Kulasiri, Don
2002-01-01
Most of the natural and biological phenomena such as solute transport in porous media exhibit variability which can not be modeled by using deterministic approaches. There is evidence in natural phenomena to suggest that some of the observations can not be explained by using the models which give deterministic solutions. Stochastic processes have a rich repository of objects which can be used to express the randomness inherent in the system and the evolution of the system over time. The attractiveness of the stochastic differential equations (SDE) and stochastic partial differential equations (SPDE) come from the fact that we can integrate the variability of the system along with the scientific knowledge pertaining to the system. One of the aims of this book is to explaim some useufl concepts in stochastic dynamics so that the scientists and engineers with a background in undergraduate differential calculus could appreciate the applicability and appropriateness of these developments in mathematics. The ideas ...
A quasilinear model for solute transport under unsaturated flow
Houseworth, J.E.; Leem, J.
2009-01-01
We developed an analytical solution for solute transport under steady-state, two-dimensional, unsaturated flow and transport conditions for the investigation of high-level radioactive waste disposal. The two-dimensional, unsaturated flow problem is treated using the quasilinear flow method for a system with homogeneous material properties. Dispersion is modeled as isotropic and is proportional to the effective hydraulic conductivity. This leads to a quasilinear form for the transport problem in terms of a scalar potential that is analogous to the Kirchhoff potential for quasilinear flow. The solutions for both flow and transport scalar potentials take the form of Fourier series. The particular solution given here is for two sources of flow, with one source containing a dissolved solute. The solution method may easily be extended, however, for any combination of flow and solute sources under steady-state conditions. The analytical results for multidimensional solute transport problems, which previously could only be solved numerically, also offer an additional way to benchmark numerical solutions. An analytical solution for two-dimensional, steady-state solute transport under unsaturated flow conditions is presented. A specific case with two sources is solved but may be generalized to any combination of sources. The analytical results complement numerical solutions, which were previously required to solve this class of problems.
Modelling multicomponent solute transport in structured soils
Beinum, van G.W.
2007-01-01
The mobility of contaminants in soil is an important factor in determining their ability to spread into the wider environment. For non-volatile substances, transport within the soil is generally dominated by transport of dissolved fractions in the soil water phase, via either diffusion or
Mathematical modeling of solute transport in the subsurface
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
GRRR. The EXPECT groundwater model for transport of solutes
Meijers R; Sauter FJ; Veling EJM; van Grinsven JJM; Leijnse A; Uffink GJM; MTV; CWM; LBG
1994-01-01
In this report the design and first test results are presented of the EXPECT groundwater module for transport of solutes GRRR (GRoundwater source Receptor Relationships). This model is one of the abiotic compartment modules of the EXPECT model. The EXPECT model is a tool for scenario development
Coupling between solute transport and chemical reactions models
Samper, J.; Ajora, C.
1993-01-01
During subsurface transport, reactive solutes are subject to a variety of hydrodynamic and chemical processes. The major hydrodynamic processes include advection and convection, dispersion and diffusion. The key chemical processes are complexation including hydrolysis and acid-base reactions, dissolution-precipitation, reduction-oxidation, adsorption and ion exchange. The combined effects of all these processes on solute transport must satisfy the principle of conservation of mass. The statement of conservation of mass for N mobile species leads to N partial differential equations. Traditional solute transport models often incorporate the effects of hydrodynamic processes rigorously but oversimplify chemical interactions among aqueous species. Sophisticated chemical equilibrium models, on the other hand, incorporate a variety of chemical processes but generally assume no-flow systems. In the past decade, coupled models accounting for complex hydrological and chemical processes, with varying degrees of sophistication, have been developed. The existing models of reactive transport employ two basic sets of equations. The transport of solutes is described by a set of partial differential equations, and the chemical processes, under the assumption of equilibrium, are described by a set of nonlinear algebraic equations. An important consideration in any approach is the choice of primary dependent variables. Most existing models cannot account for the complete set of chemical processes, cannot be easily extended to include mixed chemical equilibria and kinetics, and cannot handle practical two and three dimensional problems. The difficulties arise mainly from improper selection of the primary variables in the transport equations. (Author) 38 refs
The secret to successful solute-transport modeling
Konikow, Leonard F.
2011-01-01
Modeling subsurface solute transport is difﬁcult—more so than modeling heads and ﬂows. The classical governing equation does not always adequately represent what we see at the ﬁeld scale. In such cases, commonly used numerical models are solving the wrong equation. Also, the transport equation is hyperbolic where advection is dominant, and parabolic where hydrodynamic dispersion is dominant. No single numerical method works well for all conditions, and for any given complex ﬁeld problem, where seepage velocity is highly variable, no one method will be optimal everywhere. Although we normally expect a numerically accurate solution to the governing groundwater-ﬂow equation, errors in concentrations from numerical dispersion and/or oscillations may be large in some cases. The accuracy and efﬁciency of the numerical solution to the solute-transport equation are more sensitive to the numerical method chosen than for typical groundwater-ﬂow problems. However, numerical errors can be kept within acceptable limits if sufﬁcient computational effort is expended. But impractically long
Solute transport model for radioisotopes in layered soil
Essel, P.
2010-01-01
The study considered the transport of a radioactive solute in solution from the surface of the earth down through the soil to the ground water when there is an accidental or intentional spillage of a radioactive material on the surface. The finite difference method was used to model the spatial and temporal profile of moisture content in a soil column using the θ-based Richard's equation leading to solution of the convective-dispersive equation for non-adsorbing solutes numerically. A matlab code has been generated to predict the transport of the radioactive contaminant, spilled on the surface of a vertically heterogeneous soil made up of two layers to determine the residence time of the solute in the unsaturated zone, the time it takes the contaminant to reach the groundwater and the amount of the solute entering the groundwater in various times and the levels of pollution in those times. The model predicted that, then there is a spillage of 7.2g of tritium, on the surface of the ground at the study area, it will take two years for the radionuclide to enter the groundwater and fifteen years to totally leave the unsaturated zone. There is therefore the need to try as much as possible to avoid intentional or accidental spillage of the radionuclide since it has long term effect. (au)
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...
Composite Transport Model and Water and Solute Transport across Plant Roots: An Update
Yangmin X. Kim
2018-02-01
Full Text Available The present review examines recent experimental findings in root transport phenomena in terms of the composite transport model (CTM. It has been a well-accepted conceptual model to explain the complex water and solute flows across the root that has been related to the composite anatomical structure. There are three parallel pathways involved in the transport of water and solutes in roots – apoplast, symplast, and transcellular paths. The role of aquaporins (AQPs, which facilitate water flows through the transcellular path, and root apoplast is examined in terms of the CTM. The contribution of the plasma membrane bound AQPs for the overall water transport in the whole plant level was varying depending on the plant species, age of roots with varying developmental stages of apoplastic barriers, and driving forces (hydrostatic vs. osmotic. Many studies have demonstrated that the apoplastic barriers, such as Casparian bands in the primary anticlinal walls and suberin lamellae in the secondary cell walls, in the endo- and exodermis are not perfect barriers and unable to completely block the transport of water and some solute transport into the stele. Recent research on water and solute transport of roots with and without exodermis triggered the importance of the extension of conventional CTM adding resistances that arrange in series (epidermis, exodermis, mid-cortex, endodermis, and pericycle. The extension of the model may answer current questions about the applicability of CTM for composite water and solute transport of roots that contain complex anatomical structures with heterogeneous cell layers.
Composite Transport Model and Water and Solute Transport across Plant Roots: An Update.
Kim, Yangmin X; Ranathunge, Kosala; Lee, Seulbi; Lee, Yejin; Lee, Deogbae; Sung, Jwakyung
2018-01-01
The present review examines recent experimental findings in root transport phenomena in terms of the composite transport model (CTM). It has been a well-accepted conceptual model to explain the complex water and solute flows across the root that has been related to the composite anatomical structure. There are three parallel pathways involved in the transport of water and solutes in roots - apoplast, symplast, and transcellular paths. The role of aquaporins (AQPs), which facilitate water flows through the transcellular path, and root apoplast is examined in terms of the CTM. The contribution of the plasma membrane bound AQPs for the overall water transport in the whole plant level was varying depending on the plant species, age of roots with varying developmental stages of apoplastic barriers, and driving forces (hydrostatic vs. osmotic). Many studies have demonstrated that the apoplastic barriers, such as Casparian bands in the primary anticlinal walls and suberin lamellae in the secondary cell walls, in the endo- and exodermis are not perfect barriers and unable to completely block the transport of water and some solute transport into the stele. Recent research on water and solute transport of roots with and without exodermis triggered the importance of the extension of conventional CTM adding resistances that arrange in series (epidermis, exodermis, mid-cortex, endodermis, and pericycle). The extension of the model may answer current questions about the applicability of CTM for composite water and solute transport of roots that contain complex anatomical structures with heterogeneous cell layers.
Mathematical modeling of fluid and solute transport in peritoneal dialysis
Waniewski, Jacek
2001-01-01
Optimization of peritoneal dialysis schedule and dialysis fluid composition needs, among others, methods for quantitative assessment of fluid and solute transport. Furthermore, an integrative quantitative description of physiological processes within the tissue, which contribute to the net transfer of fluid and solutes, is necessary for interpretation of the data and for predictions of the outcome of possible intervention into the peritoneal transport system. The current pro...
Assessment of applications of transport models on regional scale solute transport
Guo, Z.; Fogg, G. E.; Henri, C.; Pauloo, R.
2017-12-01
Regional scale transport models are needed to support the long-term evaluation of groundwater quality and to develop management strategies aiming to prevent serious groundwater degradation. The purpose of this study is to evaluate the capacity of previously-developed upscaling approaches to accurately describe main solute transport processes including the capture of late-time tails under changing boundary conditions. Advective-dispersive contaminant transport in a 3D heterogeneous domain was simulated and used as a reference solution. Equivalent transport under homogeneous flow conditions were then evaluated applying the Multi-Rate Mass Transfer (MRMT) model. The random walk particle tracking method was used for both heterogeneous and homogeneous-MRMT scenarios under steady state and transient conditions. The results indicate that the MRMT model can capture the tails satisfactorily for plume transported with ambient steady-state flow field. However, when boundary conditions change, the mass transfer model calibrated for transport under steady-state conditions cannot accurately reproduce the tailing effect observed for the heterogeneous scenario. The deteriorating impact of transient boundary conditions on the upscaled model is more significant for regions where flow fields are dramatically affected, highlighting the poor applicability of the MRMT approach for complex field settings. Accurately simulating mass in both mobile and immobile zones is critical to represent the transport process under transient flow conditions and will be the future focus of our study.
Demonstrations in Solute Transport Using Dyes: Part II. Modeling.
Butters, Greg; Bandaranayake, Wije
1993-01-01
A solution of the convection-dispersion equation is used to describe the solute breakthrough curves generated in the demonstrations in the companion paper. Estimation of the best fit model parameters (solute velocity, dispersion, and retardation) is illustrated using the method of moments for an example data set. (Author/MDH)
Solute transport modelling with the variable temporally dependent ...
Pintu Das
2018-02-07
Feb 7, 2018 ... in a finite domain with time-dependent sources and dis- tance-dependent dispersivities. Also, existing ... solute transport in multi-layered porous media using gen- eralized integral transform technique with .... methods for solving the fractional reaction-–sub-diffusion equation. To solve numerically the Eqs.
Ground-water solute transport modeling using a three-dimensional scaled model
Crider, S.S.
1987-01-01
Scaled models are used extensively in current hydraulic research on sediment transport and solute dispersion in free surface flows (rivers, estuaries), but are neglected in current ground-water model research. Thus, an investigation was conducted to test the efficacy of a three-dimensional scaled model of solute transport in ground water. No previous results from such a model have been reported. Experiments performed on uniform scaled models indicated that some historical problems (e.g., construction and scaling difficulties; disproportionate capillary rise in model) were partly overcome by using simple model materials (sand, cement and water), by restricting model application to selective classes of problems, and by physically controlling the effect of the model capillary zone. Results from these tests were compared with mathematical models. Model scaling laws were derived for ground-water solute transport and used to build a three-dimensional scaled model of a ground-water tritium plume in a prototype aquifer on the Savannah River Plant near Aiken, South Carolina. Model results compared favorably with field data and with a numerical model. Scaled models are recommended as a useful additional tool for prediction of ground-water solute transport
Applications of stochastic models to solute transport in fractured rocks
Gelhar, L.W.
1987-01-01
A stochastic theory for flow and solute transport in a single variable aperture fracture bounded by sorbing porous matrix into which solutes may diffuse, is developed using a perturbation approximation and spectral solution techniques which assume local statistical homogeneity. The theory predicts that the effective aperture of the fracture for mean solute displacement will be larger than the aperture required to calculate the large-scale flow resistance of the fracture. This ratio of apertures is a function of the variance of the logarithm of the apertures. The theory also predicts the macrodispersion coefficient for large-scale transport in the fracture. The resulting macrodispersivity is proportional to the variance of the logaperture and to its correlation scale. When variable surface sorption is included, it is found that the macrodispersivity is increased significantly, in some cases more than an order of magnitude. It is also shown that the effective retardation coefficient for the sorptively heterogeneous fracture is found by simply taking the arithmetic mean of the local surface sorption coefficient. Matrix diffusion is also shown to increase the fracture macrodispesivity at very large times. A reexamination of the results of four different field tracer tests in crystalline rock in Sweden and Canada shows aperture ratios and dispersivities that are consistent with the stochastic theory. The variance of the natural logarithm of the aperture is found to be in the range of 3 to 6 and the correlation scales for logaperture ranges from .2 to 1.2 meters. Detailed recommendations for additional field investigations at scales ranging from a few meters up to a kilometer are presented. (orig.)
New methods For Modeling Transport Of Water And Solutes In Soils
Møldrup, Per
Recent models for water and solute transport in unsaturated soils have been mechanistically based but numerically very involved. This dissertation concerns the development of mechanistically-based but numerically simple models for calculating and analyzing transport of water and solutes in soil...
Joshi, Nitin; Ojha, C. S. P.; Sharma, P. K.
2012-10-01
In this study a conceptual model that accounts for the effects of nonequilibrium contaminant transport in a fractured porous media is developed. Present model accounts for both physical and sorption nonequilibrium. Analytical solution was developed using the Laplace transform technique, which was then numerically inverted to obtain solute concentration in the fracture matrix system. The semianalytical solution developed here can incorporate both semi-infinite and finite fracture matrix extent. In addition, the model can account for flexible boundary conditions and nonzero initial condition in the fracture matrix system. The present semianalytical solution was validated against the existing analytical solutions for the fracture matrix system. In order to differentiate between various sorption/transport mechanism different cases of sorption and mass transfer were analyzed by comparing the breakthrough curves and temporal moments. It was found that significant differences in the signature of sorption and mass transfer exists. Applicability of the developed model was evaluated by simulating the published experimental data of Calcium and Strontium transport in a single fracture. The present model simulated the experimental data reasonably well in comparison to the model based on equilibrium sorption assumption in fracture matrix system, and multi rate mass transfer model.
Warsta, L.; Karvonen, T.
2017-12-01
There are currently 25 shooting and training areas in Finland managed by The Finnish Defence Forces (FDF), where military activities can cause contamination of open waters and groundwater reservoirs. In the YMPYRÄ project, a computer software framework is being developed that combines existing open environmental data and proprietary information collected by FDF with computational models to investigate current and prevent future environmental problems. A data centric philosophy is followed in the development of the system, i.e. the models are updated and extended to handle available data from different areas. The results generated by the models are summarized as easily understandable flow and risk maps that can be opened in GIS programs and used in environmental assessments by experts. Substances investigated with the system include explosives and metals such as lead, and both surface and groundwater dominated areas can be simulated. The YMPYRÄ framework is composed of a three dimensional soil and groundwater flow model, several solute transport models and an uncertainty assessment system. Solute transport models in the framework include particle based, stream tube and finite volume based approaches. The models can be used to simulate solute dissolution from source area, transport in the unsaturated layers to groundwater and finally migration in groundwater to water extraction wells and springs. The models can be used to simulate advection, dispersion, equilibrium adsorption on soil particles, solubility and dissolution from solute phase and dendritic solute decay chains. Correct numerical solutions were confirmed by comparing results to analytical 1D and 2D solutions and by comparing the numerical solutions to each other. The particle based and stream tube type solute transport models were useful as they could complement the traditional finite volume based approach which in certain circumstances produced numerical dispersion due to piecewise solution of the
Stochastic models of solute transport in highly heterogeneous geologic media
Semenov, V.N.; Korotkin, I.A.; Pruess, K.; Goloviznin, V.M.; Sorokovikova, O.S.
2009-09-15
A stochastic model of anomalous diffusion was developed in which transport occurs by random motion of Brownian particles, described by distribution functions of random displacements with heavy (power-law) tails. One variant of an effective algorithm for random function generation with a power-law asymptotic and arbitrary factor of asymmetry is proposed that is based on the Gnedenko-Levy limit theorem and makes it possible to reproduce all known Levy {alpha}-stable fractal processes. A two-dimensional stochastic random walk algorithm has been developed that approximates anomalous diffusion with streamline-dependent and space-dependent parameters. The motivation for introducing such a type of dispersion model is the observed fact that tracers in natural aquifers spread at different super-Fickian rates in different directions. For this and other important cases, stochastic random walk models are the only known way to solve the so-called multiscaling fractional order diffusion equation with space-dependent parameters. Some comparisons of model results and field experiments are presented.
DeAngelis, D.L.; Yeh, G.T.; Huff, D.D.
1984-10-01
This report documents a model, FRACPORT, that simulates the transport of a solute through a fractured porous matrix. The model should be useful in analyzing the possible transport of radionuclides from shallow-land burial sites in humid environments. The use of the model is restricted to transport through saturated zones. The report first discusses the general modeling approach used, which is based on the Integrated Compartmental Method. The basic equations of solute transport are then presented. The model, which assumes a known water velocity field, solves these equations on two different time scales; one related to rapid transport of solute along fractures and the other related to slower transport through the porous matrix. FRACPORT is validated by application to a simple example of fractured porous medium transport that has previously been analyzed by other methods. Then its utility is demonstrated in analyzing more complex cases of pulses of solute into a fractured matrix. The report serves as a user's guide to FRACPORT. A detailed description of data input, along with a listing of input for a sample problem, is provided. 16 references, 18 figures, 3 tables.
Xu, Zhijie; Tartakovsky, Alexandre M.
2017-09-01
This work presents a hierarchical model for solute transport in bounded layered porous media with random permeability. The model generalizes the Taylor-Aris dispersion theory to stochastic transport in random layered porous media with a known velocity covariance function. In the hierarchical model, we represent (random) concentration in terms of its cross-sectional average and a variation function. We derive a one-dimensional stochastic advection-dispersion-type equation for the average concentration and a stochastic Poisson equation for the variation function, as well as expressions for the effective velocity and dispersion coefficient. We observe that velocity fluctuations enhance dispersion in a non-monotonic fashion: the dispersion initially increases with correlation length λ, reaches a maximum, and decreases to zero at infinity. Maximum enhancement can be obtained at the correlation length about 0.25 the size of the porous media perpendicular to flow.
Stochastic forward and inverse groundwater flow and solute transport modeling
Janssen, G.M.C.M.
2008-01-01
Keywords: calibration, inverse modeling, stochastic modeling, nonlinear biodegradation, stochastic-convective, advective-dispersive, travel time, network design, non-Gaussian distribution, multimodal distribution, representers
This thesis offers three new approaches that contribute
Abrams , Robert H.; Loague, Keith
2000-01-01
This paper, the first of two parts [see Abrams and Loague, this issue], takes the compartmentalized approach for the geochemical evolution of redox zones presented by Abrams et al. [1998] and embeds it within a solute transport framework. In this paper the compartmentalized approach is generalized to facilitate the description of its incorporation into a solute transport simulator. An equivalent formulation is developed which removes any discontinuities that may occur when switching compartments. Rate‐limited redox reactions are modeled with a modified Monod relationship that allows either the organic substrate or the electron acceptor to be the rate‐limiting reactant. Thermodynamic constraints are used to inhibit lower‐energy redox reactions from occurring under infeasible geochemical conditions without imposing equilibrium on the lower‐energy reactions. The procedure used allows any redox reaction to be simulated as being kinetically limited or thermodynamically limited, depending on local geochemical conditions. Empirical reaction inhibition methods are not needed. The sequential iteration approach (SIA), a technique which allows the number of solute transport equations to be reduced, is adopted to solve the coupled geochemical/solute transport problem. When the compartmentalized approach is embedded within the SIA, with the total analytical concentration of each component as the dependent variable in the transport equation, it is possible to reduce the number of transport equations even further than with the unmodified SIA. A one‐dimensional, coupled geochemical/solute transport simulation is presented in which redox zones evolve dynamically in time and space. The compartmentalized solute transport (COMPTRAN) model described in this paper enables the development of redox zones to be simulated under both kinetic and thermodynamic constraints. The modular design of COMPTRAN facilitates the use of many different, preexisting solute transport and
Roman Cherniha
2016-06-01
Full Text Available The nonlinear mathematical model for solute and fluid transport induced by the osmotic pressure of glucose and albumin with the dependence of several parameters on the hydrostatic pressure is described. In particular, the fractional space available for macromolecules (albumin was used as a typical example and fractional fluid void volume were assumed to be different functions of hydrostatic pressure. In order to find non-uniform steady-state solutions analytically, some mathematical restrictions on the model parameters were applied. Exact formulae (involving hypergeometric functions for the density of fluid flux from blood to tissue and the fluid flux across tissues were constructed. In order to justify the applicability of the analytical results obtained, a wide range of numerical simulations were performed. It was found that the analytical formulae can describe with good approximation the fluid and solute transport (especially the rate of ultrafiltration for a wide range of values of the model parameters.
