas Mountains to areas outside the watershed and for drinking water demands (6.3%). The results suggest that the catchment has on average significant water surplus to cover drinking water and irrigation demands. However, the situation is different during the dry years, where the majority of the reaches (85% of the river network are perennial and temporary) completely dry up as a result of the limited rainfall and the substantial water abstraction for irrigation purposes. There is a large variability in the

Mathematical model formulation and validation of water and solute transport in whole hamster pancreatic islets.

Science.gov (United States)

Benson, James D; Benson, Charles T; Critser, John K

2014-08-01

Optimization of cryopreservation protocols for cells and tissues requires accurate models of heat and mass transport. Model selection often depends on the configuration of the tissue. Here, a mathematical and conceptual model of water and solute transport for whole hamster pancreatic islets has been developed and experimentally validated incorporating fundamental biophysical data from previous studies on individual hamster islet cells while retaining whole-islet structural information. It describes coupled transport of water and solutes through the islet by three methods: intracellularly, intercellularly, and in combination. In particular we use domain decomposition techniques to couple a transmembrane flux model with an interstitial mass transfer model. The only significant undetermined variable is the cellular surface area which is in contact with the intercellularly transported solutes, Ais. The model was validated and Ais determined using a 3×3 factorial experimental design blocked for experimental day. Whole islet physical experiments were compared with model predictions at three temperatures, three perfusing solutions, and three islet size groups. A mean of 4.4 islets were compared at each of the 27 experimental conditions and found to correlate with a coefficient of determination of 0.87±0.06 (mean ± SD). Only the treatment variable of perfusing solution was found to be significant (p<0.05). We have devised a model that retains much of the intrinsic geometric configuration of the system, and thus fewer laboratory experiments are needed to determine model parameters and thus to develop new optimized cryopreservation protocols. Additionally, extensions to ovarian follicles and other concentric tissue structures may be made. Copyright © 2014 Elsevier Inc. All rights reserved.

Liquid water transport mechanism in the gas diffusion layer

Energy Technology Data Exchange (ETDEWEB)

Zhou, P.; Wu, C.W. [State Key Laboratory of Structure Analysis for Industrial Equipment, Department of Engineering Mechanics, Faculty of Vehicle Engineering and Mechanics, Dalian University of Technology, Dalian 116024 (China)

2010-03-01

We developed an equivalent capillary model of a microscale fiber-fence structure to study the microscale evolution and transport of liquid in a porous media and to reveal the basic principles of water transport in gas diffusion layer (GDL). Analytical solutions using the model show that a positive hydraulic pressure is needed to drive the liquid water to penetrate through the porous GDL even consisting of the hydrophilic fibers. Several possible contributions for the water configuration, such as capillary pressure, gravity, vapor condensation, wettability and microstructures of the GDL, are discussed using the lattice Boltzmann method (LBM). It is found that the distribution manners of the fibers and the spatial mixed-wettability in the GDL also play an important role in the transport of liquid water. (author)

Using a simple model for water and nitrogen transport in soil in the practical works of Horticulture

Directory of Open Access Journals (Sweden)

A. Lidón

2017-08-01

Full Text Available Simulation models for the transport of water and nitrogen in the soil are useful tools for evaluating the consequences  of  different  crop  management  practices  without  waiting  until  the  end  of  the  crop  cycle.  Particularly,  simple compartmental models for the transport of water and nitrogen are based on the solution of mass balance equations for  the  water  and  a  system  of  ordinary  differential  equations  for  the  nitrogen  cycle.  In this work, these models are used to evaluate different possible scenarios of irrigation and nitrogen fertilization in a cauliflower crop, as a practical work for the students of Horticulture course. The results show that different irrigation and fertilization strategies lead to different results for the nitrate leaching, water drainage and nitrogen uptake.

CFD Model of Water Droplet Transport for ISS Hygiene Activity

Science.gov (United States)

Son, Chang H.

2011-01-01

The goal of the study is to assess the impacts of free water propagation in the Waste and Hygiene Compartment (WHC). Free water can be generated inside the WHC in small quantities due to crew hygiene activity. To mitigate potential impact of free water in Node 3 cabin the WHC doorway is enclosed by a waterproof bump-out, Kabin, with openings at the top and bottom. At the overhead side of the rack, there is a screen that prevents large drops of water from exiting. However, as the avionics fan in the WHC causes airflow toward the deck side of the rack, small quantities of free water may exit at the bottom of the Kabin. A Computational Fluid Dynamics (CFD) analysis of Node 3 cabin airflow made possible to identify the paths of water transport. The Node 3 airflow was computed for several ventilation scenarios. To simulate the droplet transport the Lagrangian discrete phase approach was used. Various initial droplet distributions were considered in the study. The droplet diameter was varied in the range of 2-20 mm. The results of the computations showed that most of the drops fall to the rack surface not far from the WHC curtain. The probability of the droplet transport to the adjacent rack surface with electronic equipment was predicted.

A Process-Based Transport-Distance Model of Aeolian Transport

Science.gov (United States)

Naylor, A. K.; Okin, G.; Wainwright, J.; Parsons, A. J.

2017-12-01

We present a new approach to modeling aeolian transport based on transport distance. Particle fluxes are based on statistical probabilities of particle detachment and distributions of transport lengths, which are functions of particle size classes. A computational saltation model is used to simulate transport distances over a variety of sizes. These are fit to an exponential distribution, which has the advantages of computational economy, concordance with current field measurements, and a meaningful relationship to theoretical assumptions about mean and median particle transport distance. This novel approach includes particle-particle interactions, which are important for sustaining aeolian transport and dust emission. Results from this model are compared with results from both bulk- and particle-sized-specific transport equations as well as empirical wind tunnel studies. The transport-distance approach has been successfully used for hydraulic processes, and extending this methodology from hydraulic to aeolian transport opens up the possibility of modeling joint transport by wind and water using consistent physics. Particularly in nutrient-limited environments, modeling the joint action of aeolian and hydraulic transport is essential for understanding the spatial distribution of biomass across landscapes and how it responds to climatic variability and change.

Modeling Groundwater-Surface Water Interaction and Contaminant Transport of Chlorinated Solvent Contaminated Site

Science.gov (United States)

Yimer Ebrahim, Girma; Jonoski, Andreja; van Griensven, Ann; Dujardin, Juliette; Baetelaan, Okke; Bronders, Jan

2010-05-01

Chlorinated-solvent form one of the largest groups of environmental chemicals. Their use and misuse in industry have lead to a large entry of these chemicals into the environment, resulting in widespread dissemination and oftentimes environmental contamination. Chlorinated solvent contamination of groundwater resources has been widely reported. For instance, there has been much interest in the assessment of these contaminant levels and their evolutions with time in the groundwater body below the Vilvoorde-Machelen industrial area (Belgium). The long industrial history of the area has lead to complex patterns of pollution from multiple sources and the site has been polluted to the extent that individual plumes are not definable any more. Understanding of groundwater/surface water interaction is a critical component for determining the fate of contaminant both in streams and ground water due to the fact that groundwater and surface water are in continuous dynamic interaction in the hydrologic cycle. The interaction has practical consequences in the quantity and quality of water in either system in the sense that depletion and/or contamination of one of the system will eventually affect the other one. The transition zone between a stream and its adjacent aquifer referred to as the hyporheic zone plays a critical role in governing contaminant exchange and transformation during water exchange between the two water bodies. The hyporheic zone of Zenne River ( the main receptor ) is further complicated due to the fact that the river banks are artificially trained with sheet piles along its reach extending some 12 m below the surface. This study demonstrates the use of MODFLOW, a widely used modular three-dimensional block-centred finite difference, saturated flow model for simulating the flow and direction of movement of groundwater through aquifer and stream-aquifer interaction and the use of transport model RT3D, a three-dimensional multi-species reactive transport model

Modeling studies of water consumption for transportation fuel options: Hawaii, US-48

Science.gov (United States)

King, C. W.; Webber, M. E.

2011-12-01

There are now major drivers to move from petroleum transportation: moving to low-carbon transport life cycles for climate change mitigation, fuel diversity to reduce reliance on imported oil, and economic concerns regarding the relatively high price of oil ( $100/barrel) and the resulting impact on discretionary income. Unfortunately many transportation fuel alternatives also have some environmental impacts, particularly with regard to water consumption and biodiversity. In this presentation we will discuss the water and energy sustainability struggle ongoing in Hawai'i on the island of Maui with a brief history and discussion of energy and water modeling scenarios. The vast majority of surface water on Maui is diverted via man-made ditches for irrigation on sugar cane plantations. Maui currently allocates between 250 and 300 million gallons per day (Mgal/d) of irrigation water for sugarcane cultivation each day, and it is likely that the island could support a biofuel-focused sugarcane plantation by shifting production focus from raw sugar to ethanol. However, future water availability is likely to be less than existing water availability because Maui is growing, more water is being reserved for environmental purposes, and precipitation levels are on decline for the past two decades and some expect this trend to continue. While Maui residents cannot control precipitation patterns, they can control the levels of increased requirements for instream flow in Maui's streams. The Hawaii State Commission on Water Resource Management (CWRM) sets instream flow standards, and choosing not to restore instream flow could have what many locals consider negative environmental and cultural impacts that must be weighed against the effects of reducing surface water availability for agriculture. Instream flow standards that reduce legal withdrawals for streams that supply irrigation water would reduce the amount of surface water available for biofuel crop irrigation. Environmental

Well-to-Wheels Water Consumption: Tracking the Virtual Flow of Water into Transportation

Science.gov (United States)

Lampert, D. J.; Elgowainy, A.; Hao, C.

2015-12-01

Water and energy resources are fundamental to life on Earth and essential for the production of consumer goods and services in the economy. Energy and water resources are heavily interdependent—energy production consumes water, while water treatment and distribution consume energy. One example of this so-called energy-water nexus is the consumption of water associated with the production of transportation fuels. The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model is an analytical tool that can be used to compare the environmental impacts of different transportation fuels on a consistent basis. In this presentation, the expansion of GREET to perform life cycle water accounting or the "virtual flow" of water into transportation and other energy sectors and the associated implications will be discussed. The results indicate that increased usage of alternative fuels may increase freshwater resource consumption. The increased water consumption must be weighed against the benefits of decreased greenhouse gas and fossil energy consumption. Our analysis highlights the importance of regionality, co-product allocation, and consistent system boundaries when comparing the water intensity of alternative transportation fuel production pathways such as ethanol, biodiesel, compressed natural gas, hydrogen, and electricity with conventional petroleum-based fuels such as diesel and gasoline.

Water-Level Data Analysis for the Saturated Zone Site-Scale Flow and Transport Model

Energy Technology Data Exchange (ETDEWEB)

K. Rehfeldt

2004-10-08

This report is an updated analysis of water-level data performed to provide the ''Saturated Zone Site-Scale Flow Model'' (BSC 2004 [DIRS 170037]) (referred to as the saturated zone (SZ) site-scale flow model or site-scale SZ flow model in this report) with the configuration of the potentiometric surface, target water-level data, and hydraulic gradients for calibration of groundwater flow models. This report also contains an expanded discussion of uncertainty in the potentiometric-surface map. The analysis of the potentiometric data presented in Revision 00 of this report (USGS 2001 [DIRS 154625]) provides the configuration of the potentiometric surface, target heads, and hydraulic gradients for the calibration of the SZ site-scale flow model (BSC 2004 [DIRS 170037]). Revision 01 of this report (USGS 2004 [DIRS 168473]) used updated water-level data for selected wells through the year 2000 as the basis for estimating water-level altitudes and the potentiometric surface in the SZ site-scale flow and transport model domain based on an alternative interpretation of perched water conditions. That revision developed computer files containing: Water-level data within the model area (DTN: GS010908312332.002); A table of known vertical head differences (DTN: GS010908312332.003); and A potentiometric-surface map (DTN: GS010608312332.001) using an alternative concept from that presented by USGS (2001 [DIRS 154625]) for the area north of Yucca Mountain. The updated water-level data presented in USGS (2004 [DIRS 168473]) include data obtained from the Nye County Early Warning Drilling Program (EWDP) Phases I and II and data from Borehole USW WT-24. This document is based on Revision 01 (USGS 2004 [DIRS 168473]) and expands the discussion of uncertainty in the potentiometric-surface map. This uncertainty assessment includes an analysis of the impact of more recent water-level data and the impact of adding data from the EWDP Phases III and IV wells. In

Abstracts of the symposium on unsaturated flow and transport modeling

International Nuclear Information System (INIS)

1982-03-01

Abstract titles are: Recent developments in modeling variably saturated flow and transport; Unsaturated flow modeling as applied to field problems; Coupled heat and moisture transport in unsaturated soils; Influence of climatic parameters on movement of radionuclides in a multilayered saturated-unsaturated media; Modeling water and solute transport in soil containing roots; Simulation of consolidation in partially saturated soil materials; modeling of water and solute transport in unsaturated heterogeneous fields; Fluid dynamics and mass transfer in variably-saturated porous media; Solute transport through soils; One-dimensional analytical transport modeling; Convective transport of ideal tracers in unsaturated soils; Chemical transport in macropore-mesopore media under partially saturated conditions; Influence of the tension-saturated zone on contaminant migration in shallow water regimes; Influence of the spatial distribution of velocities in porous media on the form of solute transport; Stochastic vs deterministic models for solute movement in the field; and Stochastic analysis of flow and solute transport

Mechanisms and modeling development of water transport/phase change in catalyst layers of portion exchange membrane fuel cells

Energy Technology Data Exchange (ETDEWEB)

Xiao, Yexiang [Dept. of Thermal Engineering, Tsinghua University Beijing (China)], email: Yexiang.Xiao@energy.lth.se; Yuan, Jinliang; Sunden, Bengt [Dept. of Energy Sciences, Faculty of Engineering, Lund University (Sweden)], email: Jinliang.yuan@energy.lth.se, email: bengt.sunden@energy.lth.se

2011-07-01

Research on proton exchange membrane fuel cells has shown that incorporation of nanosized catalysts can effectively increase active areas and catalyst activity and make a great contribution to development in performance and catalyst utilization. Multiphase transport processes are as significant and complicated as water generation/transfer processes which occur in nano-structured catalyst layers. A review project has been launched aimed at gaining a comprehensive understanding of the mechanisms of water generation or transport phenomena. It covers catalytic reactions and water-phase change within the catalyst layers. The review proceeds in three main stages: Firstly, it characterizes and reconstructs the nano/micro-structured pores and solid-phases; secondly, it emphasises the importance of sensitive and consistent analysis of various water-phase change and transport schemes; and thirdly, it recommends development of microscopic models for multi-phase transport processes in the pores and the solid phases.

RADIONUCLIDE TRANSPORT MODELS UNDER AMBIENT CONDITIONS

Energy Technology Data Exchange (ETDEWEB)

S. Magnuson

2004-11-01

The purpose of this model report is to document the unsaturated zone (UZ) radionuclide transport model, which evaluates, by means of three-dimensional numerical models, the transport of radioactive solutes and colloids in the UZ, under ambient conditions, from the repository horizon to the water table at Yucca Mountain, Nevada.

Kinetic Theory and Simulation of Single-Channel Water Transport

Science.gov (United States)

Tajkhorshid, Emad; Zhu, Fangqiang; Schulten, Klaus

Water translocation between various compartments of a system is a fundamental process in biology of all living cells and in a wide variety of technological problems. The process is of interest in different fields of physiology, physical chemistry, and physics, and many scientists have tried to describe the process through physical models. Owing to advances in computer simulation of molecular processes at an atomic level, water transport has been studied in a variety of molecular systems ranging from biological water channels to artificial nanotubes. While simulations have successfully described various kinetic aspects of water transport, offering a simple, unified model to describe trans-channel translocation of water turned out to be a nontrivial task.

Measuring and modelling water transport on Skaftafellsheioi, Iceland

NARCIS (Netherlands)

Dijksma, R.; Avis, Lisette

2017-01-01

Areas with thick basaltic aquifers are used for drinking water supply and irrigation purposes, such as the Columbia River Basalt group in northwest USA and the Deccan Traps in India. However, rainfall-runoff processes in these basaltic areas are poorly understood. Cooling joints can transport large

Multicomponent mass transport model: a model for simulating migration of radionuclides in ground water

International Nuclear Information System (INIS)

Washburn, J.F.; Kaszeta, F.E.; Simmons, C.S.; Cole, C.R.

1980-07-01

This report presents the results of the development of a one-dimensional radionuclide transport code, MMT2D (Multicomponent Mass Transport), for the AEGIS Program. Multicomponent Mass Transport is a numerical solution technique that uses the discrete-parcel-random-wald (DPRW) method to directly simulate the migration of radionuclides. MMT1D accounts for: convection;dispersion; sorption-desorption; first-order radioactive decay; and n-membered radioactive decay chains. Comparisons between MMT1D and an analytical solution for a similar problem show that: MMT1D agrees very closely with the analytical solution; MMT1D has no cumulative numerical dispersion like that associated with solution techniques such as finite differences and finite elements; for current AEGIS applications, relatively few parcels are required to produce adequate results; and the power of MMT1D is the flexibility of the code in being able to handle complex problems for which analytical solution cannot be obtained. Multicomponent Mass Transport (MMT1D) codes were developed at Pacific Northwest Laboratory to predict the movement of radiocontaminants in the saturated and unsaturated sediments of the Hanford Site. All MMT models require ground-water flow patterns that have been previously generated by a hydrologic model. This report documents the computer code and operating procedures of a third generation of the MMT series: the MMT differs from previous versions by simulating the mass transport processes in systems with radionuclide decay chains. Although MMT is a one-dimensional code, the user is referred to the documentation of the theoretical and numerical procedures of the three-dimensional MMT-DPRW code for discussion of expediency, verification, and error-sensitivity analysis

Water transport through tall trees: A vertically-explicit, analytical model of xylem hydraulic conductance in stems.

Science.gov (United States)

Couvreur, Valentin; Ledder, Glenn; Manzoni, Stefano; Way, Danielle A; Muller, Erik B; Russo, Sabrina E

2018-05-08

Trees grow by vertically extending their stems, so accurate stem hydraulic models are fundamental to understanding the hydraulic challenges faced by tall trees. Using a literature survey, we showed that many tree species exhibit continuous vertical variation in hydraulic traits. To examine the effects of this variation on hydraulic function, we developed a spatially-explicit, analytical water transport model for stems. Our model allows Huber ratio, stem-saturated conductivity, pressure at 50% loss of conductivity, leaf area, and transpiration rate to vary continuously along the hydraulic path. Predictions from our model differ from a matric flux potential model parameterized with uniform traits. Analyses show that cavitation is a whole-stem emergent property resulting from nonlinear pressure-conductivity feedbacks that, with gravity, cause impaired water transport to accumulate along the path. Because of the compounding effects of vertical trait variation on hydraulic function, growing proportionally more sapwood and building tapered xylem with height, as well as reducing xylem vulnerability only at branch tips while maintaining transport capacity at the stem base, can compensate for these effects. We therefore conclude that the adaptive significance of vertical variation in stem hydraulic traits is to allow trees to grow tall and tolerate operating near their hydraulic limits. This article is protected by copyright. All rights reserved.

Quantification of osmotic water transport in vivo using fluorescent albumin.

Science.gov (United States)

Morelle, Johann; Sow, Amadou; Vertommen, Didier; Jamar, François; Rippe, Bengt; Devuyst, Olivier

2014-10-15

Osmotic water transport across the peritoneal membrane is applied during peritoneal dialysis to remove the excess water accumulated in patients with end-stage renal disease. The discovery of aquaporin water channels and the generation of transgenic animals have stressed the need for novel and accurate methods to unravel molecular mechanisms of water permeability in vivo. Here, we describe the use of fluorescently labeled albumin as a reliable indicator of osmotic water transport across the peritoneal membrane in a well-established mouse model of peritoneal dialysis. After detailed evaluation of intraperitoneal tracer mass kinetics, the technique was validated against direct volumetry, considered as the gold standard. The pH-insensitive dye Alexa Fluor 555-albumin was applied to quantify osmotic water transport across the mouse peritoneal membrane resulting from modulating dialysate osmolality and genetic silencing of the water channel aquaporin-1 (AQP1). Quantification of osmotic water transport using Alexa Fluor 555-albumin closely correlated with direct volumetry and with estimations based on radioiodinated ((125)I) serum albumin (RISA). The low intraperitoneal pressure probably accounts for the negligible disappearance of the tracer from the peritoneal cavity in this model. Taken together, these data demonstrate the appropriateness of pH-insensitive Alexa Fluor 555-albumin as a practical and reliable intraperitoneal volume tracer to quantify osmotic water transport in vivo. Copyright © 2014 the American Physiological Society.

Fluid transport with time on peritoneal dialysis: the contribution of free water transport and solute coupled water transport

NARCIS (Netherlands)

Coester, Annemieke M.; Smit, Watske; Struijk, Dirk G.; Krediet, Raymond T.

2009-01-01

Ultrafiltration in peritoneal dialysis occurs through endothelial water channels (free water transport) and together with solutes across small pores: solute coupled water transport. A review is given of cross-sectional studies and on the results of longitudinal follow-up

Modeling the Liquid Water Transport in the Gas Diffusion Layer for Polymer Electrolyte Membrane Fuel Cells Using a Water Path Network

Directory of Open Access Journals (Sweden)

Dietmar Gerteisen

2013-09-01

Full Text Available In order to model the liquid water transport in the porous materials used in polymer electrolyte membrane (PEM fuel cells, the pore network models are often applied. The presented model is a novel approach to further develop these models towards a percolation model that is based on the fiber structure rather than the pore structure. The developed algorithm determines the stable liquid water paths in the gas diffusion layer (GDL structure and the transitions from the paths to the subsequent paths. The obtained water path network represents the basis for the calculation of the percolation process with low calculation efforts. A good agreement with experimental capillary pressure-saturation curves and synchrotron liquid water visualization data from other literature sources is found. The oxygen diffusivity for the GDL with liquid water saturation at breakthrough reveals that the porosity is not a crucial factor for the limiting current density. An algorithm for condensation is included into the model, which shows that condensing water is redirecting the water path in the GDL, leading to an improved oxygen diffusion by a decreased breakthrough pressure and changed saturation distribution at breakthrough.

Water transport and energy.

Science.gov (United States)

Fricke, Wieland

2017-06-01

Water transport in plants occurs along various paths and is driven by gradients in its free energy. It is generally considered that the mode of transport, being either diffusion or bulk flow, is a passive process, although energy may be required to sustain the forces driving water flow. This review aims at putting water flow at the various organisational levels (cell, organ, plant) in the context of the energy that is required to maintain these flows. In addition, the question is addressed (1) whether water can be transported against a difference in its chemical free energy, 'water potential' (Ψ), through, directly or indirectly, active processes; and (2) whether the energy released when water is flowing down a gradient in its energy, for example during day-time transpiration and cell expansive growth, is significant compared to the energy budget of plant and cell. The overall aim of review is not so much to provide a definite 'Yes' and 'No' to these questions, but rather to stimulate discussion and raise awareness that water transport in plants has its real, associated, energy costs and potential energy gains. © 2016 John Wiley & Sons Ltd.

Modeling Fate and Transport of Rotavirus in Surface Flow by Integrating WEPP and a Pathogen Transport Model

Science.gov (United States)

Bhattarai, R.; Kalita, P. K.; Davidson, P. C.; Kuhlenschmidt, M. S.

2012-12-01

More than 3.5 million people die each year from a water related diseases in this world. Every 20 seconds, a child dies from a water-related illness. Even in a developed country like the United States, there have been at least 1870 outbreaks associated with drinking water during the period of 1920 to 2002, causing 883,806 illnesses. Most of these outbreaks are resulted due to the presence of microbial pathogens in drinking water. Rotavirus infection has been recognized as the most common cause of diarrhea in young children throughout the world. Laboratory experiments conducted at the University of Illinois have demonstrated that recovery of rotavirus has been significantly affected by climatic and soil-surface conditions like slope, soil types, and ground cover. The objective of this study is to simulate the fate and transport of Rotavirus in overland and near-surface flow using a process-based model. In order to capture the dynamics of sediment-bound pathogens, the Water Erosion Prediction Project (WEPP) is coupled with the pathogen transport model. Transport of pathogens in overland flow can be simulated mathematically by including terms for the concentration of the pathogens in the liquid phase (in suspension or free-floating) and the solid phase (adsorbed to the fine solid particles like clay and silt). Advection, adsorption, and decay processes are considered. The mass balance equations are solved using numerical technique to predict spatial and temporal changes in pathogen concentrations in two phases. Outputs from WEPP simulations (flow velocity, depth, saturated conductivity and the soil particle fraction exiting in flow) are transferred as input for the pathogen transport model. Three soil types and three different surface cover conditions have been used in the experimental investigations. Results from these conditions have been used in calibrating and validating the simulation results. Bare surface conditions have produced very good agreement between

Numerical modeling of water-vapor transport during pre-storm and COHMEX

Science.gov (United States)

Djuric, Dusan

1986-01-01

Initial conditions are designed for numerical simulation of mesocale processes in the atmosphere using the Limited Area Mesoscale Prediction System (LAMPS) model. These initial conditions represent an idealized baroclinic wave in which the transport of water vapor can be simulated. The constructed atmosphere has two homogeneous air masses, polar front, polar jet stream and a stratosphere. All these simulate the basic structure of the earth's atmosphere. The hydrostatic and geostrophic balances make it possible to evaluate mutually consistent fields of wind and of the height of isobaric surfaces.

A Sediment Transport Model for Sewers

DEFF Research Database (Denmark)

Mark, Ole; Larsson, Johan; Larsen, Torben

1993-01-01

This paper describes a mathematical model for transport processes in sewers. The model consists of three sub models, a surface model for the description of the buildup and the washoff of sediment particles from the surface area, a morphological model and an advection-dispersion model. The model i...... is being developed as a part of a study being carried out at the University of Aalborg, Denmark and VBB VIAK, Sweden. The project is funded by the Swedish Water and Waste Water Works Association and the Nordic Industrial Foundation.......This paper describes a mathematical model for transport processes in sewers. The model consists of three sub models, a surface model for the description of the buildup and the washoff of sediment particles from the surface area, a morphological model and an advection-dispersion model. The model...

Reactive Transport Modeling of the Yucca Mountain Site, Nevada

International Nuclear Information System (INIS)

G. Bodvarsson

2004-01-01

The Yucca Mountain site has a dry climate and deep water table, with the repository located in the middle of an unsaturated zone approximately 600 m thick. Radionuclide transport processes from the repository to the water table are sensitive to the unsaturated zone flow field, as well as to sorption, matrix diffusion, radioactive decay, and colloid transport mechanisms. The unsaturated zone flow and transport models are calibrated against both physical and chemical data, including pneumatic pressure, liquid saturation, water potential, temperature, chloride, and calcite. The transport model predictions are further compared with testing specific to unsaturated zone transport: at Alcove 1 in the Exploratory Studies Facility (ESF), at Alcove 8 and Niche 3 of the ESF, and at the Busted Butte site. The models are applied to predict the breakthroughs at the water table for nonsorbing and sorbing radionuclides, with faults shown as the important paths for radionuclide transport. Daughter products of some important radionuclides, such as 239 Pu and 241 Am, have faster transport than the parents and must be considered in the unsaturated zone transport model. Colloid transport is significantly affected by colloid size, but only negligibly affected by lunetic declogging (reverse filtering) mechanisms. Unsaturated zone model uncertainties are discussed, including the sensitivity of breakthrough to the active fracture model parameter, as an example of uncertainties related to detailed flow characteristics and fracture-matrix interaction. It is expected that additional benefits from the unsaturated zone barrier for transport can be achieved by full implementation of the shadow zone concept immediately below the radionuclide release points in the waste emplacement drifts

Recent Approaches to Modeling Transport of Mercury in Surface Water and Groundwater - Case Study in Upper East Fork Poplar Creek, Oak Ridge, TN - 13349

International Nuclear Information System (INIS)

Bostick, Kent; Daniel, Anamary; Tachiev, Georgio; Malek-Mohammadi, Siamak

2013-01-01

In this case study, groundwater/surface water modeling was used to determine efficacy of stabilization in place with hydrologic isolation for remediation of mercury contaminated areas in the Upper East Fork Poplar Creek (UEFPC) Watershed in Oak Ridge, TN. The modeling simulates the potential for mercury in soil to contaminate groundwater above industrial use risk standards and to contribute to surface water contamination. The modeling approach is unique in that it couples watershed hydrology with the total mercury transport and provides a tool for analysis of changes in mercury load related to daily precipitation, evaporation, and runoff from storms. The model also allows for simulation of colloidal transport of total mercury in surface water. Previous models for the watershed only simulated average yearly conditions and dissolved concentrations that are not sufficient for predicting mercury flux under variable flow conditions that control colloidal transport of mercury in the watershed. The transport of mercury from groundwater to surface water from mercury sources identified from information in the Oak Ridge Environmental Information System was simulated using a watershed scale model calibrated to match observed daily creek flow, total suspended solids and mercury fluxes. Mercury sources at the former Building 81-10 area, where mercury was previously retorted, were modeled using a telescopic refined mesh with boundary conditions extracted from the watershed model. Modeling on a watershed scale indicated that only source excavation for soils/sediment in the vicinity of UEFPC had any effect on mercury flux in surface water. The simulations showed that colloidal transport contributed 85 percent of the total mercury flux leaving the UEFPC watershed under high flow conditions. Simulation of dissolved mercury transport from liquid elemental mercury and adsorbed sources in soil at former Building 81-10 indicated that dissolved concentrations are orders of magnitude

Recent Approaches to Modeling Transport of Mercury in Surface Water and Groundwater - Case Study in Upper East Fork Poplar Creek, Oak Ridge, TN - 13349

Energy Technology Data Exchange (ETDEWEB)

Bostick, Kent; Daniel, Anamary [Professional Project Services, Inc., Bethel Valley Road, Oak Ridge, TN, 37922 (United States); Tachiev, Georgio [Florida International University, Applied Research Center 10555 W. Flagler St., EC 2100 Miami Florida 33174 (United States); Malek-Mohammadi, Siamak [Bradley University, 413A Jobst Hall, Preoria, IL 61625 (United States)

2013-07-01

In this case study, groundwater/surface water modeling was used to determine efficacy of stabilization in place with hydrologic isolation for remediation of mercury contaminated areas in the Upper East Fork Poplar Creek (UEFPC) Watershed in Oak Ridge, TN. The modeling simulates the potential for mercury in soil to contaminate groundwater above industrial use risk standards and to contribute to surface water contamination. The modeling approach is unique in that it couples watershed hydrology with the total mercury transport and provides a tool for analysis of changes in mercury load related to daily precipitation, evaporation, and runoff from storms. The model also allows for simulation of colloidal transport of total mercury in surface water. Previous models for the watershed only simulated average yearly conditions and dissolved concentrations that are not sufficient for predicting mercury flux under variable flow conditions that control colloidal transport of mercury in the watershed. The transport of mercury from groundwater to surface water from mercury sources identified from information in the Oak Ridge Environmental Information System was simulated using a watershed scale model calibrated to match observed daily creek flow, total suspended solids and mercury fluxes. Mercury sources at the former Building 81-10 area, where mercury was previously retorted, were modeled using a telescopic refined mesh with boundary conditions extracted from the watershed model. Modeling on a watershed scale indicated that only source excavation for soils/sediment in the vicinity of UEFPC had any effect on mercury flux in surface water. The simulations showed that colloidal transport contributed 85 percent of the total mercury flux leaving the UEFPC watershed under high flow conditions. Simulation of dissolved mercury transport from liquid elemental mercury and adsorbed sources in soil at former Building 81-10 indicated that dissolved concentrations are orders of magnitude

Impact of Interfacial Water Transport in PEMFCs on Cell Performance

International Nuclear Information System (INIS)

Kotaka, Toshikazu; Tabuchi, Yuichiro; Pasaogullari, Ugur; Wang, Chao-Yang

2014-01-01

Coupled cell performance evaluation, liquid water visualization by neutron radiography (NRG) and numerical modeling based on multiphase mixture (M2) model were performed with three types of GDMs: Micro Porous Layer (MPL) free; Carbon Paper (CP) with MPL; and CP free to investigate interfacial liquid water transport phenomena in PEMFCs and its effect on cell performance. The visualized results of MPL free GDM with different wettability of bi-polar plates (BPPs) showed hydrophilic BPP improved liquid water transport at the interface between CP and channel. Numerical modeling results indicated that this difference with BPP wettability was caused by the liquid water coverage difference on CP surface. Thus, controlling liquid water coverage is the one of the key strategies for improving cell performance. Additionally, liquid water distributions across the cell for three types of GDMs were compared and significant difference in liquid water content at the interface between Catalyst Layer (CL) and GDM was observed. Numerical modeling suggests this difference is influenced by the gap at the interface and that the MPL could minimize this effect. The CP free cell (i.e. only MPL) showed the best performance and the lowest liquid water content. There were multiple impacts of interfacial liquid water transport both at CL-GDM and GDM-channel interfaces. High hydrophobicity and fine structure of MPLs contributed to enhanced liquid water transport at GDM-channel interface and as a result reduced the liquid water coverage. At the same time, MPL improves contact at the CL-GDM interface in the same manner as seen in CP with MPL case. Thus, the CP free concept showed the best performance. It is suggested that the design of the interface between each component of the PEMFC has a great impact on cell performance and plays a significant role in achievement of high current density operation and cost reduction in FCEVs

Investigation of a Water-Pond Arresting of a Dynamic Model of a Jet Transport

Science.gov (United States)

Thompson, William C.

1961-01-01

Brief dynamic-model tests have been made at the request of the Federal Aviation Agency to investigate the use of a shallow pond of water at the end of a runway as a means of arresting jet-transport aircraft when they are forced to abort on take-off or overrun on landing. Such a scheme is of particular interest for civil aircraft because it requires no modifications or attachments to the airplane and no mechanical devices in the arresting system. A modification of this scheme that uses a flexible plastic cover over the water surface has also been tested. The purpose of this paper is to present the results of a dynamic model investigation which would aid in determining whether the water-pond arresting system could be used as a means of arresting airplane overrun.

Models of Fate and Transport of Pollutants in Surface Waters

Science.gov (United States)

Okome, Gloria Eloho

2013-01-01

There is the need to answer very crucial questions of "what happens to pollutants in surface waters?" This question must be answered to determine the factors controlling fate and transport of chemicals and their evolutionary state in surface waters. Monitoring and experimental methods are used in establishing the environmental states.…

Water Transport Mediated by Other Membrane Proteins.

Science.gov (United States)

Huang, Boyue; Wang, Hongkai; Yang, Baoxue

2017-01-01

Water transport through membrane is so intricate that there are still some debates. (Aquaporins) AQPs are entirely accepted to allow water transmembrane movement depending on osmotic gradient. Cotransporters and uniporters , however, are also concerned in water homeotatsis. Urea transporter B (UT-B) has a single-channel water permeability that is similar to AQP1. Cystic fibrosis transmembrane conductance regulator (CFTR ) was initially thought as a water channel but now not believed to transport water directly. By cotranporters, water is transported by water osmosis coupling with substrates, which explains how water is transported across the isolated small intestine. This chapter provides information about water transport mediated by other membrane proteins except AQPs .