Modeling study of solute transport in the unsaturated zone. Information and data sets. Volume 1
Polzer, W.L.; Fuentes, H.R.; Springer, E.P.; Nyhan, J.W.
1986-05-01
The Environmental Science Group (HSE-12) is conducting a study to compare various approaches of modeling water and solute transport in porous media. Various groups representing different approaches will model a common set of transport data so that the state of the art in modeling and field experimentation can be discussed in a positive framework with an assessment of current capabilities and future needs in this area of research. This paper provides information and sets of data that will be useful to the modelers in meeting the objectives of the modeling study. The information and data sets include: (1) a description of the experimental design and methods used in obtaining solute transport data, (2) supporting data that may be useful in modeling the data set of interest, and (3) the data set to be modeled
Water flow and solute transport using environmental isotopes and modeling
Hussein, M.F.
2001-01-01
The deep unsaturated zone may be a useful hydrological archive in desert environments characterized by scant or sporadic rainfall and slow percolation of rainwater over decades or even centuries. This moisture archive provides a useful way to distinguish the net downward flow of recharge water, whereas the isotopic composition and concentration of the conservative solutes of the preserved moisture could be used to reconstruct the history of recharge under the prevailing deficient water balance. The major advantage of such coupled approach is to obtain independent estimates of groundwater recharge rates which are normally difficult to evaluate using the hydrological methods applied in the temperate zones. The study was conducted in the Shiekh-Zoweid/Raffa area in the northeastern coastal strip of Sinai Peninsula. Bore-holes were dry-drilled in a line perpendicular to the sea shoreline (using an 8-inch diameter hand-operated rotary rig) for the unsaturated sediment collection from successive 0.5m thick layers down to a depth of 20m. Samples were investigated for the moisture contents and the chemical and isotope composition of this moisture was determined. Physical parameters were also assessed including porosity and volumetric moisture content. Chloride mass-balance was used to calculate recharge rates through the unsaturated zone by predicting the position of the 1963-Tritium peak in the unsaturated column. Analysis of moisture, chloride and deuterium profiles showed three principle peaks (along with minor ones) in Karafin site indicating few major recharge events that have taken place during the last few decades. Adjustment of these episodes has also been attempted using two historical major rainfall events (known from nearby meteorological stations). Application of the methodology in water resources management in arid regions is discussed. (author)
Modeling of water and solute transport under variably saturated conditions: state of the art
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
Park, Chung Kyun; Lee, Jaek Wang; Baik, Min Hoon; Jeong, Jong Tae [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2012-02-15
Migration tests were performed with conservative tracers in a fractured zone that had a single fracture of about 2.5 m distance at the KURT. To interpret the migration of the tracers in the fractured rock, a solute transport model was developed. A two dimensional variable aperture channel model was adopted to describe the fractured path and hydrology, and a particle tracking method was used for solute transport. The simulation tried not only to develop a migration model of solutes for open flow environments but also to produce ideas for a better understanding of solute behaviours in indefinable fracture zones by comparing them to experimental results. The results of our simulations and experiments are described as elution and breakthrough curves, and are quantified by momentum analysis. The main retardation mechanism of nonsorbing tracers, including matrixdiffusion, was investigated.
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.
Numerical modelling of coupled fluid, heat, and solute transport in deformable fractured rock
Chan, T.; Reid, J.A.K.
1987-01-01
This paper reports on a three-dimensional (3D) finite-element code, MOTIF (model of transport in fractured/porous media), developed to model the coupled processes of groundwater flow, heat transport, brine transport, and one-species radionuclide transport in geological media. Three types of elements are available: a 3D continuum element, a planar fracture element that can be oriented in any arbitrary direction in 3D space or pipe flow in 3D space, and a line element for simulating fracture flow in 2D space or pipe flow in 3D space. As a quality-assurance measure, the MOTIF code was verified by comparison of its results with analytical solutions and other published numerical solutions
Modeling variably saturated subsurface solute transport with MODFLOW-UZF and MT3DMS
Morway, Eric D.; Niswonger, Richard G.; Langevin, Christian D.; Bailey, Ryan T.; Healy, Richard W.
2013-01-01
The MT3DMS groundwater solute transport model was modified to simulate solute transport in the unsaturated zone by incorporating the unsaturated-zone flow (UZF1) package developed for MODFLOW. The modified MT3DMS code uses a volume-averaged approach in which Lagrangian-based UZF1 fluid fluxes and storage changes are mapped onto a fixed grid. Referred to as UZF-MT3DMS, the linked model was tested against published benchmarks solved analytically as well as against other published codes, most frequently the U.S. Geological Survey's Variably-Saturated Two-Dimensional Flow and Transport Model. Results from a suite of test cases demonstrate that the modified code accurately simulates solute advection, dispersion, and reaction in the unsaturated zone. Two- and three-dimensional simulations also were investigated to ensure unsaturated-saturated zone interaction was simulated correctly. Because the UZF1 solution is analytical, large-scale flow and transport investigations can be performed free from the computational and data burdens required by numerical solutions to Richards' equation. Results demonstrate that significant simulation runtime savings can be achieved with UZF-MT3DMS, an important development when hundreds or thousands of model runs are required during parameter estimation and uncertainty analysis. Three-dimensional variably saturated flow and transport simulations revealed UZF-MT3DMS to have runtimes that are less than one tenth of the time required by models that rely on Richards' equation. Given its accuracy and efficiency, and the wide-spread use of both MODFLOW and MT3DMS, the added capability of unsaturated-zone transport in this familiar modeling framework stands to benefit a broad user-ship.
MaSTiS, microorganism and solute transport in streams, model documentation and user manual
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...
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.
Xingwei Wang
2014-01-01
Full Text Available Due to the uneven distribution of pollutions and blur edge of pollutant area, there will exist uncertainty of source term shape in advective-diffusion equation model of contaminant transport. How to generalize those irregular source terms and deal with those uncertainties is very critical but rarely studied in previous research. In this study, the fate and transport of contaminant from rectangular and elliptic source geometry were simulated based on a three-dimensional analytical solute transport model, and the source geometry generalization guideline was developed by comparing the migration of contaminant. The result indicated that the variation of source area size had no effect on pollution plume migration when the plume migrated as far as five times of source side length. The migration of pollution plume became slower with the increase of aquifer thickness. The contaminant concentration was decreasing with scale factor rising, and the differences among various scale factors became smaller with the distance to field increasing.
Modeling water flow and solute transport in unsaturated zone inside NSRAWD project
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
Modeling of water flow and solute transport in unsaturated heterogeneous fields
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
Kwong, S.; Jivkov, A.P.
2013-01-01
Deep geologic disposal of high activity and long-lived radioactive waste is being actively considered and pursued in many countries, where low permeability geological formations are used to provide long term waste contaminant with minimum impact to the environment and risk to the biosphere. A multi-barrier approach that makes use of both engineered and natural barriers (i.e. geological formations) is often used to further enhance the containment performance of the repository. As the deep repository system subjects to a variety of thermo-hydro-chemo-mechanical (THCM) effects over its long 'operational' lifespan (e.g. 0.1 to 1.0 million years, the integrity of the barrier system will decrease over time (e.g. fracturing in rock or clay)). This is broadly referred as media degradation in the present study. This modelling study examines the effects of media degradation on diffusion dominant solute transport in fractured media that are typical of deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes, while the effects of degradation is studied using a pore network model that considers the media diffusivity and network changes. Model results are presented to demonstrate the use of a 3D pore-network model, using a novel architecture, to calculate macroscopic properties of the medium such as diffusivity, subject to pore space changes as the media degrade. Results from a reactive transport model of a representative geological waste disposal package are also presented to demonstrate the effect of media property change on the solute migration behaviour, illustrating the complex interplay between kinetic biogeochemical processes and diffusion dominant transport. The initial modelling results demonstrate the feasibility of a coupled modelling approach (using pore-network model and reactive
Tran Ngoc, T.D.
2008-07-01
This Ph.D thesis presents the development of the solute transport models in unsaturated double-porosity medium, by using the asymptotic homogenization method. The obtained macroscopic models concern diffusion, diffusion-convection and dispersion-convection, according to the transport regime which is characterized by the non-dimensional numbers. The models consist of two coupled equations that show the local non-equilibrium of concentrations. The double-porosity transport models were numerically implemented using the code COMSOL Multiphysics (finite elements method), and compared with the solution of the same problem at the fine scale. The implementation allows solving the coupled equations in the macro- and micro-porosity domains (two-scale computations). The calculations of the dispersion tensor as a solution of the local boundary value problems, were also conducted. It was shown that the dispersivity depends on the saturation, the physical properties of the macro-porosity domain and the internal structure of the double-porosity medium. Finally, two series of experiments were performed on a physical model of double-porosity that is composed of a periodic assemblage of sintered clay spheres in Hostun sand HN38. The first experiment was a drainage experiment, which was conducted in order to validate the unsaturated flow model. The second series was a dispersion experiment in permanent unsaturated water flow condition (water content measured by gamma ray attenuation technique). A good agreement between the numerical simulations and the experimental observations allows the validation of the developed models. (author)
Swanson, Ryan D; Binley, Andrew; Keating, Kristina; France, Samantha; Osterman, Gordon; Day-Lewis, Frederick D.; Singha, Kamini
2015-01-01
The advection-dispersion equation (ADE) fails to describe commonly observed non-Fickian solute transport in saturated porous media, necessitating the use of other models such as the dual-domain mass-transfer (DDMT) model. DDMT model parameters are commonly calibrated via curve fitting, providing little insight into the relation between effective parameters and physical properties of the medium. There is a clear need for material characterization techniques that can provide insight into the geometry and connectedness of pore spaces related to transport model parameters. Here, we consider proton nuclear magnetic resonance (NMR), direct-current (DC) resistivity, and complex conductivity (CC) measurements for this purpose, and assess these methods using glass beads as a control and two different samples of the zeolite clinoptilolite, a material that demonstrates non-Fickian transport due to intragranular porosity. We estimate DDMT parameters via calibration of a transport model to column-scale solute tracer tests, and compare NMR, DC resistivity, CC results, which reveal that grain size alone does not control transport properties and measured geophysical parameters; rather, volume and arrangement of the pore space play important roles. NMR cannot provide estimates of more-mobile and less-mobile pore volumes in the absence of tracer tests because these estimates depend critically on the selection of a material-dependent and flow-dependent cutoff time. Increased electrical connectedness from DC resistivity measurements are associated with greater mobile pore space determined from transport model calibration. CC was hypothesized to be related to length scales of mass transfer, but the CC response is unrelated to DDMT.
A lattice Boltzmann model for solute transport in open channel flow
Wang, Hongda; Cater, John; Liu, Haifei; Ding, Xiangyi; Huang, Wei
2018-01-01
A lattice Boltzmann model of advection-dispersion problems in one-dimensional (1D) open channel flows is developed for simulation of solute transport and pollutant concentration. The hydrodynamics are calculated based on a previous lattice Boltzmann approach to solving the 1D Saint-Venant equations (LABSVE). The advection-dispersion model is coupled with the LABSVE using the lattice Boltzmann method. Our research recovers the advection-dispersion equations through the Chapman-Enskog expansion of the lattice Boltzmann equation. The model differs from the existing schemes in two points: (1) the lattice Boltzmann numerical method is adopted to solve the advection-dispersion problem by meso-scopic particle distribution; (2) and the model describes the relation between discharge, cross section area and solute concentration, which increases the applicability of the water quality model in practical engineering. The model is verified using three benchmark tests: (1) instantaneous solute transport within a short distance; (2) 1D point source pollution with constant velocity; (3) 1D point source pollution in a dam break flow. The model is then applied to a 50-year flood point source pollution accident on the Yongding River, which showed good agreement with a MIKE 11 solution and gauging data.
Bailey, Ryan T.; Morway, Eric D.; Niswonger, Richard G.; Gates, Timothy K.
2013-01-01
A numerical model was developed that is capable of simulating multispecies reactive solute transport in variably saturated porous media. This model consists of a modified version of the reactive transport model RT3D (Reactive Transport in 3 Dimensions) that is linked to the Unsaturated-Zone Flow (UZF1) package and MODFLOW. Referred to as UZF-RT3D, the model is tested against published analytical benchmarks as well as other published contaminant transport models, including HYDRUS-1D, VS2DT, and SUTRA, and the coupled flow and transport modeling system of CATHY and TRAN3D. Comparisons in one-dimensional, two-dimensional, and three-dimensional variably saturated systems are explored. While several test cases are included to verify the correct implementation of variably saturated transport in UZF-RT3D, other cases are included to demonstrate the usefulness of the code in terms of model run-time and handling the reaction kinetics of multiple interacting species in variably saturated subsurface systems. As UZF1 relies on a kinematic-wave approximation for unsaturated flow that neglects the diffusive terms in Richards equation, UZF-RT3D can be used for large-scale aquifer systems for which the UZF1 formulation is reasonable, that is, capillary-pressure gradients can be neglected and soil parameters can be treated as homogeneous. Decreased model run-time and the ability to include site-specific chemical species and chemical reactions make UZF-RT3D an attractive model for efficient simulation of multispecies reactive transport in variably saturated large-scale subsurface systems.
Modeling study of solute transport in the unsaturated zone: Workshop proceedings
Springer, E.P.; Fuentes, H.R.
1987-04-01
Issues addressed were the adequacy of the data for the various models, effectiveness of the models to represent the data, particular information provided by the models, the role of caisson experiments in providing fundamental knowledge of porous-media water flow and solute transport, and the importance of geochemistry to the transport of nonconservative tracers. These proceedings include the presentations made by each of the modelers; the summary document written by the panel; and a transcript of the discussions, both the discussions that followed individual presentations and the general discussion held on the second day. This publication completes the series on the workshop. Volume I in the series (NUREG/CR-4615, Vol. I) contains background information and the data sets provided each modeler
Regional flow and solute transport modeling for site suitability. Part I
Rowe, J.; Miller, I.
1979-12-01
The nature of regional flow systems in large sedimentary basins will largely determine the effectiveness of regional flow as a barrier to radionuclide escape from deep geologic repositories. The purpose of the work reported herein and the proposed future work is to develop a methodology for evaluating regional flow barriers by using numerical models. The Williston Basin was chosen as an archetype case for the regional modeling study. However, due to the simplified nature of the study, the results are not meant to represent the behavior of a repository actually placed within the Williston Basin. The major components of this Phase I study are: (1) assembly and reduction of available data; (2) formulation of a simplified geohydrologic model; (3) computer simulation of fluid flow; and (4) computer simulation of solute transport. As of this report, the first two items are essentially completed. Computer simulation of fluid flow will require some revision and further study, which will be done in the second phase of this study. Computer simulation of solute transport has been considered only on a very preliminary basis. Important conclusions of this Phase I study are as follows. Assembly and reduction of data require an extensive work effort. Generally, the parameters describing fluid flow are poorly known on a regional basis and those describing solute transport are unknown
Regional flow and solute transport modeling for site suitability. Part I
Rowe, J.; Miller, I.
1979-12-01
The nature of regional flow systems in large sedimentary basins will largely determine the effectiveness of regional flow as a barrier to radionuclide escape from deep geologic repositories. The purpose of the work reported herein and the proposed future work is to develop a methodology for evaluating regional flow barriers by using numerical models. The Williston Basin was chosen as an archetype case for the regional modeling study. However, due to the simplified nature of the study, the results are not meant to represent the behavior of a repository actually placed within the Williston Basin. The major components of this Phase I study are: (1) assembly and reduction of available data; (2) formulation of a simplified geohydrologic model; (3) computer simulation of fluid flow; and (4) computer simulation of solute transport. As of this report, the first two items are essentially completed. Computer simulation of fluid flow will require some revision and further study, which will be done in the second phase of this study. Computer simulation of solute transport has been considered only on a very preliminary basis. Important conclusions of this Phase I study are as follows. Assembly and reduction of data require an extensive work effort. Generally, the parameters describing fluid flow are poorly known on a regional basis and those describing solute transport are unknown.
Kwong, S. [National Nuclear Laboratory (United Kingdom); Jivkov, A.P. [Research Centre for Radwaste and Decommissioning and Modelling and Simulation Centre, University of Manchester (United Kingdom)
2012-07-01
Deep geologic disposal of high activity and long-lived radioactive waste is gaining increasing support in many countries, where suitable low permeability geological formation in combination with engineered barriers are used to provide long term waste contaminant and minimise the impacts to the environment and risk to the biosphere. This modelling study examines the solute transport in fractured media under low flow velocities that are relevant to a deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes. The effects of water velocity in the fracture, matrix porosity and diffusion on solute transport are investigated and discussed. Some illustrative modelled results are presented to demonstrate the use of the model to examine the effects of media degradation on solute transport, under the influences of hydrogeological (diffusion dominant) and microbially mediated chemical processes. The challenges facing the prediction of long term degradation such as cracks evolution, interaction and coalescence are highlighted. The potential of a novel microstructure informed modelling approach to account for these effects is discussed, particularly with respect to investigating multiple phenomena impact on material performance. The GRM code is used to examine the effects of media degradation for a geological waste disposal package, under the combined hydrogeological (diffusion dominant) and chemical effects in low groundwater flow conditions that are typical of deep geological disposal systems. An illustrative reactive transport modelling application demonstrates the use of the code to examine the interplay of kinetic controlled biogeochemical reactive processes with advective and diffusive transport, under the influence of media degradation. The initial model results are encouraging which show the
A computational model for simulating solute transport and oxygen consumption along the nephrons
Vallon, Volker; Edwards, Aurélie
2016-01-01
The goal of this study was to investigate water and solute transport, with a focus on sodium transport (TNa) and metabolism along individual nephron segments under differing physiological and pathophysiological conditions. To accomplish this goal, we developed a computational model of solute transport and oxygen consumption (QO2) along different nephron populations of a rat kidney. The model represents detailed epithelial and paracellular transport processes along both the superficial and juxtamedullary nephrons, with the loop of Henle of each model nephron extending to differing depths of the inner medulla. We used the model to assess how changes in TNa may alter QO2 in different nephron segments and how shifting the TNa sites alters overall kidney QO2. Under baseline conditions, the model predicted a whole kidney TNa/QO2, which denotes the number of moles of Na+ reabsorbed per moles of O2 consumed, of ∼15, with TNa efficiency predicted to be significantly greater in cortical nephron segments than in medullary segments. The TNa/QO2 ratio was generally similar among the superficial and juxtamedullary nephron segments, except for the proximal tubule, where TNa/QO2 was ∼20% higher in superficial nephrons, due to the larger luminal flow along the juxtamedullary proximal tubules and the resulting higher, flow-induced transcellular transport. Moreover, the model predicted that an increase in single-nephron glomerular filtration rate does not significantly affect TNa/QO2 in the proximal tubules but generally increases TNa/QO2 along downstream segments. The latter result can be attributed to the generally higher luminal [Na+], which raises paracellular TNa. Consequently, vulnerable medullary segments, such as the S3 segment and medullary thick ascending limb, may be relatively protected from flow-induced increases in QO2 under pathophysiological conditions. PMID:27707705
Zee, van der S.E.A.T.M.; Leijnse, A.
2013-01-01
Solute transport is of importance in view of the movement of nutrient elements, e.g. towards the plant root system, and because of a broad range of pollutants. Pollution is not necessarily man induced, but may be due to geological or geohydrological causes, e.g. in the cases of pollution with
External intermittency prediction using AMR solutions of RANS turbulence and transported PDF models
Olivieri, D. A.; Fairweather, M.; Falle, S. A. E. G.
2011-12-01
External intermittency in turbulent round jets is predicted using a Reynolds-averaged Navier-Stokes modelling approach coupled to solutions of the transported probability density function (pdf) equation for scalar variables. Solutions to the descriptive equations are obtained using a finite-volume method, combined with an adaptive mesh refinement algorithm, applied in both physical and compositional space. This method contrasts with conventional approaches to solving the transported pdf equation which generally employ Monte Carlo techniques. Intermittency-modified eddy viscosity and second-moment turbulence closures are used to accommodate the effects of intermittency on the flow field, with the influence of intermittency also included, through modifications to the mixing model, in the transported pdf equation. Predictions of the overall model are compared with experimental data on the velocity and scalar fields in a round jet, as well as against measurements of intermittency profiles and scalar pdfs in a number of flows, with good agreement obtained. For the cases considered, predictions based on the second-moment turbulence closure are clearly superior, although both turbulence models give realistic predictions of the bimodal scalar pdfs observed experimentally.