RIVER-RAD, Radionuclide Transport in Surface Waters

International Nuclear Information System (INIS)

1996-01-01

1 - Description of program or function: RIVER-RAD assesses the potential fate of radionuclides released to rivers. The model is simplified in nature and is intended to provide guidance in determining the potential importance of the surface water pathway, relevant transport mechanisms, and key radionuclides in estimating radiological dose to man. 2 - Method of solution: A compartmental linear transfer model is used in RIVER-RAD. The river system model in the code is divided into reaches (compartments) of equal size, each with a sediment compartment below it. The movement of radionuclides is represented by a series of transfers between the reaches, and between the water and sediment compartments of each reach. Within each reach (for both the water and sediment compartments), the radionuclides are assumed to be uniformly mixed. Upward volatilization is allowed from the water compartment, and the transfer of radionuclides between the reaches is determined by the flow rate of the river. Settling and resuspension velocities determine the transfer of absorbed radionuclides between the water and sediment compartments. Radioactive decay and decay-product buildup are incorporated into all transport calculations for all radionuclide chains specified by the user. Each nuclide may have unique input and removal rates. Volatilization and radiological decay are considered as linear rate constants in the model. 3 - Restrictions on the complexity of the problem: None noted

A modified QWASI model for fate and transport modeling of mercury between the water-ice-sediment in Lake Ulansuhai.

Science.gov (United States)

Liu, Yu; Li, Changyou; Anderson, Bruce; Zhang, Sheng; Shi, Xiaohong; Zhao, Shengnan

2017-06-01

Mercury contamination from industrial and agricultural drainage into lakes and rivers is a growing concern in Northern China. Lake Ulansuhai, located in Hetao irrigation district in Inner Mongolia, is the only sink for the all industrial and agricultural drainage and sole outlet for this district to the Yellow River, which is one of the main source of drinking water for the numerous cities and towns downstream. Because Ulansuahi is ice-covered during winter, the QWASI model was modified by adding an ice equation to get a more accurate understanding of the fate and transport of mercury within the lake. Both laboratory and field tests were carried out during the ice growth period. The aquivalence and mass balance approaches were used to develop the modified QWASI + ice model. The margins of error between the modelled and the measured average concentrations of Hg in ice, water, and sediment were 30%, 26.2%, and 19.8% respectively. These results suggest that the new QWASI + ice model could be used to more accurately represent the fate and transport of mercury in the seasonally ice-covered lakes, during the ice growth period. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dynamics of leaf gas exchange, xylem and phloem transport, water potential and carbohydrate concentration in a realistic 3-D model tree crown.

Science.gov (United States)

Nikinmaa, Eero; Sievänen, Risto; Hölttä, Teemu

2014-09-01

Tree models simulate productivity using general gas exchange responses and structural relationships, but they rarely check whether leaf gas exchange and resulting water and assimilate transport and driving pressure gradients remain within acceptable physical boundaries. This study presents an implementation of the cohesion-tension theory of xylem transport and the Münch hypothesis of phloem transport in a realistic 3-D tree structure and assesses the gas exchange and transport dynamics. A mechanistic model of xylem and phloem transport was used, together with a tested leaf assimilation and transpiration model in a realistic tree architecture to simulate leaf gas exchange and water and carbohydrate transport within an 8-year-old Scots pine tree. The model solved the dynamics of the amounts of water and sucrose solute in the xylem, cambium and phloem using a fine-grained mesh with a system of coupled ordinary differential equations. The simulations predicted the observed patterns of pressure gradients and sugar concentration. Diurnal variation of environmental conditions influenced tree-level gradients in turgor pressure and sugar concentration, which are important drivers of carbon allocation. The results and between-shoot variation were sensitive to structural and functional parameters such as tree-level scaling of conduit size and phloem unloading. Linking whole-tree-level water and assimilate transport, gas exchange and sink activity opens a new avenue for plant studies, as features that are difficult to measure can be studied dynamically with the model. Tree-level responses to local and external conditions can be tested, thus making the approach described here a good test-bench for studies of whole-tree physiology.

Ebullition, Plant-Mediated Transport, and Subsurface Horizontal Water Flow Dominate Methane Transport in an Arctic Sphagnum Bog

Science.gov (United States)

Wehr, R. A.; McCalley, C. K.; Logan, T. A.; Chanton, J.; Crill, P. M.; Rich, V. I.; Saleska, S. R.

2017-12-01

Emission of the greenhouse gas methane from wetlands is of prime concern in the prediction of climate change - especially emission associated with thawing permafrost, which may drive a positive feedback loop of emission and warming. In addition to the biochemistry of methane production and consumption, wetland methane emission depends critically on the transport mechanisms by which methane moves through and out of the ecosystem. We therefore developed a model of methane biochemistry and transport for a sphagnum bog representing an intermediate permafrost thaw stage in Stordalen Mire, Sweden. In order to simultaneously reproduce measured profiles of both the concentrations and isotopic compositions of both methane and carbon dioxide in the peat pore water (Fig. 1) - as well as the surface methane emission - it was necessary for the model to include ebullition, plant-mediated transport via aerenchyma, and subsurface horizontal water flow. Diffusion of gas through the pore water was relatively unimportant. As a result, 90% of the produced methane escaped the wetland rather than being consumed by methanotrophic organisms in the near-surface pore water. Our model provides a comprehensive picture of methane emission from this bog site by quantifying the vertical profiles of: acetoclastic methanogenesis, hydrogenotrophic methanogenesis, methane oxidation, aerobic respiration, ebullition, plant-mediated transport, subsurface horizontal water flow, and diffusion.

Modelling water and contaminant transport in the Rum Jungle Mine overburden heaps

International Nuclear Information System (INIS)

Pantelis, G.

1987-04-01

An outline is given of a computer model for water and contaminant transport in and around overburden heaps, with those at the Rum Jungle mine site as a specific example. The model assumes the heaps to lie on a sloping shallow aquifer with identical hydraulic properties. The simulation is carried out for a 40 year period. After the first 20 years a cover which is effectively impermeable to infiltrating rainwater and air is introduced on the heap. The restriction of oxygen supply to the heap terminates contaminant production which results from oxidation of pyrite. Leaching of contaminants from the heap in the following 20-year period is examined

Free water transport, small pore transport and the osmotic pressure gradient

NARCIS (Netherlands)

Parikova, Alena; Smit, Watske; Zweers, Machteld M.; Struijk, Dirk G.; Krediet, Raymond T.

2008-01-01

BACKGROUND: Water transport in peritoneal dialysis (PD) patients occurs through the small pores and water channels, the latter allowing free water transport (FWT). The osmotic gradient is known to be one of the major determinants of water transport. The objective of the study was to analyse the

Transport of Mars atmospheric water into high northern latitudes during a polar warming

Science.gov (United States)

Barnes, J. R.; Hollingsworth, J. L.

1988-01-01

Several numerical experiments were conducted with a simplified tracer transport model in order to attempt to examine the poleward transport of Mars atmospheric water during a polar warming like that which occurred during the winter solstice dust storm of 1977. The flow for the transport experiments was taken from numerical simulations with a nonlinear beta-plane dynamical model. Previous studies with this model have demonstrated that a polar warming having essential characteristics like those observed during the 1977 dust storm can be produced by a planetary wave mechanism analogous to that responsible for terrestrial sudden stratospheric warmings. Several numerical experiments intended to simulate water transport in the absence of any condensation were carried out. These experiments indicate that the flow during a polar warming can transport very substantial amounts of water to high northern latitudes, given that the water does not condense and fall out before reaching the polar region.

Simulation of the fate of faecal bacteria in estuarine and coastal waters based on a fractionated sediment transport model

Science.gov (United States)

Yang, Chen; Liu, Ying

2017-08-01

A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.

One-Dimensional Transport with Equilibrium Chemistry (OTEQ) - A Reactive Transport Model for Streams and Rivers

Science.gov (United States)

Runkel, Robert L.

2010-01-01

OTEQ is a mathematical simulation model used to characterize the fate and transport of waterborne solutes in streams and rivers. The model is formed by coupling a solute transport model with a chemical equilibrium submodel. The solute transport model is based on OTIS, a model that considers the physical processes of advection, dispersion, lateral inflow, and transient storage. The equilibrium submodel is based on MINTEQ, a model that considers the speciation and complexation of aqueous species, acid-base reactions, precipitation/dissolution, and sorption. Within OTEQ, reactions in the water column may result in the formation of solid phases (precipitates and sorbed species) that are subject to downstream transport and settling processes. Solid phases on the streambed may also interact with the water column through dissolution and sorption/desorption reactions. Consideration of both mobile (waterborne) and immobile (streambed) solid phases requires a unique set of governing differential equations and solution techniques that are developed herein. The partial differential equations describing physical transport and the algebraic equations describing chemical equilibria are coupled using the sequential iteration approach. The model's ability to simulate pH, precipitation/dissolution, and pH-dependent sorption provides a means of evaluating the complex interactions between instream chemistry and hydrologic transport at the field scale. This report details the development and application of OTEQ. Sections of the report describe model theory, input/output specifications, model applications, and installation instructions. OTEQ may be obtained over the Internet at http://water.usgs.gov/software/OTEQ.

Mathematical modelling of water and gas transport in layered soil covers for coal ash deposits

Energy Technology Data Exchange (ETDEWEB)

Rasmussen, A; Lindgren, M [Kemakta Consultants Co, Stockholm (SE)

1990-12-17

In the present work the dry deposition alternative is investigated. In particular the design of soil covers is treated theoretically using mathematical models. The soil cover should primarily act as a barrier against infiltrating water. This is done by having soil cover materials with low permeabilities and sloping covers thereby diverting the infiltrating water in the lateral direction. An important design aspect is that overflow should be avoided since this may cause erosional problems. Thus the design of the cover should allow for lateral water flow within the cover. In the present work we use the computer code TRUST for calculating the flow rates and the moisture contents in two layer covers (till on top of clay) for varying conditions. The calculations so far show that the hydraulic conductivity of the clay layer should be smaller than 10{sup -8} m/s. However, for the simulated longer covers (50 m) a lower hydraulic conductivity gives overflow indicating that better lateral drainage must be provided for. This can be done by increasing the thickness or hydraulic conductivity of the till layer. Simulations for different slopes give little impact, while the hydraulic conductivity of the clay layer is of major importance. Gas transport through the soil cover may be of importance if the waste contains pyrite. In the presence of oxygen and water, pyrite is oxidized producing sulphuric acid. The lowered pH will accelerate the leaching of several heavy metals. The transport rate of gas through a porous material is very sensitive to the water content, decreasing rapidly with increasing water content. In the present work a model, where the unsaturated conditions are accounted for, is outlined. A previously developed method for calculating oxygen transport and oxidation rate of pyrite in connection with mine wastes is generalized from 1D to 2D. A sample calculation illustrates the feasibility of the method. (au) (43 refs.).

Burning water: The water footprint of biofuel-based transport

NARCIS (Netherlands)

Gerbens-Leenes, Winnie; Hoekstra, Arjen Ysbert

2010-01-01

The trend towards substitution of conventional transport fuels by biofuels requires additional water. The EU aims to replace 10 percent of total transport fuels by biofuels by 2020. This study calculates the water footprint (WF) of different transport modes using bio-ethanol, biodiesel or

Simulating liquid water for determining its structural and transport properties

International Nuclear Information System (INIS)

Arismendi-Arrieta, Daniel; Medina, Juan S.; Fanourgakis, George S.; Prosmiti, Rita; Delgado-Barrio, Gerardo

2014-01-01

Molecular dynamics simulations are carried out for calculating structural and transport properties of pure liquid water, such as radial distribution functions and self-diffusion and viscosity coefficients, respectively. We employed reparameterized versions of the ab initio water potential by Niesar, Clementi and Corongiu (NCC). In order to investigate the role of the electrostatic contribution, the partial charges of the NCC model are adjusted so that to reproduce the dipole moment values of the SPC/E, SPC/Fw and TIP4P/2005 water models. The single and collective transport coefficients are obtained by employing the Green–Kubo relations at various temperatures. Additionally, in order to overcome convergence difficulties arising from the long correlation times of the stress-tensor autocorrelation functions, a previously reported fitting scheme was employed. The present results indicate that there is a significant relationship between the dipole moment value of the model, and the calculated transport coefficients. We found that by adjusting the molecular dipole moment of the NCC to the value of the TIP4P/2005, the obtained values for the self-diffusion and viscosity coefficients are in better agreement with experiment, compared to the values obtained with the original NCC model. Even though the predictions of the present model exhibits an overall correct behavior, we conclude that further improvements are still required. In order to achieve that, a careful reparameterization of the repulsion–dispersion terms of the potential model is proposed. Also, the effect of the inclusion of many-body effects such as polarizability, should also be investigated. - Highlights: ► Transport properties of liquid water are important in bio-simulations. ► Self-diffusion coefficient, shear and bulk viscosities calculations from NVE molecular dynamics simulations. ► Their comparison with experimental data provides information on intermolecular forces, and serve to develop water

Water injection into vapor- and liquid-dominated reservoirs: Modeling of heat transfer and mass transport

Energy Technology Data Exchange (ETDEWEB)

Pruess, K.; Oldenburg, C.; Moridis, G.; Finsterle, S. [Lawrence Berkeley National Lab., CA (United States)

1997-12-31

This paper summarizes recent advances in methods for simulating water and tracer injection, and presents illustrative applications to liquid- and vapor-dominated geothermal reservoirs. High-resolution simulations of water injection into heterogeneous, vertical fractures in superheated vapor zones were performed. Injected water was found to move in dendritic patterns, and to experience stronger lateral flow effects than predicted from homogeneous medium models. Higher-order differencing methods were applied to modeling water and tracer injection into liquid-dominated systems. Conventional upstream weighting techniques were shown to be adequate for predicting the migration of thermal fronts, while higher-order methods give far better accuracy for tracer transport. A new fluid property module for the TOUGH2 simulator is described which allows a more accurate description of geofluids, and includes mineral dissolution and precipitation effects with associated porosity and permeability change. Comparisons between numerical simulation predictions and data for laboratory and field injection experiments are summarized. Enhanced simulation capabilities include a new linear solver package for TOUGH2, and inverse modeling techniques for automatic history matching and optimization.

Guidelines for selecting codes for ground-water transport modeling of low-level waste burial sites. Executive summary

International Nuclear Information System (INIS)

Simmons, C.S.; Cole, C.R.

1985-05-01

This document was written to provide guidance to managers and site operators on how ground-water transport codes should be selected for assessing burial site performance. There is a need for a formal approach to selecting appropriate codes from the multitude of potentially useful ground-water transport codes that are currently available. Code selection is a problem that requires more than merely considering mathematical equation-solving methods. These guidelines are very general and flexible and are also meant for developing systems simulation models to be used to assess the environmental safety of low-level waste burial facilities. Code selection is only a single aspect of the overall objective of developing a systems simulation model for a burial site. The guidance given here is mainly directed toward applications-oriented users, but managers and site operators need to be familiar with this information to direct the development of scientifically credible and defensible transport assessment models. Some specific advice for managers and site operators on how to direct a modeling exercise is based on the following five steps: identify specific questions and study objectives; establish costs and schedules for achieving answers; enlist the aid of professional model applications group; decide on approach with applications group and guide code selection; and facilitate the availability of site-specific data. These five steps for managers/site operators are discussed in detail following an explanation of the nine systems model development steps, which are presented first to clarify what code selection entails

Models for the transport of low energy electrons in water and the yield of hydrated electrons at early times

International Nuclear Information System (INIS)

Brenner, D.J.; Miller, J.H.; Ritchie, R.H.; Bichsel, H.

1985-01-01

An insulator model with four experimental energy bands was used to fit the optical properties of liquid water and to extend these data to non-zero momentum transfer. Inelastic mean free paths derived from this dielectric response function provided the basic information necessary to degrade high energy electrons to the subexcitation energy domain. Two approaches for the transport of subexcitation electrons were investigated. (i) Gas phase cross sections were used to degrade subexcitation electrons to thermal energy and the thermalization lengths were scaled to unit density. (ii) Thermalization lengths were estimated by age-diffusion theory with a stopping power deduced from the data on liquid water and transport cross sections derived from elastic scattering in water vapor. Theoretical ranges were compared to recent experimental results. A stochastic model was used to calculate the rapid diffusion and reaction of hydrated electrons with other radiolysis products. The sensitivity of the calculated yields to the model assumptions and comparison with experimental data are discussed

The function of 7D-cadherins: a mathematical model predicts physiological importance for water transport through simple epithelia

Directory of Open Access Journals (Sweden)

Walcher Sebastian

2011-06-01

Full Text Available Abstract Background 7D-cadherins like LI-cadherin are cell adhesion molecules and represent exceptional members of the cadherin superfamily. Although LI-cadherin was shown to act as a functional Ca2+-dependent adhesion molecule, linking neighboring cells together, and to be dysregulated in a variety of diseases, the physiological role is still enigmatic. Interestingly 7D-cadherins occur only in the lateral plasma membranes of cells from epithelia of water transporting tissues like the gut, the liver or the kidney. Furthermore LI-cadherin was shown to exhibit a highly cooperative Ca2+-dependency of the binding activity. Thus it is tempting to assume that LI-cadherin regulates the water transport through the epithelium in a passive fashion by changing its binding activity in dependence on the extracellular Ca2+. Results We developed a simple mathematical model describing the epithelial lining of a lumen with a content of variable osmolarity covering an interstitium of constant osmolarity. The width of the lateral intercellular cleft was found to influence the water transport significantly. In the case of hypertonic luminal content a narrow cleft is necessary to further increase concentration of the luminal content. If the cleft is too wide, the water flux will change direction and water is transported into the lumen. Electron microscopic images show that in fact areas of the gut can be found where the lateral intercellular cleft is narrow throughout the lateral cell border whereas in other areas the lateral intercellular cleft is widened. Conclusions Our simple model clearly predicts that changes of the width of the lateral intercellular cleft can regulate the direction and efficiency of water transport through a simple epithelium. In a narrow cleft the cells can increase the concentration of osmotic active substances easily by active transport whereas if the cleft is wide, friction is reduced but the cells can hardly build up high osmotic

Modeling electrokinetic transport in phenol contaminated soils

Energy Technology Data Exchange (ETDEWEB)

Zorn, R.; Haus, R.; Czurda, K. [Dept. of Applied Geology, Univ. Karlsruhe (Germany)

2001-07-01

Numerical simulations are compared to laboratory experiments of electroremediation in soils contaminated by phenolic pollutants. The developing pH affects the electrokinetic transport behaviour of phenol. It is found that a water chemistry model must be included in an electrokinetic mass transport model to describe the process of electroremediation more accurately, if no buffering system is used at the electrodes. In the case of controlling the pH at the electrode compartments only a simplified chemical reaction model must be included in the numerical code to match the experimental phenolic transport. (orig.)

Analytical solutions for benchmarking cold regions subsurface water flow and energy transport models: one-dimensional soil thaw with conduction and advection

Science.gov (United States)

Kurylyk, Barret L.; McKenzie, Jeffrey M; MacQuarrie, Kerry T. B.; Voss, Clifford I.

2014-01-01

Numerous cold regions water flow and energy transport models have emerged in recent years. Dissimilarities often exist in their mathematical formulations and/or numerical solution techniques, but few analytical solutions exist for benchmarking flow and energy transport models that include pore water phase change. This paper presents a detailed derivation of the Lunardini solution, an approximate analytical solution for predicting soil thawing subject to conduction, advection, and phase change. Fifteen thawing scenarios are examined by considering differences in porosity, surface temperature, Darcy velocity, and initial temperature. The accuracy of the Lunardini solution is shown to be proportional to the Stefan number. The analytical solution results obtained for soil thawing scenarios with water flow and advection are compared to those obtained from the finite element model SUTRA. Three problems, two involving the Lunardini solution and one involving the classic Neumann solution, are recommended as standard benchmarks for future model development and testing.

An Updated Site Scale Saturated Zone Ground Water Transport Model For Yucca Mountain

International Nuclear Information System (INIS)

S. Kelkar; H. Viswanathan; A. Eddebbarrh; M. Ding; P. Reimus; B. Robinson; B. Arnold; A. Meijer

2006-01-01

The Yucca Mountain site scale saturated zone transport model has been revised to incorporate the updated flow model based on a hydrogeologic framework model using the latest lithology data, increased grid resolution that better resolves the geology within the model domain, updated Kd distributions for radionuclides of interest, and updated retardation factor distributions for colloid filtration. The resulting numerical transport model is used for performance assessment predictions of radionuclide transport and to guide future data collection and modeling activities. The transport model results are validated by comparing the model transport pathways with those derived from geochemical data, and by comparing the transit times from the repository footprint to the compliance boundary at the accessible environment with those derived from 14 C-based age estimates. The transport model includes the processes of advection, dispersion, fracture flow, matrix diffusion, sorption, and colloid-facilitated transport. The transport of sorbing radionuclides in the aqueous phase is modeled as a linear, equilibrium process using the Kd model. The colloid-facilitated transport of radionuclides is modeled using two approaches: the colloids with irreversibly embedded radionuclides undergo reversible filtration only, while the migration of radionuclides that reversibly sorb to colloids is modeled with modified values for sorption coefficient and matrix diffusion coefficients. Model breakthrough curves for various radionuclides at the compliance boundary are presented along with their sensitivity to various parameters

Development of a Coupled Ocean-Hydrologic Model to Simulate Pollutant Transport in Singapore Coastal Waters

Science.gov (United States)

Chua, V. P.

2015-12-01

Intensive agricultural, economic and industrial activities in Singapore and Malaysia have made our coastal areas under high risk of water pollution. A coupled ocean-hydrologic model is employed to perform three-dimensional simulations of flow and pollutant transport in Singapore coastal waters. The hydrologic SWAT model is coupled with the coastal ocean SUNTANS model by outputting streamflow and pollutant concentrations from the SWAT model and using them as inputs for the SUNTANS model at common boundary points. The coupled model is calibrated with observed sea surface elevations and velocities, and high correlation coefficients that exceed 0.97 and 0.91 are found for sea surface elevations and velocities, respectively. The pollutants are modeled as Gaussian passive tracers, and are released at five upstream locations in Singapore coastal waters. During the Northeast monsoon, pollutants released in Source 1 (Johor River), Source 2 (Tiram River), Source 3 (Layang River) and Source 4 (Layau River) enter the Singapore Strait after 4 days of release and reach Sentosa Island within 9 days. Meanwhile, pollutants released in Source 5 (Kallang River) reach Sentosa Island after 4 days. During the Southwest monsoon, the dispersion time is roughly doubled, with pollutants from Sources 1 - 4 entering the Singapore Strait only after 12 days of release due to weak currents.

Transport behavior of water molecules through two-dimensional nanopores

International Nuclear Information System (INIS)

Zhu, Chongqin; Li, Hui; Meng, Sheng

2014-01-01

Water transport through a two-dimensional nanoporous membrane has attracted increasing attention in recent years thanks to great demands in water purification and desalination applications. However, few studies have been reported on the microscopic mechanisms of water transport through structured nanopores, especially at the atomistic scale. Here we investigate the microstructure of water flow through two-dimensional model graphene membrane containing a variety of nanopores of different size by using molecular dynamics simulations. Our results clearly indicate that the continuum flow transits to discrete molecular flow patterns with decreasing pore sizes. While for pores with a diameter ≥15 Å water flux exhibits a linear dependence on the pore area, a nonlinear relationship between water flux and pore area has been identified for smaller pores. We attribute this deviation from linear behavior to the presence of discrete water flow, which is strongly influenced by the water-membrane interaction and hydrogen bonding between water molecules

Effect of gravity on colloid transport through water-saturated columns packed with glass beads: modeling and experiments.

Science.gov (United States)

Chrysikopoulos, Constantinos V; Syngouna, Vasiliki I

2014-06-17

The role of gravitational force on colloid transport in water-saturated columns packed with glass beads was investigated. Transport experiments were performed with colloids (clays: kaolinite KGa-1b, montmorillonite STx-1b). The packed columns were placed in various orientations (horizontal, vertical, and diagonal) and a steady flow rate of Q = 1.5 mL/min was applied in both up-flow and down-flow modes. All experiments were conducted under electrostatically unfavorable conditions. The experimental data were fitted with a newly developed, analytical, one-dimensional, colloid transport model. The effect of gravity is incorporated in the mathematical model by combining the interstitial velocity (advection) with the settling velocity (gravity effect). The results revealed that flow direction influences colloid transport in porous media. The rate of particle deposition was shown to be greater for up-flow than for down-flow direction, suggesting that gravity was a significant driving force for colloid deposition.

Integration into JRODOS the models of radionuclide transport in rivers, reservoirs and coastal waters to support the emergency response in early accidental stages

Energy Technology Data Exchange (ETDEWEB)

Zheleznyak, M.; Bezhenar, R.; Boyko, O.; Ievdin, I.; Koshebutsky, V.; Maderich, V. [Institute of Mathematical Machines and Systems, National Academy of Sciences of Ukraine (Ukraine); Raskob, W.; Trybushnyi, D. [Karlsruhe Institute of Technology, Institut fuer Kern- und Energietechnik (Germany)

2014-07-01

The decision support system for offsite nuclear emergency management RODOS (Real-time on-line decision support), developed under several EC RTD Framework Programs, contains many models related to support decision making in case of a nuclear or radiological emergency. Based on the request of the end users, it was re-engineered based on the JAVA technology and further named JRODOS. The consequences of the Fukushima Daiichi Nuclear Power Plant accident clearly demonstrated the importance of modeling tools predicting the radionuclide transport in marine and freshwater environment and assessing the doses to the public via the aquatic food chain to improve decision making in general. As a consequence, such an activity was launched as part of the European project PREPARE aiming to integrate the 3-dimensional model THREETOX for the radionuclide transport in coastal waters, estuaries, deep lakes, and reservoirs into hydrological model chain of JRODOS - JHDM (JRODOS Hydrological Dispersion Module). So far JHDM contains several aquatic radionuclide transport models describing the sequence of the processes 'atmospheric fallout to watershed' - 'radionuclide inflow to a river net' - 'radionuclide transport in river' - 'doses via aquatic pathways'. The implementation of the THREETOX model into this chain by developing also a user friendly interface will extend the applicability of JRODOS to deep fresh water bodies and marine coastal waters. This paper describes the assessment capabilities of this advanced model chain for two examples of the JRODOS implementation in Ukraine. JRODOS is installed in the emergency centers for two Ukrainian Nuclear Power Plants (NPP) - Zaporizzhya NPP (ZNPP) and Rivne NPP (RNPP). The different models of the JHDM were customized for these NPPs taking into account the characteristics of the water bodies in the surroundings of the NPPs. For the RNPP, located at the bank of the Sozh River which is a tributary of the

Numerical analysis of coupled water transport in wood with a focus on the coupling parameter sorption

DEFF Research Database (Denmark)

Hozjan, T.; Turk, G.; Rodman, U.

2011-01-01

This paper presents a study of sorption rate function in a so-called multi-Fickian or multi-phase model. This model describes the complex moisture transport system in wood, which consists of separate water-vapour and bound-water diffusion interacting through sorption. In the numerical example inf...... influence of the sorption rate function on water transport is presented. It can be seen that the sorption rate function has a noticeable influence on coupled water transport in wood....

On the development and benchmarking of an approach to model gas transport in fractured media with immobile water storage

Science.gov (United States)

Harp, D. R.; Ortiz, J. P.; Pandey, S.; Karra, S.; Viswanathan, H. S.; Stauffer, P. H.; Anderson, D. N.; Bradley, C. R.

2017-12-01

In unsaturated fractured media, the rate of gas transport is much greater than liquid transport in many applications (e.g., soil vapor extraction operations, methane leaks from hydraulic fracking, shallow CO2 transport from geologic sequestration operations, and later-time radionuclide gas transport from underground nuclear explosions). However, the relatively immobile pore water can inhibit or promote gas transport for soluble constituents by providing storage. In scenarios with constant pressure gradients, the gas transport will be retarded. In scenarios with reversing pressure gradients (i.e. barometric pressure variations) pore water storage can enhance gas transport by providing a ratcheting mechanism. Recognizing the computational efficiency that can be gained using a single-phase model and the necessity of considering pore water storage, we develop a Richard's solution approach that includes kinetic dissolution/volatilization of constituents. Henry's Law governs the equilibrium gaseous/aqueous phase partitioning in the approach. The approach is implemented in a development branch of the PFLOTRAN simulator. We verify the approach with analytical solutions of: (1) 1D gas diffusion, (2) 1D gas advection, (3) sinusoidal barometric pumping of a fracture, and (4) gas transport along a fracture with uniform flow and diffusive walls. We demonstrate the retardation of gas transport in cases with constant pressure gradients and the enhancement of gas transport with reversing pressure gradients. The figure presents the verification of our approach to the analytical solution of barometric pumping of a fracture from Nilson et al (1991) where the x-axis "Horizontal axis" is the distance into the matrix block from the fracture.

Development and application of a catchment scale pesticide fate and transport model for use in drinking water risk assessment.

Science.gov (United States)

Pullan, S P; Whelan, M J; Rettino, J; Filby, K; Eyre, S; Holman, I P

2016-09-01

This paper describes the development and application of IMPT (Integrated Model for Pesticide Transport), a parameter-efficient tool for predicting diffuse-source pesticide concentrations in surface waters used for drinking water supply. The model was applied to a small UK headwater catchment with high frequency (8h) pesticide monitoring data and to five larger catchments (479-1653km(2)) with sampling approximately every 14days. Model performance was good for predictions of both flow (Nash Sutcliffe Efficiency generally >0.59 and PBIAS water resources to support operational and strategic risk assessments. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Reactive transport modelling to infer changes in soil hydraulic properties induced by non-conventional water irrigation

Science.gov (United States)

Valdes-Abellan, Javier; Jiménez-Martínez, Joaquín; Candela, Lucila; Jacques, Diederik; Kohfahl, Claus; Tamoh, Karim

2017-06-01

The use of non-conventional water (e.g., treated wastewater, desalinated water) for different purposes is increasing in many water scarce regions of the world. Its use for irrigation may have potential drawbacks, because of mineral dissolution/precipitation processes, such as changes in soil physical and hydraulic properties (e.g., porosity, permeability), modifying infiltration and aquifer recharge processes or blocking root growth. Prediction of soil and groundwater impacts is essential for achieving sustainable agricultural practices. A numerical model to solve unsaturated water flow and non-isothermal multicomponent reactive transport has been modified implementing the spatio-temporal evolution of soil physical and hydraulic properties. A long-term process simulation (30 years) of agricultural irrigation with desalinated water, based on a calibrated/validated 1D numerical model in a semi-arid region, is presented. Different scenarios conditioning reactive transport (i.e., rainwater irrigation, lack of gypsum in the soil profile, and lower partial pressure of CO2 (pCO2)) have also been considered. Results show that although boundary conditions and mineral soil composition highly influence the reactive processes, dissolution/precipitation of carbonate species is triggered mainly by pCO2, closely related to plant roots. Calcite dissolution occurs in the root zone, precipitation takes place under it and at the soil surface, which will lead a root growth blockage and a direct soil evaporation decrease, respectively. For the studied soil, a gypsum dissolution up to 40 cm depth is expected at long-term, with a general increase of porosity and hydraulic conductivity.

Passive water and ion transport by cotransporters

DEFF Research Database (Denmark)

Loo, D D; Hirayama, B A; Meinild, A K

1999-01-01

the Lp of control oocytes. Passive Na+ transport (Na+ leak) was obtained from the blocker-sensitive Na+ currents in the absence of substrates (glucose and GABA). 2. Passive Na+ and water transport through SGLT1 were blocked by phlorizin with the same sensitivity (inhibitory constant (Ki), 3-5 micro......1. The rabbit Na+-glucose (SGLT1) and the human Na+-Cl--GABA (GAT1) cotransporters were expressed in Xenopus laevis oocytes, and passive Na+ and water transport were studied using electrical and optical techniques. Passive water permeabilities (Lp) of the cotransporters were determined from......M). When Na+ was replaced with Li+, phlorizin also inhibited Li+ and water transport, but with a lower affinity (Ki, 100 microM). When Na+ was replaced by choline, which is not transported, the SGLT1 Lp was indistinguishable from that in Na+ or Li+, but in this case water transport was less sensitive...

CFD Lagrangian Modeling of Water Droplet Transport for ISS Hygiene Activity Application

Science.gov (United States)

Son, Chang H.

2013-01-01

The goal of this study was to assess the impacts of free water propagation in the Waste and Hygiene Compartment (WHC) installed in Node 3. Free water can be generated inside the WHC in small quantities due to crew hygiene activity. To mitigate potential impact of free water in Node 3 cabin the WHC doorway is enclosed by a waterproof bump-out, Kabin, with openings at the top and bottom. At the overhead side of the rack, there is a screen that prevents large drops of water from exiting. However, as the avionics fan in the WHC causes airflow toward the deck side of the rack, small quantities of free water may exit at the bottom of the Kabin. A Computational Fluid Dynamics (CFD) analysis of Node 3 cabin airflow enable identifying the paths of water transport. To simulate the droplet transport the Lagrangian discrete phase approach was used. Various initial droplet distributions were considered in the study. The droplet diameter was varied in the range of 5-20 mm. The results of the computations showed that most of the drops fall to the rack surface not far from the WHC curtain.

On water transport in polymer electrolyte membranes during the passage of current

DEFF Research Database (Denmark)

Berning, Torsten

2011-01-01

This article discusses an approach to model the water transport in the membranes of PEM fuel cells during operation. Starting from a frequently utilized equation the various transport mechanisms are analyzed in detail. It is shown that the commonly used approach to simply balance the electro......-osmotic drag (EOD) with counter diffusion and/or hydraulic permeation is flawed, and that any net transport of water through the membrane is caused by diffusion. Depending on the effective drag the cathode side of the membrane may experience a lower hydration than the anode side. The effect of a water......-uptake layer on the net water transport will also be pictured. Finally, the effect of EOD is visualized using “Newton’s cradle”....

The water footprint of biofuel-based transport

NARCIS (Netherlands)

Gerbens-Leenes, Winnie; Hoekstra, Arjen Ysbert

2011-01-01

The EU target to replace 10 percent of transport fuels by renewables by 2020 requires additional water. This study calculates water footprints (WFs) of transport modes using first generation bio-ethanol, biodiesel or bio-electricity and of European transport if 10 percent of transport fuels is

Effect of river discharge and geometry on tides and net water transport in an estuarine network, an idealized model applied to the Yangtze Estuary

NARCIS (Netherlands)

Alebregtse, N. C.|info:eu-repo/dai/nl/345704304; de Swart, H. E.|info:eu-repo/dai/nl/073449725

2016-01-01

Tidal propagation in, and division of net water transport over different channels in an estuarine network are analyzed using a newly developed idealized model. The water motion in this model is governed by the cross-sectionally averaged shallow water equations and is forced by tides at the seaward

Water Transport and Removal in PEMFC Gas Flow Channel with Various Water Droplet Locations and Channel Surface Wettability

Directory of Open Access Journals (Sweden)

Yanzhou Qin

2018-04-01

Full Text Available Water transport and removal in the proton exchange membrane fuel cell (PEMFC is critically important to fuel cell performance, stability, and durability. Water emerging locations on the membrane-electrode assembly (MEA surface and the channel surface wettability significantly influence the water transport and removal in PEMFC. In most simulations of water transport and removal in the PEMFC flow channel, liquid water is usually introduced at the center of the MEA surface, which is fortuitous, since water droplet can emerge randomly on the MEA surface in PEMFC. In addition, the commonly used no-slip wall boundary condition greatly confines the water sliding features on hydrophobic MEA/channel surfaces, degrading the simulation accuracy. In this study, water droplet is introduced with various locations along the channel width direction on the MEA surface, and water transport and removal is investigated numerically using an improved model incorporating the sliding flow property by using the shear wall boundary condition. It is found that the water droplet can be driven to the channel sidewall by aerodynamics when the initial water location deviates from the MEA center to a certain amount, forming the water corner flow in the flow channel. The channel surface wettability on the water transport is also studied and is shown to have a significant impact on the water corner flow in the flow channel.