Benchmarking the invariant embedding method against analytical solutions in model transport problems
Malin, Wahlberg; Imre, Pazsit
2005-01-01
The purpose of this paper is to demonstrate the use of the invariant embedding method in a series of model transport problems, for which it is also possible to obtain an analytical solution. Due to the non-linear character of the embedding equations, their solution can only be obtained numerically. However, this can be done via a robust and effective iteration scheme. In return, the domain of applicability is far wider than the model problems investigated in this paper. The use of the invariant embedding method is demonstrated in three different areas. The first is the calculation of the energy spectrum of reflected (sputtered) particles from a multiplying medium, where the multiplication arises from recoil production. Both constant and energy dependent cross sections with a power law dependence were used in the calculations. The second application concerns the calculation of the path length distribution of reflected particles from a medium without multiplication. This is a relatively novel and unexpected application, since the embedding equations do not resolve the depth variable. The third application concerns the demonstration that solutions in an infinite medium and a half-space are interrelated through embedding-like integral equations, by the solution of which the reflected flux from a half-space can be reconstructed from solutions in an infinite medium or vice versa. In all cases the invariant embedding method proved to be robust, fast and monotonically converging to the exact solutions. (authors)
Pouran, Behdad; Arbabi, Vahid; Weinans, Harrie; Zadpoor, Amir A
2016-11-01
Transport of solutes helps to regulate normal physiology and proper function of cartilage in diarthrodial joints. Multiple studies have shown the effects of characteristic parameters such as concentration of proteoglycans and collagens and the orientation of collagen fibrils on the diffusion process. However, not much quantitative information and accurate models are available to help understand how the characteristics of the fluid surrounding articular cartilage influence the diffusion process. In this study, we used a combination of micro-computed tomography experiments and biphasic-solute finite element models to study the effects of three parameters of the overlying bath on the diffusion of neutral solutes across cartilage zones. Those parameters include bath size, degree of stirring of the bath, and the size and concentration of the stagnant layer that forms at the interface of cartilage and bath. Parametric studies determined the minimum of the finite bath size for which the diffusion behavior reduces to that of an infinite bath. Stirring of the bath proved to remarkably influence neutral solute transport across cartilage zones. The well-stirred condition was achieved only when the ratio of the diffusivity of bath to that of cartilage was greater than ≈1000. While the thickness of the stagnant layer at the cartilage-bath interface did not significantly influence the diffusion behavior, increase in its concentration substantially elevated solute concentration in cartilage. Sufficient stirring attenuated the effects of the stagnant layer. Our findings could be used for efficient design of experimental protocols aimed at understanding the transport of molecules across articular cartilage. Copyright © 2016 Elsevier Ltd. All rights reserved.
Modeling particle-facilitated solute transport using the C-Ride module of HYDRUS
Simunek, Jiri; Bradford, Scott A.
2017-04-01
Strongly sorbing chemicals (e.g., heavy metals, radionuclides, pharmaceuticals, and/or explosives) in soils are associated predominantly with the solid phase, which is commonly assumed to be stationary. However, recent field- and laboratory-scale observations have shown that, in the presence of mobile colloidal particles (e.g., microbes, humic substances, clays and metal oxides), the colloids could act as pollutant carriers and thus provide a rapid transport pathway for strongly sorbing contaminants. Such transport can be further accelerated since these colloidal particles may travel through interconnected larger pores where the water velocity is relatively high. Additionally, colloidal particles have a considerable adsorption capacity for other species present in water because of their large specific surface areas and their high concentrations in soil-water and groundwater. As a result, the transport of contaminants can be significantly, sometimes dramatically, enhanced when they are adsorbed to mobile colloids. To address this problem, we have developed the C-Ride module for HYDRUS-1D. This one-dimensional numerical module is based on the HYDRUS-1D software package and incorporates mechanisms associated with colloid and colloid-facilitated solute transport in variably saturated porous media. This numerical model accounts for both colloid and solute movement due to convection, diffusion, and dispersion in variably-saturated soils, as well as for solute movement facilitated by colloid transport. The colloids transport module additionally considers processes of attachment/detachment to/from the solid phase, straining, and/or size exclusion. Various blocking and depth dependent functions can be used to modify the attachment and straining coefficients. The module additionally considers the effects of changes in the water content on colloid/bacteria transport and attachment/detachment to/from solid-water and air-water interfaces. For example, when the air
Groundwater and solute transport modeling at Hyporheic zone of upper part Citarum River
Iskandar, Irwan; Farazi, Hendy; Fadhilah, Rahmat; Purnandi, Cipto; Notosiswoyo, Sudarto
2017-06-01
Groundwater and surface water interaction is an interesting topic to be studied related to the water resources and environmental studies. The study of interaction between groundwater and river water at the Upper Part Citarum River aims to know the contribution of groundwater to the river or reversely and also solute transport of dissolved ions between them. Analysis of drill logs, vertical electrical sounding at the selected sections, measurement of dissolved ions, and groundwater modeling were applied to determine the flow and solute transport phenomena at the hyporheic zone. It showed the hyporheic zone dominated by silt and clay with hydraulic conductivity range from 10-4∼10-8 m/s. The groundwater flowing into the river with very low gradient and it shows that the Citarum River is a gaining stream. The groundwater modeling shows direct seepage of groundwater into the Citarum River is only 186 l/s, very small compared to the total discharge of the river. Total dissolved ions of the groundwater ranged from 200 to 480 ppm while the river water range from 200 to 2,000 ppm. Based on solute transport modeling it indicates dissolved ions dispersion of the Citarum River into groundwater may occur in some areas such as Bojongsoang-Dayeuh Kolot and Nanjung. This situation would increase the dissolved ions in groundwater in the region due to the contribution of the Citarum River. The results of the research can be a reference for further studies related to the mechanism of transport of the pollutants in the groundwater around the Citarum River.
Garratt, T.J.
1989-05-01
Compartment models for the transport of radionuclides in the biosphere are conventionally solved using a numerical time-stepping procedure. This report examines an alternative method based on the numerical inversion of Laplace transforms, which is potentially more efficient and accurate for some classes of problem. The central problem considered is the most efficient and robust technique for solving the Laplace-transformed rate equations. The conclusion is that Gaussian elimination is the most efficient and robust solution method. A general compartment model has been implemented on a personal computer and used to solve a realistic case including radionuclide decay chains. (author)
Gustafsson, Lars-Goeran; Sassner, Mona; Bosson, Emma
2008-12-01
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
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
Modelling transport of water and solutes in future wetlands in Forsmark
Vikstroem, Maria; Gustafsson, Lars-Goeran [DHI Water and Environment AB, Vaexjoe (Sweden)
2006-03-15
been analyzed. Results from the transport modelling show that a solute in the bedrock is transported quickly towards the peat surface in discharge areas for Bolundsfjaerden. After around 10 years, a stationary condition is reached. For the recharge area that develops in large parts of the mire, the solute is transported through horizontal dispersion, which results in much lower concentrations. The solute concentration is at the lowest where the overland water pressure is at the highest close to the south western inlet. Puttan has a vertical flow pattern that differs from Bolundsfjaerden. The pressure from water on the peat surface is considerably lower and for a major part of the year Puttan is a discharge area with an upwards flow direction. The spatial distribution of solutes is more even over the surface than for Bolundsfjaerden, but higher concentrations are found around today's shoreline. A solute reaching the wetland through surface runoff is transported relatively slow through the mire at Bolundsfjaerden. Due to the recharge conditions, the solute is spread to the underlying soil layers. The vertical solute transport follows the discharge and recharge areas, where high concentrations, up to the source strength, are reached in major parts of the formation, while lower concentrations are reached in the discharge areas and underneath clay sediment.
Modelling transport of water and solutes in future wetlands in Forsmark
Vikstroem, Maria; Gustafsson, Lars-Goeran
2006-03-01
analyzed. Results from the transport modelling show that a solute in the bedrock is transported quickly towards the peat surface in discharge areas for Bolundsfjaerden. After around 10 years, a stationary condition is reached. For the recharge area that develops in large parts of the mire, the solute is transported through horizontal dispersion, which results in much lower concentrations. The solute concentration is at the lowest where the overland water pressure is at the highest close to the south western inlet. Puttan has a vertical flow pattern that differs from Bolundsfjaerden. The pressure from water on the peat surface is considerably lower and for a major part of the year Puttan is a discharge area with an upwards flow direction. The spatial distribution of solutes is more even over the surface than for Bolundsfjaerden, but higher concentrations are found around today's shoreline. A solute reaching the wetland through surface runoff is transported relatively slow through the mire at Bolundsfjaerden. Due to the recharge conditions, the solute is spread to the underlying soil layers. The vertical solute transport follows the discharge and recharge areas, where high concentrations, up to the source strength, are reached in major parts of the formation, while lower concentrations are reached in the discharge areas and underneath clay sediment
Transport of fluid and solutes in the body II. Model validation and implications.
Gyenge, C C; Bowen, B D; Reed, R K; Bert, J L
1999-09-01
A mathematical model of short-term whole body fluid, protein, and ion distribution and transport developed earlier [see companion paper: C. C. Gyenge, B. D. Bowen, R. K. Reed, and J. L. Bert. Am. J. Physiol. 277 (Heart Circ. Physiol. 46): H1215-H1227, 1999] is validated using experimental data available in the literature. The model was tested against data measured for the following three types of experimental infusions: 1) hyperosmolar saline solutions with an osmolarity in the range of 2,000-2,400 mosmol/l, 2) saline solutions with an osmolarity of approximately 270 mosmol/l and composition comparable with Ringer solution, and 3) an isosmotic NaCl solution with an osmolarity of approximately 300 mosmol/l. Good agreement between the model predictions and the experimental data was obtained with respect to the trends and magnitudes of fluid shifts between the intra- and extracellular compartments, extracellular ion and protein contents, and hematocrit values. The model is also able to yield information about inaccessible or difficult-to-measure system variables such as intracellular ion contents, cellular volumes, and fluid fluxes across the vascular capillary membrane, data that can be used to help interpret the behavior of the system.
Kovac, D.; Otto, G.; Hobler, G.
2005-01-01
In this paper we present a model of amorphous pocket formation that is based on binary collision simulations to generate the distribution of deposited energy, and on numerical solution of the heat transport equation to describe the quenching process. The heat transport equation is modified to consider the heat of melting when the melting temperature is crossed at any point in space. It is discretized with finite differences on grid points that coincide with the crystallographic lattice sites, which allows easy determination of molten atoms. Atoms are considered molten if the average of their energy and the energy of their neighbors meets the melting criterion. The results obtained with this model are in good overall agreement with published experimental data on P, As, Te and Tl implantations in Si and with data on the polyatomic effect at cryogenic temperature
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
Kim, Jaisoo; Sung, Kijune; Corapcioglu, M. Yavuz; Drew, Malcolm C
2004-09-01
A contaminant transport model was developed to simulate the fate and transport of organic compounds such as TNT (2,4,6-trinitrotoluene), using the single-root system. Onions were planted for this system with 50-ml plastic tubes. Mass in the soil, soil solution, root and leaf was monitored using {sup 14}C-TNT. Model parameters were acquired from the experiments in the single-root system and were used to simulate total TNT concentration in soil, providing the average concentrations in the rhizosphere and bulk soil as well as root and leaf compartments. Because the existing RCF (root concentration factor) and TSCF (transpiration stream concentration factor) equations based on log K{sub ow} (octanol-water partition coefficient) were not correlated to TNT uptake, a new term, root uptake rate (R{sub ur}), and a new T{sub scf} equation, based on the experimental data, were introduced in the proposed model. The results from both modeling and experimental studies showed higher concentrations of TNT in the rhizosphere than in the bulk soil, because mass transported from the surrounding soil into the rhizosphere was higher than that by root uptake.
Mohammadi, Mohammad Hossein; Vanclooster, Marnik
2012-05-01
Solute transport in partially saturated soils is largely affected by fluid velocity distribution and pore size distribution within the solute transport domain. Hence, it is possible to describe the solute transport process in terms of the pore size distribution of the soil, and indirectly in terms of the soil hydraulic properties. In this paper, we present a conceptual approach that allows predicting the parameters of the Convective Lognormal Transfer model from knowledge of soil moisture and the Soil Moisture Characteristic (SMC), parameterized by means of the closed-form model of Kosugi (1996). It is assumed that in partially saturated conditions, the air filled pore volume act as an inert solid phase, allowing the use of the Arya et al. (1999) pragmatic approach to estimate solute travel time statistics from the saturation degree and SMC parameters. The approach is evaluated using a set of partially saturated transport experiments as presented by Mohammadi and Vanclooster (2011). Experimental results showed that the mean solute travel time, μ(t), increases proportionally with the depth (travel distance) and decreases with flow rate. The variance of solute travel time σ²(t) first decreases with flow rate up to 0.4-0.6 Ks and subsequently increases. For all tested BTCs predicted solute transport with μ(t) estimated from the conceptual model performed much better as compared to predictions with μ(t) and σ²(t) estimated from calibration of solute transport at shallow soil depths. The use of μ(t) estimated from the conceptual model therefore increases the robustness of the CLT model in predicting solute transport in heterogeneous soils at larger depths. In view of the fact that reasonable indirect estimates of the SMC can be made from basic soil properties using pedotransfer functions, the presented approach may be useful for predicting solute transport at field or watershed scales. Copyright © 2012 Elsevier B.V. All rights reserved.
Preliminary model of fluid and solute distribution and transport during hemorrhage.
Gyenge, C C; Bowen, B D; Reed, R K; Bert, J L
2003-01-01
The distribution and transport of fluid, ions, and other solutes (plasma proteins and glucose) are described in a mathematical model of unresuscitated hemorrhage. The model is based on balances of each material in both the circulation and its red blood cells, as well as in a whole-body tissue compartment along with its cells. Exchange between these four compartments occurs by a number of different mechanisms. The hemorrhage model has as its basis a validated model, due to Gyenge et al., of fluid and solute exchange in the whole body of a standard human. Hypothetical but physiologically based features such as glucose and small ion releases along with cell membrane changes are incorporated into the hemorrhage model to describe the system behavior, particularly during larger hemorrhages. Moderate (10%-30% blood volume loss) and large (> 30% blood loss) hemorrhage dynamics are simulated and compared with available data. The model predictions compare well with the available information for both types of hemorrhages and provide a reasonable description of the progression of a large hemorrhage from the compensatory phase through vascular collapse.
Numerical modeling of solute transport in deformable unsaturated layered soil
Sheng Wu
2017-07-01
Full Text Available The effect of soil stratification was studied through numerical investigation based on the coupled model of solute transport in deformable unsaturated soil. The theoretical model implied two-way coupled excess pore pressure and soil deformation based on Biot's consolidation theory as well as a one-way coupled volatile pollutant concentration field developed from the advection-diffusion theory. Embedded in the model, the degree of saturation, fluid compressibility, self-weight of the soil matrix, porosity variance, longitudinal dispersion, and linear sorption were computed. Based on simulation results of a proposed three-layer landfill model using the finite element method, the multi-layer effects are discussed with regard to the hydraulic conductivity, shear modulus, degree of saturation, molecular diffusion coefficient, and thickness of each layer. Generally speaking, contaminants spread faster in a stratified field with a soft and highly permeable top layer; soil parameters of the top layer are more critical than the lower layers but controlling soil thicknesses will alter the results. This numerical investigation showed noticeable impacts of stratified soil properties on solute migration results, demonstrating the importance of correctly modeling layered soil instead of simply assuming the averaged properties across the soil profile.
Zhang, Guoxiang; Zheng, Zuoping; Wan, Jiamin
2004-01-28
Concentrated aqueous solutions (CAS) have unique thermodynamic and physical properties. Chemical components in CAS are incompletely dissociated, especially those containing divalent or polyvalent ions. The problem is further complicated by the interaction between CAS flow processes and the naturally heterogeneous sediments. As the CAS migrates through the porous media, the composition may be altered subject to fluid-rock interactions. To effectively model reactive transport of CAS, we must take into account ion-interaction. A combination of the Pitzer ion-interaction and the ion-association model would be an appropriate way to deal with multiple-component systems if the Pitzer' parameters and thermodynamic data of dissolved components and the related minerals are available. To quantify the complicated coupling of CAS flow and transport, as well as the involved chemical reactions in natural and engineered systems, we have substantially extended an existing reactive biogeochemical transport code, BIO-CORE{sup 2D}{copyright}, by incorporating a comprehensive Pitzer ion-interaction model. In the present paper, the model, and two test cases against measured data were briefly introduced. Finally we present an application to simulate a laboratory column experiment studying the leakage of the high alkaline waste fluid stored in Hanford (a site of the U.S. Department of Energy, located in Washington State, USA). With the Pitzer ion-interaction ionic activity model, our simulation captures measured pH evolution. The simulation indicates that all the reactions controlling the pH evolution, including cation exchanges, mineral precipitation and dissolution, are coupled.
Coupled Fluid, Energy, and Solute Transport (CFEST) model: Formulation and user's manual
Gupta, S.K.; Cole, C.R.; Kincaid, C.T.; Monti, A.M.
1987-10-01
The CFEST (Coupled Fluid, Energy, and Solute Transport) code has been developed to analyze coupled hydrologic, thermal, and solute transport processes. It treats single-pahse Darcy ground-water flow in a horizontal or vertical plane, or in fully three-dimensional space under nonisothermal conditions. The code has the capability to model discontinuous and continuous layering, time-dependent and constant sources/sinks, and transient as well as steady-stae ground-water flow. The code offers a wide choice of boundary conditions such as precsribed heads, nodal injection or withdrawal, constant or spatially varying infiltration rates, and welemental source/sink. Initial conditions for the flow analysis can be prescribed pressure or hydraulic head. The heterogeneity in aquifer permeability and porosity can be described by geologic unit or explicity for given elements. Three-dimensional elelments are generated from user-defined well logs at each surface node. To facilitate interaction between disciplines, support programs are provided to plot the finite element grid, well logs, contour maps of input and output parameters, and vertical cross sections. Ground-water travel paths and times and volumetric rates from a specified point can be determined from support programs. This report includes governing partial differential equations, finite element formulation, a use's manual, verification test examples, sample problems, and source listings. 36 refs., 121 figs., 36 tabs
Davit, Y.; Wood, B. D.; Debenest, G.; Quintard, M.
2012-01-01
In this work, we study the transient behavior of homogenized models for solute transport in two-region porous media. We focus on the following three models: (1) a time non-local, two-equation model (2eq-nlt). This model does not rely on time
Evaluation of unsaturated-zone solute-transport models for studies of agricultural chemicals
Nolan, Bernard T.; Bayless, E. Randall; Green, Christopher T.; Garg, Sheena; Voss, Frank D.; Lampe, David C.; Barbash, Jack E.; Capel, Paul D.; Bekins, Barbara A.
2005-01-01
Seven unsaturated-zone solute-transport models were tested with two data sets to select models for use by the Agricultural Chemical Team of the U.S. Geological Survey's National Water-Quality Assessment Program. The data sets were from a bromide tracer test near Merced, California, and an atrazine study in the White River Basin, Indiana. In this study the models are designated either as complex or simple based on the water flux algorithm. The complex models, HYDRUS2D, LEACHP, RZWQM, and VS2DT, use Richards' equation to simulate water flux and are well suited to process understanding. The simple models, CALF, GLEAMS, and PRZM, use a tipping-bucket algorithm and are more amenable to extrapolation because they require fewer input parameters. The purpose of this report is not to endorse a particular model, but to describe useful features, potential capabilities, and possible limitations that emerged from working with the model input data sets. More rigorous assessment of model applicability involves proper calibration, which was beyond the scope of this study.
Shutang Zhu
2008-01-01
Full Text Available The coupling of groundwater movement and reactive transport during groundwater recharge with wastewater leads to a complicated mathematical model, involving terms to describe convection-dispersion, adsorption/desorption and/or biodegradation, and so forth. It has been found very difficult to solve such a coupled model either analytically or numerically. The present study adopts operator-splitting techniques to decompose the coupled model into two submodels with different intrinsic characteristics. By applying an upwind finite difference scheme to the finite volume integral of the convection flux term, an implicit solution procedure is derived to solve the convection-dominant equation. The dispersion term is discretized in a standard central-difference scheme while the dispersion-dominant equation is solved using either the preconditioned Jacobi conjugate gradient (PJCG method or Thomas method based on local-one-dimensional scheme. The solution method proposed in this study is applied to the demonstration project of groundwater recharge with secondary effluent at Gaobeidian sewage treatment plant (STP successfully.