Modelling animal waste pathogen transport from agricultural land to streams

International Nuclear Information System (INIS)

Pandey, Pramod K; Soupir, Michelle L; Ikenberry, Charles

2014-01-01

The transport of animal waste pathogens from crop land to streams can potentially elevate pathogen levels in stream water. Applying animal manure into crop land as fertilizers is a common practice in developing as well as in developed countries. Manure application into the crop land, however, can cause potential human health. To control pathogen levels in ambient water bodies such as streams, improving our understanding of pathogen transport at farm scale as well as at watershed scale is required. To understand the impacts of crop land receiving animal waste as fertilizers on stream's pathogen levels, here we investigate pathogen indicator transport at watershed scale. We exploited watershed scale hydrological model to estimate the transport of pathogens from the crop land to streams. Pathogen indicator levels (i.e., E. coli levels) in the stream water were predicted. With certain assumptions, model results are reasonable. This study can be used as guidelines for developing the models for calculating the impacts of crop land's animal manure on stream water

Modeling Phosphorus Transport and Cycling in the Greater Everglades Ecosystem

Science.gov (United States)

James, A. I.; Grace, K. A.; Jawitz, J. W.; Muller, S.; Munoz-Carpena, R.; Flaig, E. G.

2005-12-01

A solute transport model was used to predict phosphorus mobility in the northern Everglades. Over the past several decades, agricultural drainage waters discharged into the northern Everglades, have been enriched in phosphorus (P) relative to the historic rainfall-driven inputs. While methods of reducing total P concentrations in the discharge water have been actively pursued through implementation of agricultural Best Management Practices (BMPs), a major parallel effort has focused on the construction of a network of constructed wetlands for P removal before these waters enter the Everglades. This study describes the development of a water quality model for P transport and cycling and its application to a large constructed wetland: Stormwater Treatment Area 1 West (STA 1W), located southeast of Lake Okeechobee on the eastern perimeter of the Everglades Agricultural Area (EAA). In STA 1W agricultural nutrients such as phosphorus (P) are removed from EAA runoff before entering the adjacent Water Conservation Areas (WCAs) and the Everglades. STA 1W is divided by levees into 4 cells, which are flooded for most of the year; thus the dominant mechanism for flow and transport is overland flow. P is removed either through deposition into sediments or is taken up by plants; in either case the soils end up being significantly enriched in P. The model has been applied and calibrated to several years of water quality data from Cell 4 within STA 1W. Most existing P models have been applied to agricultural/upland systems, with only a few relevant to treatment wetlands such as STA 1W. To ensure sufficient flexibility in selecting appropriate system components and reactions, the model has been designed to incorporate a wide range of user-selectable mechanisms for P uptake and release parameters between soils and inflowing water. The model can track a large number of mobile and nonmobile components and utilizes a Godunov-style operator-splitting technique for the transported

Sediment Transport Model for a Surface Irrigation System

Directory of Open Access Journals (Sweden)

Damodhara R. Mailapalli

2013-01-01

Full Text Available Controlling irrigation-induced soil erosion is one of the important issues of irrigation management and surface water impairment. Irrigation models are useful in managing the irrigation and the associated ill effects on agricultural environment. In this paper, a physically based surface irrigation model was developed to predict sediment transport in irrigated furrows by integrating an irrigation hydraulic model with a quasi-steady state sediment transport model to predict sediment load in furrow irrigation. The irrigation hydraulic model simulates flow in a furrow irrigation system using the analytically solved zero-inertial overland flow equations and 1D-Green-Ampt, 2D-Fok, and Kostiakov-Lewis infiltration equations. Performance of the sediment transport model was evaluated for bare and cropped furrow fields. The results indicated that the sediment transport model can predict the initial sediment rate adequately, but the simulated sediment rate was less accurate for the later part of the irrigation event. Sensitivity analysis of the parameters of the sediment module showed that the soil erodibility coefficient was the most influential parameter for determining sediment load in furrow irrigation. The developed modeling tool can be used as a water management tool for mitigating sediment loss from the surface irrigated fields.

STREAMFLOW AND WATER QUALITY REGRESSION MODELING ...

African Journals Online (AJOL)

... downstream Obigbo station show: consistent time-trends in degree of contamination; linear and non-linear relationships for water quality models against total dissolved solids (TDS), total suspended sediment (TSS), chloride, pH and sulphate; and non-linear relationship for streamflow and water quality transport models.

Uncertainty associated with selected environmental transport models

International Nuclear Information System (INIS)

Little, C.A.; Miller, C.W.

1979-11-01

A description is given of the capabilities of several models to predict accurately either pollutant concentrations in environmental media or radiological dose to human organs. The models are discussed in three sections: aquatic or surface water transport models, atmospheric transport models, and terrestrial and aquatic food chain models. Using data published primarily by model users, model predictions are compared to observations. This procedure is infeasible for food chain models and, therefore, the uncertainty embodied in the models input parameters, rather than the model output, is estimated. Aquatic transport models are divided into one-dimensional, longitudinal-vertical, and longitudinal-horizontal models. Several conclusions were made about the ability of the Gaussian plume atmospheric dispersion model to predict accurately downwind air concentrations from releases under several sets of conditions. It is concluded that no validation study has been conducted to test the predictions of either aquatic or terrestrial food chain models. Using the aquatic pathway from water to fish to an adult for 137 Cs as an example, a 95% one-tailed confidence limit interval for the predicted exposure is calculated by examining the distributions of the input parameters. Such an interval is found to be 16 times the value of the median exposure. A similar one-tailed limit for the air-grass-cow-milk-thyroid for 131 I and infants was 5.6 times the median dose. Of the three model types discussed in this report,the aquatic transport models appear to do the best job of predicting observed concentrations. However, this conclusion is based on many fewer aquatic validation data than were availaable for atmospheric model validation

Online estimation of radionuclide transportation in water environment

International Nuclear Information System (INIS)

Yi-Jing Zhang; Li-Sheng Hu

2017-01-01

Transportation evaluation of the radionuclide waste discharged from nuclear power plants is an essential licensing issue, especially for inland sites. Basically, the dynamics of radionuclide transportation are nonlinear and time-varying. Motivated by its time-consuming computation, the work proposed an online estimation method for the radionuclide waste in water surface. After extracting the nonlinearity of factors influencing radionuclide transportation, the method utilizes transfer function and generalized autoregressive conditional heteroskedasticity models to perform deterministic and probabilistic estimations. It turns out that, the resulting predictions show high accuracy and can optimize the online discharge management of radioactive waste for nuclear power plants. (author)

Coupling of transport and geochemical models

International Nuclear Information System (INIS)

Noy, D.J.

1986-01-01

This report considers mass transport in the far-field of a radioactive waste repository, and detailed geochemical modelling of the ground-water in the near-field. A parallel approach to this problem of coupling transport and geochemical codes is the subject of another CEC report (ref. EUR 10226). Both studies were carried out in the framework of the CEC project MIRAGE. (Migration of radionuclides in the geosphere)

The coordinated development of China＇ s inland water transport%The coordinated development of China' s inland water transport

Institute of Scientific and Technical Information of China (English)

Deng Aimin; Tian Feng; Haasis H.D; Mao Lang; Cai Jia

2012-01-01

The coordinated development is the core of sustainable development and the hot issue of international research. Inland water transport (IWT) is an important part of the water resources exploiting system and comprehensive transport system under socio-economic context of river basin, and also the country' s sustainable development priorities to achieve resource-conserving and environment-friendly strategy. Based on the coordinated development content, the paper combined Germany' s successful development experience, explored the elements and problem of the coordinated development of IWT system of China' s national economic strategy and basin economy, water resourse system, comprehensive transport system, and system itself, and their countermeasures and suggestions, in order to facilitate rapid and coordinated development of China' s inland water transport.

Transport Studies and Modeling in PEM Fuel Cells

Energy Technology Data Exchange (ETDEWEB)

Mittelsteadt, Cortney K. [Giner, Inc., Auburndale, MA (United States); Xu, Hui [Giner, Inc., Auburndale, MA (United States); Brawn, Shelly [Giner, Inc., Auburndale, MA (United States)

2014-07-30

This project’s aim was to develop fuel cell components (i.e. membranes, gas-diffusion media (GDM), bipolar plates and flow fields) that possess specific properties (i.e. water transport and conductivity). A computational fluid dynamics model was developed to elucidate the effect of certain parameters on these specific properties. Ultimately, the model will be used to determine sensitivity of fuel cell performance to component properties to determine limiting components and to guide research. We have successfully reached our objectives and achieved most of the milestones of this project. We have designed and synthesized a variety of hydrocarbon block polymer membranes with lower equivalent weight, structure, chemistry, phase separation and process conditions. These membranes provide a broad selection with optimized water transport properties. We have also designed and constructed a variety of devices that are capable of accurately measuring the water transport properties (water uptake, water diffusivity and electro-osmatic drag) of these membranes. These transport properties are correlated to the membranes’ structures derived from X-ray and microscopy techniques to determine the structure-property relationship. We successfully integrated hydrocarbon membrane MEAs with a current distribution board (CBD) to study the impact of hydrocarbon membrane on water transport in fuel cells. We have designed and fabricated various GDM with varying substrate, diffusivity and micro-porous layers (MPL) and characterized their pore structure, tortuosity and hydrophobicity. We have derived a universal chart (MacMullin number as function of wet proofing and porosity) that can be used to characterize various GDM. The abovementioned GDMs have been evaluated in operating fuel cells; their performance is correlated to various pore structure, tortuosity and hydrophobicity of the GDM. Unfortunately, determining a universal relationship between the MacMullin number and these properties

Transport of Water in Semicrystalline Block Copolymer Membranes

Science.gov (United States)

Hallinan, Daniel; Oparaji, Onyekachi

Poly(styrene)-block-poly(ethylene oxide) (PS- b-PEO) is a semicrystalline block copolymer (BCP) with interesting properties. It is mechanically tough, amphiphilic, and has a polar phase. The mechanical toughness is due to the crystallinity of PEO and the high glass transition temperature of PS, as well as the morphological structure of the BCP. The polymer has high CO2, water, and salt solubility that derive from the polar PEO component. Potential applications include CO2 separation, water purification, and lithium air batteries. In all of the aforementioned applications, water transport is an important parameter. The presence of water can also affect thermal and mechanical properties. Water transport and thermal and mechanical properties of a lamellar PS- b-PEO copolymer have been measured as a function of water activity. Water transport can be affected by the heterogeneous nature of a semicrystalline BCP. Therefore, Fourier transform infrared - attenuated total reflectance (FTIR-ATR) spectroscopy has been employed, because water transport and polymer swelling can be measured simultaneously. The effect of BCP structure on transport has been investigated by comparing water transport in PS- b-PEO to a PEO homopolymer. The crystalline content of the PEO and the presence of glassy PS lamellae will be used to explain the transport results.

Conceptual and Numerical Models for UZ Flow and Transport

International Nuclear Information System (INIS)

Liu, H.

2000-01-01

The purpose of this Analysis/Model Report (AMR) is to document the conceptual and numerical models used for modeling of unsaturated zone (UZ) fluid (water and air) flow and solute transport processes. This is in accordance with ''AMR Development Plan for U0030 Conceptual and Numerical Models for Unsaturated Zone (UZ) Flow and Transport Processes, Rev 00''. The conceptual and numerical modeling approaches described in this AMR are used for models of UZ flow and transport in fractured, unsaturated rock under ambient and thermal conditions, which are documented in separate AMRs. This AMR supports the UZ Flow and Transport Process Model Report (PMR), the Near Field Environment PMR, and the following models: Calibrated Properties Model; UZ Flow Models and Submodels; Mountain-Scale Coupled Processes Model; Thermal-Hydrologic-Chemical (THC) Seepage Model; Drift Scale Test (DST) THC Model; Seepage Model for Performance Assessment (PA); and UZ Radionuclide Transport Models

Molecular mechanisms of water transport in the eye

DEFF Research Database (Denmark)

Hamann, Steffen

2002-01-01

The four major sites for ocular water transport, the corneal epithelium and endothelium, the ciliary epithelium, and the retinal pigment epithelium, are reviewed. The cornea has an inherent tendency to swell, which is counteracted by its two surface cell layers, the corneal epithelium...... and endothelium. The bilayered ciliary epithelium secretes the aqueous humor into the posterior chamber, and the retinal pigment epithelium transports water from the retinal to the choroidal site. For each epithelium, ion transport mechanisms are associated with fluid transport, but the exact molecular coupling...... sites between ion and water transport remain undefined. In the retinal pigment epithelium, a H+-lactate cotransporter transports water. This protein could be the site of coupling between salt and water in this epithelium. The distribution of aquaporins does not suggest a role for these proteins...

Atmospheric water vapor transport: Estimation of continental precipitation recycling and parameterization of a simple climate model. M.S. Thesis

Science.gov (United States)

Brubaker, Kaye L.; Entekhabi, Dara; Eagleson, Peter S.

1991-01-01

The advective transport of atmospheric water vapor and its role in global hydrology and the water balance of continental regions are discussed and explored. The data set consists of ten years of global wind and humidity observations interpolated onto a regular grid by objective analysis. Atmospheric water vapor fluxes across the boundaries of selected continental regions are displayed graphically. The water vapor flux data are used to investigate the sources of continental precipitation. The total amount of water that precipitates on large continental regions is supplied by two mechanisms: (1) advection from surrounding areas external to the region; and (2) evaporation and transpiration from the land surface recycling of precipitation over the continental area. The degree to which regional precipitation is supplied by recycled moisture is a potentially significant climate feedback mechanism and land surface-atmosphere interaction, which may contribute to the persistence and intensification of droughts. A simplified model of the atmospheric moisture over continents and simultaneous estimates of regional precipitation are employed to estimate, for several large continental regions, the fraction of precipitation that is locally derived. In a separate, but related, study estimates of ocean to land water vapor transport are used to parameterize an existing simple climate model, containing both land and ocean surfaces, that is intended to mimic the dynamics of continental climates.

Predicting soil, water, and air concentrations of environmental contaminants locally and regionally: Multimedia transport and transformation models

International Nuclear Information System (INIS)

McKone, T.E.; Daniels, J.I.

1991-10-01

Environmental scientists recognize that the environment functions as a complex, interconnected system. A realistic risk-management strategy for many contaminants requires a comprehensive and integrated assessment of local and regional transport and transformation processes. In response to this need, we have developed multimedia models that simulate the movement and transformation of chemicals as they spread through air, water, biota, soils, sediments, surface water, and ground water. Each component of the environment is treated as a homogeneous subsystem that can exchange water, nutrients, and chemical contaminants with other adjacent compartments. In this paper, we illustrate the use of multimedia models and measurements as tools for screening the potential risks of contaminants released to air and deposited onto soil and plants. The contaminant list includes the volatile organic compounds (VOCs) tetrachloroethylene (PCE) and trichloroethylene (TCE), the semi-volatile organic compound benzo(a)pyrene, and the radionuclides tritium and uranium-238. We examine how chemical properties effect both the ultimate route and quantity of human and ecosystem contact and identify sensitivities and uncertainties in the model results

Mathematical simulation of sediment and contaminant transport in surface waters. Annual report, October 1977--September 1978

International Nuclear Information System (INIS)

Onishi, Y.; Arnold, E.M.; Serne, R.J.; Cowan, C.E.; Thompson, F.L.; Mayer, D.W.

1979-01-01

Various pathways exist for exposure of humans and biota to radioactive materials released from nuclear facilities. Hydrologic transport (liquid pathway) is one element in the evaluation of the total radiation dose to man. Mathematical models supported by well-planned field data collection programs can be useful tools in assessing the hydrologic transport and ultimate fate of radionuclides. Radionuclides with high distribution coefficients or radionuclides in surface waters with high suspended sediment concentrations are, to a great extent, adsorbed by river and marine sediments. Thus, otherwise dilute contaminants are concentrated. Contaminated sediments may be deposited on the river and ocean beds creating a significant pathway to man. Contaminated bed sediment in turn may become a long-term source of pollution through desorption and resuspension. In order to assess migration and accumulation of radionuclides in surface waters, mathematical models must correctly simulate essential mechanisms of radionuclide transport. The objectives of this study were: (1) to conduct a critical review of (a) radionuclide transport models as well as sediment transport and representative water quality models in rivers, estuaries, oceans, lakes, and reservoirs, and (b) adsorption and desorption mechanisms of radionuclides with sediments in surface waters; (2) to synthesize a mathematical model capable of predicting short- and long-term transport and accumulation of radionuclides in marine environments

Predicting soil, water and air concentrations of environmental contaminants locally and regionally; multimedia transport and transformation models

International Nuclear Information System (INIS)

McKone, T.E.; Daniels, J.I.

1991-01-01

Environmental scientists recognize that the environment functions as a complex, interconnected system. A realistic risk-management strategy for many contaminants requires a comprehensive and integrated assessment of local and regional transport and transformation processes. In response to this need, we have developed multimedia models that simulate the movement and transformation of chemicals as they spread through air, water, biota, soils, sediments, surface water and ground water. Each component of the environment is treated as a homogeneous subsystem that can exchange water, nutrients, and chemical contaminants with other adjacent compartments. In this paper, we illustrate the use of multimedia models and measurements as tools for screening the potential risks of contaminants released to air and deposited onto soil and plants. The contaminant list includes the volatile organic compounds (VOCs) tetrachloroethylene (PCE) and trichloroethylene (TCE), the semi-volatile organic compound benzo(a)pyrene, and the radionuclides tritium and uranium-238. We examine how chemical properties effect both the ultimate route and quantity of human and ecosystem contact and identify sensitivities and uncertainties in the model results. We consider the advantages of multimedia models relative to environmental monitoring data. (au)

The treatment of water-conducting features in groundwater flow and transport modelling of the Borrowdale Volcanic Group in Nirex 97

International Nuclear Information System (INIS)

Jackson, C.P.; Norris, S.; Todman, S.J.; Watson, S.P.

1999-01-01

In the Nirex 97 assessment of the post-closure performance of a repository at Sellafield, the potential repository host rock was the Borrowdale Volcanic Group (BVG). The treatment of water-conducting features in groundwater flow and transport modelling of the BVG is discussed. Groundwater flow in the BVG is predominantly through a subset of the total set of discontinuities - the Flowing Features (FFs). FFs can be identified in core samples by the presence of recent calcite. In boreholes, the FFs are clustered, and the clustering appears to be significant hydro-geologically. However, there is uncertainty about the connectivity of the clusters. A range of models is possible, from the case of isolated clusters to the case where the clusters form a well-connected network. The radiological risk from the repository was determined from radionuclide transport calculations based on the groundwater flow fields obtained from the regional-scale flow calculations. For rocks, such as the BVG, in which groundwater flows predominantly through discontinuities, diffusion into immobile water int the rock matrix between the discontinuities was modelled. Data from the site characterization and research programmes could be used to develop and parameterize groundwater flow and transport models for use in repository performance assessments. (author)

WATER SUPPLY OF TRANSPORT OBJECTS

OpenAIRE

Badyuk, N. S.

2009-01-01

Badyuk N. S. WATER SUPPLY OF TRANSPORT OBJECTS. АКТУАЛЬНЫЕ ПРОБЛЕМЫ ТРАНСПОРТНОЙ МЕДИЦИНЫ № 3 (17), 2009 г. P. 96-104 DOI http://dx.doi.org/10.5281/zenodo.1020024 http://dspace.nbuv.gov.ua/bitstream/handle/123456789/23091/13-Badyuk.pdf?sequence=1 WATER SUPPLY OF TRANSPORT OBJECTS Badyuk N. S. Ukrainian Research Institute for Medicine of Transport, Odessa, Ukraine Summary In the work presented they discuss several peculiarities of wa...

Water transport by the renal Na(+)-dicarboxylate cotransporter

DEFF Research Database (Denmark)

Meinild, A K; Loo, D D; Pajor, A M

2000-01-01

. This solute-coupled influx of water took place in the absence of, and even against, osmotic gradients. There was a strict stoichiometric relationship between Na(+), substrate, and water transport of 3 Na(+), 1 dicarboxylate, and 176 water molecules/transport cycle. These results indicate that the renal Na......This study investigated the ability of the renal Na(+)-dicarboxylate cotransporter, NaDC-1, to transport water. Rabbit NaDC-1 was expressed in Xenopus laevis oocytes, cotransporter activity was measured as the inward current generated by substrate (citrate or succinate), and water transport...... was monitored by the changes in oocyte volume. In the absence of substrates, oocytes expressing NaDC-1 showed an increase in osmotic water permeability, which was directly correlated with the expression level of NaDC-1. When NaDC-1 was transporting substrates, there was a concomitant increase in oocyte volume...

Roles and significance of water conducting features for transport models in performance assessment

International Nuclear Information System (INIS)

Carrera, J.; Sanchez-Vila, X.; Medina, A.

1999-01-01

The term water conducting features (WCF) refers to zones of high hydraulic conductivity. In the context of waste disposal, it is further implied that they are narrow so that chances of sampling them are low. Yet, they may carry significant amounts of water. Moreover, their relatively small volumetric water content causes solutes to travel fast through them. Water-conducting features are a rather common feature of natural media. The fact that they have become a source of concern in recent years, reflects more the increased level of testing and monitoring than any intrinsic property of low permeability media. Accurate simulations of solute transport require a realistic accounting for water conducting features. Methods are presented to do so and examples are shown to illustrate these methods. Since detailed accounting of WCF's will not be possible in actual performance assessments, efforts should be directed towards typification, so as to identify the essential effects of WCF's on solute transport through different types of rocks. Field evidence suggests that, although individual WCF's may be difficult to characterize, their effects are quite predictable. (author)

Radionuclide Transport Models Under Ambient Conditions

International Nuclear Information System (INIS)

Moridis, G.; Hu, Q.

2001-01-01

The purpose of Revision 00 of this Analysis/Model Report (AMR) is to evaluate (by means of 2-D semianalytical and 3-D numerical models) the transport of radioactive solutes and colloids in the unsaturated zone (UZ) under ambient conditions from the potential repository horizon to the water table at Yucca Mountain (YM), Nevada

Water Distribution and Removal Model

International Nuclear Information System (INIS)

Y. Deng; N. Chipman; E.L. Hardin

2005-01-01

The design of the Yucca Mountain high level radioactive waste repository depends on the performance of the engineered barrier system (EBS). To support the total system performance assessment (TSPA), the Engineered Barrier System Degradation, Flow, and Transport Process Model Report (EBS PMR) is developed to describe the thermal, mechanical, chemical, hydrological, biological, and radionuclide transport processes within the emplacement drifts, which includes the following major analysis/model reports (AMRs): (1) EBS Water Distribution and Removal (WD and R) Model; (2) EBS Physical and Chemical Environment (P and CE) Model; (3) EBS Radionuclide Transport (EBS RNT) Model; and (4) EBS Multiscale Thermohydrologic (TH) Model. Technical information, including data, analyses, models, software, and supporting documents will be provided to defend the applicability of these models for their intended purpose of evaluating the postclosure performance of the Yucca Mountain repository system. The WD and R model ARM is important to the site recommendation. Water distribution and removal represents one component of the overall EBS. Under some conditions, liquid water will seep into emplacement drifts through fractures in the host rock and move generally downward, potentially contacting waste packages. After waste packages are breached by corrosion, some of this seepage water will contact the waste, dissolve or suspend radionuclides, and ultimately carry radionuclides through the EBS to the near-field host rock. Lateral diversion of liquid water within the drift will occur at the inner drift surface, and more significantly from the operation of engineered structures such as drip shields and the outer surface of waste packages. If most of the seepage flux can be diverted laterally and removed from the drifts before contacting the wastes, the release of radionuclides from the EBS can be controlled, resulting in a proportional reduction in dose release at the accessible environment

Water Distribution and Removal Model

Energy Technology Data Exchange (ETDEWEB)

Y. Deng; N. Chipman; E.L. Hardin

2005-08-26

The design of the Yucca Mountain high level radioactive waste repository depends on the performance of the engineered barrier system (EBS). To support the total system performance assessment (TSPA), the Engineered Barrier System Degradation, Flow, and Transport Process Model Report (EBS PMR) is developed to describe the thermal, mechanical, chemical, hydrological, biological, and radionuclide transport processes within the emplacement drifts, which includes the following major analysis/model reports (AMRs): (1) EBS Water Distribution and Removal (WD&R) Model; (2) EBS Physical and Chemical Environment (P&CE) Model; (3) EBS Radionuclide Transport (EBS RNT) Model; and (4) EBS Multiscale Thermohydrologic (TH) Model. Technical information, including data, analyses, models, software, and supporting documents will be provided to defend the applicability of these models for their intended purpose of evaluating the postclosure performance of the Yucca Mountain repository system. The WD&R model ARM is important to the site recommendation. Water distribution and removal represents one component of the overall EBS. Under some conditions, liquid water will seep into emplacement drifts through fractures in the host rock and move generally downward, potentially contacting waste packages. After waste packages are breached by corrosion, some of this seepage water will contact the waste, dissolve or suspend radionuclides, and ultimately carry radionuclides through the EBS to the near-field host rock. Lateral diversion of liquid water within the drift will occur at the inner drift surface, and more significantly from the operation of engineered structures such as drip shields and the outer surface of waste packages. If most of the seepage flux can be diverted laterally and removed from the drifts before contacting the wastes, the release of radionuclides from the EBS can be controlled, resulting in a proportional reduction in dose release at the accessible environment. The purposes

Modelling freight transport

NARCIS (Netherlands)

Tavasszy, L.A.; Jong, G. de

2014-01-01

Freight Transport Modelling is a unique new reference book that provides insight into the state-of-the-art of freight modelling. Focusing on models used to support public transport policy analysis, Freight Transport Modelling systematically introduces the latest freight transport modelling

A Stochastic Multi-Media Model of Microbial Transport in Watersheds

Science.gov (United States)

Yeghiazarian, L.; Safwat, A.; Whiteaker, T.; Teklitz, A.; Nietch, C.; Maidment, D. R.; Best, E. P.

2012-12-01

Fecal contamination is the leading cause of surface-water impairment in the US, and fecal pathogens are capable of triggering massive outbreaks of gastrointestinal disease. The difficulty in prediction of water contamination has its roots in the stochastic variability of fecal pathogens in the environment, and in the complexity of microbial dynamics and interactions on the soil surface and in water. To address these challenges, we have developed a stochastic model whereby the transport of microorganisms in watersheds is considered in two broad categories: microorganisms that are attached to mineral or organic substrates in suspended sediment; and unattached microorganisms suspended in overland flow. The interactions of microorganisms with soil particles on the soil surface and in the overland flow lead to transitions of microorganisms between solid and aqueous media. The strength of attachment of microorganisms to soil particles is determined by the chemical characteristics of soils which are highly correlated with the particle size. The particle size class distribution in the suspended sediment is predicted by the Water Erosion Prediction Project (WEPP). The model is integrated with ArcGIS, resulting in a general transport-modeling framework applicable to a variety of biological and chemical surface water contaminants. Simulations are carried out for a case study of contaminant transport in the East Fork Little Miami River Watershed in Ohio. Model results include the spatial probability distribution of microbes in the watershed and can be used for assessment of (1) mechanisms dominating microbial transport, and (2) time and location of highest likelihood of microbial occurrence, thus yielding information on best water sampling strategies.

Seasonal Water Transport in the Atmosphere of Mars: Applications of a Mars General Circulation Model Using Mars Global Surveyor Data

Science.gov (United States)

Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

1999-01-01

This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. We present below a summary of progress made during the duration of this JRI. The focus of this JRI has been to investigate seasonal water vapor transport in the atmosphere of Mars and its effects on the planet's present climate. To this end, the primary task has been to adapt a new dynamical processor for the adiabatic tendencies of the atmospheric circulation into the NASA Ames Mars general circulation model (MGCM). Using identical boundary and initial conditions, several comparative tests between the new and old MGCMs have been performed and the nature of the simulated circulations have been diagnosed. With confidence that the updated version of the Ames MGCM produces quite similar mean and eddy circulation statistics, the new climate model is well poised as a tool to pursue fundamental questions related to the spatial and seasonal variations of atmospheric water vapor on Mars, and to explore exchanges of water with non-atmospheric reservoirs and transport within its atmosphere. In particular, the role of surface sources and sinks can be explored, the range of water-vapor saturation altitudes can be investigated, and plausible precipitation mechanisms can be studied, for a range of atmospheric dust loadings. Such future investigations can contribute to a comprehensive study of surface inventories, exchange mechanisms, and the relative importance of atmospheric transport Mars' water cycle. A listing of presentations made and manuscripts submitted during the course of this project is provided.

A deterministic-probabilistic model for contaminant transport. User manual

Energy Technology Data Exchange (ETDEWEB)

Schwartz, F W; Crowe, A

1980-08-01

This manual describes a deterministic-probabilistic contaminant transport (DPCT) computer model designed to simulate mass transfer by ground-water movement in a vertical section of the earth's crust. The model can account for convection, dispersion, radioactive decay, and cation exchange for a single component. A velocity is calculated from the convective transport of the ground water for each reference particle in the modeled region; dispersion is accounted for in the particle motion by adding a readorn component to the deterministic motion. The model is sufficiently general to enable the user to specify virtually any type of water table or geologic configuration, and a variety of boundary conditions. A major emphasis in the model development has been placed on making the model simple to use, and information provided in the User Manual will permit changes to the computer code to be made relatively easily for those that might be required for specific applications. (author)

Quasi-three dimensional dynamic modeling of a proton exchange membrane fuel cell with consideration of two-phase water transport through a gas diffusion layer

International Nuclear Information System (INIS)

Kang, Sanggyu

2015-01-01

Water management is one of the challenging issues for low-temperature PEMFCs (proton exchange membrane fuel cells). When liquid water is formed at the GDL (gas diffusion layer), the pathway of reactant gas can be blocked, which inhibits the electrochemical reaction of PEMFC. Thus, liquid water transport through GDL is a critical factor determining the performance of a PEMFC. In present study, quasi-three dimensional dynamic modeling of PEMFC with consideration of two-phase water transport through GDL is developed. To investigate the distributions of PEMFC characteristics, including current density, species mole fraction, and membrane hydration, the PEMFC was discretized into twenty control volumes along the anode channel. To resolve the mass and energy conservation, the PEMFC is discretized into eleven and fifteen control volumes in the perpendicular direction, respectively. The dynamic variation of PEMFC characteristics of cell voltage, overvoltage of activation and ohmic, liquid water saturation through a GDL, and oxygen concentration were captured during transient behavior. - Highlights: • A quasi-three dimensional two-phase dynamic model of PEMFC is developed. • Presented model is validated by comparison with experimental data. • Two-phase model is compared with one-phase model at steady-states and transients.

Assessment of the contamination of drinking water supply wells by pesticides from surface water resources using a finite element reactive transport model and global sensitivity analysis techniques

DEFF Research Database (Denmark)

Malaguerra, Flavio; Albrechtsen, Hans-Jørgen; Binning, Philip John

2013-01-01

A reactive transport model is employed to evaluate the potential for contamination of drinking water wells by surface water pollution. The model considers various geologic settings, includes sorption and degradation processes and is tested by comparison with data from a tracer experiment where...... fluorescein dye injected in a river is monitored at nearby drinking water wells. Three compounds were considered: an older pesticide MCPP (Mecoprop) which is mobile and relatively persistent, glyphosate (Roundup), a newer biodegradable and strongly sorbing pesticide, and its degradation product AMPA. Global...... sensitivity analysis using the Morris method is employed to identify the dominant model parameters. Results show that the characteristics of clay aquitards (degree of fracturing and thickness), pollutant properties and well depths are crucial factors when evaluating the risk of drinking water well...

Water transport in desert alluvial soil

International Nuclear Information System (INIS)

Kearl, P.M.

1982-04-01

Safe storage of radioactive waste buried in an arid alluvial soil requires extensive site characterization of the physical process influencing moisture movement which could act as a transport medium for the migration of radionuclides. The field portion of this study included an infiltration plot instrumented with thermocouple psychrometers and neturon moisture probe access holes. Baseline information shows a zone of higher moisture content at approximately 1.5 m (5 ft) in depth. A sprinkler system simulated a 500-year precipitation event. Results revealed water penetrated the soil to 0.9 m (2.9 ft). Due to the low moisture content, vapor transport was primarily responsible for water movement at this depth. Temperature gradients are substantially responsible for vapor transport by preferentially sorting water-vapor molecules from the surrounding air by using the soil as a molecular sieve. Adsorbed and capillary water vapor pressure increases in response to a temperature increase and releases additional water to the soil pore atmosphere to be diffused away

Transport properties site descriptive model. Guidelines for evaluation and modelling

International Nuclear Information System (INIS)

Berglund, Sten; Selroos, Jan-Olof

2004-04-01

transport properties, and hence the guidelines in this report, involve two main categories of parameters: Parameters that characterise the retention properties of geologic materials. These parameters quantify the diffusion and sorption properties of intact and altered rock, fracture coatings and fracture-filling materials, and are described within the framework of the 3D geometric models devised by Geology. Parameters that characterise solute transport along flow paths (flow-related transport parameters). These parameters include the 'F-parameter' and 'water travel time', tw, and parameters that account for spatial variability in diffusion and sorption. The flow-related parameters are obtained by means of particle tracking simulations in groundwater flow models

ALGE3D: A Three-Dimensional Transport Model

Science.gov (United States)

Maze, G. M.

2017-12-01

Of the top 10 most populated US cities from a 2015 US Census Bureau estimate, 7 of the cities are situated near the ocean, a bay, or on one of the Great Lakes. A contamination of the water ways in the United States could be devastating to the economy (through tourism and industries such as fishing), public health (from direct contact, or contaminated drinking water), and in some cases even infrastructure (water treatment plants). Current national response models employed by emergency response agencies have well developed models to simulate the effects of hazardous contaminants in riverine systems that are primarily driven by one-dimensional flows; however in more complex systems, such as tidal estuaries, bays, or lakes, a more complex model is needed. While many models exist, none are capable of quick deployment in emergency situations that could contain a variety of release situations including a mixture of both particulate and dissolved chemicals in a complex flow area. ALGE3D, developed at the Department of Energy's (DOE) Savannah River National Laboratory (SRNL), is a three-dimensional hydrodynamic code which solves the momentum, mass, and energy conservation equations to predict the movement and dissipation of thermal or dissolved chemical plumes discharged into cooling lakes, rivers, and estuaries. ALGE3D is capable of modeling very complex flows, including areas with tidal flows which include wetting and drying of land. Recent upgrades have increased the capabilities including the transport of particulate tracers, allowing for more complete modeling of the transport of pollutants. In addition the model is capable of coupling with a one-dimension riverine transport model or a two-dimension atmospheric deposition model in the event that a contamination event occurs upstream or upwind of the water body.

Modelling transport of storm-water pollutants using the distributed Multi-Hydro platform on an urban catchment near Paris

Science.gov (United States)

Hong, Yi; Bonhomme, Celine; Giangola-Murzyn, Agathe; Schertzer, Daniel; Chebbo, Ghassan

2015-04-01

Nowadays, the increasingly use of vehicles causes expanding contaminated storm-water runoff from roads and the associated quarters. Besides, the current utilization of city's separated sewer systems underlines the needs for evaluating precisely the growing impact of these polluted effluents on receiving water bodies. Nevertheless, traditional means of water quality modelling had shown its limits (Kanso, 2004), more accurate modelling schemes are hence required. In this paper, we found that the application of physically based and fully distributed model coupled with detailed high-resolution data is a promising approach to reproduce the various dynamics and interactions of water quantity/quality processes in urban or peri-urban environment. Over recent years, the physically based and spatially distributed numerical platform Multi-Hydro (MH) has been developed at Ecole des Ponts ParisTech (El-Tabach et al. , 2009 ; Gires et al., 2013 ; Giangola-Murzyn et al., 2014). This platform is particularly adapted for representing the hydrological processes for medium size watersheds, including the surface runoff, drainage water routing and the infiltrations on permeable zones. It is formed by the interactive coupling of several independent modules, which depend on generally used open-access models. In the framework of the ANR (French National Agency for Research) Trafipollu project, a new extension of MH, MH-quality, was set up for the water-quality modelling. MH-quality was used for the simulation of pollutant transport on a peri-urban and highly trafficked catchment located near Paris (Le Perreux-sur-Marne, 0.2 km2). The set-up of this model is based on the detailed description of urban land use features. For this purpose, 15 classes of urban land uses relevant to water quality modelling were defined in collaboration with the National Institute of Geography of France (IGN) using Digital Orthophoto Quadrangles (5cm). The delimitation of the urban catchment was then performed

Heat Transfer in Directional Water Transport Fabrics

Directory of Open Access Journals (Sweden)

Chao Zeng

2016-10-01

Full Text Available Directional water transport fabrics can proactively transfer moisture from the body. They show great potential in making sportswear and summer clothing. While moisture transfer has been previously reported, heat transfer in directional water transport fabrics has been little reported in research literature. In this study, a directional water transport fabric was prepared using an electrospraying technique and its heat transfer properties under dry and wet states were evaluated, and compared with untreated control fabric and the one pre-treated with NaOH. All the fabric samples showed similar heat transfer features in the dry state, and the equilibrium temperature in the dry state was higher than for the wet state. Wetting considerably enhanced the thermal conductivity of the fabrics. Our studies indicate that directional water transport treatment assists in moving water toward one side of the fabric, but has little effect on thermal transfer performance. This study may be useful for development of “smart” textiles for various applications.

Numerical investigations for insulation particle transport phenomena in water flow

International Nuclear Information System (INIS)

Krepper, E.; Grahn, A.; Alt, S.; Kaestner, W.; Kratzsch, A.; Seeliger, A.

2005-01-01

The investigation of insulation debris generation, transport and sedimentation gains importance regarding the reactor safety research for PWR and BWR considering the long term behaviour of emergency core coolant systems during all types of LOCA. The insulation debris released near the break during LOCA consists of a mixture of very different particles concerning size, shape, consistence and other properties. Some fraction of the released insulation debris will be transported into the reactor sump where it may affect emergency core cooling. Open questions of generic interest are e.g. the sedimentation of the insulation debris in a water pool, possible re-suspension, transport in the sump water flow, particle load on strainers and corresponding difference pressure. A joint research project in cooperation with Institute of Process Technology, Process Automation and Measuring Technology (IPM) Zittau deals with the experimental investigation and the development of CFD models for the description of particle transport phenomena in coolant flow. While experiments are performed at the IPM-Zittau, theoretical work is concentrated at Forschungszentrum Rossendorf. In the present paper the basic concepts for CFD modelling are described and first results including feasibility studies are shown. During the ongoing work further results are expected. (author)

Simulation of water movement and NaCl transport

International Nuclear Information System (INIS)

Li Xun; Zheng Zhihong; Yang Zeping

2008-01-01

Modeling of water flow and solute transport in the near-field of a high-level radioactive waste repository with TOUGH2 is done. The results show that salt accumulation in buffer material is not so significant, precipitation does not occur throughout the period covered by our simualtions. Further more, the changeable law of volumetric water content, liquid velocity and dissolved concentration of sodium chloride with simulated time or distance are attained, which is the base of understanding evolvement of near-field. (authors)

Students' Conceptions of Water Transport

Science.gov (United States)

Rundgren, Carl-Johan; Rundgren, Shu-Nu Chang; Schonborn, Konrad J.

2010-01-01

Understanding diffusion of water into and out of the cell through osmosis is fundamental to the learning and teaching of biology. Although this process is thought of as occurring directly across the lipid bilayer, the majority of water transport is actually mediated by specialised transmembrane water-channels called aquaporins. This study…

A coupled hydrodynamic-hydrochemical modeling for predicting mineral transport in a natural acid drainage system.

Science.gov (United States)

Zegers Risopatron, G., Sr.; Navarro, L.; Montserrat, S., Sr.; McPhee, J. P.; Niño, Y.

2017-12-01

The geochemistry of water and sediments, coupled with hydrodynamic transport in mountainous channels, is of particular interest in central Chilean Andes due to natural occurrence of acid waters. In this paper, we present a coupled transport and geochemical model to estimate and understand transport processes and fate of minerals at the Yerba Loca Basin, located near Santiago, Chile. In the upper zone, water presentes low pH ( 3) and high concentrations of iron, aluminum, copper, manganese and zinc. Acidity and minerals are the consequence of water-rock interactions in hydrothermal alteration zones, rich in sulphides and sulphates, covered by seasonal snow and glaciers. Downstream, as a consequence of neutral to alkaline lateral water contributions (pH >7) along the river, pH increases and concentration of solutes decreases. The mineral transport model has three components: (i) a hydrodynamic model, where we use HEC-RAS to solve 1D Saint-Venant equations, (ii) a sediment transport model to estimate erosion and sedimentation rates, which quantify minerals transference between water and riverbed and (iii) a solute transport model, based on the 1D OTIS model which takes into account the temporal delay in solutes transport that typically is observed in natural channels (transient storage). Hydrochemistry is solved using PHREEQC, a software for speciation and batch reaction. Our results show that correlation between mineral precipitation and dissolution according to pH values changes along the river. Based on pH measurements (and according to literature) we inferred that main minerals in the water system are brochantite, ferrihydrite, hydrobasaluminite and schwertmannite. Results show that our model can predict the transport and fate of minerals and metals in the Yerba Loca Basin. Mineral dissolution and precipitation process occur for limited ranges of pH values. When pH values are increased, iron minerals (schwertmannite) are the first to precipitate ( 2.5

A 3-D functional-structural grapevine model that couples the dynamics of water transport with leaf gas exchange.

Science.gov (United States)

Zhu, Junqi; Dai, Zhanwu; Vivin, Philippe; Gambetta, Gregory A; Henke, Michael; Peccoux, Anthony; Ollat, Nathalie; Delrot, Serge

2017-12-23

Predicting both plant water status and leaf gas exchange under various environmental conditions is essential for anticipating the effects of climate change on plant growth and productivity. This study developed a functional-structural grapevine model which combines a mechanistic understanding of stomatal function and photosynthesis at the leaf level (i.e. extended Farqhuhar-von Caemmerer-Berry model) and the dynamics of water transport from soil to individual leaves (i.e. Tardieu-Davies model). The model included novel features that account for the effects of xylem embolism (fPLC) on leaf hydraulic conductance and residual stomatal conductance (g0), variable root and leaf hydraulic conductance, and the microclimate of individual organs. The model was calibrated with detailed datasets of leaf photosynthesis, leaf water potential, xylem sap abscisic acid (ABA) concentration and hourly whole-plant transpiration observed within a soil drying period, and validated with independent datasets of whole-plant transpiration under both well-watered and water-stressed conditions. The model well captured the effects of radiation, temperature, CO2 and vapour pressure deficit on leaf photosynthesis, transpiration, stomatal conductance and leaf water potential, and correctly reproduced the diurnal pattern and decline of water flux within the soil drying period. In silico analyses revealed that decreases in g0 with increasing fPLC were essential to avoid unrealistic drops in leaf water potential under severe water stress. Additionally, by varying the hydraulic conductance along the pathway (e.g. root and leaves) and changing the sensitivity of stomatal conductance to ABA and leaf water potential, the model can produce different water use behaviours (i.e. iso- and anisohydric). The robust performance of this model allows for modelling climate effects from individual plants to fields, and for modelling plants with complex, non-homogenous canopies. In addition, the model provides a

Process-based reactive transport model to quantify arsenic mobility during aquifer storage and recovery of potable water.

Science.gov (United States)

Wallis, Ilka; Prommer, Henning; Pichler, Thomas; Post, Vincent; Norton, Stuart B; Annable, Michael D; Simmons, Craig T

2011-08-15

Aquifer storage and recovery (ASR) is an aquifer recharge technique in which water is injected in an aquifer during periods of surplus and withdrawn from the same well during periods of deficit. It is a critical component of the long-term water supply plan in various regions, including Florida, USA. Here, the viability of ASR as a safe and cost-effective water resource is currently being tested at a number of sites due to elevated arsenic concentrations detected during groundwater recovery. In this study, we developed a process-based reactive transport model of the coupled physical and geochemical mechanisms controlling the fate of arsenic during ASR. We analyzed multicycle hydrochemical data from a well-documented affected southwest Floridan site and evaluated a conceptual/numerical model in which (i) arsenic is initially released during pyrite oxidation triggered by the injection of oxygenated water (ii) then largely complexes to neo-formed hydrous ferric oxides before (iii) being remobilized during recovery as a result of both dissolution of hydrous ferric oxides and displacement from sorption sites by competing anions.

Fuel cell water transport

Science.gov (United States)

Vanderborgh, Nicholas E.; Hedstrom, James C.

1990-01-01

The moisture content and temperature of hydrogen and oxygen gases is regulated throughout traverse of the gases in a fuel cell incorporating a solid polymer membrane. At least one of the gases traverses a first flow field adjacent the solid polymer membrane, where chemical reactions occur to generate an electrical current. A second flow field is located sequential with the first flow field and incorporates a membrane for effective water transport. A control fluid is then circulated adjacent the second membrane on the face opposite the fuel cell gas wherein moisture is either transported from the control fluid to humidify a fuel gas, e.g., hydrogen, or to the control fluid to prevent excess water buildup in the oxidizer gas, e.g., oxygen. Evaporation of water into the control gas and the control gas temperature act to control the fuel cell gas temperatures throughout the traverse of the fuel cell by the gases.

Heat and water transport in soils and across the soil-atmosphere interface: 1. Theory and different model concepts

DEFF Research Database (Denmark)

Vanderborght, Jan; Fetzer, Thomas; Mosthaf, Klaus

2017-01-01

on a theoretical level by identifying the underlying simplifications that are made for the different compartments of the system: porous medium, free flow and their interface, and by discussing how processes not explicitly considered are parameterized. Simplifications can be grouped into three sets depending......Evaporation is an important component of the soil water balance. It is composed of water flow and transport processes in a porous medium that are coupled with heat fluxes and free air flow. This work provides a comprehensive review of model concepts used in different research fields to describe...

Speciation and transport of radionuclides in ground water

International Nuclear Information System (INIS)

Robertson, D.E.; Toste, A.P.; Abel, K.H.; Cowan, C.E.; Jenne, E.A.; Thomas, C.W.

1984-01-01

Studies of the chemical speciation of a number of radionuclides migrating in a slightly contaminated ground water plume are identifying the most mobile species and providing an opportunity to test and/or validate geochemical models of radionuclide transport in ground waters. Results to date have shown that most of the migrating radionuclides are present in anionic or nonionic forms. These include anionic forms of 55 Fe, 60 Co, /sup 99m/Tc, 106 Ru, 131 I, and nonionic forms of 63 Ni and 125 Sb. Strontium-70 and a small fraction of the mobile 60 Co are the only cationic radionuclides which have been detected moving in the ground water plume beyond 30 meters from the source. A comparison of the observed chemical forms with the predicted species calculated from modeling thermodynamic data and ground water chemical parameters has indicated a good agreement for most of the radioelements in the system, including Tc, Np, Cs, Sr, Ce, Ru, Sb, Zn, and Mn. The discrepancies between observed and calculated solutions species were noted for Fe, Co, Ni and I. Traces of Fe, Co, and Ni were observed to migrate in anionic or nonionic forms which the calculations failed to predict. These anionic/nonionic species may be organic complexes having enhanced mobility in ground waters. The radioiodine, for example, was shown to behave totally as an anion but further investigation revealed that 49-57% of this anionic iodine was organically bound. The ground water and aqueous extracts of trench sediments contain a wide variety of organic compounds, some of which could serve as complexing agents for the radionuclides. These results indicate the need for further research at a variety of field sites in defining precisely the chemical forms of the mobile radionuclide species, and in better understanding the role of dissolved organic materials in ground water transport of radionuclides

Modeling Np and Pu transport with a surface complexation model and spatially variant sorption capacities: Implications for reactive transport modeling and performance assessments of nuclear waste disposal sites

Science.gov (United States)

Glynn, P.D.

2003-01-01

One-dimensional (1D) geochemical transport modeling is used to demonstrate the effects of speciation and sorption reactions on the ground-water transport of Np and Pu, two redox-sensitive elements. Earlier 1D simulations (Reardon, 1981) considered the kinetically limited dissolution of calcite and its effect on ion-exchange reactions (involving 90Sr, Ca, Na, Mg and K), and documented the spatial variation of a 90Sr partition coefficient under both transient and steady-state chemical conditions. In contrast, the simulations presented here assume local equilibrium for all reactions, and consider sorption on constant potential, rather than constant charge, surfaces. Reardon's (1981) seminal findings on the spatial and temporal variability of partitioning (of 90Sr) are reexamined and found partially caused by his assumption of a kinetically limited reaction. In the present work, sorption is assumed the predominant retardation process controlling Pu and Np transport, and is simulated using a diffuse-double-layer-surface-complexation (DDLSC) model. Transport simulations consider the infiltration of Np- and Pu-contaminated waters into an initially uncontaminated environment, followed by the cleanup of the resultant contamination with uncontaminated water. Simulations are conducted using different spatial distributions of sorption capacities (with the same total potential sorption capacity, but with different variances and spatial correlation structures). Results obtained differ markedly from those that would be obtained in transport simulations using constant Kd, Langmuir or Freundlich sorption models. When possible, simulation results (breakthrough curves) are fitted to a constant K d advection-dispersion transport model and compared. Functional differences often are great enough that they prevent a meaningful fit of the simulation results with a constant K d (or even a Langmuir or Freundlich) model, even in the case of Np, a weakly sorbed radionuclide under the

Fish larval transport in the coastal waters through ecological modelling

Digital Repository Service at National Institute of Oceanography (India)

George, G.

are as follows: (i) to find out the influence of environmental parameters on the biology of the given ecosystem (ii) to track larval transport and biological abundance in relation to environmental vari- ables (iii) to compare biological abundance and fish larval... include the following investigations: (i) analysis of satellite chlorophyll data along the southwest coastal waters of India to derive a biological calender for sardine (ii) tracking the larval survival and establish a link between food and sardine inter...

A post audit and inverse modeling in reactive transport: 50 years of artificial recharge in the Amsterdam Water Supply Dunes

Science.gov (United States)

Karlsen, R. H.; Smits, F. J. C.; Stuyfzand, P. J.; Olsthoorn, T. N.; van Breukelen, B. M.

2012-08-01

SummaryThis article describes the post audit and inverse modeling of a 1-D forward reactive transport model. The model simulates the changes in water quality following artificial recharge of pre-treated water from the river Rhine in the Amsterdam Water Supply Dunes using the PHREEQC-2 numerical code. One observation dataset is used for model calibration, and another dataset for validation of model predictions. The total simulation time of the model is 50 years, from 1957 to 2007, with recharge composition varying on a monthly basis and the post audit is performed 26 years after the former model simulation period. The post audit revealed that the original model could reasonably predict conservative transport and kinetic redox reactions (oxygen and nitrate reduction coupled to the oxidation of soil organic carbon), but showed discrepancies in the simulation of cation exchange. Conceptualizations of the former model were inadequate to accurately simulate water quality changes controlled by cation exchange, especially concerning the breakthrough of potassium and magnesium fronts. Changes in conceptualization and model design, including the addition of five flow paths, to a total of six, and the use of parameter estimation software (PEST), resulted in a better model to measurement fit and system representation. No unique parameter set could be found for the model, primarily due to high parameter correlations, and an assessment of the predictive error was made using a calibration constrained Monte-Carlo method, and evaluated against field observations. The predictive error was found to be low for Na+ and Ca2+, except for greater travel times, while the K+ and Mg2+ error was restricted to the exchange fronts at some of the flow paths. Optimized cation exchange coefficients were relatively high, especially for potassium, but still within the observed range in literature. The exchange coefficient for potassium agrees with strong fixation on illite, a main clay mineral in

Dynamic modeling of interfacial structures via interfacial area transport equation

International Nuclear Information System (INIS)

Seungjin, Kim; Mamoru, Ishii

2005-01-01

The interfacial area transport equation dynamically models the two-phase flow regime transitions and predicts continuous change of the interfacial area concentration along the flow field. Hence, when employed in the numerical thermal-hydraulic system analysis codes, it eliminates artificial bifurcations stemming from the use of the static flow regime transition criteria. Accounting for the substantial differences in the transport phenomena of various sizes of bubbles, the two-group interfacial area transport equations have been developed. The group 1 equation describes the transport of small-dispersed bubbles that are either distorted or spherical in shapes, and the group 2 equation describes the transport of large cap, slug or churn-turbulent bubbles. The source and sink terms in the right-hand-side of the transport equations have been established by mechanistically modeling the creation and destruction of bubbles due to major bubble interaction mechanisms. In the present paper, the interfacial area transport equations currently available are reviewed to address the feasibility and reliability of the model along with extensive experimental results. These include the data from adiabatic upward air-water two-phase flow in round tubes of various sizes, from a rectangular duct, and from adiabatic co-current downward air-water two-phase flow in round pipes of two sizes. (authors)

Multiscale modeling of a rectifying bipolar nanopore: explicit-water versus implicit-water simulations.

Science.gov (United States)

Ható, Zoltán; Valiskó, Mónika; Kristóf, Tamás; Gillespie, Dirk; Boda, Dezsö

2017-07-21

In a multiscale modeling approach, we present computer simulation results for a rectifying bipolar nanopore at two modeling levels. In an all-atom model, we use explicit water to simulate ion transport directly with the molecular dynamics technique. In a reduced model, we use implicit water and apply the Local Equilibrium Monte Carlo method together with the Nernst-Planck transport equation. This hybrid method makes the fast calculation of ion transport possible at the price of lost details. We show that the implicit-water model is an appropriate representation of the explicit-water model when we look at the system at the device (i.e., input vs. output) level. The two models produce qualitatively similar behavior of the electrical current for different voltages and model parameters. Looking at the details of concentration and potential profiles, we find profound differences between the two models. These differences, however, do not influence the basic behavior of the model as a device because they do not influence the z-dependence of the concentration profiles which are the main determinants of current. These results then address an old paradox: how do reduced models, whose assumptions should break down in a nanoscale device, predict experimental data? Our simulations show that reduced models can still capture the overall device physics correctly, even though they get some important aspects of the molecular-scale physics quite wrong; reduced models work because they include the physics that is necessary from the point of view of device function. Therefore, reduced models can suffice for general device understanding and device design, but more detailed models might be needed for molecular level understanding.

Optimum design for effective water transport through a double-layered porous hydrogel inspired by plant leaves

Science.gov (United States)

Kim, Hyejeong; Kim, Hyeonjeong; Huh, Hyungkyu; Hwang, Hyung Ju; Lee, Sang Joon

2014-11-01

Plant leaves are generally known to have optimized morphological structure in response to environmental changes for efficient water usage. However, the advantageous features of plant leaves are not fully utilized in engineering fields yet, since the optimum design in internal structure of plant leaves is unclear. In this study, the tissue organization of the hydraulic pathways inside plant leaves was investigated. Water transport through double-layered porous hydrogel models analogous to mesophyll cells was experimentally observed. In addition, computational experiment and theoretical analysis were applied to the model systems to find the optimal design for efficient water transport. As a result, the models with lower porosity or with pores distributed widely in the structure exhibit efficient mass transport. Our theoretical prediction supports that structural features of plant leaves guarantee sufficient water supply as survival strategy. This study may provide a new framework for investigating the biophysical principles governing the morphological optimization of plant leaves and for designing microfluidic devices to enhance mass transport ability. This study was supported by the National Research Foundation of Korea and funded by the Korean government.

Climatic Analysis of Oceanic Water Vapor Transports Based on Satellite E-P Datasets

Science.gov (United States)

Smith, Eric A.; Sohn, Byung-Ju; Mehta, Vikram

2004-01-01

Understanding the climatically varying properties of water vapor transports from a robust observational perspective is an essential step in calibrating climate models. This is tantamount to measuring year-to-year changes of monthly- or seasonally-averaged, divergent water vapor transport distributions. This cannot be done effectively with conventional radiosonde data over ocean regions where sounding data are generally sparse. This talk describes how a methodology designed to derive atmospheric water vapor transports over the world oceans from satellite-retrieved precipitation (P) and evaporation (E) datasets circumvents the problem of inadequate sampling. Ultimately, the method is intended to take advantage of the relatively complete and consistent coverage, as well as continuity in sampling, associated with E and P datasets obtained from satellite measurements. Independent P and E retrievals from Special Sensor Microwave Imager (SSM/I) measurements, along with P retrievals from Tropical Rainfall Measuring Mission (TRMM) measurements, are used to obtain transports by solving a potential function for the divergence of water vapor transport as balanced by large scale E - P conditions.

Shallow water table effects on water, sediment, and pesticide transport in vegetative filter strips - Part 2: model coupling, application, factor importance, and uncertainty

Science.gov (United States)

Lauvernet, Claire; Muñoz-Carpena, Rafael

2018-01-01

Vegetative filter strips are often used for protecting surface waters from pollution transferred by surface runoff in agricultural watersheds. In Europe, they are often prescribed along the stream banks, where a seasonal shallow water table (WT) could decrease the buffer zone efficiency. In spite of this potentially important effect, there are no systematic experimental or theoretical studies on the effect of this soil boundary condition on the VFS efficiency. In the companion paper (Muñoz-Carpena et al., 2018), we developed a physically based numerical algorithm (SWINGO) that allows the representation of soil infiltration with a shallow water table. Here we present the dynamic coupling of SWINGO with VFSMOD, an overland flow and transport mathematical model to study the WT influence on VFS efficiency in terms of reductions of overland flow, sediment, and pesticide transport. This new version of VFSMOD was applied to two contrasted benchmark field studies in France (sandy-loam soil in a Mediterranean semicontinental climate, and silty clay in a temperate oceanic climate), where limited testing of the model with field data on one of the sites showed promising results. The application showed that for the conditions of the studies, VFS efficiency decreases markedly when the water table is 0 to 1.5 m from the surface. In order to evaluate the relative importance of WT among other input factors controlling VFS efficiency, global sensitivity and uncertainty analysis (GSA) was applied on the benchmark studies. The most important factors found for VFS overland flow reduction were saturated hydraulic conductivity and WT depth, added to sediment characteristics and VFS dimensions for sediment and pesticide reductions. The relative importance of WT varied as a function of soil type (most important at the silty-clay soil) and hydraulic loading (rainfall + incoming runoff) at each site. The presence of WT introduced more complex responses dominated by strong interactions in

Spent nuclear fuel transportation casks evaluation for water in-leakage

International Nuclear Information System (INIS)

Shah, M.J.; Huang, D.T.; Guttmann, J.; Klymyshyn, N.A.; Koeppel, B.J.; Adkins, H.E.

2004-01-01

The United States Nuclear Regulatory Commission (USNRC) is responsible for licensing commercial spent fuel storage and transportation systems. To ensure that the regulations are risk-informed, and do not place unnecessary regulatory burden on the industry, the USNRC has been examining its regulations that apply to spent fuel transportation casks for maintaining sub-criticality under hypothetical accident conditions. Code of Federal Regulations, Title 10, Part 71[1] (10 CFR 71), section 71.55(b) requires that, for evaluation of sub-criticality for fissile material packages, water moderation should be assumed to occur to the most reactive credible extent consistent with the chemical and physical form of the contents. This requirement is based on a defense-in-depth policy, and accounts for any possibility of water intrusion into the package. This program is designed to quantify the margins of safety of certified transportation casks to water intrusion following hypothetical accident conditions. This paper describes the current status of analytical work being performed to evaluate two USNRC-certified spent fuel transportation casks, HI-STAR 100[2] and TN-68[3]. The analytical work is performed using the ANSYS registered [4] and LS-DYNA trademark [5] finite element analysis (FEA) codes. The models are sufficiently detailed in the areas of bolt closure interfaces and containment boundaries to evaluate the likelihood water in-leakage under free drop hypothetical accident conditions of 10 CFR 71.73

Complexity in the validation of ground-water travel time in fractured flow and transport systems

International Nuclear Information System (INIS)

Davies, P.B.; Hunter, R.L.; Pickens, J.F.

1991-01-01

Ground-water travel time is a widely used concept in site assessment for radioactive waste disposal. While ground-water travel time was originally conceived to provide a simple performance measure for evaluating repository sites, its definition in many flow and transport environments is ambiguous. The U.S. Department of Energy siting guidelines (10 CFR 960) define ground-water travel time as the time required for a unit volume of water to travel between two locations, calculated by dividing travel-path length by the quotient of average ground-water flux and effective porosity. Defining a meaningful effective porosity in a fractured porous material is a significant problem. Although the Waste Isolation Pilot Plant (WIPP) is not subject to specific requirements for ground-water travel time, travel times have been computed under a variety of model assumptions. Recently completed model analyses for WIPP illustrate the difficulties in applying a ground-water travel-time performance measure to flow and transport in fractured, fully saturated flow systems. Computer code used: SWIFT II (flow and transport code). 4 figs., 12 refs

Model-based analysis of water management in alkaline direct methanol fuel cells

Science.gov (United States)

Weinzierl, C.; Krewer, U.

2014-12-01

Mathematical modelling is used to analyse water management in Alkaline Direct Methanol Fuel Cells (ADMFCs) with an anion exchange membrane as electrolyte. Cathodic water supply is identified as one of the main challenges and investigated at different operation conditions. Two extreme case scenarios are modelled to study the feasible conditions for sufficient water supply. Scenario 1 reveals that water supply by cathodic inlet is insufficient and, thus, water transport through membrane is essential for ADMFC operation. The second scenario is used to analyse requirements on water transport through the membrane for different operation conditions. These requirements are influenced by current density, evaporation rate, methanol cross-over and electro-osmotic drag of water. Simulations indicate that water supply is mainly challenging for high current densities and demands on high water diffusion are intensified by water drag. Thus, current density might be limited by water transport through membrane. The presented results help to identify important effects and processes in ADMFCs with a polymer electrolyte membrane and to understand these processes. Furthermore, the requirements identified by modelling show the importance of considering water transport through membrane besides conductivity and methanol cross-over especially for designing new membrane materials.

Sediment transport following water transfer from Yangtze River to Taihu Basin

Directory of Open Access Journals (Sweden)

Zheng Gong

2011-12-01

Full Text Available To meet the increasing need of fresh water and to improve the water quality of Taihu Lake, water transfer from the Yangtze River was initiated in 2002. This study was performed to investigate the sediment distribution along the river course following water transfer. A rainfall-runoff model was first built to calculate the runoff of the Taihu Basin in 2003. Then, the flow patterns of river networks were simulated using a one-dimensional river network hydrodynamic model. Based on the boundary conditions of the flow in tributaries of the Wangyu River and the water level in Taihu Lake, a one-dimensional hydrodynamic and sediment transport numerical model of the Wangyu River was built to analyze the influences of the inflow rate of the water transfer and the suspended sediment concentration (SSC of inflow on the sediment transport. The results show that the water transfer inflow rate and SSC of inflow have significant effects on the sediment distribution. The higher the inflow rate or SSC of inflow is, the higher the SSC value is at certain cross-sections along the river course of water transfer. Higher inflow rate and SSC of inflow contribute to higher sediment deposition per kilometer and sediment thickness. It is also concluded that a sharp decrease of the inflow velocity at the entrance of the Wangyu River on the river course of water transfer induces intense sedimentation at the cross-section near the Changshu hydro-junction. With an increasing distance from the Changshu hydro-junction, the sediment deposition and sedimentation thickness decrease gradually along the river course.

Toward a comprehensive model of chemical transport in porous media

International Nuclear Information System (INIS)

Miller, C.W.

1983-02-01

A chemical transport model, CHEMTRN, that includes advection, dispersion/diffusion, complexation, sorption, precipitation or dissolution of solids, and the dissociation of water has been written. The transport, mass action and site constraint equations are written in a differential/algebraic form and solved simultaneously. The sorption process is modelled by either ion-exchange or surface complexation. The model has been used to investigate the applicability of a k/sub D/ model for simulating the transport of chemical species in groundwater systems, to simulate precipitation/dissolution of minerals, and to consider the effect of surface complexation on sorption

Combining Inverse and Transport Modeling to Estimate Bacterial Loading and Transport in a Tidal Embayment

Directory of Open Access Journals (Sweden)

Mac Sisson

2016-11-01

Full Text Available Poquoson River is a tidal coastal embayment located along the Western Shore of the Chesapeake Bay about 4 km south of the York River mouth in the City of Poquoson and in York County, Virginia. Its drainage area has diversified land uses, including high densities of residence, agricultural, salt marsh land uses, as well as a National Wildlife Refuge. This embayment experiences elevated bacterial concentration due to excess bacterial inputs from storm water runoff, nonpoint sources, and wash off from marshes due to tide and wind-induced set-up and set-down. Bacteria can also grow in the marsh and small tributaries. It is difficult to use a traditional watershed model to simulate bacterial loading, especially in this low-lying marsh area with abundant wildlife, while runoff is not solely driven by precipitation. An inverse approach is introduced to estimate loading from unknown sources based on observations in the embayment. The estimated loadings were combined with loadings estimated from different sources (human, wildlife, agriculture, pets, etc. and input to the watershed model. The watershed model simulated long-term flow and bacterial loading and discharged to a three-dimensional transport model driven by tide, wind, and freshwater discharge. The transport model efficiently simulates the transport and fate of the bacterial concentration in the embayment and is capable of determining the loading reduction needed to improve the water quality condition of the embayment. Combining inverse, watershed, and transport models is a sound approach for simulating bacterial transport correctly in the coastal embayment with complex unknown bacterial sources, which are not solely driven by precipitation.

Improvement of water transport mechanisms during potato drying by applying ultrasound.

Science.gov (United States)

Ozuna, César; Cárcel, Juan A; García-Pérez, José V; Mulet, Antonio

2011-11-01

The drying rate of vegetables is limited by internal moisture diffusion and convective transport mechanisms. The increase of drying air temperature leads to faster water mobility; however, it provokes quality loss in the product and presents a higher energy demand. Therefore, the search for new strategies to improve water mobility during convective drying constitutes a topic of relevant research. The aim of this work was to evaluate the use of power ultrasound to improve convective drying of potato and quantify the influence of the applied power in the water transport mechanisms. Drying kinetics of potato cubes were increased by the ultrasonic application. The influence of power ultrasound was dependent on the ultrasonic power (from 0 to 37 kW m(-3) ), the higher the applied power, the faster the drying kinetic. The diffusion model considering external resistance to mass transfer provided a good fit of drying kinetics. From modelling, it was observed a proportional and significant (P mass transfer coefficient. The ultrasonic application during drying represents an interesting alternative to traditional convective drying by shortening drying time, which may involve an energy saving concerning industrial applications. In addition, the ultrasonic effect in the water transport is based on mechanical phenomena with a low heating capacity, which is highly relevant for drying heat sensitive materials and also for obtaining high-quality dry products. Copyright © 2011 Society of Chemical Industry.

Wave-induced mass transport affects daily Escherichia coli fluctuations in nearshore water

Science.gov (United States)

Ge, Zhongfu; Whitman, Richard L.; Nevers, Meredith B.; Phanikumar, Mantha S.

2012-01-01

Characterization of diel variability of fecal indicator bacteria concentration in nearshore waters is of particular importance for development of water sampling standards and protection of public health. Significant nighttime increase in Escherichia coli (E. coli) concentration in beach water, previously observed at marine sites, has also been identified in summer 2000 from fixed locations in waist- and knee-deep waters at Chicago 63rd Street Beach, an embayed, tideless, freshwater beach with low currents at night (approximately 0.015 m s–1). A theoretical model using wave-induced mass transport velocity for advection was developed to assess the contribution of surface waves to the observed nighttime E. coli replenishment in the nearshore water. Using average wave conditions for the summer season of year 2000, the model predicted an amount of E. coli transported from water of intermediate depth, where sediment resuspension occurred intermittently, that would be sufficient to have elevated E. coli concentration in the surf and swash zones as observed. The nighttime replenishment of E. coli in the surf and swash zones revealed here is an important phase in the cycle of diel variations of E. coli concentration in nearshore water. According to previous findings in Ge et al. (Environ. Sci. Technol. 2010, 44, 6731–6737), enhanced current circulation in the embayment during the day tends to displace and deposit material offshore, which partially sets up the system by the early evening for a new period of nighttime onshore movement. This wave-induced mass transport effect, although facilitating a significant base supply of material shoreward, can be perturbed or significantly influenced by high currents (orders of magnitude larger than a typical wave-induced mass transport velocity), current-induced turbulence, and tidal forcing.

Modeling the Influence of Variable Tributary Inflow on Circulation and Contaminant Transport in a Water Supply Reservoir

Science.gov (United States)

Nguyen, L. H.; Wildman, R.

2012-12-01

This study characterizes quantitatively the flow and mixing regimes of a water supply reservoir, while also conducting numerical tracer experiments on different operation scenarios. We investigate the effects of weather events on water quality via storm water inflows. Our study site the Kensico Reservoir, New York, the penultimate reservoir of New York City's water supply, is never filtered and thus dependent on stringent watershed protection. This reservoir must meet federal drinking water standards under changing conditions such as increased suburban, commercial, and highway developments that are much higher than the rest of the watershed. Impacts from these sources on water quality are magnified by minor tributary flows subject to contaminants from development projects as other tributaries providing >99% of water to this reservoir are exceedingly clean due to management practices upstream. These threats, coupled with possible changes in the frequency/intensity of weather events due to climate change, increase the potential for contaminants to enter the reservoir and drinking water intakes. This situation provides us with the unique ability to study the effects of weather events on water quality via insignificant storm water inflows, without influence from the major tributaries due to their pristine water quality characteristics. The concentration of contaminants at the drinking water intake depends partially on transport from their point of entry in the reservoir. Thus, it is crucial to understand water circulation in this reservoir and to estimate residence times and water ages at different locations and under different hydrologic scenarios. We described water age, residence time, thermal structure, and flow dynamics of tributary plumes in Kensico Reservoir during a 22-year simulation period using a two-dimensional hydrodynamic and water quality model (CE-QUAL-W2). Our estimates of water age can reach a maximum of ~300 days in deep-reservoir-cells, with

Climate Change Intensification of Horizontal Water Vapor Transport in CMIP5

Science.gov (United States)

Lavers, D. A.; Ralph, F. M.; Waliser, D. E.; Gershunov, A.; Dettinger, M. D.