Xu, Z., E-mail: zhanjie.xu@kit.ed [Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 Karlsruhe (Germany); Travis, J.R. [Ingenieurbuero DuBois-Pitzer-Travis, 63071 Offenbach (Germany); Breitung, W.; Jordan, T. [Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 Karlsruhe (Germany)
2010-12-15
Potentially explosive dust aerosol mobilization in the vacuum vessel is an important safety issue of the ITER facility, especially in scenarios of loss of vacuum accidents. Therefore dust mobilization modeling is ongoing in Research Center Karlsuhe. At first the aerosol particle model in the GASFLOW computer code is introduced briefly. To verify the particle model, a series of particle diffusion problems are simulated in one-, two- and three-dimensions. In each problem a particle source is initially exposed to an advective gas flow. Then a dust cloud is formed in the down stream. To obtain the theoretical solution about the particle concentration in the dust cloud, the governing diffusion partial differential equations with an additional advection term are solved by using Green's function method. Different spatial and temporal characters about the particle sources are also considered, e.g., instantaneous or continuous sources, line, or volume sources and so forth. The GASFLOW simulation results about the particle concentrations and the corresponding Green's function solutions are compared case by case. Very good agreements are found between the theoretical solutions and the GASGLOW simulations, when the drag force between the micron-sized particles and the conveying gas flow meets the Stokes' law about resistance. This situation is corresponding to a very small Reynolds number based on the particle diameter, with a negligible inertia effect of the particles. This verification work shows that the particle model of the GASFLOW code can reproduce numerically particle transport and diffusion in a good way.
Schuff, M M; Gore, J P; Nauman, E A
2013-05-01
In order to better understand the mechanisms governing transport of drugs, nanoparticle-based treatments, and therapeutic biomolecules, and the role of the various physiological parameters, a number of mathematical models have previously been proposed. The limitations of the existing transport models indicate the need for a comprehensive model that includes transport in the vessel lumen, the vessel wall, and the interstitial space and considers the effects of the solute concentration on fluid flow. In this study, a general model to describe the transient distribution of fluid and multiple solutes at the microvascular level was developed using mixture theory. The model captures the experimentally observed dependence of the hydraulic permeability coefficient of the capillary wall on the concentration of solutes present in the capillary wall and the surrounding tissue. Additionally, the model demonstrates that transport phenomena across the capillary wall and in the interstitium are related to the solute concentration as well as the hydrostatic pressure. The model is used in a companion paper to examine fluid and solute transport for the simplified case of an axisymmetric geometry with no solid deformation or interconversion of mass.
Wayman, C. R.; Russo, T. A.; Li, L.; Forsythe, B.; Hoagland, B.
2017-12-01
As part of the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) project, we have collected geochemical and hydrological data from several subcatchments and four monitoring sites on the main stem of Shaver's Creek, in Huntingon county, Pennsylvania. One subcatchment (0.43 km2) is under agricultural land use, and the monitoring locations on the larger Shaver's Creek (up to 163 km2) drain watersheds with 0 to 25% agricultural area. These two scales of investigation, coupled with advances made across the SSHCZO on multiple lithologies allow us to extrapolate from the subcatchment to the larger watershed. We use geochemical surface and groundwater data to estimate the solute and water transport regimes within the catchment, and to show how lithology and land use are major controls on ground and surface water quality. One area of investigation includes the transport of nutrients between interflow and regional groundwater, and how that connectivity may be reflected in local surface waters. Water and nutrient (Nitrogen) isotopes, will be used to better understand the relative contributions of local and regional groundwater and interflow fluxes into nearby streams. Following initial qualitative modeling, multiple hydrologic and nutrient transport models (e.g. SWAT and CYCLES/PIHM) will be evaluated from the subcatchment to large watershed scales. We will evaluate the ability to simulate the contributions of regional groundwater versus local groundwater, and also impacts of agricultural land management on surface water quality. Improving estimations of groundwater contributions to stream discharge will provide insight into how much agricultural development can impact stream quality and nutrient loading.
Lehikoinen, J.
1997-01-01
This report describes the progress of the computer model for ionic transport in bentonite. The research is part of the project Microstructural and chemical parameters of bentonite as determinants of waste isolation efficiency within the Nuclear fission safety program organized by The Commission of the European Communities. The study was started by collecting a comprehensive body of available data on space-charge transport modelling and creating a conceptualization of the problem at hand. The numerical discretization of the governing equations by finite differences was also initiated. This report introduces the theoretical basis for the model, somewhat more elaborated than presented in Progress Report 1/1996, and rectifies a few mistakes appearing in that report. It also gives a brief introduction to the solution methodology of the disc retized governing equations. (orig.) (12 refs.)
Lee, Jonghyun; Rolle, Massimo; Kitanidis, Peter K
2017-09-15
Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and concentration within a block is not resolved and the combined spreading effect is approximated using resolved quantities and macroscopic parameters. This applies whether the formation is modeled as homogeneous or discretized into homogeneous blocks but the emphasis here being on the latter. The process of dispersion is typically described through the Fickian model, i.e., the dispersive flux is proportional to the gradient of the resolved concentration, commonly with the Scheidegger parameterization, which is a particular way to compute the dispersion coefficients utilizing dispersivity coefficients. Although such parameterization is by far the most commonly used in solute transport applications, its validity has been questioned. Here, our goal is to investigate the effects of heterogeneity and mass transfer limitations on block-scale longitudinal dispersion and to evaluate under which conditions the Scheidegger parameterization is valid. We compute the relaxation time or memory of the system; changes in time with periods larger than the relaxation time are gradually leading to a condition of local equilibrium under which dispersion is Fickian. The method we use requires the solution of a steady-state advection-dispersion equation, and thus is computationally efficient, and applicable to any heterogeneous hydraulic conductivity K field without requiring statistical or structural assumptions. The method was validated by comparing with other approaches such as the moment analysis and the first order perturbation method. We investigate the impact of heterogeneity, both in degree and structure, on the longitudinal dispersion coefficient and then discuss the role of local dispersion
Mishra, S.; Chakraborty, S.; DebRoy, T.
2005-01-01
A transport phenomena-based mathematical model is developed to understand liquation cracking in weldments during fusion welding. Equations of conservation of mass, momentum, heat, and solute transport are numerically solved considering nonequilibrium solidification and filler metal addition to determine the solid and liquid phase fractions in the solidifying region and the solute distribution in the weld pool. An effective partition coefficient that considers the local interface velocity and the undercooling is used to simulate solidification during welding. The calculations show that convection plays a dominant role in the solute transport inside the weld pool. The predicted weld-metal solute content agreed well with the independent experimental observations. The liquation cracking susceptibility in Al-Cu alloy weldments could be reliably predicted by the model based on the computed solidifying weld-metal composition and solid fraction considering nonequilibrium solidification
Arbabi, Vahid; Pouran, Behdad; Weinans, Harrie; Zadpoor, Amir A
2016-06-14
Charged and uncharged solutes penetrate through cartilage to maintain the metabolic function of chondrocytes and to possibly restore or further breakdown the cartilage tissue in different stages of osteoarthritis. In this study the transport of charged solutes across the various zones of cartilage was quantified, taken into account the physicochemical interactions between the solute and the cartilage constituents. A multiphasic finite-bath finite element (FE) model was developed to simulate equine cartilage diffusion experiments that used a negatively charged contrast agent (ioxaglate) in combination with serial micro-computed tomography (micro-CT) to measure the diffusion. By comparing the FE model with the experimental data both the diffusion coefficient of ioxaglate and the fixed charge density (FCD) were obtained. In the multiphasic model, cartilage was divided into multiple (three) zones to help understand how diffusion coefficient and FCD vary across cartilage thickness. The direct effects of charged solute-FCD interaction on diffusion were investigated by comparing the diffusion coefficients derived from the multiphasic and biphasic-solute models. We found a relationship between the FCD obtained by the multiphasic model and ioxaglate partitioning obtained from micro-CT experiments. Using our multi-zone multiphasic model, diffusion coefficient of the superficial zone was up to ten-fold higher than that of the middle zone, while the FCD of the middle zone was up to almost two-fold higher than that of the superficial zone. In conclusion, the developed finite-bath multiphasic model provides us with a non-destructive method by which we could obtain both diffusion coefficient and FCD of different cartilage zones. The outcomes of the current work will also help understand how charge of the bath affects the diffusion of a charged molecule and also predict the diffusion behavior of a charged solute across articular cartilage. Copyright © 2016 Elsevier Ltd. All
Atlabachew, Abunu; Shu, Longcang; Wu, Peipeng; Zhang, Yongjie; Xu, Yang
2018-03-01
This laboratory study improves the understanding of the impacts of horizontal hydraulic gradient, artificial recharge, and groundwater pumping on solute transport through aquifers. Nine experiments and numerical simulations were carried out using a sand tank. The variable-density groundwater flow and sodium chloride transport were simulated using the three-dimensional numerical model SEAWAT. Numerical modelling results successfully reproduced heads and concentrations observed in the sand tank. A higher horizontal hydraulic gradient enhanced the migration of sodium chloride, particularly in the groundwater flow direction. The application of constant artificial recharge increased the spread of the sodium chloride plume in both the longitudinal and lateral directions. In addition, groundwater pumping accelerated spreading of the sodium chloride plume towards the pumping well. Both higher hydraulic gradient and pumping rate generated oval-shaped plumes in the horizontal plane. However, the artificial recharge process produced stretched plumes. These effects of artificial recharge and groundwater pumping were greater under higher hydraulic gradient. The concentration breakthrough curves indicated that emerging solutions never attained the concentration of the originally injected solution. This is probably because of sorption of sodium chloride onto the silica sand and/or the exchange of sodium chloride between the mobile and immobile liquid domains. The fingering and protruding plume shapes in the numerical models constitute instability zones produced by buoyancy-driven flow. Overall, the results have substantiated the influences of hydraulic gradient, boundary condition, artificial recharge, pumping rate and density differences on solute transport through a homogeneous unconfined aquifer. The implications of these findings are important for managing liquid wastes.
Samper, J.; Ajora, C. (Instituto de Ciencias de la Tierra, CSIC, Barcerlona (Spain))
1993-01-01
During subsurface transport, reactive solutes are subject to a variety of hydrodynamic and chemical processes. The major hydrodynamic processes include advection and convection, dispersion and diffusion. The key chemical processes are complexation including hydrolysis and acid-base reactions, dissolution-precipitation, reduction-oxidation, adsorption and ion exchange. The combined effects of all these processes on solute transport must satisfy the principle of conservation of mass. The statement of conservation of mass for N mobile species leads to N partial differential equations. Traditional solute transport models often incorporate the effects of hydrodynamic processes rigorously but oversimplify chemical interactions among aqueous species. Sophisticated chemical equilibrium models, on the other hand, incorporate a variety of chemical processes but generally assume no-flow systems. In the past decade, coupled models accounting for complex hydrological and chemical processes, with varying degrees of sophistication, have been developed. The existing models of reactive transport employ two basic sets of equations. The transport of solutes is described by a set of partial differential equations, and the chemical processes, under the assumption of equilibrium, are described by a set of nonlinear algebraic equations. An important consideration in any approach is the choice of primary dependent variables. Most existing models cannot account for the complete set of chemical processes, cannot be easily extended to include mixed chemical equilibria and kinetics, and cannot handle practical two and three dimensional problems. The difficulties arise mainly from improper selection of the primary variables in the transport equations. (Author) 38 refs.
Solute carrier transporters: Pharmacogenomics research ...
Aghogho
2010-12-27
Dec 27, 2010 ... This paper reviews the solute carrier transporters and highlights the fact that there is much to be learnt from .... transporters, drug targets, effect or proteins and meta- ... basolateral or apical plasma membrane of polarized cells,.
Jin, Byung-Ju; Smith, Alex J.
2016-01-01
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. PMID:27836940
Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel
2013-04-01
simulations differ in lateral scale reaching from 0.2 m to 1.5 m, while the height of the domain is kept constant to 1.5m. Strong material heterogeneity is realized through vertical layers of coarse and fine sand. Both materials remain permanently under liquid-flow-dominated ('stage1') evaporation conditions. Spatial moments as well as the dilution index (Kitanidis, 1994) are used for quantification of transport behaviour. Results show that, while all simulations led to anomalous transport, infiltration-evaporation cycles lead to faster solute leaching rates than solely infiltration at the same net-infiltration rate in both homogeneous and heterogeneous media. Flow and transport-paths significantly differed between infiltration and evaporation, resulting in lateral water fluxes and hence lateral solute transport. Variation of the width of the model domain shows faster leaching rates for domains with small horizontal extent.
A proposed strategy for the validation of ground-water flow and solute transport models
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
Transport of fluid and solutes in the body I. Formulation of a mathematical model.
Gyenge, C C; Bowen, B D; Reed, R K; Bert, J L
1999-09-01
A compartmental model of short-term whole body fluid, protein, and ion distribution and transport is formulated. The model comprises four compartments: a vascular and an interstitial compartment, each with an embedded cellular compartment. The present paper discusses the assumptions on which the model is based and describes the equations that make up the model. Fluid and protein transport parameters from a previously validated model as well as ionic exchange parameters from the literature or from statistical estimation [see companion paper: C. C. Gyenge, B. D. Bowen, R. K. Reed, and J. L. Bert. Am. J. Physiol. 277 (Heart Circ. Physiol. 46): H1228-H1240, 1999] are used in formulating the model. The dynamic model has the ability to simulate 1) transport across the capillary membrane of fluid, proteins, and small ions and their distribution between the vascular and interstitial compartments; 2) the changes in extracellular osmolarity; 3) the distribution and transport of water and ions associated with each of the cellular compartments; 4) the cellular transmembrane potential; and 5) the changes of volume in the four fluid compartments. The validation and testing of the proposed model against available experimental data are presented in the companion paper.
State-of-the-art in modeling solute and sediment transport in rivers
Sayre, W.W.
1980-01-01
This overview is structured around a comprehensive general model based on the conservation of mass principle as applied to dissolved and particulate constituents in rivers, with a few restricted but more specific examples that illustrate the state-of-the-art in modeling typical physical, chemical, and biological processes undergone by selected constituents in rivers. These examples include: simplified one- and two-dimensional formulations focusing on the hydrodynamic advection and dispersion mechanisms; a two-dimensional biochemial oxygen demand-dissolved oxygen model; a one-dimensional polychlorinated biphenyl model that includes uptake and release of constituent by suspended sediment, and deposition and erosion of contaminated particles; and a one-dimensional sediment transport model that accounts for interactions between the flow and the bed, and is capable of tracking dispersing slugs of sediment through cycles of erosion, entrainment, transport in suspension and as bed load, and burial and storage in the bed
Molinero, J.; Samper, J.
2003-01-01
Several countries around the world are considering the final disposal of high-level radioactive waste in deep repositories located in fractured granite formations. Evaluating the long term safety of such repositories requires sound conceptual and numerical models which must consider simultaneously groundwater flow, solute transport and chemical and radiological processes. These models are being developed from data and knowledge gained from in situ experiments carried out at deep underground laboratories such as that of Aspo, Sweden, constructed in fractured granite. The Redox Zone Experiment is one of such experiments performed at Aspo in order to evaluate the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Previous authors interpreted hydrochemical and isotopic data of this experiment using a mass-balance approach based on a qualitative description of groundwater flow conditions. Such an interpretation, however, is subject to uncertainties related to an over-simplified conceptualization of groundwater flow. Here we present numerical models of groundwater flow and solute transport for this fracture zone. The first model is based on previously published conceptual model. It presents noticeable un consistencies and fails to match simultaneously observed draw downs and chloride breakthrough curves. To overcome its limitations, a revised flow and transport model is presented which relies directly on available hydrodynamic and transport parameters, is based on the identification of appropriate flow and transport boundary conditions and uses, when needed, solute data extrapolated from nearby fracture zones. A significant quantitative improvement is achieved with the revised model because its results match simultaneously drawdown and chloride data. Other improvements are qualitative and include: ensuring consistency of hydrodynamic and hydrochemical data and avoiding
Guan, C.; Xie, H.J.; Wang, Y.Z.; Chen, Y.M.; Jiang, Y.S.; Tang, X.W.
2014-01-01
An analytical model for solute advection and dispersion in a two-layered liner consisting of a geosynthetic clay liner (GCL) and a soil liner (SL) considering the effect of biodegradation was proposed. The analytical solution was derived by Laplace transformation and was validated over a range of parameters using the finite-layer method based software Pollute v7.0. Results show that if the half-life of the solute in GCL is larger than 1 year, the degradation in GCL can be neglected for solute transport in GCL/SL. When the half-life of GCL is less than 1 year, neglecting the effect of degradation in GCL on solute migration will result in a large difference of relative base concentration of GCL/SL (e.g., 32% for the case with half-life of 0.01 year). The 100-year solute base concentration can be reduced by a factor of 2.2 when the hydraulic conductivity of the SL was reduced by an order of magnitude. The 100-year base concentration was reduced by a factor of 155 when the half life of the contaminant in the SL was reduced by an order of magnitude. The effect of degradation is more important in approving the groundwater protection level than the hydraulic conductivity. The analytical solution can be used for experimental data fitting, verification of complicated numerical models and preliminary design of landfill liner systems. - Highlights: •Degradation of contaminants was considered in modeling solute transport in GCL/SL. •Analytical solutions were derived for assessment of GCL/SL with degradation. •Degradation in GCL can be ignored as half-life is larger than 1 year. •Base concentration is more sensitive to half-life of SL than to permeability of SL
Guan, C. [Institute of Hydrology and Water Resources Engineering, Zhejiang University, Hangzhou 310058 (China); Xie, H.J., E-mail: xiehaijian@zju.edu.cn [Institute of Hydrology and Water Resources Engineering, Zhejiang University, Hangzhou 310058 (China); MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou 310058 (China); Wang, Y.Z.; Chen, Y.M.; Jiang, Y.S.; Tang, X.W. [MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou 310058 (China)
2014-01-01
An analytical model for solute advection and dispersion in a two-layered liner consisting of a geosynthetic clay liner (GCL) and a soil liner (SL) considering the effect of biodegradation was proposed. The analytical solution was derived by Laplace transformation and was validated over a range of parameters using the finite-layer method based software Pollute v7.0. Results show that if the half-life of the solute in GCL is larger than 1 year, the degradation in GCL can be neglected for solute transport in GCL/SL. When the half-life of GCL is less than 1 year, neglecting the effect of degradation in GCL on solute migration will result in a large difference of relative base concentration of GCL/SL (e.g., 32% for the case with half-life of 0.01 year). The 100-year solute base concentration can be reduced by a factor of 2.2 when the hydraulic conductivity of the SL was reduced by an order of magnitude. The 100-year base concentration was reduced by a factor of 155 when the half life of the contaminant in the SL was reduced by an order of magnitude. The effect of degradation is more important in approving the groundwater protection level than the hydraulic conductivity. The analytical solution can be used for experimental data fitting, verification of complicated numerical models and preliminary design of landfill liner systems. - Highlights: •Degradation of contaminants was considered in modeling solute transport in GCL/SL. •Analytical solutions were derived for assessment of GCL/SL with degradation. •Degradation in GCL can be ignored as half-life is larger than 1 year. •Base concentration is more sensitive to half-life of SL than to permeability of SL.
User's guide to revised method-of-characteristics solute-transport model (MOC--version 31)
Konikow, Leonard F.; Granato, G.E.; Hornberger, G.Z.
1994-01-01
The U.S. Geological Survey computer model to simulate two-dimensional solute transport and dispersion in ground water (Konikow and Bredehoeft, 1978; Goode and Konikow, 1989) has been modified to improve management of input and output data and to provide progressive run-time information. All opening and closing of files are now done automatically by the program. Names of input data files are entered either interactively or using a batch-mode script file. Names of output files, created automatically by the program, are based on the name of the input file. In the interactive mode, messages are written to the screen during execution to allow the user to monitor the status and progress of the simulation and to anticipate total running time. Information reported and updated during a simulation include the current pumping period and time step, number of particle moves, and percentage completion of the current time step. The batch mode enables a user to run a series of simulations consecutively, without additional control. A report of the model's activity in the batch mode is written to a separate output file, allowing later review. The user has several options for creating separate output files for different types of data. The formats are compatible with many commercially available applications, which facilitates graphical postprocessing of model results. Geohydrology and Evaluation of Stream-Aquifer Relations in the Apalachicola-Chattahoochee-Flint River Basin, Southeastern Alabama, Northwestern Florida, and Southwestern Georgia By Lynn J. Torak, Gary S. Davis, George A. Strain, and Jennifer G. Herndon Abstract The lower Apalachieola-Chattahoochec-Flint River Basin is underlain by Coastal Plain sediments of pre-Cretaceous to Quaternary age consisting of alternating units of sand, clay, sandstone, dolomite, and limestone that gradually thicken and dip gently to the southeast. The stream-aquifer system consism of carbonate (limestone and dolomite) and elastic sediments
Gylling, B.
1997-01-01
The Channel Network model and its computer implementation, the code CHAN3D, for simulations of fluid flow and transport of solutes have been developed. The tool may be used for performance and safety assessments of deep lying repositories in fractured rocks for nuclear and other hazardous wastes, e.g. chemical wastes. It may also be used to simulate and interpret field experiments of flow and transport in large or small scale. Fluid flow and solute transport in fractured media are of interest in the performance assessment of a repository for hazardous waste, located at depth in crystalline rock, with potential release of solutes. Fluid flow in fractured rock is found to be very unevenly distributed due to the heterogeneity of the medium. The water will seek the easiest path, channels, under a prevailing pressure gradient. Solutes in the flowing water may be transported through preferential paths and migrate from the water in the fractures into the stagnant water in the rock matrix. There, sorbing solutes may be sorbed on the micro surfaces within the matrix. The diffusion into the matrix and the sorption process may significantly retard the transport of species and increase the time available for radionuclide decay. Channelling and matrix diffusion contribute to the dispersion of solutes in the water. Important for performance assessment is that channeling may cause a portion of the solutes to arrive much faster than the rest of the solutes. Simulations of field experiments at the Aespoe Hard Rock Laboratory using the Channel Network model have been performed. The application of the model to the site and the simulation results of the pumping and tracer tests are presented. The results show that the model is capable of describing the hydraulic gradient and of predicting flow rates and tracer transport obtained in the experiments. The data requirements for the Channel Network model have been investigated to determine which data are the most important for predictions
Faure, M.H.