2015-12-01

The global water cycle is hypothesized to intensify with a warming Earth's atmosphere. To determine associated hydrological changes, most previous research has used precipitation scenarios without considering changes to the horizontal water vapor transport (IVT). As few studies have analyzed the IVT, and given that many extreme precipitation and flood events are driven by intense water vapor transport, it is the aim of this study to investigate projected changes to global IVT. Furthermore, this approach can identify climatological changes to the IVT between water source and sink regions. Using 22 global circulation models from the Climate Model Intercomparison Project Phase 5 (CMIP5) we evaluate, globally, the mean, standard deviation, and the 95th percentile of IVT from the historical simulations (1979-2005) and two emissions scenarios (2073-2099); representative concentration pathways (RCP4.5 and RCP8.5). This analysis is undertaken for December, January, and February (Boreal winter); and for June, July, and August (Austral winter). The CMIP5 historical multi-model mean has good agreement with the fields from the ECMWF ERA-Interim reanalysis, which provides confidence in the models' signal. In the future, under more extreme emissions (RCP8.5), multi-model mean IVT increases by 30-40% in the North Pacific and North Atlantic storm tracks and in the equatorial Pacific Ocean trade winds. The Arctic region has the largest relative IVT increase especially in Boreal winter. Analysis of low-altitude moisture and winds suggest that these projected changes are mainly due to higher atmospheric water vapor content.

A simulation of water pollution model parameter estimation

Science.gov (United States)

Kibler, J. F.

1976-01-01

A parameter estimation procedure for a water pollution transport model is elaborated. A two-dimensional instantaneous-release shear-diffusion model serves as representative of a simple transport process. Pollution concentration levels are arrived at via modeling of a remote-sensing system. The remote-sensed data are simulated by adding Gaussian noise to the concentration level values generated via the transport model. Model parameters are estimated from the simulated data using a least-squares batch processor. Resolution, sensor array size, and number and location of sensor readings can be found from the accuracies of the parameter estimates.

User manual of the multicompenent variably - saturated flow and transport model HP1

International Nuclear Information System (INIS)

Jacques, D.; Simunek, J.

2005-06-01

This report describes a new comprehensive simulation tool HP1 (HYDRUS1D-PHREEQC) that was obtained by coupling the HYDRUS-1D one-dimensional variably-saturated water flow and solute transport model with the PHREEQC geochemical code. The HP1 code incorporates modules simulating (1) transient water flow in variably-saturated media, (2) transport of multiple components, and (3) mixed equilibrium/kinetic geochemical reactions. The program numerically solves the Richards equation for variably-saturated water flow and advection-dispersion type equations for heat and solute transport. The flow equation incorporates a sink term to account for water uptake by plant roots. The heat transport equation considers transport due to conduction and convection with flowing water. The solute transport equations consider advective-dispersive transport in the liquid phase. The program can simulate a broad range of low-temperature biogeochemical reactions in water, soil and ground water systems including interactions with minerals, gases, exchangers, and sorption surfaces, based on thermodynamic equilibrium, kinetics, or mixed equilibrium-kinetic reactions. The program may be used to analyze water and solute movement in unsaturated, partially saturated, or fully saturated porous media. The flow region may be composed of nonuniform soils or sediments. Flow and transport can occur in the vertical, horizontal, or a generally inclined direction. The water flow part of the model can deal with prescribed head and flux boundaries, boundaries controlled by atmospheric conditions, as well as free drainage boundary conditions. The governing flow and transport equations were solved numerically using Galerkin-type linear finite element schemes. To test the accuracy of the coupling procedures implemented in HP1, simulation results were compared with (i) HYDRUS-1D for transport problems of multiple components subject to sequential first-order decay, (ii) PHREEQC for steady-state flow conditions, and

Plant–Water Relations (1): Uptake and Transport

Science.gov (United States)

2014-01-01

Summary Plants, like all living things, are mostly water. Water is the matrix of life, and its availability determines the distribution and productivity of plants on earth. Vascular plants evolved structures that enable them to transport water long distances with little input of energy, but the hollow tracheary elements are just one of many adaptations that enable plants to cope with a very dry atmosphere. This lecture examines the physical laws that govern water uptake and transport, the biological properties of cells and plant tissues that facilitate it, and the strategies that enable plants to survive in diverse environments

Effects of water content on reactive transport of Sr in Chernobyl sand columns

International Nuclear Information System (INIS)

Szenknect, S.; Dewiere, L.; Ardois, C.; Gaudet, J.P.

2005-01-01

Full text of publication follows: While transport of non-reactive solutes has been studied extensively in unsaturated porous media, much less is known about the factors that control the transport of sorbing solutes in unsaturated conditions. Three laboratory techniques were used to analyze the transport of Sr in the aeolian sand from Chernobyl Pilot Site [1] in both saturated and unsaturated flow conditions. Batch experiments were performed to study the chemical equilibrium state of the soil/solution system. Stirred flow-through reactor (SFTR) experiments were performed to study the kinetics and reversibility of sorption reactions at the surface of solid particles. Column experiments were also performed in saturated and unsaturated steady flow conditions. Experimental data pointed out a non-linear, instantaneous and reversible sorption process of Sr. A suitable cation-exchange model was used to describe the solute/soil reaction. The former model was coupled with transport models to describe behavior of Sr in saturated [2] and unsaturated flow conditions. Transport properties of sand packed columns have been determined with an inert tracer (HTO). BTCs obtained under saturated conditions exhibit a small amount of dispersion compared to those obtained under unsaturated conditions. Classical advection-dispersion model described successfully saturated tritium breakthrough curves (BTCs), whereas a mobile-immobile model (MIM) was required to described asymmetrical unsaturated BTCs. The MIM assumes that the porous medium contains a mobile water phase in which convective-dispersive transport occurs, and a immobile water phase with which solutes can exchange with a first order kinetic. In our experiments, transport by advection in the mobile phase is the predominant process whatever the flow conditions and mass transfer rate between the mobile and immobile regions is the predominant process for broadening the BTCs. Since dispersion is blurred by mass transfer resistance, the

Quantification of free water transport in peritoneal dialysis

NARCIS (Netherlands)

Smit, Watske; Struijk, Dirk G.; Ho-Dac-Pannekeet, Marja M.; Krediet, Raymond T.

2004-01-01

BACKGROUND: In peritoneal dialysis (PD) total net ultrafiltration (NUF) is dependent on transport through small pores and through water channels in the peritoneum. These channels are impermeable to solutes, and therefore, crystalloid osmotic-induced free water transport occurs through them. Several

Moditored unsaturated soil transport processes as a support for large scale soil and water management

Science.gov (United States)

Vanclooster, Marnik

2010-05-01

The current societal demand for sustainable soil and water management is very large. The drivers of global and climate change exert many pressures on the soil and water ecosystems, endangering appropriate ecosystem functioning. The unsaturated soil transport processes play a key role in soil-water system functioning as it controls the fluxes of water and nutrients from the soil to plants (the pedo-biosphere link), the infiltration flux of precipitated water to groundwater and the evaporative flux, and hence the feed back from the soil to the climate system. Yet, unsaturated soil transport processes are difficult to quantify since they are affected by huge variability of the governing properties at different space-time scales and the intrinsic non-linearity of the transport processes. The incompatibility of the scales between the scale at which processes reasonably can be characterized, the scale at which the theoretical process correctly can be described and the scale at which the soil and water system need to be managed, calls for further development of scaling procedures in unsaturated zone science. It also calls for a better integration of theoretical and modelling approaches to elucidate transport processes at the appropriate scales, compatible with the sustainable soil and water management objective. Moditoring science, i.e the interdisciplinary research domain where modelling and monitoring science are linked, is currently evolving significantly in the unsaturated zone hydrology area. In this presentation, a review of current moditoring strategies/techniques will be given and illustrated for solving large scale soil and water management problems. This will also allow identifying research needs in the interdisciplinary domain of modelling and monitoring and to improve the integration of unsaturated zone science in solving soil and water management issues. A focus will be given on examples of large scale soil and water management problems in Europe.

Macroscopic Modeling of Transport Phenomena in Direct Methanol Fuel Cells

DEFF Research Database (Denmark)

Olesen, Anders Christian

An increasing need for energy efficiency and high energy density has sparked a growing interest in direct methanol fuel cells for portable power applications. This type of fuel cell directly generates electricity from a fuel mixture consisting of methanol and water. Although this technology...... surpasses batteries in important areas, fundamental research is still required to improve durability and performance. Particularly the transport of methanol and water within the cell structure is difficult to study in-situ. A demand therefore exist for the fundamental development of mathematical models...... for studying their transport. In this PhD dissertation the macroscopic transport phenomena governing direct methanol fuel cell operation are analyzed, discussed and modeled using the two-fluid approach in the computational fluid dynamics framework of CFX 14. The overall objective of this work is to extend...

Water transport in gas diffusion media for PEM fuel cells. Experimental and numerical investigation

Energy Technology Data Exchange (ETDEWEB)

Roth, Joerg

2010-08-20

The water flux in partially saturated hydrophobic carbon fibre paper for polymer electrolyte membrane fuel cell applications is investigated and compared with the frequently used constitutive two-phase flow model based on Darcy's law. Further, the first steps towards a math-based material design for gas diffusion media are explored in this thesis. Two self-developed ex-situ experiments to investigate the liquid water transport are introduced. The first is a newly developed buoyancy-based measurement of the pressuresaturation relationship on thin porous material with an accuracy of 0.5 kPa for the pressure and {+-} 5% for the saturation. The second experiment measures the pressure drop in dependence of flow rates down to magnitudes of {mu}L/s across the partially saturated thin porous material. This flow rate is relevant for the fuel cell application. The liquid water transport through Toray 060 carbon fibre paper, impregnated with 7% and 10% PTFE is investigated at wet and dry boundary conditions. The experiments are also accompanied by analytical and numerical free surface modelling with the consideration of the material morphology and liquid-solid interaction. The imbibing and draining cases of an arrangement of six fibres at varying solid-liquid interaction and boundary conditions are studied with 'Surface Evolver'. In order to evaluate the findings of ex-situ and modelling work for applicability to water transport in fuel cell operation, the technique of nuclear magnetic resonance (NMR) imaging is assessed. The focus is on the visualisation of 2D and 3D water distribution in the operating fuel cell. The compatibility of the NMR experiment with fuel cell operation in relation to material selection, operating temperature, and current density is addressed. NMR imaging is employed for different current densities, stoichiometries, and fuel cell arrangements. The fuel cell arrangements differ by the cathode diffusion medium. Plain, hydrophobic, and

Reactive transport modeling of nitrogen in Seine River sediments

Science.gov (United States)

Akbarzadeh, Z.; Laverman, A.; Raimonet, M.; Rezanezhad, F.; Van Cappellen, P.

2016-02-01

Biogeochemical processes in sediments have a major impact on the fate and transport of nitrogen (N) in river systems. Organic matter decomposition in bottom sediments releases inorganic N species back to the stream water, while denitrification, anammox and burial of organic matter remove bioavailable N from the aquatic environment. To simulate N cycling in river sediments, a multi-component reactive transport model has been developed in MATLAB®. The model includes 3 pools of particulate organic N, plus pore water nitrate, nitrite, nitrous oxide and ammonium. Special attention is given to the production and consumption of nitrite, a N species often neglected in early diagenetic models. Although nitrite is usually considered to be short-lived, elevated nitrite concentrations have been observed in freshwater streams, raising concerns about possible toxic effects. We applied the model to sediment data sets collected at two locations in the Seine River, one upstream, the other downstream, of the largest wastewater treatment plant (WWTP) of the Paris conurbation. The model is able to reproduce the key features of the observed pore water depth profiles of the different nitrogen species. The modeling results show that the presence of oxygen in the overlying water plays a major role in controlling the exchanges of nitrite between the sediments and the stream water. In August 2012, sediments upstream of the WWTP switch from being a sink to a source of nitrite as the overlying water becomes anoxic. Downstream sediments remain a nitrite sink in oxic and anoxic conditions. Anoxic bottom waters at the upstream location promote denitrification, which produces nitrite, while at the downstream site, anammox and DNRA are important removal processes of nitrite.

Shallow water table effects on water, sediment, and pesticide transport in vegetative filter strips – Part 2: model coupling, application, factor importance, and uncertainty

Directory of Open Access Journals (Sweden)

C. Lauvernet

2018-01-01

Full Text Available Vegetative filter strips are often used for protecting surface waters from pollution transferred by surface runoff in agricultural watersheds. In Europe, they are often prescribed along the stream banks, where a seasonal shallow water table (WT could decrease the buffer zone efficiency. In spite of this potentially important effect, there are no systematic experimental or theoretical studies on the effect of this soil boundary condition on the VFS efficiency. In the companion paper (Muñoz-Carpena et al., 2018, we developed a physically based numerical algorithm (SWINGO that allows the representation of soil infiltration with a shallow water table. Here we present the dynamic coupling of SWINGO with VFSMOD, an overland flow and transport mathematical model to study the WT influence on VFS efficiency in terms of reductions of overland flow, sediment, and pesticide transport. This new version of VFSMOD was applied to two contrasted benchmark field studies in France (sandy-loam soil in a Mediterranean semicontinental climate, and silty clay in a temperate oceanic climate, where limited testing of the model with field data on one of the sites showed promising results. The application showed that for the conditions of the studies, VFS efficiency decreases markedly when the water table is 0 to 1.5 m from the surface. In order to evaluate the relative importance of WT among other input factors controlling VFS efficiency, global sensitivity and uncertainty analysis (GSA was applied on the benchmark studies. The most important factors found for VFS overland flow reduction were saturated hydraulic conductivity and WT depth, added to sediment characteristics and VFS dimensions for sediment and pesticide reductions. The relative importance of WT varied as a function of soil type (most important at the silty-clay soil and hydraulic loading (rainfall + incoming runoff at each site. The presence of WT introduced more complex responses dominated by strong

Influence of root-water-uptake parameterization on simulated heat transport in a structured forest soil

Science.gov (United States)

Votrubova, Jana; Vogel, Tomas; Dohnal, Michal; Dusek, Jaromir

2015-04-01

Coupled simulations of soil water flow and associated transport of substances have become a useful and increasingly popular tool of subsurface hydrology. Quality of such simulations is directly affected by correctness of its hydraulic part. When near-surface processes under vegetation cover are of interest, appropriate representation of the root water uptake becomes essential. Simulation study of coupled water and heat transport in soil profile under natural conditions was conducted. One-dimensional dual-continuum model (S1D code) with semi-separate flow domains representing the soil matrix and the network of preferential pathways was used. A simple root water uptake model based on water-potential-gradient (WPG) formulation was applied. As demonstrated before [1], the WPG formulation - capable of simulating both the compensatory root water uptake (in situations when reduced uptake from dry layers is compensated by increased uptake from wetter layers), and the root-mediated hydraulic redistribution of soil water - enables simulation of more natural soil moisture distribution throughout the root zone. The potential effect on heat transport in a soil profile is the subject of the present study. [1] Vogel T., M. Dohnal, J. Dusek, J. Votrubova, and M. Tesar. 2013. Macroscopic modeling of plant water uptake in a forest stand involving root-mediated soil-water redistribution. Vadose Zone Journal, 12, 10.2136/vzj2012.0154. The research was supported by the Czech Science Foundation Project No. 14-15201J.

A new modelling approach to simulate preferential flow and transport in water repellent porous media: Model structure and validation

NARCIS (Netherlands)

Ritsema, C.J.; Dam, van J.C.; Dekker, L.W.; Oostindie, K.

2005-01-01

Water repellent soil and surface layers exhibit a complex flow and transport mechanism. Knowledge of the underlying principles is essential, for instance, to simulate water availability for crops and to estimate leaching potentials of agrichemicals. The present study aims to introduce and apply a

Use of a watershed model to characterize the fate and transport of fluometuron, a soil-applied cotton herbicide, in surface water

Science.gov (United States)

Coupe, R.H.

2007-01-01

The Soil and Water Assessment Tool (SWAT) was used to characterize the fate and transport of fluometuron (a herbicide used on cotton) in the Bogue Phalia Basin in northwestern Mississippi, USA. SWAT is a basin-scale watershed model, able to simulate hydrological, chemical, and sediment transport processes. After adjustments to a few parameters (specifically the SURLAG variable, the runoff curve number, Manning's N for overland flow, soil available water capacity, and the base-flow alpha factor) the SWAT model fit the observed streamflow well (the Coefficient of Efficiency and R2 were greater than 60). The results from comparing observed fluometuron concentrations with simulated concentrations were reasonable. The simulated concentrations (which were daily averages) followed the pattern of observed concentrations (instantaneous values) closely, but could be off in magnitude at times. Further calibration might have improved the fit, but given the uncertainties in the input data, it was not clear that any improvement would be due to a better understanding of the input variables. ?? 2007 Taylor & Francis.

The Economics of Bulk Water Transport in Southern California

Directory of Open Access Journals (Sweden)

Andrew Hodges

2014-12-01

Full Text Available Municipalities often face increasing demand for limited water supplies with few available alternative sources. Under some circumstances, bulk water transport may offer a viable alternative. This case study documents a hypothetical transfer between a water utility district in northern California and urban communities located on the coast of central and southern California. We compare bulk water transport costs to those of constructing a new desalination facility, which is the current plan of many communities for increasing supplies. We find that using water bags to transport fresh water between northern and southern California is in some instances a low-cost alternative to desalination. The choice is constrained, however, by concerns about reliability and, thus, risk. Case-study results demonstrate the challenges of water supply augmentation in water-constrained regions.

Mathematical modeling of solute transport in the subsurface

International Nuclear Information System (INIS)

Naymik, T.G.

1987-01-01

A review of key works on solute transport models indicates that solute transport processes with the exception of advection are still poorly understood. Solute transport models generally do a good job when they are used to test scientific concepts and hypotheses, investigate natural processes, systematically store and manage data, and simulate mass balance of solutes under certain natural conditions. Solute transport models generally are not good for predicting future conditions with a high degree of certainty, or for determining concentrations precisely. The mathematical treatment of solute transport far surpasses their understanding of the process. Investigations of the extent of groundwater contamination and methods to remedy existing problems show the along-term nature of the hazard. Industrial organic compounds may be immiscible in water, highly volatile, or complexed with inorganic as well as other organic compounds; many remain stable in nature almost indefinitely. In the worst case, future disposal of hazardous waste may be restricted to deep burial, as is proposed for radioactive wastes. For investigations pertinent to transport of radionuclides from a geologic repository, the process cannot be fully understood without adequate thermodynamic and kinetic data bases

Modelling and numerical simulation of the corrosion product transport in the pressurised water reactor primary circuit

International Nuclear Information System (INIS)

Marchetto, C.

2002-05-01

During operation of pressurised water reactor, corrosion of the primary circuit alloys leads to the release of metallic species such as iron, nickel and cobalt in the primary fluid. These corrosion products are implicated in different transport phenomena and are activated in the reactor core where they are submitted to neutron flux. The radioactive corrosion products are afterwards present in the out of flux parts of primary circuit where they generate a radiation field. The first part of this study deals with the modelling of the corrosion: product transport phenomena. In particular, considering the current state of the art, corrosion and release mechanisms are described empirically, which allows to take into account the material surface properties. New mass balance equations describing the corrosion product behaviour are thus obtained. The numerical resolution of these equations is implemented in the second part of this work. In order to obtain large time steps, we choose an implicit time scheme. The associated system is linearized from the Newton method and is solved by a preconditioned GMRES method. Moreover, a time step auto-adaptive management based on Newton iterations is performed. Consequently, an efficient resolution has been implemented, allowing to describe not only the quasi-steady evolutions but also the fast transients. In a last step, numerical simulations are carried out in order to validate the new corrosion product transport modelling and to illustrate the capabilities of this modelling. Notably, the numerical results obtained indicate that the code allows to restore the on-site observations underlining the influence of material surface properties on reactor contamination. (author)

Three dimensional heat transport modeling in Vossoroca reservoir

Science.gov (United States)

Arcie Polli, Bruna; Yoshioka Bernardo, Julio Werner; Hilgert, Stephan; Bleninger, Tobias

2017-04-01

Freshwater reservoirs are used for many purposes as hydropower generation, water supply and irrigation. In Brazil, according to the National Energy Balance of 2013, hydropower energy corresponds to 70.1% of the Brazilian demand. Superficial waters (which include rivers, lakes and reservoirs) are the most used source for drinking water supply - 56% of the municipalities use superficial waters as a source of water. The last two years have shown that the Brazilian water and electricity supply is highly vulnerable and that improved management is urgently needed. The construction of reservoirs affects physical, chemical and biological characteristics of the water body, e.g. stratification, temperature, residence time and turbulence reduction. Some water quality issues related to reservoirs are eutrophication, greenhouse gas emission to the atmosphere and dissolved oxygen depletion in the hypolimnion. The understanding of the physical processes in the water body is fundamental to reservoir management. Lakes and reservoirs may present a seasonal behavior and stratify due to hydrological and meteorological conditions, and especially its vertical distribution may be related to water quality. Stratification can control heat and dissolved substances transport. It has been also reported the importance of horizontal temperature gradients, e.g. inflows and its density and processes of mass transfer from shallow to deeper regions of the reservoir, that also may impact water quality. Three dimensional modeling of the heat transport in lakes and reservoirs is an important tool to the understanding and management of these systems. It is possible to estimate periods of large vertical temperature gradients, inhibiting vertical transport and horizontal gradients, which could be responsible for horizontal transport of heat and substances (e.g. differential cooling or inflows). Vossoroca reservoir was constructed in 1949 by the impoundment of São João River and is located near to

Transport and sorption of volatile organic compounds and water vapor in porous media

Energy Technology Data Exchange (ETDEWEB)

Lin, Tsair-Fuh [Univ. of California, Berkeley, CA (United States)

1995-07-01

To gain insight on the controlling mechanisms for VOC transport in porous media, the relations among sorbent properties, sorption equilibrium and intraparticle diffusion processes were studied at the level of individual sorbent particles and laboratory columns for soil and activated carbon systems. Transport and sorption of VOCs and water vapor were first elucidated within individual dry soil mineral grains. Soil properties, sorption capacity, and sorption rates were measured for 3 test soils; results suggest that the soil grains are porous, while the sorption isotherms are nonlinear and adsorption-desorption rates are slow and asymmetric. An intragranular pore diffusion model coupled with the nonlinear Freundlich isotherm was developed to describe the sorption kinetic curves. Transport of benzene and water vapor within peat was studied; partitioning and sorption kinetics were determined with an electrobalance. A dual diffusion model was developed. Transport of benzene in dry and moist soil columns was studied, followed by gaseous transport and sorption in activated carbon. The pore diffusion model provides good fits to sorption kinetics for VOCs to soil and VOC to granular activated carbon and activated carbon fibers. Results of this research indicate that: Intraparticle diffusion along with a nonlinea sorption isotherm are responsible for the slow, asymmetric sorption-desorption. Diffusion models are able to describe results for soil and activated carbon systems; when combined with mass transfer equations, they predict column breakthrough curves for several systems. Although the conditions are simplified, the mechanisms should provide insight on complex systems involving transport and sorption of vapors in porous media.

Uncertainty in reactive transport geochemical modelling

International Nuclear Information System (INIS)

Oedegaard-Jensen, A.; Ekberg, C.

2005-01-01

Full text of publication follows: Geochemical modelling is one way of predicting the transport of i.e. radionuclides in a rock formation. In a rock formation there will be fractures in which water and dissolved species can be transported. The composition of the water and the rock can either increase or decrease the mobility of the transported entities. When doing simulations on the mobility or transport of different species one has to know the exact water composition, the exact flow rates in the fracture and in the surrounding rock, the porosity and which minerals the rock is composed of. The problem with simulations on rocks is that the rock itself it not uniform i.e. larger fractures in some areas and smaller in other areas which can give different water flows. The rock composition can be different in different areas. In additions to this variance in the rock there are also problems with measuring the physical parameters used in a simulation. All measurements will perturb the rock and this perturbation will results in more or less correct values of the interesting parameters. The analytical methods used are also encumbered with uncertainties which in this case are added to the uncertainty from the perturbation of the analysed parameters. When doing simulation the effect of the uncertainties must be taken into account. As the computers are getting faster and faster the complexity of simulated systems are increased which also increase the uncertainty in the results from the simulations. In this paper we will show how the uncertainty in the different parameters will effect the solubility and mobility of different species. Small uncertainties in the input parameters can result in large uncertainties in the end. (authors)

Modeling of water and solute transport under variably saturated conditions: state of the art

International Nuclear Information System (INIS)

Lappala, E.G.

1980-01-01

This paper reviews the equations used in deterministic models of mass and energy transport in variably saturated porous media. Analytic, quasi-analytic, and numerical solution methods to the nonlinear forms of transport equations are discussed with respect to their advantages and limitations. The factors that influence the selection of a modeling method are discussed in this paper; they include the following: (1) the degree of coupling required among the equations describing the transport of liquids, gases, solutes, and energy; (2) the inclusion of an advection term in the equations; (3) the existence of sharp fronts; (4) the degree of nonlinearity and hysteresis in the transport coefficients and boundary conditions; (5) the existence of complex boundaries; and (6) the availability and reliability of data required by the models

Modeling Water Exchange and Contaminant Transport through a Baltic Coastal Region

International Nuclear Information System (INIS)

Engqvist, Anders; Doeoes, Kristofer; Andrejev, Oleg

2006-01-01

The water exchange of the Baltic coastal zone is characterized by its seasonally varying regimes. In the safety assessment of a potential repository for spent nuclear fuel, it is important to assess the consequences of a hypothetical leak of radionuclides through the seabed into a waterborne transport phase. In particular, estimates of the associated residence times in the near-shore coastal zone are of interest. There are several methods to quantify such measures, of which three are presented here. Using the coastal location of Forsmark (Sweden) as an example, methods based on passive tracers, particle trajectories, and the average age distribution of exogenous water parcels are compared for a representative one-year cycle. Tracer-based methods can simulate diffusivity more realistically than the other methods. Trajectory-based methods can handle Lagrangian dispersion processes due to advection but neglect diffusion on the sub-grid scale. The method based on the concept of average age (AvA) of exogenous water can include all such sources simultaneously not only boundary water bodies but also various (fresh)water discharges. Due to the inclusion of sub-grid diffusion this method gives a smoother measure of the water renewal. It is shown that backward in time trajectories and AvA-times are basically equipollent methods, yielding correlated results within the limits set by the diffusivity

A multimedia fate and chemical transport modeling system for pesticides: I. Model development and implementation

International Nuclear Information System (INIS)

Li Rong; Yang Fuquan; Sloan, James J; Scholtz, M Trevor

2011-01-01

We have combined the US EPA MM5/MCIP/SMOKE/CMAQ modeling system with a dynamic soil model, the pesticide emission model (PEM), to create a multimedia chemical transport model capable of describing the important physical and chemical processes involving pesticides in the soil, in the atmosphere, and on the surface of vegetation. These processes include: agricultural practices (e.g. soil tilling and pesticide application mode); advection and diffusion of pesticides, moisture, and heat in the soil; partitioning of pesticides between soil organic carbon and interstitial water and air; emissions from the soil to the atmosphere; gas-particle partitioning and transport in the atmosphere; and atmospheric chemistry and dry and wet deposition of pesticides to terrestrial and water surfaces. The modeling system was tested by simulating toxaphene in a domain that covers most of North America for the period from 1 January 2000 to 31 December 2000. The results show obvious transport of the pesticide from the heavily contaminated soils in the southern United States and Mexico to water bodies including the Atlantic Ocean, the Gulf of Mexico and the Great Lakes, leading to significant dry and wet deposition into these ecosystems. The spatial distributions of dry and wet depositions differ because of their different physical mechanisms; the former follows the distribution of air concentrations whereas the latter is more biased to the North East due to the effect of precipitation.

A multimedia fate and chemical transport modeling system for pesticides: I. Model development and implementation

Energy Technology Data Exchange (ETDEWEB)

Li Rong; Yang Fuquan; Sloan, James J [Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L 3G1 (Canada); Scholtz, M Trevor, E-mail: sloanj@connect.uwaterloo.ca [ORTECH Environmental, 2395 Speakman Drive, Mississauga, ON L5K 1B3 (Canada)

2011-07-15

We have combined the US EPA MM5/MCIP/SMOKE/CMAQ modeling system with a dynamic soil model, the pesticide emission model (PEM), to create a multimedia chemical transport model capable of describing the important physical and chemical processes involving pesticides in the soil, in the atmosphere, and on the surface of vegetation. These processes include: agricultural practices (e.g. soil tilling and pesticide application mode); advection and diffusion of pesticides, moisture, and heat in the soil; partitioning of pesticides between soil organic carbon and interstitial water and air; emissions from the soil to the atmosphere; gas-particle partitioning and transport in the atmosphere; and atmospheric chemistry and dry and wet deposition of pesticides to terrestrial and water surfaces. The modeling system was tested by simulating toxaphene in a domain that covers most of North America for the period from 1 January 2000 to 31 December 2000. The results show obvious transport of the pesticide from the heavily contaminated soils in the southern United States and Mexico to water bodies including the Atlantic Ocean, the Gulf of Mexico and the Great Lakes, leading to significant dry and wet deposition into these ecosystems. The spatial distributions of dry and wet depositions differ because of their different physical mechanisms; the former follows the distribution of air concentrations whereas the latter is more biased to the North East due to the effect of precipitation.

A multimedia fate and chemical transport modeling system for pesticides: I. Model development and implementation

Science.gov (United States)

Li, Rong; Scholtz, M. Trevor; Yang, Fuquan; Sloan, James J.

2011-07-01

We have combined the US EPA MM5/MCIP/SMOKE/CMAQ modeling system with a dynamic soil model, the pesticide emission model (PEM), to create a multimedia chemical transport model capable of describing the important physical and chemical processes involving pesticides in the soil, in the atmosphere, and on the surface of vegetation. These processes include: agricultural practices (e.g. soil tilling and pesticide application mode); advection and diffusion of pesticides, moisture, and heat in the soil; partitioning of pesticides between soil organic carbon and interstitial water and air; emissions from the soil to the atmosphere; gas-particle partitioning and transport in the atmosphere; and atmospheric chemistry and dry and wet deposition of pesticides to terrestrial and water surfaces. The modeling system was tested by simulating toxaphene in a domain that covers most of North America for the period from 1 January 2000 to 31 December 2000. The results show obvious transport of the pesticide from the heavily contaminated soils in the southern United States and Mexico to water bodies including the Atlantic Ocean, the Gulf of Mexico and the Great Lakes, leading to significant dry and wet deposition into these ecosystems. The spatial distributions of dry and wet depositions differ because of their different physical mechanisms; the former follows the distribution of air concentrations whereas the latter is more biased to the North East due to the effect of precipitation.

Complexity in the validation of ground-water travel time in fractured flow and transport systems

International Nuclear Information System (INIS)

Davies, P.B; Hunter, R.L.; Pickens, J.F.

1991-02-01

Ground-water travel time is a widely used concept in site assessment for radioactive waste disposal. While ground-water travel time was originally conceived to provide a simple performance measure for evaluating repository sites, its definition in many flow and transport environments is ambiguous. The US Department of Energy siting guidelines (10 CFR 960) define ground-water travel time as the time required for a unit volume of water to travel between two locations, calculated by dividing travel-path length by the quotient of average ground-water flux and effective porosity. Defining a meaningful effective porosity in a fractured porous material is a significant problem. Although the Waste Isolation Pilot Plant (WIPP) is not subject to specific requirements for ground-water travel time, travel times have been computed under a variety of model assumptions. Recently completed model analyses for WIPP illustrate the difficulties in applying a ground-water travel-time performance measure to flow and transport in fractured, fully saturated flow systems. 12 refs., 4 figs

Osmoregulation and epithelial water transport: lessons from the intestine of marine teleost fish.

Science.gov (United States)

Whittamore, Jonathan M

2012-01-01

For teleost fish living in seawater, drinking the surrounding medium is necessary to avoid dehydration. This is a key component of their osmoregulatory strategy presenting the challenge of excreting excess salts while achieving a net retention of water. The intestine has an established role in osmoregulation, and its ability to effectively absorb fluid is crucial to compensating for water losses to the hyperosmotic environment. Despite this, the potential for the teleost intestine to serve as a comparative model for detailed, integrative experimental studies on epithelial water transport has so far gone largely untapped. The following review aims to present an assessment of the teleost intestine as a fluid-transporting epithelium. Beginning with a brief overview of marine teleost osmoregulation, emphasis shifts to the processing of ingested seawater by the gastrointestinal tract and the characteristics of intestinal ion and fluid transport. Particular attention is given to acid-base transfers by the intestine, specifically bicarbonate secretion, which creates the distinctly alkaline gut fluids responsible for the formation of solid calcium carbonate precipitates. The respective contributions of these unique features to intestinal fluid absorption, alongside other recognised ion transport processes, are then subsequently considered within the wider context of the classic physiological problem of epithelial water transport.

Coupling between a geochemical model and a transport model of dissolved elements

International Nuclear Information System (INIS)

Jacquier, P.

1988-10-01

In order to assess the safety analysis of an underground repository, the transport of radioelements in groundwater and their interactions with the geological medium are modelled. The objective of this work is the setting up and experimental validation of the coupling of a geochemical model with a transport model of dissolved elements. A laboratory experiment was developed at the CEA center of Cadarache. Flow-through experiments were carried out on columns filled with crushed limestone, where several inflow conditions were taken into account as the temperature, the presence of a pollutant (strontium chloride) at different concentrations. The results consist of the evolution of the chemical composition of the water at the outlet of the column. The final aim of the study is to explain these results with a coupled model where geochemical and transport phenomena are modelled in a two-step procedure. This code, called STELE, was built by introducing a geochemical code, CHIMERE, into an existing transport code, METIS. At this stage, the code CHIMERE can take into account: any chemical reaction in aqueous phase (complexation, acid-base reaction, redox equilibrium), dissolution-precipitation of minerals and solid phases, dissolution-degassing of gas. The paper intends to describe the whole process leading to the coupling which can be forecasted over the next years between geochemical and transport models

Modeling coupled nanoparticle aggregation and transport in porous media: a Lagrangian approach.