1994-03-01
Understanding the mechanisms which control the transient transport of particles and radionuclides in natural and artificial porous media is a key problem for the assessment of safety of radioactive waste disposals. An experimental study has been performed to characterize the clayey particle mobility in porous media: a laboratory- made column, packed with an unconsolidated sand bentonite (5% weight) sample, is flushed with a salt solution. An original method of salinity gradient allowed us to show and to quantify some typical behaviours of this system: threshold effects in the peptization of particles, creation of preferential pathways, formation of immobile water zones induce solute-transfer limitation. The mathematical modelling accounts for a phenomenological law, where the distribution of particles between the stagnant water zone and the porous medium is a function of sodium chloride concentration. This distribution function is associated with a radionuclide adsorption model, and is included in a convective dispersive transport model with stagnant water zones. It allowed us to simulate the particle and solute transport when the salt environment is modified. The complete model has been validated with experiments involving cesium, calcium and neptunium in a sodium chloride gradient. (author). refs., figs., tabs
Winston, Richard B.; Konikow, Leonard F.; Hornberger, George Z.
2018-02-16
In the traditional method of characteristics for groundwater solute-transport models, advective transport is represented by moving particles that track concentration. This approach can lead to global mass-balance problems because in models of aquifers having complex boundary conditions and heterogeneous properties, particles can originate in cells having different pore volumes and (or) be introduced (or removed) at cells representing fluid sources (or sinks) of varying strengths. Use of volume-weighted particles means that each particle tracks solute mass. In source or sink cells, the changes in particle weights will match the volume of water added or removed through external fluxes. This enables the new method to conserve mass in source or sink cells as well as globally. This approach also leads to potential efficiencies by allowing the number of particles per cell to vary spatially—using more particles where concentration gradients are high and fewer where gradients are low. The approach also eliminates the need for the model user to have to distinguish between “weak” and “strong” fluid source (or sink) cells. The new model determines whether solute mass added by fluid sources in a cell should be represented by (1) new particles having weights representing appropriate fractions of the volume of water added by the source, or (2) distributing the solute mass added over all particles already in the source cell. The first option is more appropriate for the condition of a strong source; the latter option is more appropriate for a weak source. At sinks, decisions whether or not to remove a particle are replaced by a reduction in particle weight in proportion to the volume of water removed. A number of test cases demonstrate that the new method works well and conserves mass. The method is incorporated into a new version of the U.S. Geological Survey’s MODFLOW–GWT solute-transport model.
Garcia, R.D.M.
2015-01-01
Highlights: • An improved 1-D model of 3-D particle transport in ducts is studied. • The cases of isotropic and directional incidence are treated with the ADO method. • Accurate numerical results are reported for ducts of circular cross section. • A comparison with results of other authors is included. • The ADO method is found to be very efficient. - Abstract: An analytical discrete-ordinates solution is developed for the problem of particle transport in ducts, as described by a one-dimensional model constructed with two basis functions. Two types of particle incidence are considered: isotropic incidence and incidence described by the Dirac delta distribution. Accurate numerical results are tabulated for the reflection probabilities of semi-infinite ducts and the reflection and transmission probabilities of finite ducts. It is concluded that the developed solution is more efficient than commonly used numerical implementations of the discrete-ordinates method.
Minimum requirements for predictive pore-network modeling of solute transport in micromodels
Mehmani, Yashar; Tchelepi, Hamdi A.
2017-10-01
Pore-scale models are now an integral part of analyzing fluid dynamics in porous materials (e.g., rocks, soils, fuel cells). Pore network models (PNM) are particularly attractive due to their computational efficiency. However, quantitative predictions with PNM have not always been successful. We focus on single-phase transport of a passive tracer under advection-dominated regimes and compare PNM with high-fidelity direct numerical simulations (DNS) for a range of micromodel heterogeneities. We identify the minimum requirements for predictive PNM of transport. They are: (a) flow-based network extraction, i.e., discretizing the pore space based on the underlying velocity field, (b) a Lagrangian (particle tracking) simulation framework, and (c) accurate transfer of particles from one pore throat to the next. We develop novel network extraction and particle tracking PNM methods that meet these requirements. Moreover, we show that certain established PNM practices in the literature can result in first-order errors in modeling advection-dominated transport. They include: all Eulerian PNMs, networks extracted based on geometric metrics only, and flux-based nodal transfer probabilities. Preliminary results for a 3D sphere pack are also presented. The simulation inputs for this work are made public to serve as a benchmark for the research community.
de Vries, Enno T.; Raoof, Amir; van Genuchten, Martinus Th.
2017-07-01
Many environmental and agricultural applications involve the transport of water and dissolved constituents through aggregated soil profiles, or porous media that are structured, fractured or macroporous in other ways. During the past several decades, various process-based macroscopic models have been used to simulate contaminant transport in such media. Many of these models consider advective-dispersive transport through relatively large inter-aggregate pore domains, while exchange with the smaller intra-aggregate pores is assumed to be controlled by diffusion. Exchange of solute between the two domains is often represented using a first-order mass transfer coefficient, which is commonly obtained by fitting to observed data. This study aims to understand and quantify the solute exchange term by applying a dual-porosity pore-scale network model to relatively large domains, and analysing the pore-scale results in terms of the classical dual-porosity (mobile-immobile) transport formulation. We examined the effects of key parameters (notably aggregate porosity and aggregate permeability) on the main dual-porosity model parameters, i.e., the mobile water fraction (ϕm) and the mass transfer coefficient (α). Results were obtained for a wide range of aggregate porosities (between 0.082 and 0.700). The effect of aggregate permeability was explored by varying pore throat sizes within the aggregates. Solute breakthrough curves (BTCs) obtained with the pore-scale network model at several locations along the domain were analysed using analytical solutions of the dual-porosity model to obtain estimates of ϕm and α. An increase in aggregate porosity was found to decrease ϕm and increase α, leading to considerable tailing in the BTCs. Changes in the aggregate pore throat size affected the relative flow velocity between the intra- and inter-aggregate domains. Higher flow velocities within the aggregates caused a change in the transport regime from diffusion dominated to more
Liu, Longcheng; Neretnieks, Ivars; Shahkarami, Pirouz; Meng, Shuo; Moreno, Luis
2018-02-01
A simple and robust solution is developed for the problem of solute transport along a single fracture in a porous rock. The solution is referred to as the solution to the single-flow-path model and takes the form of a convolution of two functions. The first function is the probability density function of residence-time distribution of a conservative solute in the fracture-only system as if the rock matrix is impermeable. The second function is the response of the fracture-matrix system to the input source when Fickian-type dispersion is completely neglected; thus, the effects of Fickian-type dispersion and matrix diffusion have been decoupled. It is also found that the solution can be understood in a way in line with the concept of velocity dispersion in fractured rocks. The solution is therefore extended into more general cases to also account for velocity variation between the channels. This leads to a development of the multi-channel model followed by detailed statistical descriptions of channel properties and sensitivity analysis of the model upon changes in the model key parameters. The simulation results obtained by the multi-channel model in this study fairly well agree with what is often observed in field experiments—i.e. the unchanged Peclet number with distance, which cannot be predicted by the classical advection-dispersion equation. In light of the findings from the aforementioned analysis, it is suggested that forced-gradient experiments can result in considerably different estimates of dispersivity compared to what can be found in natural-gradient systems for typical channel widths.
Modeling the solute transport by particle-tracing method with variable weights
Jiang, J.
2016-12-01
Particle-tracing method is usually used to simulate the solute transport in fracture media. In this method, the concentration at one point is proportional to number of particles visiting this point. However, this method is rather inefficient at the points with small concentration. Few particles visit these points, which leads to violent oscillation or gives zero value of concentration. In this paper, we proposed a particle-tracing method with variable weights. The concentration at one point is proportional to the sum of the weights of the particles visiting it. It adjusts the weight factors during simulations according to the estimated probabilities of corresponding walks. If the weight W of a tracking particle is larger than the relative concentration C at the corresponding site, the tracking particle will be splitted into Int(W/C) copies and each copy will be simulated independently with the weight W/Int(W/C) . If the weight W of a tracking particle is less than the relative concentration C at the corresponding site, the tracking particle will be continually tracked with a probability W/C and the weight will be adjusted to be C. By adjusting weights, the number of visiting particles distributes evenly in the whole range. Through this variable weights scheme, we can eliminate the violent oscillation and increase the accuracy of orders of magnitudes.
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.
Solute transport in crystalline rocks at Aspö--I: geological basis and model calibration.
Mazurek, Martin; Jakob, Andreas; Bossart, Paul
2003-03-01
Water-conducting faults and fractures were studied in the granite-hosted Aspö Hard Rock Laboratory (SE Sweden). On a scale of decametres and larger, steeply dipping faults dominate and contain a variety of different fault rocks (mylonites, cataclasites, fault gouges). On a smaller scale, somewhat less regular fracture patterns were found. Conceptual models of the fault and fracture geometries and of the properties of rock types adjacent to fractures were derived and used as input for the modelling of in situ dipole tracer tests that were conducted in the framework of the Tracer Retention Understanding Experiment (TRUE-1) on a scale of metres. After the identification of all relevant transport and retardation processes, blind predictions of the breakthroughs of conservative to moderately sorbing tracers were calculated and then compared with the experimental data. This paper provides the geological basis and model calibration, while the predictive and inverse modelling work is the topic of the companion paper [J. Contam. Hydrol. 61 (2003) 175]. The TRUE-1 experimental volume is highly fractured and contains the same types of fault rocks and alterations as on the decametric scale. The experimental flow field was modelled on the basis of a 2D-streamtube formalism with an underlying homogeneous and isotropic transmissivity field. Tracer transport was modelled using the dual porosity medium approach, which is linked to the flow model by the flow porosity. Given the substantial pumping rates in the extraction borehole, the transport domain has a maximum width of a few centimetres only. It is concluded that both the uncertainty with regard to the length of individual fractures and the detailed geometry of the network along the flowpath between injection and extraction boreholes are not critical because flow is largely one-dimensional, whether through a single fracture or a network. Process identification and model calibration were based on a single uranine breakthrough
Mortuza, S.M.; Taufique, M.F.N.; Banerjee, Soumik, E-mail: soumik.banerjee@wsu.edu
2017-02-01
Highlights: • The model determined the surface coverage of solution-processed film on perovskite. • Calculated surface density map provides insight into morphology of the monolayer. • Carbonyl oxygen atom of PCBM strongly attaches to the (110) surface of perovskite. • Uniform distribution of clusters on perovskite surface at lower PCBM concentration. • Deposition rate of PCBM on the surface is very high at initial stage of film growth. - Abstract: The power conversion efficiency (PCE) of planar perovskite solar cells (PSCs) has reached up to ∼20%. However, structural and chemicals defects that lead to hysteresis in the perovskite based thin film pose challenges. Recent work has shown that thin films of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) deposited on the photo absorption layer, using solution processing techniques, minimize surface pin holes and defects thereby increasing the PCE. We developed and employed a multiscale model based on molecular dynamics (MD) and kinetic Monte Carlo (kMC) to establish a relationship between deposition rate and surface coverage on perovskite surface. The MD simulations of PCBMs dispersed in chlorobenzene, sandwiched between (110) perovskite substrates, indicate that PCBMs are deposited through anchoring of the oxygen atom of carbonyl group to the exposed lead (Pb) atom of (110) perovskite surface. Based on rates of distinct deposition events calculated from MD, kMC simulations were run to determine surface coverage at much larger time and length scales than accessible by MD alone. Based on the model, a generic relationship is established between deposition rate of PCBMs and surface coverage on perovskite crystal. The study also provides detailed insights into the morphology of the deposited film.
Mortuza, S.M.; Taufique, M.F.N.; Banerjee, Soumik
2017-01-01
Highlights: • The model determined the surface coverage of solution-processed film on perovskite. • Calculated surface density map provides insight into morphology of the monolayer. • Carbonyl oxygen atom of PCBM strongly attaches to the (110) surface of perovskite. • Uniform distribution of clusters on perovskite surface at lower PCBM concentration. • Deposition rate of PCBM on the surface is very high at initial stage of film growth. - Abstract: The power conversion efficiency (PCE) of planar perovskite solar cells (PSCs) has reached up to ∼20%. However, structural and chemicals defects that lead to hysteresis in the perovskite based thin film pose challenges. Recent work has shown that thin films of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) deposited on the photo absorption layer, using solution processing techniques, minimize surface pin holes and defects thereby increasing the PCE. We developed and employed a multiscale model based on molecular dynamics (MD) and kinetic Monte Carlo (kMC) to establish a relationship between deposition rate and surface coverage on perovskite surface. The MD simulations of PCBMs dispersed in chlorobenzene, sandwiched between (110) perovskite substrates, indicate that PCBMs are deposited through anchoring of the oxygen atom of carbonyl group to the exposed lead (Pb) atom of (110) perovskite surface. Based on rates of distinct deposition events calculated from MD, kMC simulations were run to determine surface coverage at much larger time and length scales than accessible by MD alone. Based on the model, a generic relationship is established between deposition rate of PCBMs and surface coverage on perovskite crystal. The study also provides detailed insights into the morphology of the deposited film.
Stanko Ružičić
2012-12-01
Full Text Available Conceptual model of flow and solute transport in unsaturated zone at Kosnica site, which is the basis for modeling pollution migration through the unsaturated zone to groundwater, is set up. The main characteristics of the unsaturated zone of the Kosnica site are described. Detailed description of investigated profile of unsaturated zone, with all necessary analytical results performed and used in building of conceptual models, is presented. Experiments that are in progress and processes which are modeled are stated. Monitoring of parameters necessary for calibration of models is presented. The ultimate goal of research is risk assessment of groundwater contamination at Kosnica site that has its source in or on unsaturated zone.
Nourtier-Mazauric, E.
2003-03-15
This thesis presents a thermodynamic and kinetic model of interactions between a fluid and ideal solid solutions represented by several end-members. The reaction between a solid solution and the aqueous solution results from the competition between the stoichiometric dissolution of the initial solid solution and the co-precipitation of the least soluble solid solution in the fluid at considered time. This model was implemented in ARCHIMEDE, a computer code of reactive transport in porous media, then applied to various examples. In the case of binary solid solutions, a graphical method allowed to determine the compositions of the precipitating solid solutions, with the aid of the end-member chemical potentials. The obtained program could be used to notably model the diagenesis of clayey or carbonated oil reservoirs, or the ground pollutant dispersion. (author)
Skouras, Eugene D.; Jaho, Sofia; Pavlakou, Efstathia I.; Sygouni, Varvara; Petsi, Anastasia; Paraskeva, Christakis A.
2015-04-01
The deposition of salts in porous media is a major engineering phenomenon encountered in a plethora of industrial and environmental applications where in some cases is desirable and in other not (oil production, geothermal systems, soil stabilization etc). Systematic approach of these problems requires knowledge of the key mechanisms of precipitating salts within the porous structures, in order to develop new methods to control the process. In this work, the development and the solution of spatiotemporally variable mass balances during salt solution mixing along specific pores were performed. Both analytical models and finite differences CFD models were applied for the study of flow and transport with simultaneous homogeneous and heterogeneous nucleation (by crystal growth on the surface of the pores) in simple geometries, while unstructured finite elements and meshless methods were developed and implemented for spatial discretization, reconstruction, and solution of transport equations and homogeneous / heterogeneous reactions in more complex geometries. At initial stages of this work, critical problem parameters were identified, such as the characteristics of the porosity, the number of dissolved components, etc. The parameters were then used for solving problems which correspond to available experimental data. For each combination of ions and materials, specific data and process characteristics were included: (a) crystal kinetics (nucleation, growth rates or reaction surface rates of crystals, critical suspension concentrations), (b) physico-chemical properties (bulk density, dimensions of generated crystals, ion diffusion coefficients in the solution), (c) operating parameters (macroscopic velocity, flow, or pressure gradient of the solution, ion concentration) (d) microfluidic data (geometry, flow area), (e) porosity data in Darcy description (initial porosity, specific surface area, tortuosity). During the modeling of flow and transport in three
Underdown, C. G.; Boutt, D. F.; Hynek, S. A.; Munk, L. A.
2017-12-01
Importance of transience in managed groundwater systems is generally determined by timeframe of management decisions. Watersheds with management times shorter than the aquifer (watershed) response time, or the time it takes a watershed to recover from a change in hydrologic state, would not include the new state and are treated as steady-state. However, these watersheds will experience transient response between hydrologic states. Watershed response time is a function of length. Therefore flat, regional watersheds characteristic of the Great Basin have long response times. Defining watershed extents as the area in which the water budget is balanced means inputs equal outputs. Steady-state budgets in the Great Basin have been balanced by extending watershed boundaries to include more area for recharge; however, the length and age of requisite flow paths are poorly constrained and often unrealistic. Inclusion of stored water in hydrologic budget calculations permits water balance within smaller contributing areas. As groundwater flow path lengths, depths, and locations differ between steady-state and transient systems, so do solute transport mechanisms. To observe how transience affects response time and solute transport, a refined (transient) version of the USGS steady-state groundwater flow model of the Great Basin is evaluated. This model is used to assess transient changes in contributing area for Clayton Valley, a lithium-brine producing endorheic basin in southwestern Nevada. Model runs of various recharge, discharge and storage bounds are created from conceptual models based upon historical climate data. Comparing results of the refined model to USGS groundwater observations allows for model validation and comparison against the USGS steady-state model. The transient contributing area to Clayton Valley is 85% smaller than that calculated from the steady-state solution, however several long flow paths important to both water and solute budgets at Clayton Valley
Aespoe Task Force on modelling of groundwater flow and transport of solutes. Review of Task 6C
Black, John; Hodgkinson, David
2005-03-01
This report forms part of an independent review of the specifications, execution and results of Task 6 of the Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes, which is seeking to provide a bridge between site characterization (SC) and performance assessment (PA) approaches to solute transport in fractured rock. The present report is concerned solely with Task 6C, which relates to the construction and parametrisation of a block-scale hydrostructural model of the TRUE Block Scale region of the Aespoe Hard Rock laboratory. The task objectives, specifications and outcome are summarised and reviewed. Also, consideration is given to how the hydrostructural model might affect the outcomes of Task 6D and 6E. The main conclusions of this review are summarised below: The Task 6C hydrostructural model is a more comprehensive approach to quantitatively describing a volume of fractured rock than has been achieved hitherto. The idea of including solute retention characteristics as indices attached to individual fractures is an efficient device resulting in a whole volume of fractured rock described by a few spreadsheets. The hydrostructural model is clearly defined and provides a useful test bed for Tasks 6D and 6E. It would have been beneficial if the specifications for Task 6C had been more clearly defined as a hierarchy of requirements, and performance measures had been defined and evaluated to allow comparison of alternative approaches. The device used to reduce connectivity, namely reducing the average size of background fractures, has the effect of producing a final model with an 'unnatural' gap in the overall distribution of fracture sizes. It appears that the exploratory boreholes could be important conductive structures within the region of the 200 m block even though they are segmented into shorter sections by packers. If correct, this implies that the boreholes should be included explicitly in the model if close replication of TRUE Block
Davit, Y.
2012-07-26
In this work, we study the transient behavior of homogenized models for solute transport in two-region porous media. We focus on the following three models: (1) a time non-local, two-equation model (2eq-nlt). This model does not rely on time constraints and, therefore, is particularly useful in the short-time regime, when the timescale of interest (t) is smaller than the characteristic time (τ 1) for the relaxation of the effective macroscale parameters (i. e., when t ≤ τ 1); (2) a time local, two-equation model (2eq). This model can be adopted when (t) is significantly larger than (τ 1) (i.e., when t≫τ 1); and (3) a one-equation, time-asymptotic formulation (1eq ∞). This model can be adopted when (t) is significantly larger than the timescale (τ 2) associated with exchange processes between the two regions (i. e., when t≫τ 2). In order to obtain insight into this transient behavior, we combine a theoretical approach based on the analysis of spatial moments with numerical and analytical results in several simple cases. The main result of this paper is to show that there is only a weak asymptotic convergence of the solution of (2eq) towards the solution of (1eq ∞) in terms of standardized moments but, interestingly, not in terms of centered moments. The physical interpretation of this result is that deviations from the Fickian situation persist in the limit of long times but that the spreading of the solute is eventually dominating these higher order effects. © 2012 Springer Science+Business Media B.V.