Science.gov (United States)

Taghavy, Amir; Pennell, Kurt D; Abriola, Linda M

2015-01-01

Changes in nanoparticle size and shape due to particle-particle interactions (i.e., aggregation or agglomeration) may significantly alter particle mobility and retention in porous media. To date, however, few modeling studies have considered the coupling of transport and particle aggregation processes. The majority of particle transport models employ an Eulerian modeling framework and are, consequently, limited in the types of collisions and aggregate sizes that can be considered. In this work, a more general Lagrangian modeling framework is developed and implemented to explore coupled nanoparticle aggregation and transport processes. The model was verified through comparison of model simulations to published results of an experimental and Eulerian modeling study (Raychoudhury et al., 2012) of carboxymethyl cellulose (CMC)-modified nano-sized zero-valent iron particle (nZVI) transport and retention in water-saturated sand columns. A model sensitivity analysis reveals the influence of influent particle concentration (ca. 70 to 700 mg/L), primary particle size (10-100 nm) and pore water velocity (ca. 1-6 m/day) on particle-particle, and, consequently, particle-collector interactions. Model simulations demonstrate that, when environmental conditions promote particle-particle interactions, neglecting aggregation effects can lead to under- or over-estimation of nanoparticle mobility. Results also suggest that the extent to which higher order particle-particle collisions influence aggregation kinetics will increase with the fraction of primary particles. This work demonstrates the potential importance of time-dependent aggregation processes on nanoparticle mobility and provides a numerical model capable of capturing/describing these interactions in water-saturated porous media. Copyright © 2014 Elsevier B.V. All rights reserved.

Water-quality conditions and suspended-sediment transport in the Wilson and Trask Rivers, northwestern Oregon, water years 2012–14

Science.gov (United States)

Sobieszczyk, Steven; Bragg, Heather M.; Uhrich, Mark A.

2015-07-28

In October 2011, the U.S. Geological Survey began investigating and monitoring water-quality conditions and suspended-sediment transport in the Wilson and Trask Rivers, northwestern Oregon. Water temperature, specific conductance, turbidity, and dissolved oxygen were measured every 15–30 minutes in both streams using real-time instream water-quality monitors. In conjunction with the monitoring effort, suspended-sediment samples were collected and analyzed to model the amount of suspended sediment being transported by each river. Over the course of the 3-year study, which ended in September 2014, nearly 600,000 tons (t) of suspended-sediment material entered Tillamook Bay from these two tributaries. 

Approach for delineation of contributing areas and zones of transport to selected public-supply wells using a regional ground-water flow model, Palm Beach County, Florida

Science.gov (United States)

Renken, R.A.; Patterson, R.D.; Orzol, L.L.; Dixon, Joann

2001-01-01

Rapid urban development and population growth in Palm Beach County, Florida, have been accompanied with the need for additional freshwater withdrawals from the surficial aquifer system. To maintain water quality, County officials protect capture areas and determine zones of transport of municipal supply wells. A multistep process was used to help automate the delineation of wellhead protection areas. A modular ground-water flow model (MODFLOW) Telescopic Mesh Refinement program (MODTMR) was used to construct an embedded flow model and combined with particle tracking to delineate zones of transport to supply wells; model output was coupled with a geographic information system. An embedded flow MODFLOW model was constructed using input and output file data from a preexisting three-dimensional, calibrated model of the surficial aquifer system. Three graphical user interfaces for use with the geographic information software, ArcView, were developed to enhance the telescopic mesh refinement process. These interfaces include AvMODTMR for use with MODTMR; AvHDRD to build MODFLOW river and drain input files from dynamically segmented linear (canals) data sets; and AvWELL Refiner, an interface designed to examine and convert well coverage spatial data layers to a MODFLOW Well package input file. MODPATH (the U.S. Geological Survey particle-tracking postprocessing program) and MODTOOLS (the set of U.S. Geological Survey computer programs to translate MODFLOW and MODPATH output to a geographic information system) were used to map zones of transport. A steady-state, five-layer model of the Boca Raton area was created using the telescopic mesh refinement process and calibrated to average conditions during January 1989 to June 1990. A sensitivity analysis of various model parameters indicates that the model is most sensitive to changes in recharge rates, hydraulic conductivity for layer 1, and leakance for layers 3 and 4 (Biscayne aquifer). Recharge (58 percent); river (canal

Discrete element modelling of bedload transport

Science.gov (United States)

Loyer, A.; Frey, P.

2011-12-01

Discrete element modelling (DEM) has been widely used in solid mechanics and in granular physics. In this type of modelling, each individual particle is taken into account and intergranular interactions are modelled with simple laws (e.g. Coulomb friction). Gravity and contact forces permit to solve the dynamical behaviour of the system. DEM is interesting to model configurations and access to parameters not directly available in laboratory experimentation, hence the term "numerical experimentations" sometimes used to describe DEM. DEM was used to model bedload transport experiments performed at the particle scale with spherical glass beads in a steep and narrow flume. Bedload is the larger material that is transported on the bed on stream channels. It has a great geomorphic impact. Physical processes ruling bedload transport and more generally coarse-particle/fluid systems are poorly known, arguably because granular interactions have been somewhat neglected. An existing DEM code (PFC3D) already computing granular interactions was used. We implemented basic hydrodynamic forces to model the fluid interactions (buoyancy, drag, lift). The idea was to use the minimum number of ingredients to match the experimental results. Experiments were performed with one-size and two-size mixtures of coarse spherical glass beads entrained by a shallow turbulent and supercritical water flow down a steep channel with a mobile bed. The particle diameters were 4 and 6mm, the channel width 6.5mm (about the same width as the coarser particles) and the channel inclination was typically 10%. The water flow rate and the particle rate were kept constant at the upstream entrance and adjusted to obtain bedload transport equilibrium. Flows were filmed from the side by a high-speed camera. Using image processing algorithms made it possible to determine the position, velocity and trajectory of both smaller and coarser particles. Modelled and experimental particle velocity and concentration depth

Transport properties of supercooled confined water

International Nuclear Information System (INIS)

Mallamace, F.; Baglioni, P.; Corsaro, C.; Spooren, J.; Stanley, H.E.; Chen, S.-H.

2011-01-01

We present an overview of recent experiments performed on water in the deeply supercooled region, a temperature region of fundamental importance in the science of water. We examine data generated by nuclear magnetic resonance, quasi-elastic neutron scattering, Fourier-transform infrared spectroscopy, and Raman spectroscopy, and study water confined in nanometer-scale environments. When contained within small pores, water does not crystallize and can be supercooled well below its homogeneous nucleation temperature T H. On this basis, it is possible to carry out a careful analysis of the well-known thermodynamic anomalies of water. Studying the temperature and pressure dependencies of water dynamics, we show that the liquid-liquid phase transition (LLPT) hypothesis represents a reliable model for describing liquid water. In this model, liquid water is a mixture of two different local structures: a low density liquid (LDL) and a high-density liquid (HDL). The LLPT line terminates at a low-T liquid-liquid critical point. We discuss the following experimental findings: 1.) the crossover from non-Arrhenius behavior at high T to Arrhenius behavior at low T in transport parameters; 2.) the breakdown of the Stokes-Einstein relation; 3.) the existence of a Widom line, which is the locus of points corresponding to a maximum correlation length in the P-T phase diagram and which ends in the liquid-liquid critical point; 4.) the direct observation of the LDL phase; and 5.) the minimum in the density at approximately 70 K below the temperature of the density maximum. In our opinion these results strongly support the LLPT hypothesis. All of the basic science and technology community should be impressed by the fact that, although the few ideas (apparently elementary) developed concerning water approximately 27 centuries ago have changed very little up to now, because of the current expansion in our knowledge in this area, they can begin to change in the near future.

Advanced transport modeling of toroidal plasmas with transport barriers

International Nuclear Information System (INIS)

Fukuyama, A.; Murakami, S.; Honda, M.; Izumi, Y.; Yagi, M.; Nakajima, N.; Nakamura, Y.; Ozeki, T.

2005-01-01

Transport modeling of toroidal plasmas is one of the most important issue to predict time evolution of burning plasmas and to develop control schemes in reactor plasmas. In order to describe the plasma rotation and rapid transition self-consistently, we have developed an advanced scheme of transport modeling based on dynamical transport equation and applied it to the analysis of transport barrier formation. First we propose a new transport model and examine its behavior by the use of conventional diffusive transport equation. This model includes the electrostatic toroidal ITG mode and the electromagnetic ballooning mode and successfully describes the formation of internal transport barriers. Then the dynamical transport equation is introduced to describe the plasma rotation and the radial electric field self-consistently. The formation of edge transport barriers is systematically studied and compared with experimental observations. The possibility of kinetic transport modeling in velocity space is also examined. Finally the modular structure of integrated modeling code for tokamaks and helical systems is discussed. (author)

The contribution of free water transport and small pore transport to the total fluid removal in peritoneal dialysis

NARCIS (Netherlands)

Parikova, Alena; Smit, Watske; Struijk, Dirk G.; Zweers, Machteld M.; Krediet, Raymond T.

2005-01-01

BACKGROUND: Water transport in peritoneal dialysis (PD) patients is across the small pores and water channels, the latter allowing free water transport. The objective of the study was to investigate the contribution of each transport route on transcapillary ultrafiltration (TCUF). METHODS: Standard

Assessment the effect of homogenized soil on soil hydraulic properties and soil water transport

Science.gov (United States)

Mohawesh, O.; Janssen, M.; Maaitah, O.; Lennartz, B.

2017-09-01

Soil hydraulic properties play a crucial role in simulating water flow and contaminant transport. Soil hydraulic properties are commonly measured using homogenized soil samples. However, soil structure has a significant effect on the soil ability to retain and to conduct water, particularly in aggregated soils. In order to determine the effect of soil homogenization on soil hydraulic properties and soil water transport, undisturbed soil samples were carefully collected. Five different soil structures were identified: Angular-blocky, Crumble, Angular-blocky (different soil texture), Granular, and subangular-blocky. The soil hydraulic properties were determined for undisturbed and homogenized soil samples for each soil structure. The soil hydraulic properties were used to model soil water transport using HYDRUS-1D.The homogenized soil samples showed a significant increase in wide pores (wCP) and a decrease in narrow pores (nCP). The wCP increased by 95.6, 141.2, 391.6, 3.9, 261.3%, and nCP decreased by 69.5, 10.5, 33.8, 72.7, and 39.3% for homogenized soil samples compared to undisturbed soil samples. The soil water retention curves exhibited a significant decrease in water holding capacity for homogenized soil samples compared with the undisturbed soil samples. The homogenized soil samples showed also a decrease in soil hydraulic conductivity. The simulated results showed that water movement and distribution were affected by soil homogenizing. Moreover, soil homogenizing affected soil hydraulic properties and soil water transport. However, field studies are being needed to find the effect of these differences on water, chemical, and pollutant transport under several scenarios.

Fate and transport modelling of uranium in Port Hope Harbour

International Nuclear Information System (INIS)

Pinilla, C.E.; Garisto, N.; Peters, R.

2010-01-01

Fate and transport modelling of contaminants in Port Hope Harbour and near-shore Lake Ontario was undertaken in support of an ecological and human health risk assessment. Uranium concentrations in the Harbour and near-shore Lake Ontario due to groundwater and storm water loadings were estimated with a state-of-the-art 3D hydrodynamic and contaminant transport model (ECOMSED). The hydrodynamic model was simplified to obtain a first estimate of the flow pattern in the Harbour. The model was verified with field data using a tracer (fluoride). The modelling results generally showed good agreement with the tracer field data. (author)

The Effect of Inhomogeneous Compression on Water Transport in the Cathode of a Proton Exchange Membrane Fuel Cell

DEFF Research Database (Denmark)

Olesen, Anders Christian; Berning, Torsten; Kær, Søren Knudsen

2012-01-01

A three-dimensional, multicomponent, two-fluid model developed in the commercial CFD package CFX 13 (ANSYS Inc.) is used to investigate the effect of porous media compression on water transport in a proton exchange membrane fuel cell (PEMFC). The PEMFC model only consist of the cathode channel, gas....... Furthermore, the presence of irreducible liquid water is taken into account. In order to account for compression, porous media morphology variations are specified based on the gas diffusion layer (GDL) through-plane strain and intrusion which are stated as a function of compression. These morphology...... variations affect gas and liquid water transport, and hence liquid water distribution and the risk of blocking active sites. Hence, water transport is studied under GDL compression in order to investigate the qualitative effects. Two simulation cases are compared; one with and one without compression....

Water induced sediment levitation enhances downslope transport on Mars.

Science.gov (United States)

Raack, Jan; Conway, Susan J; Herny, Clémence; Balme, Matthew R; Carpy, Sabrina; Patel, Manish R

2017-10-27

On Mars, locally warm surface temperatures (~293 K) occur, leading to the possibility of (transient) liquid water on the surface. However, water exposed to the martian atmosphere will boil, and the sediment transport capacity of such unstable water is not well understood. Here, we present laboratory studies of a newly recognized transport mechanism: "levitation" of saturated sediment bodies on a cushion of vapor released by boiling. Sediment transport where this mechanism is active is about nine times greater than without this effect, reducing the amount of water required to transport comparable sediment volumes by nearly an order of magnitude. Our calculations show that the effect of levitation could persist up to ~48 times longer under reduced martian gravity. Sediment levitation must therefore be considered when evaluating the formation of recent and present-day martian mass wasting features, as much less water may be required to form such features than previously thought.

A model describing water and salt migration in concrete during wetting/drying cycles

NARCIS (Netherlands)

Arends, T.; Taher, A.; van der Zanden, A.J.J.; Brouwers, H.J.H.; Bilek, V.; Kersner, Z.

2014-01-01

In order to predict the life span of concrete structures, models describing the migration of chloride are needed. In this paper, a start is made with a simple, theoretical model describing water and chloride transport in a concrete sample. First, transport of water in concrete is considered with

Development of a Life Cycle Inventory of Water Consumption Associated with the Production of Transportation Fuels

Energy Technology Data Exchange (ETDEWEB)

Lampert, David J. [Argonne National Lab. (ANL), Argonne, IL (United States); Cai, Hao [Argonne National Lab. (ANL), Argonne, IL (United States); Wang, Zhichao [Argonne National Lab. (ANL), Argonne, IL (United States); Keisman, Jennifer [Argonne National Lab. (ANL), Argonne, IL (United States); Wu, May [Argonne National Lab. (ANL), Argonne, IL (United States); Han, Jeongwoo [Argonne National Lab. (ANL), Argonne, IL (United States); Dunn, Jennifer [Argonne National Lab. (ANL), Argonne, IL (United States); Sullivan, John L. [Argonne National Lab. (ANL), Argonne, IL (United States); Elgowainy, Amgad [Argonne National Lab. (ANL), Argonne, IL (United States); Wang, Michael [Argonne National Lab. (ANL), Argonne, IL (United States); Keisman, Jennifer [American Association for the Advancemetn of Science (AAAS), Washington, DC (United States)

2015-10-01

The production of all forms of energy consumes water. To meet increased energy demands, it is essential to quantify the amount of water consumed in the production of different forms of energy. By analyzing the water consumed in different technologies, it is possible to identify areas for improvement in water conservation and reduce water stress in energy-producing regions. The transportation sector is a major consumer of energy in the United States. Because of the relationships between water and energy, the sustainability of transportation is tied to management of water resources. Assessment of water consumption throughout the life cycle of a fuel is necessary to understand its water resource implications. To perform a comparative life cycle assessment of transportation fuels, it is necessary first to develop an inventory of the water consumed in each process in each production supply chain. The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) model is an analytical tool that can used to estimate the full life-cycle environmental impacts of various transportation fuel pathways from wells to wheels. GREET is currently being expanded to include water consumption as a sustainability metric. The purpose of this report was to document data sources and methodologies to estimate water consumption factors (WCF) for the various transportation fuel pathways in GREET. WCFs reflect the quantity of freshwater directly consumed per unit production for various production processes in GREET. These factors do not include consumption of precipitation or low-quality water (e.g., seawater) and reflect only water that is consumed (i.e., not returned to the source from which it was withdrawn). The data in the report can be combined with GREET to compare the life cycle water consumption for different transportation fuels.

Application of two-barrier model of radioactive agent transport in sea water for analyzing artificial radionuclide release from containers with radioactive waste dumped in Kara Sea

Energy Technology Data Exchange (ETDEWEB)

Grishin, Denis S.; Laykin, Andrey I.; Kuchin, Nickolay L.; Platovskikh, Yuri A. [Krylov State Research Center, Saint Petersburg, 44 Moskovskoe shosse, 196158 (Russian Federation)

2014-07-01

Modeling of artificial radionuclide transport in sea water is crucial for prognosis of radioecological situation in regions where dumping of radioactive waste had been made and/or accidents with nuclear submarines had taken place. Distribution of artificial radionuclides in bottom sediments can be a detector of radionuclide release from dumped or sunk objects to marine environment. Proper model can determine the dependence between radionuclide distribution in sediments and radionuclide release. Following report describes two-barrier model of radioactive agent transport in sea water. It was tested on data from 1994 - 2013 expeditions to Novaya Zemlya bays, where regular dumping of solid radioactive waste was practiced by the former USSR from the early 1960's until 1990. Two-barrier model agrees with experimental data and allows more accurate determination of time and intensity of artificial radionuclide release from dumped containers. (authors)

Characterizing the transplanar and in-plane water transport properties of fabrics under different sweat rate: Forced Flow Water Transport Tester

Science.gov (United States)

Tang, K. P. M.; Chau, K. H.; Kan, C. W.; Fan, J. T.

2015-11-01

The water absorption and transport properties of fabrics are critical to wear comfort, especially for sportswear and protective clothing. A new testing apparatus, namely Forced Flow Water Transport Tester (FFWTT), was developed for characterizing the transplanar and in-plane wicking properties of fabrics based on gravimetric and image analysis technique. The uniqueness of this instrument is that the rate of water supply is adjustable to simulate varying sweat rates with reference to the specific end-use conditions ranging from sitting, walking, running to other strenuous activities. This instrument is versatile in terms of the types of fabrics that can be tested. Twenty four types of fabrics with varying constructions and surface finishes were tested. The results showed that FFWTT was highly sensitive and reproducible in differentiating these fabrics and it suggests that water absorption and transport properties of fabrics are sweat rate-dependent. Additionally, two graphic methods were proposed to map the direction of liquid transport and its relation to skin wetness, which provides easy and direct comparison among different fabrics. Correlation analysis showed that FFWTT results have strong correlation with subjective wetness sensation, implying validity and usefulness of the instrument.

An analytical model for predicting transport in a coupled vadose/phreatic system

International Nuclear Information System (INIS)

Tomasko, D.

1997-05-01

A simple analytical model is presented for predicting the transport of a contaminant in both the unsaturated (vadose) and saturated (phreatic) zones following a surficial spill. The model incorporates advection, dispersion, adsorption, and first-order decay in both zones and couples the transport processes at the water table. The governing equation is solved by using the method of Laplace transforms, with numerical inversion of the Laplace space equation for concentration. Because of the complexity of the functional form for the Laplace space solution, a numerical methodology using the real and imaginary parts of a Fourier series was implemented. To reduce conservatism in the model, dilution at the water table was also included. Verification of the model is demonstrated by its ability to reproduce the source history at the surface and to replicate appropriate one-dimensional transport through either the vadose or phreatic zone. Because of its simplicity and lack of detailed input data requirements, the model is recommended for scoping calculations

Transport of nanoparticles with dispersant through biofilm coated drinking water sand filters.

Science.gov (United States)

Li, Zhen; Aly Hassan, Ashraf; Sahle-Demessie, Endalkachew; Sorial, George A

2013-11-01

This article characterizes, experimentally and theoretically, the transport and retention of engineered nanoparticles (NP) through sand filters at drinking water treatment plants (DWTPs) under realistic conditions. The transport of four commonly used NPs (ZnO, CeO2, TiO2, and Ag, with bare surfaces and coating agents) through filter beds filled with sands from either acid washed and calcined, freshly acquired filter media, and used filter media from active filter media, were investigated. The study was conducted using water obtained upstream of the sand filter at DWTP. The results have shown that capping agents have a determinant importance in the colloidal stability and transport of NPs through the different filter media. The presence of the biofilm in used filter media increased adsorption of NPs but its effects in retaining capped NPs was less significant. The data was used to build a mathematical model based on the advection-dispersion equation. The model was used to simulate the performance of a scale-up sand filter and the effects on filtration cycle of traditional sand filtration system used in DWTPs. Published by Elsevier Ltd.

A hybrid model to predict the entrainment and subsurface transport of oil

International Nuclear Information System (INIS)

Spaulding, M.L.; Odulo, A.; Kolluru, V.S.

1992-01-01

The entrainment of surface oil into the water column and its subsequent subsurface transport and dispersion are predicted by a hybrid analytic-numerical solution to the advective diffusion equation. Total oil or selected hydrocarbon component concentrations in the water column are predicted. Assuming that the principal mechanism for entrainment is due to breaking waves, the oil entrainment rate is specified using the empirically based algorithm of Delvigne and Sweeney (1988). The subsurface transport model explicitly accounts for buoyant forces on dispersed oil by droplet size. Application of the model to an analytic test case and several hypothetical scenarios illustrates the model's utility. 35 refs., 8 figs., 2 tabs

Modeling thermal dynamics of active layer soils and near-surface permafrost using a fully coupled water and heat transport model

Science.gov (United States)

Jiang, Yueyang; Zhuang, Qianlai; O'Donnell, Jonathan A.

2012-01-01

Thawing and freezing processes are key components in permafrost dynamics, and these processes play an important role in regulating the hydrological and carbon cycles in the northern high latitudes. In the present study, we apply a well-developed soil thermal model that fully couples heat and water transport, to simulate the thawing and freezing processes at daily time steps across multiple sites that vary with vegetation cover, disturbance history, and climate. The model performance was evaluated by comparing modeled and measured soil temperatures at different depths. We use the model to explore the influence of climate, fire disturbance, and topography (north- and south-facing slopes) on soil thermal dynamics. Modeled soil temperatures agree well with measured values for both boreal forest and tundra ecosystems at the site level. Combustion of organic-soil horizons during wildfire alters the surface energy balance and increases the downward heat flux through the soil profile, resulting in the warming and thawing of near-surface permafrost. A projection of 21st century permafrost dynamics indicates that as the climate warms, active layer thickness will likely increase to more than 3 meters in the boreal forest site and deeper than one meter in the tundra site. Results from this coupled heat-water modeling approach represent faster thaw rates than previously simulated in other studies. We conclude that the discussed soil thermal model is able to well simulate the permafrost dynamics and could be used as a tool to analyze the influence of climate change and wildfire disturbance on permafrost thawing.

Seasonal variability of water transport through the Straits of Gibraltar, Sicily and Corsica, derived from a high-resolution model of the Mediterranean circulation

Science.gov (United States)

Béranger, K.; Mortier, L.; Crépon, M.

2005-08-01

The variability of the water transport through three major straits of the Mediterranean Sea (Gibraltar, Sicily and Corsica) was investigated using a high-resolution model. This model of the Mediterranean circulation was developed in the context of the Mercator project. The region of interest is the western Mediterranean between the Strait of Gibraltar and the Strait of Sicily. The major water masses and the winter convection in the Gulf of Lions were simulated. The model reproduced the meso-scale and large-scale patterns of the circulation in very good agreement with recent observations. The western and the eastern gyres of the Alboran Sea were observed but high interannual variability was noticed. The Algerian Current splits into several branches at the longitude of the Strait of Sicily level, forming the Tyrrhenian branch, and, the Atlantic Ionian Stream and the Atlantic Tunisian Current in the eastern Mediterranean. The North Current retroflexed north of the Balearic Islands and a dome structure was observed in the Gulf of Lions. The cyclonic barotropic Algerian gyre, which was recently observed during the MATER and ELISA experiment, was evidenced in the simulation. From time-series of 10-day mean transport, the three straits presented a high variability at short time-scales. The transport was generally maximum, in April for the Strait of Gibraltar, in November for the Strait of Sicily, and in January for the Strait of Corsica. The amplitudes of the transport through the Straits of Gibraltar (0.11 Sv) and Sicily (0.30 Sv) presented a weaker seasonal variability than that of the Strait of Corsica (0.70 Sv). The study of the relation between transport and wind forcing showed that the transport through the Strait of Gibraltar is dependent on local zonal wind over short time-scales (70%), which was not the case for the other straits (less than 30%). The maximum (minimum) of the transport occurred for an eastward (westward) wind stress in the strait. An interannual

Suberized transport barriers in Arabidopsis, barley and rice roots: From the model plant to crop species.

Science.gov (United States)

Kreszies, Tino; Schreiber, Lukas; Ranathunge, Kosala

2018-02-07

Water is the most important prerequisite for life and plays a major role during uptake and transport of nutrients. Roots are the plant organs that take up the major part of water, from the surrounding soil. Water uptake is related to the root system architecture, root growth, age and species dependent complex developmental changes in the anatomical structures. The latter is mainly attributed to the deposition of suberized barriers in certain layers of cell walls, such as endo- and exodermis. With respect to water permeability, changes in the suberization of roots are most relevant. Water transport or hydraulic conductivity of roots (Lp r ) can be described by the composite transport model and is known to be very variable between plant species and growth conditions and root developmental states. In this review, we summarize how anatomical structures and apoplastic barriers of roots can diversely affect water transport, comparing the model plant Arabidopsis with crop plants, such as barley and rice. Results comparing the suberin amounts and water transport properties indicate that the common assumption that suberin amount negatively correlates with water and solute transport through roots may not always be true. The composition, microstructure and localization of suberin may also have a great impact on the formation of efficient barriers to water and solutes. Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.

UZ Colloid Transport Model

International Nuclear Information System (INIS)

McGraw, M.

2000-01-01

The UZ Colloid Transport model development plan states that the objective of this Analysis/Model Report (AMR) is to document the development of a model for simulating unsaturated colloid transport. This objective includes the following: (1) use of a process level model to evaluate the potential mechanisms for colloid transport at Yucca Mountain; (2) Provide ranges of parameters for significant colloid transport processes to Performance Assessment (PA) for the unsaturated zone (UZ); (3) Provide a basis for development of an abstracted model for use in PA calculations

Modeling gravity effects on water retention and gas transport characteristics in plant growth substrates

DEFF Research Database (Denmark)

Deepagoda Thuduwe Kankanamge Kelum, Chamindu; Jones, Scott B.; Tuller, Markus

2014-01-01

utilization to conserve energy and to limit transport costs, native materials mined on Moon or Mars are of primary interest for plant growth media in a future outpost, while terrestrial porous substrates with optimal growth media characteristics will be useful for onboard plant growth during space missions....... Due to limited experimental opportunities and prohibitive costs, liquid and gas behavior in porous substrates under reduced gravity conditions has been less studied and hence remains poorly understood. Based on ground-based measurements, this study examined water retention, oxygen diffusivity and air...... that estimates the gas percolation threshold based on the pore size distribution. The model successfully captured measured data for all investigated media and demonstrated the implications of the poorly-understood shift in gas percolation threshold with improved gas percolation in reduced gravity. Finally, using...

Simulations of Ground-Water Flow, Transport, Age, and Particle Tracking near York, Nebraska, for a Study of Transport of Anthropogenic and Natural Contaminants (TANC) to Public-Supply Wells

Science.gov (United States)

Clark, Brian R.; Landon, Matthew K.; Kauffman, Leon J.; Hornberger, George Z.

2008-01-01

Contamination of public-supply wells has resulted in public-health threats and negative economic effects for communities that must treat contaminated water or find alternative water supplies. To investigate factors controlling vulnerability of public-supply wells to anthropogenic and natural contaminants using consistent and systematic data collected in a variety of principal aquifer settings in the United States, a study of Transport of Anthropogenic and Natural Contaminants to public-supply wells was begun in 2001 as part of the U.S. Geological Survey National Water-Quality Assessment Program. The area simulated by the ground-water flow model described in this report was selected for a study of processes influencing contaminant distribution and transport along the direction of ground-water flow towards a public-supply well in southeastern York, Nebraska. Ground-water flow is simulated for a 60-year period from September 1, 1944, to August 31, 2004. Steady-state conditions are simulated prior to September 1, 1944, and represent conditions prior to use of ground water for irrigation. Irrigation, municipal, and industrial wells were simulated using the Multi-Node Well package of the modular three-dimensional ground-water flow model code, MODFLOW-2000, which allows simulation of flow and solutes through wells that are simulated in multiple nodes or layers. Ground-water flow, age, and transport of selected tracers were simulated using the Ground-Water Transport process of MODFLOW-2000. Simulated ground-water age was compared to interpreted ground-water age in six monitoring wells in the unconfined aquifer. The tracer chlorofluorocarbon-11 was simulated directly using Ground-Water Transport for comparison with concentrations measured in six monitoring wells and one public supply well screened in the upper confined aquifer. Three alternative model simulations indicate that simulation results are highly sensitive to the distribution of multilayer well bores where leakage

Plant water relations I: uptake and transport

Science.gov (United States)

Plants, like all living things, are mostly water. Water is the matrix of life, and its availability determines the distribution and productivity of plants on earth. Vascular plants evolved structures that enable them to transport water long distances with little input of energy, but the hollow trach...

Developing a particle tracking surrogate model to improve inversion of ground water - Surface water models

Science.gov (United States)

Cousquer, Yohann; Pryet, Alexandre; Atteia, Olivier; Ferré, Ty P. A.; Delbart, Célestine; Valois, Rémi; Dupuy, Alain

2018-03-01

The inverse problem of groundwater models is often ill-posed and model parameters are likely to be poorly constrained. Identifiability is improved if diverse data types are used for parameter estimation. However, some models, including detailed solute transport models, are further limited by prohibitive computation times. This often precludes the use of concentration data for parameter estimation, even if those data are available. In the case of surface water-groundwater (SW-GW) models, concentration data can provide SW-GW mixing ratios, which efficiently constrain the estimate of exchange flow, but are rarely used. We propose to reduce computational limits by simulating SW-GW exchange at a sink (well or drain) based on particle tracking under steady state flow conditions. Particle tracking is used to simulate advective transport. A comparison between the particle tracking surrogate model and an advective-dispersive model shows that dispersion can often be neglected when the mixing ratio is computed for a sink, allowing for use of the particle tracking surrogate model. The surrogate model was implemented to solve the inverse problem for a real SW-GW transport problem with heads and concentrations combined in a weighted hybrid objective function. The resulting inversion showed markedly reduced uncertainty in the transmissivity field compared to calibration on head data alone.

Combining multimedia models with integrated urban water system models for micropollutants

DEFF Research Database (Denmark)

De Keyser, W.; Gevaert, V.; Verdonck, F.

2010-01-01

Integrated urban water system (IUWS) modeling aims at assessing the quality of the surface water receiving the urban emissions through sewage treatment plants, combined sewer overflows (CSOS) and stormwater drainage systems However, some micropollutants tend to appear in more than one environmental...... medium (air, water, sediment, soil, groundwater, etc) In this work, a multimedia fate and transport model (MFTM) is "wrapped around" a dynamic IUWS model for organic micropollutants to enable integrated environmental assessment The combined model was tested on a hypothetical catchment using two scenarios...... on the one hand a reference scenario with a combined sewerage system and on the other hand a stormwater infiltration pond scenario, as an example of a sustainable urban drainage system (SUDS) A case for Bis(2-ethylhexyl) phthalate (DEHP) was simulated and resulted in reduced surface water concentrations...

The Structure and Transport of Water and Hydrated Ions Within Hydrophobic, Nanoscale Channels

International Nuclear Information System (INIS)

Holt, J.K.; Herberg, J.L.; Wu, Y.; Schwegler, E.; Mehta, A.

2009-01-01

The purpose of this project includes an experimental and modeling investigation into water and hydrated ion structure and transport at nanomaterials interfaces. This is a topic relevant to understanding the function of many biological systems such as aquaporins that efficiently shuttle water and ion channels that permit selective transport of specific ions across cell membranes. Carbon nanotubes (CNT) are model nanoscale, hydrophobic channels that can be functionalized, making them artificial analogs for these biological channels. This project investigates the microscopic properties of water such as water density distributions and dynamics within CNTs using Nuclear Magnetic Resonance (NMR) and the structure of hydrated ions at CNT interfaces via X-ray Absorption Spectroscopy (XAS). Another component of this work is molecular simulation, which can predict experimental measurables such as the proton relaxation times, chemical shifts, and can compute the electronic structure of CNTs. Some of the fundamental questions this work is addressing are: (1) what is the length scale below which nanoscale effects such as molecular ordering become important, (2) is there a relationship between molecular ordering and transport?, and (3) how do ions interact with CNT interfaces? These are questions of interest to the scientific community, but they also impact the future generation of sensors, filters, and other devices that operate on the nanometer length scale. To enable some of the proposed applications of CNTs as ion filtration media and electrolytic supercapacitors, a detailed knowledge of water and ion structure at CNT interfaces is critical.

Principles and approaches for numerical modelling of sediment transport in sewers

DEFF Research Database (Denmark)

Mark, Ole; Larsen, Torben; Appelgren, Cecilia

1994-01-01

model MOUSE ST which describes the sediment transport in sewers. This paper discusses the applicability and the limitations of various modelling approaches and sediment transport formulations in MOUSE ST. The study was founded by the Swedish Water and Waste Works Association and the Nordic Industrial......A study has been carried out at the University of Aalborg, Denmark and VBB VIAK, Sweden with the objectives to describe the effect of sediment deposits on the hydraulic capacity of sewer systems and to investigate the sediment transport in sewer systems. A results of the study is a mathematical...

Development of laboratory experiments serving as a basis for modeling the transport behaviour of arsenate, lead, cadmium and copper in water-saturated columns

International Nuclear Information System (INIS)

Hamer, K.

1993-01-01

The aim of the study was to work out laboratory experiments which might serve as a link between the bench and the application of CoTAM (Column Transport and Absorption Model) in real practice, thus thanking the development of this computer model which is to permit the simulation of the transport behaviour of heavy metals in porous aquilers. Efforts were made to find a process-oriented concept so as to provide a wide field of application. In developing the model and the laboratory experiments, this meant studying all the processes in groundwater separately as far as possible and avoiding case-specific sum parameters. The work centered on an examination of sorption processes during transport in groundwater, as this combination of processes is always found in natural porous aquifers. In water-saturated-column experiments on combinations of arenaceous quartz, feldspar, montmorillonite, goethite, peat and manganese oxide as the aquifer material, the transport of cadmium, copper, lead and arsenate was simulated on the bench scale. These case examples served to study sorption processes and their diverse kinetics as well as hydrodynamic processes. (orig./BBR) [de

Far-reaching transport of Pearl River plume water by upwelling jet in the northeastern South China Sea

Science.gov (United States)

Chen, Zhaoyun; Pan, Jiayi; Jiang, Yuwu; Lin, Hui

2017-09-01

Satellite images from the Moderate Resolution Imaging Spectroradiometer (MODIS) show that there was a belt of turbid water appearing along an upwelling front near the Chinese coast of Guangdong, and indicate that the turbid water of the Pearl River plume water could be transported to a far-reaching area east of the Taiwan Bank. Numerical modeling results are consistent with the satellite observations, and reveal that a strong jet exists at the upwelling front with a speed as high as 0.8 m s- 1, which acts as a pathway for transporting the high-turbidity plume water. The dynamical analysis suggests that geostrophic equilibrium dominates in the upwelling front and plume areas, and the baroclinicity of the upwelling front resulting from the horizontal density gradient is responsible for the generation of the strong jet, which enhances the far-reaching transport of the terrigenous nutrient-rich water of the Pearl River plume. Model sensitivity analyses also confirm that this jet persists as long as the upwelling front exists, even when the wind subsides and becomes insignificant. Further idealized numerical model experiments indicate that the formation and persistence of the upwelling front jet depend on the forcing strength of the upwelling-favorable wind. The formation time of the jet varies from 15 to 158 h as the stress of the upwelling-favorable wind changes from 0.2 to 0.01 N m- 2. With the persistent transport of the nutrient-rich plume water, biophysical activities can be promoted significantly in the far-reaching destination area of the oligotrophic water.

Rainfall-induced fecal indicator organisms transport from manured fields: model sensitivity analysis.

Science.gov (United States)

Martinez, Gonzalo; Pachepsky, Yakov A; Whelan, Gene; Yakirevich, Alexander M; Guber, Andrey; Gish, Timothy J

2014-02-01

Microbial quality of surface waters attracts attention due to food- and waterborne disease outbreaks. Fecal indicator organisms (FIOs) are commonly used for the microbial pollution level evaluation. Models predicting the fate and transport of FIOs are required to design and evaluate best management practices that reduce the microbial pollution in ecosystems and water sources and thus help to predict the risk of food and waterborne diseases. In this study we performed a sensitivity analysis for the KINEROS/STWIR model developed to predict the FIOs transport out of manured fields to other fields and water bodies in order to identify input variables that control the transport uncertainty. The distributions of model input parameters were set to encompass values found from three-year experiments at the USDA-ARS OPE3 experimental site in Beltsville and publicly available information. Sobol' indices and complementary regression trees were used to perform the global sensitivity analysis of the model and to explore the interactions between model input parameters on the proportion of FIO removed from fields. Regression trees provided a useful visualization of the differences in sensitivity of the model output in different parts of the input variable domain. Environmental controls such as soil saturation, rainfall duration and rainfall intensity had the largest influence in the model behavior, whereas soil and manure properties ranked lower. The field length had only moderate effect on the model output sensitivity to the model inputs. Among the manure-related properties the parameter determining the shape of the FIO release kinetic curve had the largest influence on the removal of FIOs from the fields. That underscored the need to better characterize the FIO release kinetics. Since the most sensitive model inputs are available in soil and weather databases or can be obtained using soil water models, results indicate the opportunity of obtaining large-scale estimates of FIO

Model validation studies of water flow and radionuclide transport in vegetated soils using lysimeter data

Energy Technology Data Exchange (ETDEWEB)

Butler, A.; Jining Chen [Imperial College of Science, Technology and Medicine, London (United Kingdom)] [and others

1996-09-01

Model Uncertainty and Validation was one of the four themes of BIOMOVS II which had been identified by the programme's steering committee. It arose out of a concern that biosphere assessment models are generally simplified representations of highly complex environmental systems which, therefore, include a degree of uncertainty in their outputs. This uncertainty may be due to inadequate representations of the physical, chemical and biological processes; issues associated with scaling up highly non-linear systems; problems of model identification, in particular user interpretation. Therefore, during the course of the 5 year (1991-1996) BIOMOVS II programme a number of working sub-groups reestablished to address these issues. This document is the final report of the Prediction of Upward Migration of Radionuclides in Lysimeters sub-group which was established towards the end of the programme, late in 1994. It describes the 'blind' application of various hydrological and radiochemical transport models to experiment data derived from vegetated lysimeters. In order to investigate soil-to-plant transfer processes affecting the radionuclide migration from contaminated near surface water tables into arable crops, a lysimeter experiment has been undertaken at Imperial College, funded by UK Nirex Ltd. Detailed observations of climate, soil hydrology, plant growth and radiochemical migration were collected on the uptake of various radionuclides by a winter wheat crop. A selected set of data was made available to members of BIOMOVS II in order to allow them to test relevant components of current versions of assessment code. This was a challenging task owing to the rather unusual experimental design, in particular, the introduction of radionuclides at the base of the lysimeter, 5 cm below a fixed water table, and their subsequent upward migration through the soil. The comprehensive hydrological data set available provided various modelers, particularly those

Model validation studies of water flow and radionuclide transport in vegetated soils using lysimeter data

International Nuclear Information System (INIS)

Butler, A.; Jining Chen

1996-09-01

Model Uncertainty and Validation was one of the four themes of BIOMOVS II which had been identified by the programme's steering committee. It arose out of a concern that biosphere assessment models are generally simplified representations of highly complex environmental systems which, therefore, include a degree of uncertainty in their outputs. This uncertainty may be due to inadequate representations of the physical, chemical and biological processes; issues associated with scaling up highly non-linear systems; problems of model identification, in particular user interpretation. Therefore, during the course of the 5 year (1991-1996) BIOMOVS II programme a number of working sub-groups reestablished to address these issues. This document is the final report of the Prediction of Upward Migration of Radionuclides in Lysimeters sub-group which was established towards the end of the programme, late in 1994. It describes the 'blind' application of various hydrological and radiochemical transport models to experiment data derived from vegetated lysimeters. In order to investigate soil-to-plant transfer processes affecting the radionuclide migration from contaminated near surface water tables into arable crops, a lysimeter experiment has been undertaken at Imperial College, funded by UK Nirex Ltd. Detailed observations of climate, soil hydrology, plant growth and radiochemical migration were collected on the uptake of various radionuclides by a winter wheat crop. A selected set of data was made available to members of BIOMOVS II in order to allow them to test relevant components of current versions of assessment code. This was a challenging task owing to the rather unusual experimental design, in particular, the introduction of radionuclides at the base of the lysimeter, 5 cm below a fixed water table, and their subsequent upward migration through the soil. The comprehensive hydrological data set available provided various modelers, particularly those involved in tritium

Patterned gradient surface for spontaneous droplet transportation and water collection: simulation and experiment

International Nuclear Information System (INIS)

Tan, Xianhua; Zhu, Yiying; Shi, Tielin; Tang, Zirong; Liao, Guanglan

2016-01-01

We demonstrate spontaneous droplet transportation and water collection on wedge-shaped gradient surfaces consisting of alternating hydrophilic and hydrophobic regions. Droplets on the surfaces are modeled and simulated to analyze the Gibbs free energy and free energy gradient distributions. Big half-apex angle and great wettability difference result in considerable free energy gradient, corresponding to large driving force for spontaneous droplet transportation, thus causing the droplets to move towards the open end of the wedge-shaped hydrophilic regions, where the Gibbs free energy is low. Gradient surfaces are then fabricated and tested. Filmwise condensation begins on the hydrophilic regions, forming wedge-shaped tracks for water collection. Dropwise condensation occurs on the hydrophobic regions, where the droplet size distribution and departure diameters are controlled by the width of the regions. Condensate water from both the hydrophilic and hydrophobic regions are collected directionally to the open end of the wedge-shaped hydrophilic regions, agreeing with the simulations. Directional droplet transport and controllable departure diameters make the branched gradient surfaces more efficient than smooth surfaces for water collection, which proves that gradient surfaces are potential in water collection, microfluidic devices, anti-fogging and self-cleaning. (paper)

Modelling phosphorus transport and its response to climate change at upper stream of Poyang Lake-the largest fresh water lake in China

Science.gov (United States)

Jiang, Sanyuan; Zhang, Qi

2017-04-01

Phosphorus losses from excessive fertilizer application and improper land exploitation were found to be the limiting factor for freshwater quality deterioration and eutrophication. Phosphorus transport from uplands to river is related to hydrological, soil erosion and sediment transport processes, which is impacted by several physiographic and meteorological factors. The objective of this study was to investigate the spatiotemporal variation of phosphorus losses and response to climate change at a typical upstream tributary (Le'An river) of Poyang Lake. To this end, a process-oriented hydrological and nutrient transport model HYPE (Hydrological Predictions for the Environment) was set up for discharge and phosphorus transport simulation at Le'An catchment. Parameter ESTimator (PEST) was combined with HYPE model for parameter sensitivity analysis and optimisation. In runoff modelling, potential evapotranspiration rate of the dominant land use (forest) is most sensitive; parameters of surface runoff rate and percolation capacity for the red soil are also very sensitive. In phosphorus transport modelling, the exponent of equation for soil erosion processes induced by surface runoff is most sensitive, coefficient of adsorption/desorption processes for red soil is also very sensitive. Flow dynamics and water balance were simulated well at all sites for the whole period (1978-1986) with NSE≥0.80 and PBIAS≤14.53%. The optimized hydrological parameter set were transferable for the independent period (2009-2010) with NSE≥0.90 and highest PBIAS of -7.44% in stream flow simulation. Seasonal dynamics and balance of stream water TP (Total Phosphorus ) concentrations were captured satisfactorily indicated by NSE≥0.53 and highest PBIAS of 16.67%. In annual scale, most phosphorus is transported via surface runoff during heavy storm flow events, which may account for about 70% of annual TP loads. Based on future climate change analysis under three different emission

Shallow water table effects on water, sediment, and pesticide transport in vegetative filter strips - Part 1: nonuniform infiltration and soil water redistribution

OpenAIRE

Munoz Carpena, R.; Lauvernet, C.; Carluer, N.

2018-01-01

Vegetation buffers like vegetative filter strips (VFSs) are often used to protect water bodies from surface runoff pollution from disturbed areas. Their typical placement in floodplains often results in the presence of a seasonal shallow water table (WT) that can decrease soil infiltration and increase surface pollutant transport during a rainfall-runoff event. Simple and robust components of hydrological models are needed to analyze the impacts of WT in the landscape. To si...

Modeling of Coastal Effluent Transport: an Approach to Linking of Far-field and Near-field Models

International Nuclear Information System (INIS)

Yang, Zhaoqing; Khangaonkar, Tarang P.

2008-01-01

One of the challenges in effluent transport modeling in coastal tidal environments is the proper calculation of initial dilution in connection with the far-field transport model. In this study, an approach of external linkage of far-field and near-field effluent transport models is presented, and applied to simulate the effluent transport in the Port Angeles Harbor, Washington in the Strait of Juan de Fuca. A near-field plume model was used to calculate the effluent initial dilution and a three-dimensional (3-D) hydrodynamic model was developed to simulate the tidal circulation and far-field effluent transport in the Port Angeles Harbor. In the present study, the hydrodynamic model was driven by tides and surface winds. Observed water surface elevation and velocity data were used to calibrate the model over a period covering the neap-spring tidal cycle. The model was also validated with observed surface drogue trajectory data. The model successfully reproduced the tidal dynamics in the study area and good agreements between model results and observed data were obtained. This study demonstrated that the linkage between the near-field and far-field models in effluent transport modeling can be achieved through iteratively adjusting the model grid sizes such that the far-field modeled dilution ratio and effluent concentration in the effluent discharge model grid cell match the concentration calculated by the near-field plume model

Modeling Soil Water Retention Curves in the Dry Range Using the Hygroscopic Water Content

DEFF Research Database (Denmark)

Chen, Chong; Hu, Kelin; Arthur, Emmanuel

2014-01-01

Accurate information on the dry end (matric potential less than −1500 kPa) of soil water retention curves (SWRCs) is crucial for studying water vapor transport and evaporation in soils. The objectives of this study were to assess the potential of the Oswin model for describing the water adsorption...... curves of soils and to predict SWRCs at the dry end using the hygroscopic water content at a relative humidity of 50% (θRH50). The Oswin model yielded satisfactory fits to dry-end SWRCs for soils dominated by both 2:1 and 1:1 clay minerals. Compared with the Oswin model, the Campbell and Shiozawa model...... for soils dominated by 2:1 and 1:1 clays, respectively. Comparison of the Oswin model combined with the Kelvin equation, with water potential estimated from θRH50 (Oswin-KRH50), CS model combined with the Arthur equation (CS-A), and CS-K model, with water potential obtained from θRH50 (CS-KRH50) indicated...

Modeling the electrochemistry of the primary circuits of light water reactors

International Nuclear Information System (INIS)

Bertuch, A.; Macdonald, D.D.; Pang, J.; Kriksunov, L.; Arioka, K.

1994-01-01

To model the corrosion behaviors of the heat transport circuits of light water reactors, a mixed potential model (NTM) has been developed and applied to both boiling water reactors (BWRs) and pressurized water reactors (PWRs). Using the data generated by the GE/UKEA-Harwell radiolysis model, electrochemical potentials (ECPs) have been calculated for the heat transport circuits of eight BWRs operating under hydrogen water chemistry (HWC). By modeling the corrosion behaviors of these reactors, the effectiveness of HWC at limiting IGSCC and IASCC can be determined. For simulating PWR primary circuits, a chemical-radiolysis model (developed by the authors) was used to generate input parameters for the MPM. Corrosion potentials of Type 304 and 316 SSs in PWR primary environments were calculated using the NTM and were found to be in good agreement with the corrosion potentials measured in the laboratory for simulated PWR primary environments

Machine Learning and Deep Learning Models to Predict Runoff Water Quantity and Quality

Science.gov (United States)

Bradford, S. A.; Liang, J.; Li, W.; Murata, T.; Simunek, J.

2017-12-01

Contaminants can be rapidly transported at the soil surface by runoff to surface water bodies. Physically-based models, which are based on the mathematical description of main hydrological processes, are key tools for predicting surface water impairment. Along with physically-based models, data-driven models are becoming increasingly popular for describing the behavior of hydrological and water resources systems since these models can be used to complement or even replace physically based-models. In this presentation we propose a new data-driven model as an alternative to a physically-based overland flow and transport model. First, we have developed a physically-based numerical model to simulate overland flow and contaminant transport (the HYDRUS-1D overland flow module). A large number of numerical simulations were carried out to develop a database containing information about the impact of various input parameters (weather patterns, surface topography, vegetation, soil conditions, contaminants, and best management practices) on runoff water quantity and quality outputs. This database was used to train data-driven models. Three different methods (Neural Networks, Support Vector Machines, and Recurrence Neural Networks) were explored to prepare input- output functional relations. Results demonstrate the ability and limitations of machine learning and deep learning models to predict runoff water quantity and quality.

Interfacial and Wall Transport Models for SPACE-CAP Code

International Nuclear Information System (INIS)

Hong, Soon Joon; Choo, Yeon Joon; Han, Tae Young; Hwang, Su Hyun; Lee, Byung Chul; Choi, Hoon; Ha, Sang Jun

2009-01-01

The development project for the domestic design code was launched to be used for the safety and performance analysis of pressurized light water reactors. And CAP (Containment Analysis Package) code has been also developed for the containment safety and performance analysis side by side with SPACE. The CAP code treats three fields (gas, continuous liquid, and dispersed drop) for the assessment of containment specific phenomena, and is featured by its multidimensional assessment capabilities. Thermal hydraulics solver was already developed and now under testing of its stability and soundness. As a next step, interfacial and wall transport models was setup. In order to develop the best model and correlation package for the CAP code, various models currently used in major containment analysis codes, which are GOTHIC, CONTAIN2.0, and CONTEMPT-LT, have been reviewed. The origins of the selected models used in these codes have also been examined to find out if the models have not conflict with a proprietary right. In addition, a literature survey of the recent studies has been performed in order to incorporate the better models for the CAP code. The models and correlations of SPACE were also reviewed. CAP models and correlations are composed of interfacial heat/mass, and momentum transport models, and wall heat/mass, and momentum transport models. This paper discusses on those transport models in the CAP code

Interfacial and Wall Transport Models for SPACE-CAP Code

Energy Technology Data Exchange (ETDEWEB)

Hong, Soon Joon; Choo, Yeon Joon; Han, Tae Young; Hwang, Su Hyun; Lee, Byung Chul [FNC Tech., Seoul (Korea, Republic of); Choi, Hoon; Ha, Sang Jun [Korea Electric Power Research Institute, Daejeon (Korea, Republic of)

2009-10-15

The development project for the domestic design code was launched to be used for the safety and performance analysis of pressurized light water reactors. And CAP (Containment Analysis Package) code has been also developed for the containment safety and performance analysis side by side with SPACE. The CAP code treats three fields (gas, continuous liquid, and dispersed drop) for the assessment of containment specific phenomena, and is featured by its multidimensional assessment capabilities. Thermal hydraulics solver was already developed and now under testing of its stability and soundness. As a next step, interfacial and wall transport models was setup. In order to develop the best model and correlation package for the CAP code, various models currently used in major containment analysis codes, which are GOTHIC, CONTAIN2.0, and CONTEMPT-LT, have been reviewed. The origins of the selected models used in these codes have also been examined to find out if the models have not conflict with a proprietary right. In addition, a literature survey of the recent studies has been performed in order to incorporate the better models for the CAP code. The models and correlations of SPACE were also reviewed. CAP models and correlations are composed of interfacial heat/mass, and momentum transport models, and wall heat/mass, and momentum transport models. This paper discusses on those transport models in the CAP code.

ITE CHARACTERIZATION TO SUPPORT CONCEPTUAL MODEL DEVELOPMENT FOR SUBSURFACE RADIONUCLIDE TRANSPORT

Science.gov (United States)

Remediation of radionuclide contaminants in ground water often begins with the development of conceptual and analytical models that guide our understanding of the processes controlling radionuclide transport. The reliability of these models is often predicated on the collection o...

An Eulerian two-phase flow model for sediment transport under realistic surface waves

Science.gov (United States)

Hsu, T. J.; Kim, Y.; Cheng, Z.; Chauchat, J.

2017-12-01

Wave-driven sediment transport is of major importance in driving beach morphology. However, the complex mechanisms associated with unsteadiness, free-surface effects, and wave-breaking turbulence have not been fully understood. Particularly, most existing models for sediment transport adopt bottom boundary layer approximation that mimics the flow condition in oscillating water tunnel (U-tube). However, it is well-known that there are key differences in sediment transport when comparing to large wave flume datasets, although the number of wave flume experiments are relatively limited regardless of its importance. Thus, a numerical model which can resolve the entire water column from the bottom boundary layer to the free surface can be a powerful tool. This study reports an on-going effort to better understand and quantify sediment transport under shoaling and breaking surface waves through the creation of open-source numerical models in the OpenFOAM framework. An Eulerian two-phase flow model, SedFoam (Cheng et al., 2017, Coastal Eng.) is fully coupled with a volume-of-fluid solver, interFoam/waves2Foam (Jacobsen et al., 2011, Int. J. Num. Fluid). The fully coupled model, named SedWaveFoam, regards the air and water phases as two immiscible fluids with the interfaces evolution resolved, and the sediment particles as dispersed phase. We carried out model-data comparisons with the large wave flume sheet flow data for nonbreaking waves reported by Dohmen-Janssen and Hanes (2002, J. Geophysical Res.) and good agreements were obtained for sediment concentration and net transport rate. By further simulating a case without free-surface (mimic U-tube condition), the effects of free-surface, most notably the boundary layer streaming effect on total transport, can be quantified.

Dynamic modeling of interfacial structures via interfacial area transport equation

International Nuclear Information System (INIS)

Seungjin, Kim; Mamoru, Ishii

2004-01-01

bubbles due to surface instability. In the present paper, the interfacial area transport equations currently available are reviewed to address the feasibility and reliability of the model. Results from extensive benchmark experiments for the model evaluation are also present. These include the data from adiabatic upward air-water two-phase flow in round tubes of various sizes, from a rectangular duct, and from adiabatic co-current downward air-water two-phase flow in round pipes of two different sizes. Furthermore, some guidelines for the future study on interfacial area transport equation are discussed. (authors)

Radiation inactivation studies of renal brush border water and urea transport

International Nuclear Information System (INIS)

Verkman, A.S.; Dix, J.A.; Seifter, J.L.; Skorecki, K.L.; Jung, C.Y.; Ausiello, D.A.

1985-01-01

Radiation inactivation was used to determine the nature and molecular weight of water and urea transport pathways in brush border membrane vesicles (BBMV) isolated from rabbit renal cortex. BBMV were frozen to -50 degrees C, irradiated with 1.5 MeV electrons, thawed, and assayed for transport or enzyme activity. The freezing process had no effect on enzyme or transport kinetics. BBMV alkaline phosphatase activity gave linear ln(activity) vs. radiation dose plots with a target size of 68 +/- 3 kDa, similar to previously reported values. Water and solute transport were measured using the stopped-flow light-scattering technique. The rates of acetamide and osmotic water transport did not depend on radiation dose (0-7 Mrad), suggesting that transport of these substances does not require a protein carrier. In contrast, urea and thiourea transport gave linear ln(activity) vs. dose curves with a target size of 125-150 kDa; 400 mM urea inhibited thiourea flux by -50% at 0 and 4.7 Mrad, showing that radiation does not affect inhibitor binding to surviving transporters. These studies suggest that BBMV urea transport requires a membrane protein, whereas osmotic water transport does not

Combining multimedia models with integrated urban water system models for micropollutants

DEFF Research Database (Denmark)

De Keyser, W.; Gevaert, V.; Verdonck, F.

2009-01-01

Integrated urban water system (IUWS) modelling aims at assessing the quality of the surface water receiving the urban emissions through sewage treatment plants, combined sewer overflows (CSOs) and stormwater drainage systems. However, some micropollutants have the tendency to occur in more than one...... environmental medium. In this work, a multimedia fate and transport model (MFTM) is “wrapped around” a dynamic IUWS model for organic micropollutants to enable integrated environmental assessment. The combined model was tested on a hypothetical catchment using two scenarios: a reference scenario...... and a stormwater infiltration pond scenario, as an example of a sustainable urban drainage system (SUDS). A case for Bis(2-ethylhexyl) phthalate (DEHP) was simulated and resulted in a reduced surface water concentration for the latter scenario. However, the model also showed that this was at the expense...

Evaluating the effects of variable water chemistry on bacterial transport during infiltration.

Science.gov (United States)

Zhang, Haibo; Nordin, Nahjan Amer; Olson, Mira S

2013-07-01

Bacterial infiltration through the subsurface has been studied experimentally under different conditions of interest and is dependent on a variety of physical, chemical and biological factors. However, most bacterial transport studies fail to adequately represent the complex processes occurring in natural systems. Bacteria are frequently detected in stormwater runoff, and may present risk of microbial contamination during stormwater recharge into groundwater. Mixing of stormwater runoff with groundwater during infiltration results in changes in local solution chemistry, which may lead to changes in both bacterial and collector surface properties and subsequent bacterial attachment rates. This study focuses on quantifying changes in bacterial transport behavior under variable solution chemistry, and on comparing the influences of chemical variability and physical variability on bacterial attachment rates. Bacterial attachment rate at the soil-water interface was predicted analytically using a combined rate equation, which varies temporally and spatially with respect to changes in solution chemistry. Two-phase Monte Carlo analysis was conducted and an overall input-output correlation coefficient was calculated to quantitatively describe the importance of physiochemical variation on the estimates of attachment rate. Among physical variables, soil particle size has the highest correlation coefficient, followed by porosity of the soil media, bacterial size and flow velocity. Among chemical variables, ionic strength has the highest correlation coefficient. A semi-reactive microbial transport model was developed within HP1 (HYDRUS1D-PHREEQC) and applied to column transport experiments with constant and variable solution chemistries. Bacterial attachment rates varied from 9.10×10(-3)min(-1) to 3.71×10(-3)min(-1) due to mixing of synthetic stormwater (SSW) with artificial groundwater (AGW), while bacterial attachment remained constant at 9.10×10(-3)min(-1) in a constant

Simplified model for radioactive contaminant transport: the TRANSS code

International Nuclear Information System (INIS)

Simmons, C.S.; Kincaid, C.T.; Reisenauer, A.E.

1986-09-01

A simplified ground-water transport model called TRANSS was devised to estimate the rate of migration of a decaying radionuclide that is subject to sorption governed by a linear isotherm. Transport is modeled as a contaminant mass transmitted along a collection of streamlines constituting a streamtube, which connects a source release zone with an environmental arrival zone. The probability-weighted contaminant arrival distribution along each streamline is represented by an analytical solution of the one-dimensional advection-dispersion equation with constant velocity and dispersion coefficient. The appropriate effective constant velocity for each streamline is based on the exact travel time required to traverse a streamline with a known length. An assumption used in the model to facilitate the mathematical simplification is that transverse dispersion within a streamtube is negligible. Release of contaminant from a source is described in terms of a fraction-remaining curve provided as input information. However, an option included in the code is the calculation of a fraction-remaining curve based on four specialized release models: (1) constant release rate, (2) solubility-controlled release, (3) adsorption-controlled release, and (4) diffusion-controlled release from beneath an infiltration barrier. To apply the code, a user supplies only a certain minimal number of parameters: a probability-weighted list of travel times for streamlines, a local-scale dispersion coefficient, a sorption distribution coefficient, total initial radionuclide inventory, radioactive half-life, a release model choice, and size dimensions of the source. The code is intended to provide scoping estimates of contaminant transport and does not predict the evolution of a concentration distribution in a ground-water flow field. Moreover, the required travel times along streamlines must be obtained from a prior ground-water flow simulation

The Role of Subsurface Properties on Transport of Water and Trace Gases: 1D Simulations at Selected Mars Landing Sites.

Science.gov (United States)

Karatekin, O.; Gloesener, E.; Dehant, V. M. A.

2017-12-01

In this work, water ice stability and water vapour transport through porous martian subsurface are studied using a 1D diffusive model. The role of adsorption on water transfer in martian conditions is investigated as well as the range of parameters that have the largest effect on gas transport. In addition, adsorption kinetics is considered to examine its influence on the water vapor exchange between the subsurface and the atmosphere. As methane has been detected in the martian atmosphere, the subsurface model is then used to study methane diffusion in the CH4/CO2/H2O system from variable depths under the surface. The results of subsurface gas transport at selected locations/landing sites are shown and implications for present/future observations are discussed.

Barriers to Superfast Water Transport in Carbon Nanotube Membranes

DEFF Research Database (Denmark)

Walther, Jens Honore; Ritos, Konstantinos; Cruz-Chu, Eduardo R.

2013-01-01

Carbon nanotube (CNT) membranes hold the promise of extraordinary fast water transport for applications such as energy efficient filtration and molecular level drug delivery. However, experiments and computations have reported flow rate enhancements over continuum hydrodynamics that contradict each...... over the continuum predictions. These rates are far below those reported experimentally. The results suggest that the reported superfast water transport rates cannot be attributed to interactions of water with pristine CNTs alone....

Examination of water quality changes during transportation of different fish

Directory of Open Access Journals (Sweden)

Istvan Nemeth

2015-12-01

Full Text Available Introduction The growth of population is increasing intensively (7.3 billion people in 2015 and it generates growing importance of fish farming. Primarily, fish meat could provide protein requirements for population so more and more attention must be paid to each sections of farming, for example fish transportation. A badly organized transportation technology can significantly reduce high quality stocks which were produced over several years. Deterioration of transport may occur on each fish distinctly. Bacterial or fungal diseases appear either immediately or days later. During our work, changes in several freshwater (peaceful or predator fish species (of different ages were monitored and analyzed during transport. There were two reasons why we examined the main physical and chemical parameters of the water. On one hand, we were curious to know how much the individuals exposed to heavy loads, which we tried to identify with some stress tests. On the other hand, we would develop a national water carrier monitoring system for the practice. Materials and methods Delivery technologies (foil sack and transport tankers used in practice was applied in the experiment of the study in a real road transport. The physical and chemical data were monitored and checked with the use of multiparameter instruments and photometrial tests. Physiological and stress tests were analyzed from blood plasma of each fish, primarily plasma glucose determination was used. Results After analysis of examined fish species and each ages, it is obvious that either short or long delivery times we choose physical and chemical properties of the transport water would change dramatically, even adequate oxygen balance was ensured. Values of individuals exposed to stress were more significant compared to baseline values. Conclusion We could define concrete changes in key parameters of the transport water with the number of realtime transport implementation which is a good help to

X-radiation effect on water transport in ascite cells of Ehrlich carcinoma

International Nuclear Information System (INIS)

Barnov, V.A.; Ajvazishvili, M.A.; Kartvelishvili, I.I.; Tushishvili, D.I.

1988-01-01

Effect of local X radiation with doses 0.05 and 0.15 C/kg on water transport in ascitic cells of Erlich carcinoma is studied in rats. To study water transport through cell membranes, tritium mark was used. It is concluded that radiation effect on water transport in cells of Erlich carcinoma may be related to change in ionic permittivity of the membrane, because small changes in transmembrane ion transport affect immediately the osmotic motion of water. 5 refs

GOES WATER VAPOR TRANSPORT V1

Data.gov (United States)

National Aeronautics and Space Administration — The GOES Water Vapor Transport CD contains nineteen months of geostationary satellite-derived products spanning the 1987/1988 El Nino Southern Oscillation (ENSO)...

The use of tracer techniques in the study of soil water flows and contaminant transport

International Nuclear Information System (INIS)

Reeves, A.D.; Beven, K.J.

1990-04-01

This report reviews the use of different types of tracers in the characterisation of soil water flows and the implications of tracer studies for modelling contaminant transport. The tracers considered are a number of different anions, stable isotopes, radioactive tracers, organic dyes, fluorocarbons, gases, solid particles and water temperature. The theoretical basis for modelling the results of tracer experiments in terms of the traditional convective-dispersion equation (CDE) is outlined. A number of alternative modelling strategies are reviewed: the mobile/immobile water extension of the CDE; the Jury Transfer Function Model (TFM); the Aggregated Mixing Zone (AMZ) model and Random Particle Tracking models. The first will form the basis of the Systeme Hydrologique Europeen (SHE) contaminant transport component. The Jury and AMZ models are both linear models and are consequently limited to applications in which the flows may be considered to be quasi-steady or repeatable. Random particle tracking models have the advantage of both flexibility and applicability to transient and spatially variable flow domains. A random particle model is being implemented on a transputer workstation at Lancaster and will be used to explore the effect of sub-grid scale complexities on effective grid-scale parameter values for distributed models such as SHE. (author)

Transport of Pathogen Surrogates in Soil Treatment Units: Numerical Modeling

Directory of Open Access Journals (Sweden)

Ivan Morales

2014-04-01

Full Text Available Segmented mesocosms (n = 3 packed with sand, sandy loam or clay loam soil were used to determine the effect of soil texture and depth on transport of two septic tank effluent (STE-borne microbial pathogen surrogates—green fluorescent protein-labeled E. coli (GFPE and MS-2 coliphage—in soil treatment units. HYDRUS 2D/3D software was used to model the transport of these microbes from the infiltrative surface. Mesocosms were spiked with GFPE and MS-2 coliphage at 105 cfu/mL STE and 105–106 pfu/mL STE, respectively. In all soils, removal rates were >99.99% at 25 cm. The transport simulation compared (1 optimization; and (2 trial-and-error modeling approaches. Only slight differences between the transport parameters were observed between these approaches. Treating both the die-off rates and attachment/detachment rates as variables resulted in an overall better model fit, particularly for the tailing phase of the experiments. Independent of the fitting procedure, attachment rates computed by the model were higher in sandy and sandy loam soils than clay, which was attributed to unsaturated flow conditions at lower water content in the coarser-textured soils. Early breakthrough of the bacteria and virus indicated the presence of preferential flow in the system in the structured clay loam soil, resulting in faster movement of water and microbes through the soil relative to a conservative tracer (bromide.

Hyporheic flow and transport processes: mechanisms, models, and biogeochemical implications

Science.gov (United States)

Boano, Fulvio; Harvey, Judson W.; Marion, Andrea; Packman, Aaron I.; Revelli, Roberto; Ridolfi, Luca; Anders, Wörman

2014-01-01

Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed."

Interfacial Water-Transport Effects in Proton-Exchange Membranes

Energy Technology Data Exchange (ETDEWEB)

Kienitz, Brian; Yamada, Haruhiko; Nonoyama, Nobuaki; Weber, Adam

2009-11-19

It is well known that the proton-exchange membrane is perhaps the most critical component of a polymer-electrolyte fuel cell. Typical membranes, such as Nafion(R), require hydration to conduct efficiently and are instrumental in cell water management. Recently, evidence has been shown that these membranes might have different interfacial morphology and transport properties than in the bulk. In this paper, experimental data combined with theoretical simulations will be presented that explore the existence and impact of interfacial resistance on water transport for Nafion(R) 21x membranes. A mass-transfer coefficient for the interfacial resistance is calculated from experimental data using different permeation cells. This coefficient is shown to depend exponentially on relative humidity or water activity. The interfacial resistance does not seem to exist for liquid/membrane or membrane/membrane interfaces. The effect of the interfacial resistance is to flatten the water-content profiles within the membrane during operation. Under typical operating conditions, the resistance is on par with the water-transport resistance of the bulk membrane. Thus, the interfacial resistance can be dominant especially in thin, dry membranes and can affect overall fuel-cell performance.

Development of computer code on sodium-water reaction products transport

International Nuclear Information System (INIS)

Arikawa, H.; Yoshioka, N.; Suemori, M.; Nishida, K.

1988-01-01

The LMFBR concept eliminating the secondary sodium system has been considered to be one of the most promissing concepts for offering cost reductions. In this reactor concept, the evaluation of effects on reactor core by the sodium-water reaction products (SWRPs) during sodium-water reaction at primary steam generator becomes one of the major safety issues. In this study, the calculation code was developed as the first step of the processes of establishing the evaluation method for SWRP effects. The calculation code, called SPROUT, simulates the SWRPs transport and distribution in primary sodium system using the system geometry, thermal hydraulic data and sodium-water reacting conditions as input. This code principally models SWRPs behavior. The paper contain the modelings for SWRPs behaviors, with solution, precipation, deposition and so on, and the results and discussions of the demonstration calculation for a typical FBR plant eliminating the secondary sodium system

Nano and Mesoscale Ion and Water Transport in Perfluorosulfonic AcidMembranes

Science.gov (United States)

2017-10-01

Nano- and Mesoscale Ion and Water Transport in Perfluorosulfonic-Acid Membranes A. R. Crothers a,b , C. J. Radke a,b , A. Z. Weber a a...Berkeley, CA 94720, USA Water and aqueous cations transport along multiple length scales in perfluorosulfonic-acid membranes. Molecular interactions...as a function of hydration. A resistor network upscales the nanoscale properties to predict effective membrane ion and water transport and their

Active water transport in unicellular algae: where, why, and how.

Science.gov (United States)

Raven, John A; Doblin, Martina A

2014-12-01

The occurrence of active water transport (net transport against a free energy gradient) in photosynthetic organisms has been debated for several decades. Here, active water transport is considered in terms of its roles, where it is found, and the mechanisms by which it could occur. First there is a brief consideration of the possibility of active water transport into plant xylem in the generation of root pressure and the refilling of embolized xylem elements, and from an unsaturated atmosphere into terrestrial organisms living in habitats with limited availability of liquid water. There is then a more detailed consideration of volume and osmotic regulation in wall-less freshwater unicells, and the possibility of generation of buoyancy in marine phytoplankton such as large-celled diatoms. Calculations show that active water transport is a plausible mechanism to assist cells in upwards vertical movements, requires less energy than synthesis of low-density organic solutes, and potentially on a par with excluding certain ions from the vacuole. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Transport mechanisms through PE-CVD coatings: influence of temperature, coating properties and defects on permeation of water vapour

International Nuclear Information System (INIS)

Kirchheim, Dennis; Jaritz, Montgomery; Hopmann, Christian; Dahlmann, Rainer; Mitschker, Felix; Awakowicz, Peter; Gebhard, Maximilian; Devi, Anjana; Brochhagen, Markus; Böke, Marc

2017-01-01

Gas transport mechanisms through plastics are usually described by the temperature-dependent Arrhenius-model and compositions of several plastic layers are represented by the CLT. When it comes to thin films such as plasma-enhanced chemical vapour deposition (PE-CVD) or plasma-enhanced atomic layer deposition (PE-ALD) coatings on substrates of polymeric material, a universal model is lacking. While existing models describe diffusion through defects, these models presume that permeation does not occur by other means of transport mechanisms. This paper correlates the existing transport models with data from water vapour transmission experiments. (paper)

GOES WATER VAPOR TRANSPORT V1

Data.gov (United States)

National Aeronautics and Space Administration — The GOES Water Vapor Transport CD contains nineteen months of geostationary satellite-derived products from the GOES-8 satellite spanning the 1987-1988 El Nino...