Modelling of present and future hydrology and solute transport at Forsmark. SR-Site Biosphere
Bosson, Emma; Sassner, Mona; Sabel, Ulrika; Gustafsson, Lars-Goeran
2010-10-01
Radioactive waste from nuclear power plants in Sweden is managed by the Swedish Nuclear Fuel and Waste Management Co, SKB. SKB has performed site investigations at two different locations in Sweden, referred to as the Forsmark and Laxemar-Simpevarp areas, with the objective of siting a final repository for high-level radioactive waste. In 2009 a decision was made to focus on the Forsmark site. This decision was based on a large amount of empirical evidence suggesting Forsmark to be more suitable for a geological repository /SKB 2010b/. This report presents model results of numerical flow and transport modelling of surface water and near-surface groundwater at the Forsmark site for present and future conditions. Both temperate and periglacial climates have been simulated. Also different locations of the shoreline have been applied to the model, as well as different models of vegetation and Quaternary deposits. The modelling was performed using the modelling tool MIKE SHE and was based on the SDM-Site Forsmark MIKE SHE model (presented by Bosson et al. in SKB report R-08-09). The present work is a part of the biosphere modelling performed for the SR-Site safety assessment. The Forsmark area has a flat, small-scale topography. The study area is almost entirely below 20 m.a.s.l. (metres above sea level). There is a strong correlation between the topography of the ground surface and the ground water level in the Quaternary deposits (QD); thus, the surface water divides and the groundwater divides for the QD can be assumed to coincide. No major water courses flow through the catchment. Small brooks, which often dry out in the summer, connect the different sub-catchments with each other. The main lakes in the area, Lake Bolundsfjaerden, Lake Fiskarfjaerden, Lake Gaellsbotraesket and Lake Eckarfjaerden, all have sizes of less than one km2. The lakes are in general shallow. Approximately 70% of the catchment areas are covered by forest. Agricultural land is only present in
Modelling of present and future hydrology and solute transport at Forsmark. SR-Site Biosphere
Bosson, Emma (Swedish Nuclear Fuel and Waste Management Co., Stocholm (Sweden)); Sassner, Mona; Sabel, Ulrika; Gustafsson, Lars-Goeran (DHI Sverige AB (Sweden))
2010-10-15
Radioactive waste from nuclear power plants in Sweden is managed by the Swedish Nuclear Fuel and Waste Management Co, SKB. SKB has performed site investigations at two different locations in Sweden, referred to as the Forsmark and Laxemar-Simpevarp areas, with the objective of siting a final repository for high-level radioactive waste. In 2009 a decision was made to focus on the Forsmark site. This decision was based on a large amount of empirical evidence suggesting Forsmark to be more suitable for a geological repository /SKB 2010b/. This report presents model results of numerical flow and transport modelling of surface water and near-surface groundwater at the Forsmark site for present and future conditions. Both temperate and periglacial climates have been simulated. Also different locations of the shoreline have been applied to the model, as well as different models of vegetation and Quaternary deposits. The modelling was performed using the modelling tool MIKE SHE and was based on the SDM-Site Forsmark MIKE SHE model (presented by Bosson et al. in SKB report R-08-09). The present work is a part of the biosphere modelling performed for the SR-Site safety assessment. The Forsmark area has a flat, small-scale topography. The study area is almost entirely below 20 m.a.s.l. (metres above sea level). There is a strong correlation between the topography of the ground surface and the ground water level in the Quaternary deposits (QD); thus, the surface water divides and the groundwater divides for the QD can be assumed to coincide. No major water courses flow through the catchment. Small brooks, which often dry out in the summer, connect the different sub-catchments with each other. The main lakes in the area, Lake Bolundsfjaerden, Lake Fiskarfjaerden, Lake Gaellsbotraesket and Lake Eckarfjaerden, all have sizes of less than one km2. The lakes are in general shallow. Approximately 70% of the catchment areas are covered by forest. Agricultural land is only present in
Walton-Day, Katherine; Runkel, Robert L.; Kimball, Briant A.
2012-01-01
Spatially detailed mass-loading studies and solute-transport modeling using OTIS (One-dimensional Transport with Inflow and Storage) demonstrate how natural attenuation and loading from distinct and diffuse sources control stream water quality and affect load reductions predicted in total maximum daily loads (TMDLs). Mass-loading data collected during low-flow from Cement Creek (a low-pH, metal-rich stream because of natural and mining sources, and subject to TMDL requirements) were used to calibrate OTIS and showed spatially variable effects of natural attenuation (instream reactions) and loading from diffuse (groundwater) and distinct sources. OTIS simulations of the possible effects of TMDL-recommended remediation of mine sites showed less improvement to dissolved zinc load and concentration (14% decrease) than did the TMDL (53-63% decrease). The TMDL (1) assumed conservative transport, (2) accounted for loads removed by remediation by subtracting them from total load at the stream mouth, and (3) did not include diffuse-source loads. In OTIS, loads were reduced near their source; the resulting concentration was decreased by natural attenuation and increased by diffuse-source loads during downstream transport. Thus, by not including natural attenuation and loading from diffuse sources, the TMDL overestimated remediation effects at low flow. Use of the techniques presented herein could improve TMDLs by incorporating these processes during TMDL development.
J. Moeys
2012-07-01
Full Text Available Estimating pesticide leaching risks at the regional scale requires the ability to completely parameterise a pesticide fate model using only survey data, such as soil and land-use maps. Such parameterisations usually rely on a set of lookup tables and (pedotransfer functions, relating elementary soil and site properties to model parameters. The aim of this paper is to describe and test a complete set of parameter estimation algorithms developed for the pesticide fate model MACRO, which accounts for preferential flow in soil macropores. We used tracer monitoring data from 16 lysimeter studies, carried out in three European countries, to evaluate the ability of MACRO and this "blind parameterisation" scheme to reproduce measured solute leaching at the base of each lysimeter. We focused on the prediction of early tracer breakthrough due to preferential flow, because this is critical for pesticide leaching. We then calibrated a selected number of parameters in order to assess to what extent the prediction of water and solute leaching could be improved.
Our results show that water flow was generally reasonably well predicted (median model efficiency, ME, of 0.42. Although the general pattern of solute leaching was reproduced well by the model, the overall model efficiency was low (median ME = −0.26 due to errors in the timing and magnitude of some peaks. Preferential solute leaching at early pore volumes was also systematically underestimated. Nonetheless, the ranking of soils according to solute loads at early pore volumes was reasonably well estimated (concordance correlation coefficient, CCC, between 0.54 and 0.72. Moreover, we also found that ignoring macropore flow leads to a significant deterioration in the ability of the model to reproduce the observed leaching pattern, and especially the early breakthrough in some soils. Finally, the calibration procedure showed that improving the estimation of solute transport parameters is
Moeys, J.; Larsbo, M.; Bergström, L.; Brown, C. D.; Coquet, Y.; Jarvis, N. J.
2012-07-01
Estimating pesticide leaching risks at the regional scale requires the ability to completely parameterise a pesticide fate model using only survey data, such as soil and land-use maps. Such parameterisations usually rely on a set of lookup tables and (pedo)transfer functions, relating elementary soil and site properties to model parameters. The aim of this paper is to describe and test a complete set of parameter estimation algorithms developed for the pesticide fate model MACRO, which accounts for preferential flow in soil macropores. We used tracer monitoring data from 16 lysimeter studies, carried out in three European countries, to evaluate the ability of MACRO and this "blind parameterisation" scheme to reproduce measured solute leaching at the base of each lysimeter. We focused on the prediction of early tracer breakthrough due to preferential flow, because this is critical for pesticide leaching. We then calibrated a selected number of parameters in order to assess to what extent the prediction of water and solute leaching could be improved. Our results show that water flow was generally reasonably well predicted (median model efficiency, ME, of 0.42). Although the general pattern of solute leaching was reproduced well by the model, the overall model efficiency was low (median ME = -0.26) due to errors in the timing and magnitude of some peaks. Preferential solute leaching at early pore volumes was also systematically underestimated. Nonetheless, the ranking of soils according to solute loads at early pore volumes was reasonably well estimated (concordance correlation coefficient, CCC, between 0.54 and 0.72). Moreover, we also found that ignoring macropore flow leads to a significant deterioration in the ability of the model to reproduce the observed leaching pattern, and especially the early breakthrough in some soils. Finally, the calibration procedure showed that improving the estimation of solute transport parameters is probably more important than the
Le, Tien Dung; Moyne, Christian; Murad, Marcio A.
2015-01-01
A new three-scale model is proposed to describe the movement of ionic species of different valences in swelling clays characterized by three separate length scales (nano, micro, and macro) and two levels of porosity (nano- and micropores). At the finest (nano) scale the medium is treated as charged clay particles saturated by aqueous electrolyte solution containing monovalent and divalent ions forming the electrical double layer. A new constitutive law is constructed for the disjoining pressure based on the numerical resolution of non-local problem at the nanoscale which, in contrast to the Poisson-Boltzmann theory for point charge ions, is capable of capturing the short-range interactions between the ions due to their finite size. At the intermediate scale (microscale), the two-phase homogenized particle/electrolyte solution system is represented by swollen clay clusters (or aggregates) with the nanoscale disjoining pressure incorporated in a modified form of Terzaghi's effective principle. At the macroscale, the electro-chemical-mechanical couplings within clay clusters is homogenized with the ion transport in the bulk fluid lying in the micro pores. The resultant macroscopic picture is governed by a three-scale model wherein ion transport takes place in the bulk solution strongly coupled with the mechanics of the clay clusters which play the role of sources/sinks of mass to the bulk fluid associated with ion adsorption/desorption in the electrical double layer at the nanoscale. Within the context of the quasi-steady version of the multiscale model, wherein the electrolyte solution in the nanopores is assumed at instantaneous thermodynamic equilibrium with the bulk fluid in the micropores, we build-up numerically the ion-adsorption isotherms along with the constitutive law of the retardation coefficients of monovalent and divalent ions. In addition, the constitutive law for the macroscopic swelling pressure is reconstructed numerically showing patterns of
Colombant, Denis; Manheimer, Wallace; Schmitt, Andrew J.
2013-10-01
At least two models, ours and SNB (Schurtz-Nicolai-Busquet), and two methods of solution, direct numerical solution (DS) and Greens function (GF) are being used in multi-dimensional radiation hydrodynamics codes. We present results of a laser target implosion using both methods of solution. Although our model and SNB differ in some physical content, direct comparisons have been non-existent up to now. However a paper by Marocchino et al. has recently presented the results of two nanosecond-time-scale test problems, showing that the preheat calculated by the two models are different by about three orders of magnitude. We have rerun these problems and we find much less difference between the two than they do. One can show analytically that the results should be quite similar and are about an order of magnitude less than the maximum, and two orders of magnitude more than the minimum preheating in. We have been able to trace the somewhat different results back to the different physical assumptions made in each model. Work supported by DoE-NNSA and ONR.
Marschall, Paul; Elert, Mark
2003-09-01
The Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. The task was carried out in 1995-2000 and consisted of several modelling exercises in support of the TRUE-1 tracer tests, including predictive modelling where experimental results were not available beforehand. This report presents an overall evaluation of the achievements of Task 4. The specific objectives of the overall evaluation were to highlight innovative and successful modelling approaches developed, to assess the stages of the task which proved most beneficial for conceptual understanding of transport processes at the TRUE-1 site and to assess the success of various steering tools. A concise summary of scientific achievements is given and conclusions drawn with respect to unresolved technical issues. Recommendations are presented that can optimise the management of future modelling tasks
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.
The modelling of heat, mass and solute transport in solidification systems
Voller, V. R.; Brent, A. D.; Prakash, C.
1989-01-01
The aim of this paper is to explore the range of possible one-phase models of binary alloy solidification. Starting from a general two-phase description, based on the two-fluid model, three limiting cases are identified which result in one-phase models of binary systems. Each of these models can be readily implemented in standard single phase flow numerical codes. Differences between predictions from these models are examined. In particular, the effects of the models on the predicted macro-segregation patterns are evaluated.
Stochastic Modeling Of Field-Scale Water And Solute Transport Through The Unsaturated Zone Of Soils
Loll, Per
were previously thought not to pose a leaching threat. Thus, a reevaluation of our understanding of the mechanisms governing chemical fate in the unsaturated zone of soils has been necessary, in order for us to make better decisions regarding widely different issues such as agricultural management...... of pesticides and nutrients, and risk identification and assessment at polluted (industrial) sites. One of the key factors requiring our attention when we are trying to predict field-scale chemical leaching is spatial variability of the soil and the influence it exerts on both water and chemical transport...
Papiez, L.; Moskvin, V.; Tulovsky, V.
2001-01-01
The process of angular-spatial evolution of multiple scattering of charged particles can be described by a special case of Boltzmann integro-differential equation called Lewis equation. The underlying stochastic process for this evolution is the compound Poisson process on the surface of the unit sphere. The significant portion of events that constitute compound Poisson process that describes multiple scattering have diffusional character. This property allows to analyze the process of angular-spatial evolution of multiple scattering of charged particles as combination of soft and hard collision processes and compute appropriately its transition densities. These computations provide a method of the approximate solution to the Lewis equation. (orig.)
Bader, S.; Kooi, H.
2005-01-01
Theories of osmosis in groundwater flow are increasingly used to explain anomalies of salinity in clayey environments. However, predictive modelling through mathematical analysis can hardly be found in literature. In this paper, a model of chemical osmosis based on non-equilibrium thermodynamics, is
Electrolyte solution transport in electropolar nanotubes
Zhao Jianbing; Culligan, Patricia J; Chen Xi; Qiao Yu; Zhou Qulan; Li Yibing; Tak, Moonho; Park, Taehyo
2010-01-01
Electrolyte transport in nanochannels plays an important role in a number of emerging areas. Using non-equilibrium molecular dynamics (NEMD) simulations, the fundamental transport behavior of an electrolyte/water solution in a confined model nanoenvironment is systematically investigated by varying the nanochannel dimension, solid phase, electrolyte phase, ion concentration and transport rate. It is found that the shear resistance encountered by the nanofluid strongly depends on these material/system parameters; furthermore, several effects are coupled. The mechanisms of the nanofluidic transport characteristics are explained by considering the unique molecular/ion structure formed inside the nanochannel. The lower shear resistance observed in some of the systems studies could be beneficial for nanoconductors, while the higher shear resistance (or higher effective viscosity) observed in other systems might enhance the performance of energy dissipation devices.
Modelling of groundwater flow and solute transport in Olkiluoto. Update 2008
Loefman, J.; Pitkaenen, P.; Meszaros, F.; Keto, V.; Ahokas, H.
2009-10-01
Posiva Oy is preparing for the final disposal of spent nuclear fuel in the crystalline bedrock in Finland. Olkiluoto in Eurajoki has been selected as the primary site for the repository, subject to further detailed characterisation which is currently focused on the construction of an underground rock characterisation and research facility (the ONKALO). An essential part of the site investigation programme is analysis of the deep groundwater flow by means of numerical flow modelling. This study is the latest update concerning the site-scale flow modelling and is based on all the hydrogeological data gathered from field investigations by the end of 2007. The work is divided into two separate modelling tasks: 1) characterization of the baseline groundwater flow conditions before excavation of the ONKALO, and 2) a prediction/outcome (P/O) study of the potential hydrogeological disturbances due to the ONKALO. The flow model was calibrated by using all the available data that was appropriate for the applied, deterministic, equivalent porous medium (EPM) / dual-porosity (DP) approach. In the baseline modelling, calibration of the flow model focused on improving the agreement between the calculated results and the undisturbed observations. The calibration resulted in a satisfactory agreement with the measured pumping test responses, a very good overall agreement with the observed pressures in the deep drill holes and a fairly good agreement with the observed salinity. Some discrepancies still remained in a few single drill hole sections, because the fresh water infiltration in the model tends to dilute the groundwater too much at shallow depths. In the P/O calculations the flow model was further calibrated by using the monitoring data on the ONKALO disturbances. Having significantly more information on the inflows to the tunnel (compared with the previous study) allowed better calibration of the model, which allowed it to capture very well the observed inflow, the
Peritoneal solute transport and inflammation.
Davies, Simon J
2014-12-01
The speed with which small solutes cross the peritoneal membrane, termed peritoneal solute transport rate (PSTR), is a key measure of individual membrane performance. PSTR can be quantified easily by using the 4-hour dialysate to plasma creatinine ratio, which, although only an approximation to the diffusive characteristics of the membrane, has been well validated clinically in terms of its relationship to patient survival and changes in longitudinal membrane function. This has led to changes in peritoneal dialysis modality use and dialysis prescription. An important determinant of PSTR is intraperitoneal inflammation, as exemplified by local interleukin 6 production, which is largely independent of systemic inflammation and its relationship to comorbid conditions and increased mortality. There is no strong evidence to support the contention that the peritoneal membrane in some individuals with high PSTR is qualitatively different at the start of treatment; rather, it represents a spectrum that is determined in part by genetic factors. Both clinical and experimental evidence support the view that persistent intraperitoneal inflammation, detected as a continuously high or increasing PSTR, may predispose the membrane to progressive fibrosis. Copyright © 2014 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
Lee, Jonghyun; Rolle, Massimo; Kitanidis, Peter K.
2018-01-01
Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and conc...
Andersen, Theis Raaschou; Poulsen, Søren Erbs; Thomsen, Peter
the two field sites includes only lithological profiles from boreholes. In order to increase the density of the field data, the two areas were mapped with Electrical Resistivity Tomography (ERT). Based on the borehole information and the high-density geophysical data, detailed 3D geological models...
Task force on modelling of groundwater flow and transport of solutes. Task 5 Summary report
Rhen, Ingvar [SWECO VIAK AB, Goeteborg (Sweden); Smellie, John [Conterra AB, Uppsala (Sweden)
2003-02-01
The Aespoe Hard Rock Laboratory is located in the Simpevarp area, southeast Sweden, some 35 km north of Oskarshamn. Construction of the underground laboratory commenced in 1990 and was completed in 1995, consisting of a 3.6 km. long tunnel excavated in crystalline rock to a depth of approximately 460 m. Prior to, during and subsequent to completion, research concerning the deep geological disposal of nuclear waste in fractured crystalline rock has been carried out. Central to this research has been the characterisation of the groundwater flow system and the chemistry of the groundwaters at Aespoe prior to excavation (Pre-investigation Phase) and subsequently to monitor changes in these parameters during the evolution of laboratory construction (Construction Phase). The principle aim of the Aespoe Task 5 modelling exercise has been to compare and ultimately integrate hydrogeochemistry and hydrogeology using the input data from the pre-investigation and construction phases. The main objectives were: to assess the consistency of groundwater-flow models and hydrogeochemical mixing-reaction models through integration and comparison of hydraulic and hydrogeochemical data obtained before and during tunnel construction, and to develop a procedure for integration of hydrological and hydrogeochemical information which could be used for disposal site assessments. Task 5 commenced in 1998 and was finalised in 2002. Participating modelling teams in the project represented ANDRA (France; three modelling teams - ANTEA, ITASCA, CEA), BMWi/BGR (Germany), ENRESA (Spain), JNC (Japan), CRIEPI (Japan), Posiva (Finland) and SKB (Sweden; two modelling teams - CFE and Intera (now GeoPoint)). Experience from Task 5 has highlighted several important aspects for site investigations facilitating the possibilities for mathematically integrated modelling and consistency checks that should be taken into account for future repository performance assessments. Equally important is that Task 5 has
Task force on modelling of groundwater flow and transport of solutes. Task 5 Summary report
Rhen, Ingvar; Smellie, John
2003-02-01
The Aespoe Hard Rock Laboratory is located in the Simpevarp area, southeast Sweden, some 35 km north of Oskarshamn. Construction of the underground laboratory commenced in 1990 and was completed in 1995, consisting of a 3.6 km. long tunnel excavated in crystalline rock to a depth of approximately 460 m. Prior to, during and subsequent to completion, research concerning the deep geological disposal of nuclear waste in fractured crystalline rock has been carried out. Central to this research has been the characterisation of the groundwater flow system and the chemistry of the groundwaters at Aespoe prior to excavation (Pre-investigation Phase) and subsequently to monitor changes in these parameters during the evolution of laboratory construction (Construction Phase). The principle aim of the Aespoe Task 5 modelling exercise has been to compare and ultimately integrate hydrogeochemistry and hydrogeology using the input data from the pre-investigation and construction phases. The main objectives were: to assess the consistency of groundwater-flow models and hydrogeochemical mixing-reaction models through integration and comparison of hydraulic and hydrogeochemical data obtained before and during tunnel construction, and to develop a procedure for integration of hydrological and hydrogeochemical information which could be used for disposal site assessments. Task 5 commenced in 1998 and was finalised in 2002. Participating modelling teams in the project represented ANDRA (France; three modelling teams - ANTEA, ITASCA, CEA), BMWi/BGR (Germany), ENRESA (Spain), JNC (Japan), CRIEPI (Japan), Posiva (Finland) and SKB (Sweden; two modelling teams - CFE and Intera (now GeoPoint)). Experience from Task 5 has highlighted several important aspects for site investigations facilitating the possibilities for mathematically integrated modelling and consistency checks that should be taken into account for future repository performance assessments. Equally important is that Task 5 has
Reactive solute transport in acidic streams
Broshears, R.E.
1996-01-01
Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.