Hydrological balance and water transport processes of partially sealed soils

Science.gov (United States)

Timm, Anne; Wessolek, Gerd

2017-04-01

With increased urbanisation, soil sealing and its drastic effects on hydrological processes have received a lot of attention. Based on safety concerns, there has been a clear focus on urban drainage and prevention of urban floods caused by storm water events. For this reason, any kind of sealing is often seen as impermeable runoff generator that prevents infiltration and evaporation. While many hydrological models, especially storm water models, have been developed, there are only a handful of empirical studies actually measuring the hydrological balance of (partially) sealed surfaces. These challenge the general assumption of negligible infiltration and evaporation and show that these processes take place even for severe sealing such as asphalt. Depending on the material, infiltration from partially sealed surfaces can be equal to that of vegetated ones. Therefore, more detailed knowledge is needed to improve our understanding and models. In Berlin, two partially sealed weighable lysimeters were equipped with multiple temperature and soil moisture sensors in order to study their hydrological balance, as well as water and heat transport processes within the soil profile. This combination of methods affirms previous observations and offers new insights into altered hydrological processes of partially sealed surfaces at a small temporal scale. It could be verified that not all precipitation is transformed into runoff. Even for a relatively high sealing degree of concrete slabs with narrow seams, evaporation and infiltration may exceed runoff. Due to the lack of plant roots, the hydrological balance is mostly governed by precipitation events and evaporation generally occurs directly after rainfall. However, both surfaces allow for upward water transport from the upper underlying soil layers, sometimes resulting in relatively low evaporation rates on days without precipitation. The individual response of the surfaces differs considerably, which illustrates how

Dynamics of the Water Circulations in the Southern South China Sea and Its Seasonal Transports.

Science.gov (United States)

Daryabor, Farshid; Ooi, See Hai; Samah, Azizan Abu; Akbari, Abolghasem

2016-01-01

A three-dimensional Regional Ocean Modeling System is used to study the seasonal water circulations and transports of the Southern South China Sea. The simulated seasonal water circulations and estimated transports show consistency with observations, e.g., satellite altimeter data set and re-analysis data of the Simple Ocean Data Assimilation. It is found that the seasonal water circulations are mainly driven by the monsoonal wind stress and influenced by the water outflow/inflow and associated currents of the entire South China Sea. The intrusion of the strong current along the East Coast of Peninsular Malaysia and the eddies at different depths in all seasons are due to the conservation of the potential vorticity as the depth increases. Results show that the water circulation patterns in the northern part of the East Coast of Peninsular Malaysia are generally dominated by the geostrophic currents while those in the southern areas are due solely to the wind stress because of negligible Coriolis force there. This study clearly shows that individual surface freshwater flux (evaporation minus precipitation) controls the sea salinity balance in the Southern South China Sea thermohaline circulations. Analysis of climatological data from a high resolution Regional Ocean Modeling System reveals that the complex bathymetry is important not only for water exchange through the Southern South China Sea but also in regulating various transports across the main passages in the Southern South China Sea, namely the Sunda Shelf and the Strait of Malacca. Apart from the above, in comparision with the dynamics of the Sunda Shelf, the Strait of Malacca reflects an equally significant role in the annual transports into the Andaman Sea.

Concerted orientation induced unidirectional water transport through nanochannels.

Science.gov (United States)

Wan, Rongzheng; Lu, Hangjun; Li, Jinyuan; Bao, Jingdong; Hu, Jun; Fang, Haiping

2009-11-14

The dynamics of water inside nanochannels is of great importance for biological activities as well as for the design of molecular sensors, devices, and machines, particularly for sea water desalination. When confined in specially sized nanochannels, water molecules form a single-file structure with concerted dipole orientations, which collectively flip between the directions along and against the nanotube axis. In this paper, by using molecular dynamics simulations, we observed a net flux along the dipole-orientation without any application of an external electric field or external pressure difference during the time period of the particular concerted dipole orientations of the molecules along or against the nanotube axis. We found that this unique special-directional water transportation resulted from the asymmetric potential of water-water interaction along the nanochannel, which originated from the concerted dipole orientation of the water molecules that breaks the symmetry of water orientation distribution along the channel within a finite time period. This finding suggests a new mechanism for achieving high-flux water transportation, which may be useful for nanotechnology and biological applications.

Numerical modelling of solute transport at Forsmark with MIKE SHE. Site descriptive modelling SDM-Site Forsmark

Energy Technology Data Exchange (ETDEWEB)

Gustafsson, Lars-Goeran; Sassner, Mona (DHI Sverige AB, Stockholm (Sweden)); Bosson, Emma (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

2008-12-15

The Swedish Nuclear Fuel and Waste Management Company (SKB) is performing site investigations at two different locations in Sweden, referred to as the Forsmark and Laxemar areas, with the objective of siting a final repository for high-level radioactive waste. Data from the site investigations are used in a variety of modelling activities. This report presents model development and results of numerical transport modelling based on the numerical flow modelling of surface water and near-surface groundwater at the Forsmark site. The numerical modelling was performed using the modelling tool MIKE SHE and is based on the site data and conceptual model of the Forsmark areas. This report presents solute transport applications based on both particle tracking simulations and advection-dispersion calculations. The MIKE SHE model is the basis for the transport modelling presented in this report. Simulation cases relevant for the transport from a deep geological repository have been studied, but also the pattern of near surface recharge and discharge areas. When the main part of the modelling work presented in this report was carried out, the flow modelling of the Forsmark site was not finalised. Thus, the focus of this work is to describe the sensitivity to different transport parameters, and not to point out specific areas as discharge areas from a future repository (this is to be done later, within the framework of the safety assessment). In the last chapter, however, results based on simulations with the re-calibrated MIKE SHE flow model are presented. The results from the MIKE SHE water movement calculations were used by cycling the calculated transient flow field for a selected one-year period as many times as needed to achieve the desired simulation period. The solute source was located either in the bedrock or on top of the model. In total, 15 different transport simulation cases were studied. Five of the simulations were particle tracking simulations, whereas the rest

On the uses of a new linear scheme for stratospheric methane in global models: water source, transport tracer and radiative forcing

Directory of Open Access Journals (Sweden)

B. M. Monge-Sanz

2013-09-01

Full Text Available This study evaluates effects and applications of a new linear parameterisation for stratospheric methane and water vapour. The new scheme (CoMeCAT is derived from a 3-D full-chemistry-transport model (CTM. It is suitable for any global model, and is shown here to produce realistic profiles in the TOMCAT/SLIMCAT 3-D CTM and the ECMWF (European Centre for Medium-Range Weather Forecasts general circulation model (GCM. Results from the new scheme are in good agreement with the full-chemistry CTM CH4 field and with observations from the Halogen Occultation Experiment (HALOE. The scheme is also used to derive stratospheric water increments, which in the CTM produce vertical and latitudinal H2O variations in fair agreement with satellite observations. Stratospheric H2O distributions in the ECMWF GCM show realistic overall features, although concentrations are smaller than in the CTM run (up to 0.5 ppmv smaller above 10 hPa. The potential of the new CoMeCAT tracer for evaluating stratospheric transport is exploited to assess the impacts of nudging the free-running GCM to ERA-40 and ERA-Interim reanalyses. The nudged GCM shows similar transport patterns to the offline CTM forced by the corresponding reanalysis data. The new scheme also impacts radiation and temperature in the model. Compared to the default CH4 climatology and H2O used by the ECMWF radiation scheme, the main effect on ECMWF temperatures when considering both CH4 and H2O from CoMeCAT is a decrease of up to 1.0 K over the tropical mid/low stratosphere. The effect of using the CoMeCAT scheme for radiative forcing (RF calculations is investigated using the offline Edwards–Slingo radiative transfer model. Compared to the default model option of a tropospheric global 3-D CH4 value, the CoMeCAT distribution produces an overall change in the annual mean net RF of up to −30 mW m−2.

Spatial model of convective solute transport in brain extracellular space does not support a "glymphatic" mechanism.

Science.gov (United States)

Jin, Byung-Ju; Smith, Alex J; Verkman, Alan S

2016-12-01

A "glymphatic system," which involves convective fluid transport from para-arterial to paravenous cerebrospinal fluid through brain extracellular space (ECS), has been proposed to account for solute clearance in brain, and aquaporin-4 water channels in astrocyte endfeet may have a role in this process. Here, we investigate the major predictions of the glymphatic mechanism by modeling diffusive and convective transport in brain ECS and by solving the Navier-Stokes and convection-diffusion equations, using realistic ECS geometry for short-range transport between para-arterial and paravenous spaces. Major model parameters include para-arterial and paravenous pressures, ECS volume fraction, solute diffusion coefficient, and astrocyte foot-process water permeability. The model predicts solute accumulation and clearance from the ECS after a step change in solute concentration in para-arterial fluid. The principal and robust conclusions of the model are as follows: (a) significant convective transport requires a sustained pressure difference of several mmHg between the para-arterial and paravenous fluid and is not affected by pulsatile pressure fluctuations; (b) astrocyte endfoot water permeability does not substantially alter the rate of convective transport in ECS as the resistance to flow across endfeet is far greater than in the gaps surrounding them; and (c) diffusion (without convection) in the ECS is adequate to account for experimental transport studies in brain parenchyma. Therefore, our modeling results do not support a physiologically important role for local parenchymal convective flow in solute transport through brain ECS. © 2016 Jin et al.

Modelling reactive transport in a phosphogypsum dump, Venezia, Italia

Science.gov (United States)

Calcara, Massimo; Borgia, Andrea; Cattaneo, Laura; Bartolo, Sergio; Clemente, Gianni; Glauco Amoroso, Carlo; Lo Re, Fabio; Tozzato, Elena

2013-04-01

We develop a reactive-transport porous media flow model for a phosphogypsum dump located on the intertidal deposits of the Venetian Lagoon: 1. we construct a complex conceptual and geologic model from field data using the GMS™ graphical user interface; 2. the geological model is mapped onto a rectangular MODFLOW grid; 3. using the TMT2 FORTRAN90 code we translate this grid into the MESH, INCON and GENER input files for the TOUGH2 series of codes; 4. we run TOUGH-REACT to model flow and reactive transport in the dump and the sediments below it. The model includes 3 different dump materials (phosphogypsum, bituminous and hazardous wastes) with the pores saturated by specific fluids. The sediments below the dump are formed by an intertidal sequence of calcareous sands and silts, in addition to clays and organic deposits, all of which are initially saturated with lagoon salty waters. The recharge rain-water dilutes the dump fluids. In turn, the percolates from the dump react with the underlying sediments and the sea water that saturates them. Simulation results have been compared with chemical sampled analyses. In fact, in spite of the simplicity of our model we are able to show how the pH becomes neutral at a short distance below the dump, a fact observed during aquifer monitoring. The spatial and temporal evolution of dissolution and precipitation reactions occur in our model much alike reality. Mobility of some elements, such as divalent iron, are reduced by specific and concurrent conditions of pH from near-neutrality to moderately high values and positive redox potential; opposite conditions favour mobility of potentially toxic metals such as Cr, As Cd and Pb. Vertical movement are predominant. Trend should be therefore heavily influenced by pH and Eh values. If conditions are favourable to mobility, concentration of these substances in the bottom strata could be high. However, simulation suggest that the sediments tend to reduce the transport potential of

Water transport in graphene nano-channels

DEFF Research Database (Denmark)

Wagemann, Enrique; Oyarzua, Elton; Walther, J. H.

The transport of water in nanopores is of both fundamental and practical interest. Graphene Channels (GCs) are potential building blocks for nanofluidic devices dueto their molecularly smooth walls and exceptional mechanical properties. Numerous studies have found a significant flow rate enhancem......The transport of water in nanopores is of both fundamental and practical interest. Graphene Channels (GCs) are potential building blocks for nanofluidic devices dueto their molecularly smooth walls and exceptional mechanical properties. Numerous studies have found a significant flow rate...... between the chirality of the graphene walls and the slip length has not been established. In this study, we perform non-equilibrium molecular dynamics simulations of water flow in single- and multi-walled GCs. We examine the influence on the flow rates of dissipating the viscous heat produced...... by connecting the thermostat to the water molecules, the CNT wall atoms or both of them. From the atomic trajectories, we compute the fluid flow rates in GCs with zig-zag and armchair walls, heights from 1 to 4 nm and different number of graphene layers on the walls. A relation between the chirality, slip...

Water mass distributions and transports for the 2014 GEOVIDE cruise in the North Atlantic

Science.gov (United States)

García-Ibáñez, Maribel I.; Pérez, Fiz F.; Lherminier, Pascale; Zunino, Patricia; Mercier, Herlé; Tréguer, Paul

2018-04-01

We present the distribution of water masses along the GEOTRACES-GA01 section during the GEOVIDE cruise, which crossed the subpolar North Atlantic Ocean and the Labrador Sea in the summer of 2014. The water mass structure resulting from an extended optimum multiparameter (eOMP) analysis provides the framework for interpreting the observed distributions of trace elements and their isotopes. Central Waters and Subpolar Mode Waters (SPMW) dominated the upper part of the GEOTRACES-GA01 section. At intermediate depths, the dominant water mass was Labrador Sea Water, while the deep parts of the section were filled by Iceland-Scotland Overflow Water (ISOW) and North-East Atlantic Deep Water. We also evaluate the water mass volume transports across the 2014 OVIDE line (Portugal to Greenland section) by combining the water mass fractions resulting from the eOMP analysis with the absolute geostrophic velocity field estimated through a box inverse model. This allowed us to assess the relative contribution of each water mass to the transport across the section. Finally, we discuss the changes in the distribution and transport of water masses between the 2014 OVIDE line and the 2002-2010 mean state. At the upper and intermediate water levels, colder end-members of the water masses replaced the warmer ones in 2014 with respect to 2002-2010, in agreement with the long-term cooling of the North Atlantic Subpolar Gyre that started in the mid-2000s. Below 2000 dbar, ISOW increased its contribution in 2014 with respect to 2002-2010, with the increase being consistent with other estimates of ISOW transports along 58-59° N. We also observed an increase in SPMW in the East Greenland Irminger Current in 2014 with respect to 2002-2010, which supports the recent deep convection events in the Irminger Sea. From the assessment of the relative water mass contribution to the Atlantic Meridional Overturning Circulation (AMOC) across the OVIDE line, we conclude that the larger AMOC intensity in

Transport of hydrate slurry at high water cut

OpenAIRE

Melchuna , Aline; Cameirão , Ana; Herri , Jean-Michel; Ouabbas , Yamina; Glenat , Philippe

2014-01-01

Poster; International audience; Oil transportation in pipelines at the end of field production life implies to flow high quantities of water which represents the dominant phase. The process of crystallization of gas hydrates in this system needs to be studied and compared to the opposite one widely studied in the literature where water is the dispersed phase. The laboratory is equipped with the Archimede flow loop where the hydrate crystallization and transport are monitored. The flow loop is...

Transport and transformation of surface water masses across the ...

African Journals Online (AJOL)

Transport and transformation of surface water masses across the Mascarene Plateau during the Northeast Monsoon season. ... Mixing occurs in the central gap between intermediate water masses (Red Sea Water [RSW] and Antarctic Intermediate Water [AAIW]) as well as in the upper waters (Subtropical Surface Water ...

Ground-water monitoring and modeling at the Hanford Site

International Nuclear Information System (INIS)

Mitchell, P.J.; Freshley, M.D.

1987-01-01

The ground-water monitoring program at the Hanford Site in southeastern Washington State is continually evolving in response to changing operations at the site, changes in the ground-water flow system, movement of the constituents in the aquifers, and regulatory requirements. Sampling and analysis of ground water, along with ground-water flow and solute transport modeling are used to evaluate the movement and resulting distributions of radionuclides and hazardous chemical constituents in the unconfined aquifer. Evaluation of monitoring results, modeling, and information on waste management practices are being combined to continually improve the network of ground-water monitoring wells at the site

Ground-water monitoring and modeling at the Hanford Site

International Nuclear Information System (INIS)

Mitchell, P.J.; Freshley, M.D.

1987-01-01

The ground-water monitoring program at the Hanford Site in southeastern Washington State is continually evolving in response to changing operations at the site, changes in the ground-water flow system, movement of the constituents in the aquifers, and regulatory requirements. Sampling and analysis of ground water, along with ground-water flow and solute transport modeling are used ito evaluate the movement and resulting distributions of radionuclides and hazardous chemical constituents in the unconfined aquifer. Evaluation of monitoring results, modeling, and information on waste management practices are being combined to continually improve the network of ground-water monitoring wells at the site

Core 2D. A code for non-isothermal water flow and reactive solute transport. Users manual version 2

Energy Technology Data Exchange (ETDEWEB)

Samper, J.; Juncosa, R.; Delgado, J.; Montenegro, L. [Universidad de A Coruna (Spain)

2000-07-01

Understanding natural groundwater quality patterns, quantifying groundwater pollution and assessing the effects of waste disposal, require modeling tools accounting for water flow, and transport of heat and dissolved species as well as their complex interactions with solid and gases phases. This report contains the users manual of CORE ''2D Version V.2.0, a COde for modeling water flow (saturated and unsaturated), heat transport and multicomponent Reactive solute transport under both local chemical equilibrium and kinetic conditions. it is an updated and improved version of CORE-LE-2D V0 (Samper et al., 1988) which in turns is an extended version of TRANQUI, a previous reactive transport code (ENRESA, 1995). All these codes were developed within the context of Research Projects funded by ENRESA and the European Commission. (Author)

Core2D. A code for non-isothermal water flow and reactive solute transport. Users manual version 2

International Nuclear Information System (INIS)

Samper, J.; Juncosa, R.; Delgado, J.; Montenegro, L.

2000-01-01

Understanding natural groundwater quality patterns, quantifying groundwater pollution and assessing the effects of waste disposal, require modeling tools accounting for water flow, and transport of heat and dissolved species as well as their complex interactions with solid and gases phases. This report contains the users manual of CORE ''2D Version V.2.0, a COde for modeling water flow (saturated and unsaturated), heat transport and multicomponent Reactive solute transport under both local chemical equilibrium and kinetic conditions. it is an updated and improved version of CORE-LE-2D V0 (Samper et al., 1988) which in turns is an extended version of TRANQUI, a previous reactive transport code (ENRESA, 1995). All these codes were developed within the context of Research Projects funded by ENRESA and the European Commission. (Author)

Core 2D. A code for non-isothermal water flow and reactive solute transport. Users manual version 2

Energy Technology Data Exchange (ETDEWEB)

Samper, J; Juncosa, R; Delgado, J; Montenegro, L [Universidad de A Coruna (Spain)

2000-07-01

Understanding natural groundwater quality patterns, quantifying groundwater pollution and assessing the effects of waste disposal, require modeling tools accounting for water flow, and transport of heat and dissolved species as well as their complex interactions with solid and gases phases. This report contains the users manual of CORE ''2D Version V.2.0, a COde for modeling water flow (saturated and unsaturated), heat transport and multicomponent Reactive solute transport under both local chemical equilibrium and kinetic conditions. it is an updated and improved version of CORE-LE-2D V0 (Samper et al., 1988) which in turns is an extended version of TRANQUI, a previous reactive transport code (ENRESA, 1995). All these codes were developed within the context of Research Projects funded by ENRESA and the European Commission. (Author)

Prolonged river water pollution due to variable-density flow and solute transport in the riverbed

Science.gov (United States)

Jin, Guangqiu; Tang, Hongwu; Li, Ling; Barry, D. A.

2015-04-01

A laboratory experiment and numerical modeling were used to examine effects of density gradients on hyporheic flow and solute transport under the condition of a solute pulse input to a river with regular bed forms. Relatively low-density gradients due to an initial salt pulse concentration of 1.55 kg m-3 applied in the experiment were found to modulate significantly the pore-water flow and solute transport in the riverbed. Such density gradients increased downward flow and solute transport in the riverbed by factors up to 1.6. This resulted in a 12.2% increase in the total salt transfer from the water column to the riverbed over the salt pulse period. As the solute pulse passed, the effect of the density gradients reversed, slowing down the release of the solute back to the river water by a factor of 3.7. Numerical modeling indicated that these density effects intensified as salt concentrations in the water column increased. Simulations further showed that the density gradients might even lead to unstable flow and result in solute fingers in the bed of large bed forms. The slow release of solute from the bed back to the river led to a long tail of solute concentration in the river water. These findings have implications for assessment of impact of pollution events on river systems, in particular, long-term effects on both the river water and riverbed due to the hyporheic exchange.

Simulation of water transport through a lipid membrane

Energy Technology Data Exchange (ETDEWEB)

Marrink, S.J.; Berendsen, H.J.C. (Univ. of Groningen (Netherlands))

1994-04-14

To obtain insight in the process of water permeation through a lipid membrane we performed molecular dynamics simulations on a phospholipid (DPPC)/water system with atomic detail. Since the actual process of permeation is too slow to be studied directly, we deduced the permeation rate indirectly via computation of the free energy and diffusion rate profiles of a water molecule across the bilayer. We concluded that the permeation of water through a lipid membrane cannot be described adequately by a simple homogeneous solubility-diffusion model. Both the excess free energy and the diffusion rate strongly depend on the position in the membrane, as a result from the inhomogeneous nature of the membrane. The calculated excess free energy profile has a shallow slope and a maximum height of 26 kJ/mol. The diffusion rate is highest in the middle of the membrane where the lipid density is low. In the interfacial region almost all water molecules are bound by the lipid headgroups, and the diffusion turns out to be 1 order of magnitude smaller. The total transport process is essentially determined by the free energy barrier. 78 refs., 12 figs.

Bacteria transport simulation using APEX model in the Toenepi watershed, New Zealand

Science.gov (United States)

The Agricultural Policy/Environmental eXtender (APEX) model is a distributed, continuous, daily-time step small watershed-scale hydrologic and water quality model. In this study, the newly developed fecal-derived bacteria fate and transport subroutine was applied and evalated using APEX model. The e...

Transport of water through the tropical tropopause

Science.gov (United States)

Kley, D.; Schmeltekopf, A. L.; Kelly, K.; Winkler, R. H.; Thompson, T. L.; Mcfarland, M.

1982-01-01

Total water was measured in the high troposphere and low stratosphere over Panama during ten aircraft flights. The results show that convective storms provide the means of transporting water into the stratosphere. From a consideration of the anvil heights over different areas of the tropical zone, it follows that a negative gradient of water vapor mixing ratio with altitude must exist over most of the lower stratosphere.

Studies and research concerning BNFP: transportation of radioactive material by water

International Nuclear Information System (INIS)

Anderson, R.T.

1980-11-01

Currently there are many limitations imposed on the shipment of radioactive material from nuclear power plants. In this regard, many questions have arisen related to the feasibility of substituting water transportation of these materials as a backup or supplement to the highway and rail modes which are now in use. This study addresses the results of studies performed by Allied-General Nuclear Services concerning the water transportation of spent nuclear fuel and radwaste materials. The report presents both an overview of the possible applications, problems, and means of solution, and specific information related to one particular site. In particular, a detailed case study of a nuclear plant site located on a navigable waterway (Chesapeake Bay) was made. The study concludes that there are some real advantages in using water transport, which are particularly evident if a site is not served by rail or its primary transport route lies near populous areas. Whereas, water transport has been used extensively in Europe and Japan, it has been virtually bypassed in the United States. A recommendation is made to continue examination of water transport, including the development of necessary standards for possible future operations

Arctic water tracks retain phosphorus and transport ammonium

Science.gov (United States)

Harms, T.; Cook, C. L.; Wlostowski, A. N.; Godsey, S.; Gooseff, M. N.

2017-12-01

Hydrologic flowpaths propagate biogeochemical signals among adjacent ecosystems, but reactions may attenuate signals by retaining, removing, or transforming dissolved and suspended materials. The theory of nutrient spiraling describes these simultaneous reaction and transport processes, but its application has been limited to stream channels. We applied nutrient spiraling theory to water tracks, zero-order channels draining Arctic hillslopes that contain perennially saturated soils and flow at the surface either perennially or in response to precipitation. In the Arctic, experimental warming results in increased availability of nitrogen, the limiting nutrient for hillslope vegetation at the study site, which may be delivered to aquatic ecosystems by water tracks. Increased intensity of rain events, deeper snowpack, earlier snowmelt, and increasing thaw depth resulting from climate change might support increased transport of nutrients, but the reactive capacity of hillslope flowpaths, including sorption and uptake by plants and microbes, could counter transport to regulate solute flux. Characteristics of flowpaths might influence the opportunity for reaction, where slower flowpaths increase the contact time between solutes and soils or roots. We measured nitrogen and phosphorus uptake and transient storage of water tracks through the growing season and found that water tracks retain inorganic phosphorus, but transport ammonium. Nutrient uptake was unrelated to transient storage, suggesting high capacity for nutrient retention by shallow organic soils and vegetation. These observations indicate that increased availability of ammonium, the biogeochemical signal of warming tundra, is propagated by hillslope flowpaths, whereas water tracks attenuate delivery of phosphorus to aquatic ecosystems, where its availability typically limits production.

Modeling field scale unsaturated flow and transport processes

International Nuclear Information System (INIS)

Gelhar, L.W.; Celia, M.A.; McLaughlin, D.

1994-08-01

The scales of concern in subsurface transport of contaminants from low-level radioactive waste disposal facilities are in the range of 1 to 1,000 m. Natural geologic materials generally show very substantial spatial variability in hydraulic properties over this range of scales. Such heterogeneity can significantly influence the migration of contaminants. It is also envisioned that complex earth structures will be constructed to isolate the waste and minimize infiltration of water into the facility. The flow of water and gases through such facilities must also be a concern. A stochastic theory describing unsaturated flow and contamination transport in naturally heterogeneous soils has been enhanced by adopting a more realistic characterization of soil variability. The enhanced theory is used to predict field-scale effective properties and variances of tension and moisture content. Applications illustrate the important effects of small-scale heterogeneity on large-scale anisotropy and hysteresis and demonstrate the feasibility of simulating two-dimensional flow systems at time and space scales of interest in radioactive waste disposal investigations. Numerical algorithms for predicting field scale unsaturated flow and contaminant transport have been improved by requiring them to respect fundamental physical principles such as mass conservation. These algorithms are able to provide realistic simulations of systems with very dry initial conditions and high degrees of heterogeneity. Numerical simulation of the movement of water and air in unsaturated soils has demonstrated the importance of air pathways for contaminant transport. The stochastic flow and transport theory has been used to develop a systematic approach to performance assessment and site characterization. Hypothesis-testing techniques have been used to determine whether model predictions are consistent with observed data

ATMOS Stratospheric Deuterated Water and Implications for Tropospheric-Stratospheric Transport

Science.gov (United States)

Moyer, Elisabeth J.; Irion, Fredrick W.; Yung, Yuk L.; Gunson, Michael R.

1996-01-01

Measurements of the isotopic composition of stratospheric water by the ATMOS instrument are used to infer the convective history of stratospheric air. The average water vapor entering the stratosphere is found to be highly depleted of deuterium, with delta-D(sub w) of -670 +/- 80 (67% deuterium loss). Model calculations predict, however, that under conditions of thermodynamic equilibrium, dehydration to stratospheric mixing ratios should produce stronger depletion to delta-D(sub w) of -800 to 900 (80-90% deuterium loss). Deuterium enrichment of water vapor in ascending parcels can occur only in conditions of rapid convection; enrichments persisting into the stratosphere require that those conditions continue to near-tropopause altitudes. We conclude that either the predominant source of water vapor to the uppermost troposphere is enriched convective water, most likely evaporated cloud ice, or troposphere-stratosphere transport occurs closely associated with tropical deep convection.

Chancellor Water Colloids: Characterization and Radionuclide Associated Transport

Energy Technology Data Exchange (ETDEWEB)

Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Boukhalfa, Hakim [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-09-26

Column transport experiments were conducted in which water from the Chancellor nuclear test cavity was transported through crushed volcanic tuff from Pahute Mesa. In one experiment, the cavity water was spiked with solute ¹³⁷Cs, and in another it was spiked with ^239/240Pu(IV) nanocolloids. A third column experiment was conducted with no radionuclide spike at all, although the ¹³⁷Cs concentrations in the water were still high enough to quantify in the column effluent. The radionuclides strongly partitioned to natural colloids present in the water, which were characterized for size distribution, mass concentration, zeta potential/surface charge, critical coagulation concentration, and qualitative mineralogy. In the spiked water experiments, the unanalyzed portion of the high-concentration column effluent samples were combined and re-injected into the respective columns as a second pulse. This procedure was repeated again for a third injection. Measurable filtration of the colloids was observed after each initial injection of the Chancellor water into the columns, but the subsequent injections (spiked water experiments only) exhibited no apparent filtration, suggesting that the colloids that remained mobile after relatively short transport distances were more resistant to filtration than the initial population of colloids. It was also observed that while significant desorption of ¹³⁷Cs from the colloids occurred after the first injection in both the spiked and unspiked waters, subsequent injections of the spiked water exhibited much less ¹³⁷Cs desorption (much greater ¹³⁷Cs colloid-associated transport). This result suggests that the ¹³⁷Cs that remained associated with colloids during the first injection represented a fraction that was more strongly adsorbed to the mobile colloids than the initial ¹³⁷Cs associated with the colloids. A greater amount of the ^239/240

MaSTiS, microorganism and solute transport in streams, model documentation and user manual

Science.gov (United States)

In-stream fate and transport of solutes and microorganisms need to be understood to evaluate suitability of waters for agricultural, recreational, and household uses and eventually minimize surface water contamination. Concerns over safety of this water resulted in development of predictive models f...

Solute transport in coupled inland-coastal water systems. General conceptualisation and application to Forsmark

International Nuclear Information System (INIS)

Jarsjoe, Jerker; Destouni, Georgia; Persson, Klas; Prieto, Carmen

2007-12-01

We formulate a general theoretical conceptualisation of solute transport from inland sources to downstream recipients, considering main recipient load contributions from all different nutrient and pollutant sources that may exist within any catchment. Since the conceptualisation is model independent, its main hydrological factors and mass delivery factors can be quantified on the basis of inputs to and outputs from any considered analytical or numerical model. Some of the conceptually considered source contribution and transport pathway combinations are however commonly neglected in catchment-scale solute transport and attenuation modelling, in particular those related to subsurface sources, diffuse sources at the land surface and direct groundwater transport into the recipient. The conceptual framework provides a possible tool for clarification of underlying and often implicit model assumptions, which can be useful for e.g. inter-model comparisons. In order to further clarify and explain research questions that may be of particular importance for transport pathways from deep groundwater surrounding a repository, we concretise and interpret some selected transport scenarios for model conditions in the Forsmark area. Possible uncertainties in coastal discharge predictions, related to uncertain spatial variation of evapotranspiration within the catchment, were shown to be small for the relatively large, focused surface water discharges from land to sea, because local differences were averaged out along the length of the main water flow paths. In contrast, local flux values within the diffuse groundwater flow field from land to sea are more uncertain, although estimates of mean values and total sums of submarine groundwater discharge (SGD) along some considerable coastline length may be robust. The present results show that 80% to 90% of the total coastal discharge of Forsmark occurred through focused flows in visible streams, whereas the remaining 10% to 20% was

The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water

Science.gov (United States)

Kahre, Melinda A.; Haberle, Robert M.; Hollingsworth, Jeffery L.; Brecht, Amanda S.; Urata, Richard A.

2015-11-01

The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water.

Science.gov (United States)

Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; Brecht, A. S.; Urata, R.

2015-01-01

The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

Inverse modeling of multicomponent reactive transport through single and dual porosity media

Science.gov (United States)

Samper, Javier; Zheng, Liange; Fernández, Ana María; Montenegro, Luis

2008-06-01

Compacted bentonite is foreseen as buffer material for high-level radioactive waste in deep geological repositories because it provides hydraulic isolation, chemical stability, and radionuclide sorption. A wide range of laboratory tests were performed within the framework of FEBEX ( Full-scale Engineered Barrier EXperiment) project to characterize buffer properties and develop numerical models for FEBEX bentonite. Here we present inverse single and dual-continuum multicomponent reactive transport models of a long-term permeation test performed on a 2.5 cm long sample of FEBEX bentonite. Initial saline bentonite porewater was flushed with 5.5 pore volumes of fresh granitic water. Water flux and chemical composition of effluent waters were monitored during almost 4 years. The model accounts for solute advection and diffusion and geochemical reactions such as aqueous complexation, acid-base, cation exchange, protonation/deprotonation by surface complexation and dissolution/precipitation of calcite, chalcedony and gypsum. All of these processes are assumed at local equilibrium. Similar to previous studies of bentonite porewater chemistry on batch systems which attest the relevance of protonation/deprotonation on buffering pH, our results confirm that protonation/deprotonation is a key process in maintaining a stable pH under dynamic transport conditions. Breakthrough curves of reactive species are more sensitive to initial porewater concentration than to effective diffusion coefficient. Optimum estimates of initial porewater chemistry of saturated compacted FEBEX bentonite are obtained by solving the inverse problem of multicomponent reactive transport. While the single-continuum model reproduces the trends of measured data for most chemical species, it fails to match properly the long tails of most breakthrough curves. Such limitation is overcome by resorting to a dual-continuum reactive transport model.

Web-based reactive transport modeling using PFLOTRAN

Science.gov (United States)

Zhou, H.; Karra, S.; Lichtner, P. C.; Versteeg, R.; Zhang, Y.

2017-12-01

Actionable understanding of system behavior in the subsurface is required for a wide spectrum of societal and engineering needs by both commercial firms and government entities and academia. These needs include, for example, water resource management, precision agriculture, contaminant remediation, unconventional energy production, CO2 sequestration monitoring, and climate studies. Such understanding requires the ability to numerically model various coupled processes that occur across different temporal and spatial scales as well as multiple physical domains (reservoirs - overburden, surface-subsurface, groundwater-surface water, saturated-unsaturated zone). Currently, this ability is typically met through an in-house approach where computational resources, model expertise, and data for model parameterization are brought together to meet modeling needs. However, such an approach has multiple drawbacks which limit the application of high-end reactive transport codes such as the Department of Energy funded[?] PFLOTRAN code. In addition, while many end users have a need for the capabilities provided by high-end reactive transport codes, they do not have the expertise - nor the time required to obtain the expertise - to effectively use these codes. We have developed and are actively enhancing a cloud-based software platform through which diverse users are able to easily configure, execute, visualize, share, and interpret PFLOTRAN models. This platform consists of a web application and available on-demand HPC computational infrastructure. The web application consists of (1) a browser-based graphical user interface which allows users to configure models and visualize results interactively, and (2) a central server with back-end relational databases which hold configuration, data, modeling results, and Python scripts for model configuration, and (3) a HPC environment for on-demand model execution. We will discuss lessons learned in the development of this platform, the