The methods described in the report can be used with the modified N.R.C. version of the U.S.G.S. Solute Transport Model to predict the concentration of chemical parameters in a contaminant plume. The two volume report contains program documentation and user's manual. The program ...
Clothier, B. E.; van der Velde, M.; Green, S. R.; Gee, G. W.; Manu, V.; Menoniti, V.; Vanclooster, M.
2005-05-01
Intensification of agriculture on the raised coral atolls of the Tongan archipelago, notably through squash-pumpkin production, has lead to increased use of agrichemicals. Agrichemicals, both fertilisers and pesticides, pose a risk to these fragile environments. Sustainable land-management practices are needed for small-island developing states. On Tongatapu, solutes leaving the rootzone of the squash can rapidly find their way to the underlying freshwater lenses. These lenses are hydraulically linked to the internal lagoon, and the fringing reefs. We have used buried, non-suction fluxmeters to monitor both the quantity and quality of drainage leaving the rootzone of squash. Fertiliser is traditionally applied at planting. During establishment of the squash in 2003, some 350 mm of rain fell, with 70 % of this leaving the rootzone of this permeable soil as drainage. The concentration of nitrate-N in the drainage water was measured at around 50 mg-N/L. All of the initial fertiliser dressing had been lost, along with N mineralised from the plowed-in grass. Pesticides are needed in humid tropical environments to control weeds, pests and diseases. These chemicals can leach though the rootzone to contaminate receiving waters. We modeled the transport and fate of the presticides used in squash production, and we developed a Decision Support Tool (DST). Our DST can be used to select the best pesticides for local conditions, to tailor practices for minimising leaching losses below the rootzone, and to avoid the build-up of residues in the soil. This project, funded by the European Union and NZAID, took a multi-disciplinary approach through measurement and modeling protocols. Our DST enabled us to engage the wider community and stakeholders. There has been increased awareness of the impacts and risks associated with productive land management in the fragile hydrological environments of this small-island developing state.
Hodgkinson, David; Black, John
2005-03-01
This report forms part of an independent review of the specifications, execution and results of Task 6 of the Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes, which is seeking to provide a bridge between site characterization and performance assessment approaches to solute transport in fractured rock. The present report is concerned solely with Tasks 6b, 6b and 6b which relate to the transport of tracers on a 5-metre scale in Feature A at the TRUE-1 site. The task objectives, specifications and individual modelling team results are summarised and reviewed, and an evaluation of the overall exercise is presented. The report concludes with assessments of what has been learnt, the implications for the Task 6 objectives, and some possible future directions
Hodgkinson, David [Quintessa, Henley-on-Thames (United Kingdom); Black, John [In Situ Solutions, East Bridgford (United Kingdom)
2005-03-01
This report forms part of an independent review of the specifications, execution and results of Task 6 of the Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes, which is seeking to provide a bridge between site characterization and performance assessment approaches to solute transport in fractured rock. The present report is concerned solely with Tasks 6b, 6b and 6b which relate to the transport of tracers on a 5-metre scale in Feature A at the TRUE-1 site. The task objectives, specifications and individual modelling team results are summarised and reviewed, and an evaluation of the overall exercise is presented. The report concludes with assessments of what has been learnt, the implications for the Task 6 objectives, and some possible future directions.
Mass transport in polyelectrolyte solutions
Schipper, F. J. M.; Leyte, J. C.
1999-02-01
The self-diffusion coefficients of the three components of a salt-free heavy-water solution of polymethacrylic acid, completely neutralized with tetra-methylammonium hydroxide, were measured over a broad concentration range. Three concentration regions were observed for the self-diffusion of both the polyions and the counterions. At polyion concentrations below 0.01 mol monomer kg-1, the dilute concentration regime for the polymer, the polyion self-diffusion coefficient approaches the self-diffusion coefficient of a freely diffusing rod upon dilution. At polyelectrolyte concentrations above 0.1 mol monomer kg-1, the self-diffusion coefficients of the solvent, the counterions and the polymer decreased with concentration, suggesting that this decrease is due to a topological constraint on the motions of the components. In the intermediate-concentration region, the self-diffusion coefficients of the polyions and the counterions are independent of the concentration. The polyion dynamic behaviour is, in the intermediate- and high-concentration regions, reasonably well described by that of a hard sphere, with a radius of 3.7 nm. A correct prediction for the solvent dynamics is given by the obstruction effect of this hard sphere on the solvent. The relative counterion self-diffusion coefficient is predicted almost quantitatively over the entire concentration range with the Poisson-Boltzmann-Smoluchowski model for the spherical cell, provided that the sphere radius and the number of charges are chosen appropriately (approximately the number of charges in a persistence length). Using this model, the dependence of the counterion self-diffusion coefficient on the ionic strength, polyion concentration and counterion radius is calculated quantitatively over a large concentration range.
Bjerg, Poul Løgstrup; Ammentorp, Hans Christian; Christensen, Thomas Højlund
1993-01-01
A large-scale and long-term field experiment on cation exchange in a sandy aquifer has been modelled by a three-dimensional geochemical transport model. The geochemical model includes cation-exchange processes using a Gaines-Thomas expression, the closed carbonate system and the effects of ionic...... by batch experiments and by the composition of the cations on the exchange complex. Potassium showed a non-ideal exchange behaviour with K&z.sbnd;Ca selectivity coefficients indicating dependency on equivalent fraction and K+ concentration in the aqueous phase. The model simulations over a distance of 35 m...... and a period of 250 days described accurately the observed attenuation of Na and the expelled amounts of Ca and Mg. Also, model predictions of plateau zones, formed by interaction with the background groundwater, in general agreed satisfactorily with the observations. Transport of K was simulated over a period...
Urban Transportation: Issue and Solution
Haryati Shafii
2011-10-01
Full Text Available Generally, quality of life of urban population is heavily dependent on social facilities provided within the environment. One of the most important facilities is transportations. Study on transportation mode in an urban area is especially very important because for almost every individual living in a large and densely populated area, mobility is one of the most crucial issues in everyday life. Enhance mobility, faster journey to work and less pollution from petrol-propelled vehicles can increase the quality of life, which in turn lead to a sustainable urban living. The study present transportation mode usage issues faced by community related to quality of life in an urban area. This study identifies several issues of transportation mode in urban areas and its impact on the quality of life. The study areas are Putrajaya, Kuala Lumpur and Bandar Kajang, Selangor. The methodology used in this research is secondary and primary data. The questionnaires for the survey were distributed from May 2008 to Jun 2008. These researches were conducted on 144 respondents for to evaluate their perception of transportation mode correlated to the quality of life. The collected data were then analyzed using “Statistical Packages for the Social Science” (SPSS. The respondents comprise of 61 males and 84 females from the age group of 18 to 57 years. This study identifies the percentage of public transportation mode usage in urban area, such as buses (16.7%, train (ERL, monorail and commuter-6.4%; which is very low compared to owning personal car (45.8% and motorcycle (25.4%.The result shows owning personal car is the highest (45.8% in three study areas and monorail and taxi are the lowest (1.4%. The Chi Square Test shows that among the mode transportation with traffic jam is quite difference in Kuala Lumpur, Putrajaya and Kajang. Analysis of the Chi Square Test shows the result is 0.000 (two sides to respondent answering “yes” and analysis of Spearman
Cazalbou, J.-B.; Chassaing, P.
2002-02-01
The behavior of Reynolds-stress-transport models at the free-stream edges of turbulent flows is investigated. Current turbulent-diffusion models are found to produce propagative (possibly weak) solutions of the same type as those reported earlier by Cazalbou, Spalart, and Bradshaw [Phys. Fluids 6, 1797 (1994)] for two-equation models. As in the latter study, an analysis is presented that provides qualitative information on the flow structure predicted near the edge if a condition on the values of the diffusion constants is satisfied. In this case, the solution appears to be fairly insensitive to the residual free-stream turbulence levels needed with conventional numerical methods. The main specific result is that, depending on the diffusion model, the propagative solution can force turbulence toward definite and rather extreme anisotropy states at the edge (one- or two-component limit). This is not the case with the model of Daly and Harlow [Phys. Fluids 13, 2634 (1970)]; it may be one of the reasons why this "old" scheme is still the most widely used, even in recent Reynolds-stress-transport models. In addition, the analysis helps us to interpret some difficulties encountered in computing even very simple flows with Lumley's pressure-diffusion model [Adv. Appl. Mech. 18, 123 (1978)]. A new realizability condition, according to which the diffusion model should not globally become "anti-diffusive," is introduced, and a recalibration of Lumley's model satisfying this condition is performed using information drawn from the analysis.
Coupled geochemical and solute transport code development
Morrey, J.R.; Hostetler, C.J.
1985-01-01
A number of coupled geochemical hydrologic codes have been reported in the literature. Some of these codes have directly coupled the source-sink term to the solute transport equation. The current consensus seems to be that directly coupling hydrologic transport and chemical models through a series of interdependent differential equations is not feasible for multicomponent problems with complex geochemical processes (e.g., precipitation/dissolution reactions). A two-step process appears to be the required method of coupling codes for problems where a large suite of chemical reactions must be monitored. Two-step structure requires that the source-sink term in the transport equation is supplied by a geochemical code rather than by an analytical expression. We have developed a one-dimensional two-step coupled model designed to calculate relatively complex geochemical equilibria (CTM1D). Our geochemical module implements a Newton-Raphson algorithm to solve heterogeneous geochemical equilibria, involving up to 40 chemical components and 400 aqueous species. The geochemical module was designed to be efficient and compact. A revised version of the MINTEQ Code is used as a parent geochemical code
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
Haqshenas, S R; Ford, I J; Saffari, N
2018-01-14
Effects of acoustic waves on a phase transformation in a metastable phase were investigated in our previous work [S. R. Haqshenas, I. J. Ford, and N. Saffari, "Modelling the effect of acoustic waves on nucleation," J. Chem. Phys. 145, 024315 (2016)]. We developed a non-equimolar dividing surface cluster model and employed it to determine the thermodynamics and kinetics of crystallisation induced by an acoustic field in a mass-conserved system. In the present work, we developed a master equation based on a hybrid Szilard-Fokker-Planck model, which accounts for mass transportation due to acoustic waves. This model can determine the kinetics of nucleation and the early stage of growth of clusters including the Ostwald ripening phenomenon. It was solved numerically to calculate the kinetics of an isothermal sonocrystallisation process in a system with mass transportation. The simulation results show that the effect of mass transportation for different excitations depends on the waveform as well as the imposed boundary conditions and tends to be noticeable in the case of shock waves. The derivations are generic and can be used with any acoustic source and waveform.
Li, S.H.; Chen, C.T.
1997-01-01
Analytical solutions are developed for the problem of radionuclide transport in a system of parallel fractures situated in a porous rock matrix. A kinetic solubility-limited dissolution model is used as the inlet boundary condition. The solutions consider the following processes: (a) advective transport in the fractures, (b) mechanical dispersion and molecular diffusion along the fractures, (c) molecular diffusion from a fracture to the porous matrix, (d) molecular diffusion within the porous matrix in the direction perpendicular to the fracture axis, (e) adsorption onto the fracture wall, (f) adsorption within the porous matrix, and (g) radioactive decay. The solutions are based on the Laplace transform method. The general transient solution is in the form of a double integral that is evaluated using composite Gauss-Legendre quadrature. A simpler transient solution that is in the form of a single integral is also presented for the case that assumes negligible longitudinal dispersion along the fractures. The steady-state solutions are also provided. A number of examples are given to illustrate the effects of the following important parameters: (a) fracture spacings, (b) dissolution-rate constants, (c) fracture dispersion coefficient, (d) matrix retardation factor, and (e) fracture retardation factor
The solute carrier 6 family of transporters
Bröer, Stefan; Gether, Ulrik
2012-01-01
of these transporters is associated with a variety of diseases. Pharmacological inhibition of the neurotransmitter transporters in this family is an important strategy in the management of neurological and psychiatric disorders. This review provides an overview of the biochemical and pharmacological properties......The solute carrier 6 (SLC6) family of the human genome comprises transporters for neurotransmitters, amino acids, osmolytes and energy metabolites. Members of this family play critical roles in neurotransmission, cellular and whole body homeostasis. Malfunction or altered expression...... of the SLC6 family transporters....
Hodgkinson, David
2007-09-01
This report forms part of an independent review of the specifications, execution and results of Task 6 of the Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes, which is seeking to provide a bridge between site characterization and performance assessment approaches to modelling solute transport in fractured rock. The objectives of Task 6 are: To assess simplifications used in Performance Assessment (PA) models. To determine how, and to what extent, experimental tracer and flow experiments can constrain the range of parameters used in PA models. To support the design of Site Characterisation (SC) programmes to ensure that the results have optimal value for performance assessment calculations. To improve the understanding of site-specific flow and transport behaviour at different scales using site characterisation models. The present report is concerned with Tasks 6D, 6E, 6F and 6F2. It follows on from two previous reviews of Tasks 6A, 6B and 6B2, and Task 6C. In Task 6D the transport of tracers through a fracture network is modelled using the conditions of the C2 TRUE-Block Scale tracer test, based on the synthetic structural model developed in Task 6C. Task 6E extends the Task 6D transport calculations to a reference set of PA time scales and boundary conditions. Task 6F consists of a series of 'benchmark' studies on single features from the Task 6C hydrostructural model in order to improve the understanding of differences between the participating models. Task 6F2 utilises models set up for Tasks 6E and 6F to perform additional sensitivity studies with the aim of increasing the understanding of how models behave, the reason for differences in modelling results, and the sensitivity of models to various assumptions and parameter values. Eight modelling teams representing five organisations participated in this exercise using Discrete Fracture Network (DFN), continuum and channel network concepts implemented in a range of different codes and
Hodgkinson, David (Quintessa, Henley-on-Thames (GB))
2007-09-15
This report forms part of an independent review of the specifications, execution and results of Task 6 of the Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes, which is seeking to provide a bridge between site characterization and performance assessment approaches to modelling solute transport in fractured rock. The objectives of Task 6 are: To assess simplifications used in Performance Assessment (PA) models. To determine how, and to what extent, experimental tracer and flow experiments can constrain the range of parameters used in PA models. To support the design of Site Characterisation (SC) programmes to ensure that the results have optimal value for performance assessment calculations. To improve the understanding of site-specific flow and transport behaviour at different scales using site characterisation models. The present report is concerned with Tasks 6D, 6E, 6F and 6F2. It follows on from two previous reviews of Tasks 6A, 6B and 6B2, and Task 6C. In Task 6D the transport of tracers through a fracture network is modelled using the conditions of the C2 TRUE-Block Scale tracer test, based on the synthetic structural model developed in Task 6C. Task 6E extends the Task 6D transport calculations to a reference set of PA time scales and boundary conditions. Task 6F consists of a series of 'benchmark' studies on single features from the Task 6C hydrostructural model in order to improve the understanding of differences between the participating models. Task 6F2 utilises models set up for Tasks 6E and 6F to perform additional sensitivity studies with the aim of increasing the understanding of how models behave, the reason for differences in modelling results, and the sensitivity of models to various assumptions and parameter values. Eight modelling teams representing five organisations participated in this exercise using Discrete Fracture Network (DFN), continuum and channel network concepts implemented in a range of different
dispersion equation parameters of solute transport in agricultural
Jane
2011-08-31
Aug 31, 2011 ... fields for predicting soil quality property. Key words: ... The classical approach of modeling solute transport in porous media uses the deterministic ... concentration of the solution in the liquid phase, u0 is the mean velocity and ...
Samper, Javier; Molinero, Jorge; Changbing Yang; Guoxiang Zhang [Univ. Da Coruna (Spain)
2003-12-01
The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behaviour and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by Banwart et al. Later, Banwart presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by Molinero who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulphate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of Molinero and extends the preliminary microbial model of Zhang by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfaphe concentration, thus adding additional evidence for the possibility
Samper, Javier; Molinero, Jorge; Changbing Yang; Guoxiang Zhang
2003-12-01
The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behaviour and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by Banwart et al. Later, Banwart presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by Molinero who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulphate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of Molinero and extends the preliminary microbial model of Zhang by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfaphe concentration, thus adding additional evidence for the possibility
Samper, Javier; Molinero, Jorg; Changbing, Yang; Zhang, Guoxiang
2003-12-01
The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behavior and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by /Banwart et al, 1995/. Later, /Banwart et al, 1999/ presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by /Molinero, 2000/ who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulfate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of /Molinero, 2000/ and extends the preliminary microbial model of /Zhang, 2001/ by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfate concentration, thus
Molinero, J.; Samper, J.
2003-07-01
Several countries around the world are considering the final disposal of high-level radioactive waste in deep repositories located in fractured granite formations. Evaluating the long term safety of such repositories requires sound conceptual and numerical models which must consider simultaneously groundwater flow, solute transport and chemical and radiological processes. These models are being developed from data and knowledge gained from in situ experiments carried out at deep underground laboratories such as that of Aspo, Sweden, constructed in fractured granite. The Redox Zone Experiment is one of such experiments performed at Aspo in order to evaluate the effects of the construction of the access tunnel on the hydrogeological and hydrochemical conditions of a fracture zone intersected by the tunnel. Previous authors interpreted hydrochemical and isotopic data of this experiment using a mass-balance approach based on a qualitative description of groundwater flow conditions. Such an interpretation, however, is subject to uncertainties related to an over-simplified conceptualization of groundwater flow. Here we present numerical models of groundwater flow and solute transport for this fracture zone. The first model is based on previously published conceptual model. It presents noticeable un consistencies and fails to match simultaneously observed draw downs and chloride breakthrough curves. To overcome its limitations, a revised flow and transport model is presented which relies directly on available hydrodynamic and transport parameters, is based on the identification of appropriate flow and transport boundary conditions and uses, when needed, solute data extrapolated from nearby fracture zones. A significant quantitative improvement is achieved with the revised model because its results match simultaneously drawdown and chloride data. Other improvements are qualitative and include: ensuring consistency of hydrodynamic and hydrochemical data and avoiding
Zehe, E.; Klaus, J.
2011-12-01
Rapid flow in connected preferential flow paths is crucial for fast transport of water and solutes through soils, especially at tile drained field sites. The present study tests whether an explicit treatment of worm burrows is feasible for modeling water flow, bromide and pesticide transport in structured heterogeneous soils with a 2-dimensional Richards based model. The essence is to represent worm burrows as morphologically connected paths of low flow resistance and low retention capacity in the spatially highly resolved model domain. The underlying extensive database to test this approach was collected during an irrigation experiment, which investigated transport of bromide and the herbicide Isoproturon at a 900 sqm tile drained field site. In a first step we investigated whether the inherent uncertainty in key data causes equifinality i.e. whether there are several spatial model setups that reproduce tile drain event discharge in an acceptable manner. We found a considerable equifinality in the spatial setup of the model, when key parameters such as the area density of worm burrows and the maximum volumetric water flows inside these macropores were varied within the ranges of either our measurement errors or measurements reported in the literature. Thirteen model runs yielded a Nash-Sutcliffe coefficient of more than 0.9. Also, the flow volumes were in good accordance and peak timing errors where less than or equal to 20 min. In the second step we investigated thus whether this "equifinality" in spatial model setups may be reduced when including the bromide tracer data into the model falsification process. We simulated transport of bromide for the 13 spatial model setups, which performed best with respect to reproduce tile drain event discharge, without any further calibration. Four of this 13 model setups allowed to model bromide transport within fixed limits of acceptability. Parameter uncertainty and equifinality could thus be reduced. Thirdly, we selected
Peritoneal fluid transport in CAPD patients with different transport rates of small solutes.
Sobiecka, Danuta; Waniewski, Jacek; Weryński, Andrzej; Lindholm, Bengt
2004-01-01
Continuous ambulatory peritoneal dialysis (CAPD) patients with high peritoneal solute transport rate often have inadequate peritoneal fluid transport. It is not known whether this inadequate fluid transport is due solely to a too rapid fall of osmotic pressure, or if the decreased effectiveness of fluid transport is also a contributing factor. To analyze fluid transport parameters and the effectiveness of dialysis fluid osmotic pressure in the induction of fluid flow in CAPD patients with different small solute transport rates. 44 CAPD patients were placed in low (n = 6), low-average (n = 13), high-average (n = 19), and high (n = 6) transport groups according to a modified peritoneal equilibration test (PET). The study involved a 6-hour peritoneal dialysis dwell with 2 L 3.86% glucose dialysis fluid for each patient. Radioisotopically labeled serum albumin was added as a volume marker.The fluid transport parameters (osmotic conductance and fluid absorption rate) were estimated using three mathematical models of fluid transport: (1) Pyle model (model P), which describes ultrafiltration rate as an exponential function of time; (2) model OS, which is based on the linear relationship of ultrafiltration rate and overall osmolality gradient between dialysis fluid and blood; and (3) model G, which is based on the linear relationship between ultrafiltration rate and glucose concentration gradient between dialysis fluid and blood. Diffusive mass transport coefficients (K(BD)) for glucose, urea, creatinine, potassium, and sodium were estimated using the modified Babb-Randerson-Farrell model. The high transport group had significantly lower dialysate volume and glucose and osmolality gradients between dialysate and blood, but significantly higher K(BD) for small solutes compared with the other transport groups. Osmotic conductance, fluid absorption rate, and initial ultrafiltration rate did not differ among the transport groups for model OS and model P. Model G yielded
System Convergence in Transport Modelling
Rich, Jeppe; Nielsen, Otto Anker; Cantarella, Guilio E.
2010-01-01
A fundamental premise of most applied transport models is the existence and uniqueness of an equilibrium solution that balances demand x(t) and supply t(x). The demand consists of the people that travel in the transport system and on the defined network, whereas the supply consists of the resulting...... level-of-service attributes (e.g., travel time and cost) offered to travellers. An important source of complexity is the congestion, which causes increasing demand to affect travel time in a non-linear way. Transport models most often involve separate models for traffic assignment and demand modelling...... iterating between a route-choice (demand) model and a time-flow (supply) model. It is generally recognised that a simple iteration scheme where the level-of-service level is fed directly to the route-choice and vice versa may exhibit an unstable pattern and lead to cyclic unstable solutions. It can be shown...
Pirouzmand, Ahmad; Hadad, Kamal
2011-01-01
Highlights: → This paper describes the solution of time-independent neutron transport equation. → Using a novel method based on cellular neural networks (CNNs) coupled with P N method. → Utilize the CNN model to simulate spatial scalar flux distribution in steady state. → The accuracy, stability, and capabilities of CNN model are examined in x-y geometry. - Abstract: This paper describes a novel method based on using cellular neural networks (CNN) coupled with spherical harmonics method (P N ) to solve the time-independent neutron transport equation in x-y geometry. To achieve this, an equivalent electrical circuit based on second-order form of neutron transport equation and relevant boundary conditions is obtained using CNN method. We use the CNN model to simulate spatial response of scalar flux distribution in the steady state condition for different order of spherical harmonics approximations. The accuracy, stability, and capabilities of CNN model are examined in 2D Cartesian geometry for fixed source and criticality problems.
Reexamining ultrafiltration and solute transport in groundwater
Neuzil, C. E.; Person, Mark
2017-06-01
Geologic ultrafiltration—slowing of solutes with respect to flowing groundwater—poses a conundrum: it is consistently observed experimentally in clay-rich lithologies, but has been difficult to identify in subsurface data. Resolving this could be important for clarifying clay and shale transport properties at large scales as well as interpreting solute and isotope patterns for applications ranging from nuclear waste repository siting to understanding fluid transport in tectonically active environments. Simulations of one-dimensional NaCl transport across ultrafiltering clay membrane strata constrained by emerging data on geologic membrane properties showed different ultrafiltration effects than have often been envisioned. In relatively high-permeability advection-dominated regimes, salinity increases occurred mostly within membrane units while their effluent salinity initially fell and then rose to match solute delivery. In relatively low-permeability diffusion-dominated regimes, salinity peaked at the membrane upstream boundary and effluent salinity remained low. In both scenarios, however, only modest salinity changes (up to ˜3 g L-1) occurred because of self-limiting tendencies; membrane efficiency declines as salinity rises, and although sediment compaction increases efficiency, it is also decreases permeability and allows diffusive transport to dominate. It appears difficult for ultrafiltration to generate brines as speculated, but widespread and less extreme ultrafiltration effects in the subsurface could be unrecognized. Conditions needed for ultrafiltration are present in settings that include topographically-driven flow systems, confined aquifer systems subjected to injection or withdrawal, compacting basins, and accretionary complexes.
Solute transport in aggregated and layered porous media
Koch, S.
1993-01-01
This work is a contribution to research in soil physics dealing with solute transport in porous media. The influence of structural inhomogeneities on solute transport is investigated. Detailed experiments at the laboratory scale are used to enlighten distinct processes which cannot be studied separately at field scale. Two main aspects are followed up: (i) to show the influence of aggregation of a porous medium on breakthrough time and spreading of an inert tracer and consequences on the estimation of parameter values of models describing solute transport in aggregated systems, (ii) to investigate the influences on the dispersion process when stratification is perpendicular to the direction of flow. Several concepts of modelling solute transport in soil are discussed. Models based on the convection-dispersion equation (CDE) are emphasized because they are used here to model solute transport experiments conducted with aggregated porous media. Stochastic concepts are introduced to show the limitations of the deterministic CDE approaches. Experiments are done in columns containing two kinds of solid phases and were saturated with water. The solid phases are porous and solid glass beads exhibiting a distinctly unimodal or bimodal pore size distribution. Experimental breakthrough curves (BTCs) are modelled with the CDE, a bicontinuum model with a phenomenological mass transfer rate and a bicontinuum spherical diffusion model. Experiments are also done in columns that are unsaturated containing porous materials that are layered. Flow is made at a steady rate. It is shown that layer boundaries have a severe influence on lateral mixing. They may force streamlines to converge or cause a lateral redistribution of solutes. (author) figs., tabs., 122 refs
Pathogen transport in groundwater systems: contrasts with traditional solute transport
Hunt, Randall J.; Johnson, William P.
2017-06-01
Water quality affects many aspects of water availability, from precluding use to societal perceptions of fit-for-purpose. Pathogen source and transport processes are drivers of water quality because they have been responsible for numerous outbreaks resulting in large economic losses due to illness and, in some cases, loss of life. Outbreaks result from very small exposure (e.g., less than 20 viruses) from very strong sources (e.g., trillions of viruses shed by a single infected individual). Thus, unlike solute contaminants, an acute exposure to a very small amount of contaminated water can cause immediate adverse health effects. Similarly, pathogens are larger than solutes. Thus, interactions with surfaces and settling become important even as processes important for solutes such as diffusion become less important. These differences are articulated in "Colloid Filtration Theory", a separate branch of pore-scale transport. Consequently, understanding pathogen processes requires changes in how groundwater systems are typically characterized, where the focus is on the leading edges of plumes and preferential flow paths, even if such features move only a very small fraction of the aquifer flow. Moreover, the relatively short survival times of pathogens in the subsurface require greater attention to very fast (solute transport mechanisms discussed here, a more encompassing view of water quality and source water protection is attained. With this more holistic view and theoretical understanding, better evaluations can be made regarding drinking water vulnerability and the relation between groundwater and human health.
Gwo, J.P.; Jardine, P.M.; Yeh, G.T.; Wilson, G.V.
1995-04-01
Matrix diffusion, a diffusive mass transfer process,in the structured soils and geologic units at ORNL, is believe to be an important subsurface mass transfer mechanism; it may affect off-site movement of radioactive wastes and remediation of waste disposal sites by locally exchanging wastes between soil/rock matrix and macropores/fractures. Advective mass transfer also contributes to waste movement but is largely neglected by researchers. This report presents the first documented 2-D multiregion solute transport code (MURT) that incorporates not only diffusive but also advective mass transfer and can be applied to heterogeneous porous media under transient flow conditions. In this report, theoretical background is reviewed and the derivation of multiregion solute transport equations is presented. Similar to MURF (Gwo et al. 1994), a multiregion subsurface flow code, multiplepore domains as suggested by previous investigators (eg, Wilson and Luxmoore 1988) can be implemented in MURT. Transient or steady-state flow fields of the pore domains can be either calculated by MURF or by modelers. The mass transfer process is briefly discussed through a three-pore-region multiregion solute transport mechanism. Mass transfer equations that describe mass flux across pore region interfaces are also presented and parameters needed to calculate mass transfer coefficients detailed. Three applications of MURT (tracer injection problem, sensitivity analysis of advective and diffusive mass transfer, hillslope ponding infiltration and secondary source problem) were simulated and results discussed. Program structure of MURT and functions of MURT subroutiness are discussed so that users can adapt the code; guides for input data preparation are provided in appendices
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
Samper, J.; Font, I.; Yang, C.; Montenegro, L.
2004-12-01
The reference concept for a HLW repository in clay in Spain includes a 75 cm thick bentonite buffer which surrounds canisters. A concrete sustainment 20 cm thick is foreseen between the bentonite buffer and the clay formation. The long term geochemical evolution of the near field is affected by a high-pH hyperalkaline plume induced by concrete. Numerical models of multicomponent reactive transport have been developped in order to quantify the evolution of the system over 1 Ma. Water flow is negligible once the bentonite buffer is saturated after about 20 years. Therefore, solute transport occurs mainly by diffusion. Models account for aqueous complexation, acid-base and redox reactions, cation exchange, and mineral dissolution precipitation in the bentonite, the concrete and the clay formation. Numerical results obtained witth CORE2D indicate that the high-pH plume causes significant changes in porewater chemistry both in the bentonite buffer and the clay formation. Porosity changes caused by mineral dissolution/precipitation are extremely important. Therefore, coupled modes of diffusion and reactive transport accounting for changes in porosity caused by mineral precipitation are required in order to obtain realistic predictions.
Exact solution of the neutron transport equation in spherical geometry
Anli, Fikret; Akkurt, Abdullah; Yildirim, Hueseyin; Ates, Kemal [Kahramanmaras Suetcue Imam Univ. (Turkey). Faculty of Sciences and Letters
2017-03-15
Solution of the neutron transport equation in one dimensional slab geometry construct a basis for the solution of neutron transport equation in a curvilinear geometry. Therefore, in this work, we attempt to derive an exact analytical benchmark solution for both neutron transport equations in slab and spherical medium by using P{sub N} approximation which is widely used in neutron transport theory.
End-Member Formulation of Solid Solutions and Reactive Transport
Lichtner, Peter C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-09-01
A model for incorporating solid solutions into reactive transport equations is presented based on an end-member representation. Reactive transport equations are solved directly for the composition and bulk concentration of the solid solution. Reactions of a solid solution with an aqueous solution are formulated in terms of an overall stoichiometric reaction corresponding to a time-varying composition and exchange reactions, equivalent to reaction end-members. Reaction rates are treated kinetically using a transition state rate law for the overall reaction and a pseudo-kinetic rate law for exchange reactions. The composition of the solid solution at the onset of precipitation is assumed to correspond to the least soluble composition, equivalent to the composition at equilibrium. The stoichiometric saturation determines if the solid solution is super-saturated with respect to the aqueous solution. The method is implemented for a simple prototype batch reactor using Mathematica for a binary solid solution. Finally, the sensitivity of the results on the kinetic rate constant for a binary solid solution is investigated for reaction of an initially stoichiometric solid phase with an undersaturated aqueous solution.
Baveye, Philippe C.; Pot, Valérie; Garnier, Patricia
2017-12-01
In the last decade, X-ray computed tomography (CT) has become widely used to characterize the geometry and topology of the pore space of soils and natural porous media. Regardless of the resolution of CT images, a fundamental problem associated with their use, for example as a starting point in simulation efforts, is that sub-resolution pores are not detected. Over the last few years, a particular type of modeling method, known as ;Grey; or ;Partial Bounce Back; Lattice-Boltzmann (LB), has been adopted by increasing numbers of researchers to try to account for sub-resolution pores in the modeling of water and solute transport in natural porous media. In this short paper, we assess the extent to which Grey LB methods indeed offer a workable solution to the problem at hand. We conclude that, in spite of significant computational advances, a major experimental hurdle related to the evaluation of the penetrability of sub-resolution pores, is blocking the way ahead. This hurdle will need to be cleared before Grey LB can become a credible option in the microscale modeling of soils and sediments. A necessarily interdisciplinary effort, involving both modelers and experimentalists, is needed to clear the path forward.
Stochastic analysis of transport of conservative solutes in caisson experiments
Dagan, G.
1995-01-01
The Los Alamos National Laboratory has conducted in the past a series of experiments of transport of conservative and reactive solutes. The experimental setup and the experimental results are presented in a series of reports. The main aim of the experiments was to validate models of transport of solutes in unsaturated flow at the caisson intermediate scale, which is much larger than the one pertaining to laboratory columns. First attempts to analyze the experimental results were by one-dimensional convective-dispersion models. These models could not explain the observed solute breakthrough curves and particularly the large solute dispersion in the caisson effluent Since there were some question marks about the uniformity of water distribution at the caisson top, the transport experiments were repeated under conditions of saturated flow. In these experiments constant heads were applied at the top and the bottom of the caisson and the number of concentration monitoring stations was quadrupled. The analysis of the measurements by the same one-dimensional model indicated clearly that the fitted dispersivity is much larger than the pore-sole dispersivity and that it grows with the distance in an approximately linear fashion. This led to the conclusion, raised before, that transport in the caisson is dominated by heterogeneity effects, i.e. by spatial variability of the material Such effects cannot be captured by traditional one-dimensional models. In order to account for the effect of heterogeneity, the saturated flow experiments have been analyzed by using stochastic transport modeling. The apparent linear growth of dispersivity with distance suggested that the system behaves like a stratified one. Consequently, the model of Dagan and Bresier has been adopted in order to interpret concentration measurements. In this simple model the caisson is viewed as a bundle of columns of different permeabilities, which are characterized by a p.d.f. (probability denasity function)
Kukushkin, A. B.; Sdvizhenskii, P. A.
2017-12-01
The results of accuracy analysis of automodel solutions for Lévy flight-based transport on a uniform background are presented. These approximate solutions have been obtained for Green’s function of the following equations: the non-stationary Biberman-Holstein equation for three-dimensional (3D) radiative transfer in plasma and gases, for various (Doppler, Lorentz, Voigt and Holtsmark) spectral line shapes, and the 1D transport equation with a simple longtailed step-length probability distribution function with various power-law exponents. The results suggest the possibility of substantial extension of the developed method of automodel solution to other fields far beyond physics.
Weyand, Torben [Bonn Univ. (Germany); Gesellschaft fuer Reaktorsicherheit mbH (GRS), Koeln (Germany); Bracke, Guido [Gesellschaft fuer Reaktorsicherheit mbH (GRS), Koeln (Germany); Reichert, Barbara [Bonn Univ. (Germany)
2014-03-15
The safe confinement of radioactive materials in the containment providing zone of the host rock (CPRZ) over a period of one million years is required for a final repository for highly radioactive heat-generating waste (BMU 2010). In order to assess the safe containment of radionuclides in the CPRZ a sound understanding of the ongoing processes in a repository is necessary. These processes include the transport and chemical interactions of the radionuclide {sup 14}C in the gas phase and in highly saline solutions in a final repository for radioactive waste. The geochemical code PHREEQC /PAR 13/ was used to study the chemical interactions of CO{sub 2} and {sup 14}C as {sup 14}CO{sub 2} during transport in the gas phase and highly saline solutions. The model and scenario was based on the concept for a repository in Gorleben /BOL 11/. A gas generation of CO{sub 2} containing {sup 14}C was assumed since the disposed containers with the radioactive waste corrode /LAR 13/. The advective transport is triggered by gas generation. The physical dissolution of CO{sub 2}, chemical equilibria with aquatic carbon-containing species (e. g. HCO{sub 3}{sup -}(aq), CO{sub 3}{sup 2-}(aq)) and solid phases (e. g. magnesite, MgCO{sub 3}) coupled with transport were modelled. Due to the addition of dissolved MgCl{sub 2} in the crushed salt backfill of the main drift the aquatic species MgCO{sub 3}(aq) and the mineral MgCO{sub 3}(s) is formed. The influence of CO{sub 2} partial pressure and the chemical interactions in the presence of dissolved Fe{sup 2+}, Ca{sup 2+}, Mg{sup 2+} and K{sup +} were studied. Due to the physical solution, the CO{sub 2} partial pressure has a major influence on the transport of {sup 14}C. In the presence of calcium CaCO{sub 3}(aq), the minerals calcite (CaCO{sub 3}(s)) and dolomite (MgCa(CO{sub 3}){sub 2}(s)) were formed in the highly saline solutions. No siderite (FeCO{sub 3}) in the presence of Fe{sup 2+} was formed. The transport of {sup 14}C was delayed
Nonrelativistic grey Sn-transport radiative-shock solutions
Ferguson, J. M.; Morel, J. E.; Lowrie, R. B.
2017-01-01
We present semi-analytic radiative-shock solutions in which grey Sn-transport is used to model the radiation, and we include both constant cross sections and cross sections that depend on temperature and density. These new solutions solve for a variable Eddington factor (VEF) across the shock domain, which allows for interesting physics not seen before in radiative-shock solutions. Comparisons are made with the grey nonequilibrium-diffusion radiative-shock solutions of Lowrie and Edwards [1], which assumed that the Eddington factor is constant across the shock domain. It is our experience that the local Mach number is monotonic when producing nonequilibrium-diffusion solutions, but that this monotonicity may disappear while integrating the precursor region to produce Sn-transport solutions. For temperature- and density-dependent cross sections we show evidence of a spike in the VEF in the far upstream portion of the radiative-shock precursor. We show evidence of an adaptation zone in the precursor region, adjacent to the embedded hydrodynamic shock, as conjectured by Drake [2, 3], and also confirm his expectation that the precursor temperatures adjacent to the Zel’dovich spike take values that are greater than the downstream post-shock equilibrium temperature. We also show evidence that the radiation energy density can be nonmonotonic under the Zel’dovich spike, which is indicative of anti-diffusive radiation flow as predicted by McClarren and Drake [4]. We compare the angle dependence of the radiation flow for the Sn-transport and nonequilibriumdiffusion radiation solutions, and show that there are considerable differences in the radiation flow between these models across the shock structure. Lastly, we analyze the radiation flow to understand the cause of the adaptation zone, as well as the structure of the Sn-transport radiation-intensity solutions across the shock structure.
Numerical solution of the radionuclide transport equation
Hadermann, J.; Roesel, F.
1983-11-01
A numerical solution of the one-dimensional geospheric radionuclide chain transport equation based on the pseudospectral method is developed. The advantages of this approach are flexibility in incorporating space and time dependent migration parameters, arbitrary boundary conditions and solute rock interactions as well as efficiency and reliability. As an application the authors investigate the impact of non-linear sorption isotherms on migration in crystalline rock. It is shown that non-linear sorption, in the present case a Freundlich isotherm, may reduce concentration at the geosphere outlet by orders of magnitude provided the migration time is comparable or larger than the half-life of the nuclide in question. The importance of fixing dispersivity within the continuum approach is stressed. (Auth.)
Filho, J. F. P.; Barichello, L. B.
2013-01-01
In this work, an analytical discrete ordinates method is used to solve a nodal formulation of a neutron transport problem in x, y-geometry. The proposed approach leads to an important reduction in the order of the associated eigenvalue systems, when combined with the classical level symmetric quadrature scheme. Auxiliary equations are proposed, as usually required for nodal methods, to express the unknown fluxes at the boundary introduced as additional unknowns in the integrated equations. Numerical results, for the problem defined by a two-dimensional region with a spatially constant and isotropically emitting source, are presented and compared with those available in the literature. (authors)
Modelling of transport phenomena
Itoh, Kimitaka; Itoh, Sanae; Fukuyama, Atsushi.
1993-09-01
In this review article, we discuss key features of the transport phenomena and theoretical modelling to understand them. Experimental observations have revealed the nature of anomalous transport, i.e., the enhancement of the transport coefficients by the gradients of the plasma profiles, the pinch phenomena, the radial profile of the anomalous transport coefficients, the variation of the transport among the Bohm diffusion, Pseudo-classical confinement, L-mode and variety of improved confinement modes, and the sudden jumps such as L-H transition. Starting from the formalism of the transport matrix, the modelling based on the low frequency instabilities are reviewed. Theoretical results in the range of drift wave frequency are examined. Problems in theories based on the quasilinear and mixing-length estimates lead to the renewal of the turbulence theory, and the physics picture of the self-sustained turbulence is discussed. The theory of transport using the fluid equation of plasma is developed, showing that the new approach is very promising in explaining abovementioned characteristics of anomalous transport in both L-mode and improved confinement plasmas. The interference of the fluxes is the key to construct the physics basis of the bifurcation theory for the L-H transition. The present status of theories on the mechanisms of improved confinement is discussed. Modelling on the nonlocal nature of transport is briefly discussed. Finally, the impact of the anomalous transport on disruptive phenomena is also described. (author) 95 refs
Abstracts of the symposium on unsaturated flow and transport modeling
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
Transport of reactive and nonreactive solutes
Garabedian, S.P.; Leblanc, D.R.
1990-01-01
A natural-gradient tracer test was conducted on Cape Cod, Massachusetts, to examine the transport and dispersion of solutes in a sand and gravel aquifer. A nonreactive tracer, bromide, and two reactive tracers, lithium and molybdate, were injected as a pulse in July 1985 and monitored in three dimensions for 3 years as they moved 280 meters downgradient through an array of multilevel samplers. The tracer transport was quantified using spatial moments. The calculated total mass of bromide for each sampling date varied from 86 to 105 percent of the injected mass, and the center of mass moved at a nearly constant horizontal velocity of 0.42 meters per day. The bromide cloud also moved downward about 4 meters, probably because of density-induced sinking and accretion of areal recharge from precipitation. After 200 meters of transport, the bromide cloud was more than 80 meters long but only 14 meters wide and 6 meters thick. The change in longitudinal dispersivity had reached a constant value (0.96 meters). The transverse horizontal and transverse vertical dispersivities were much smaller (1.8 centimeters and 1.5 millimeters, respectively) than the longitudinal value. The lithium and molybdate clouds followed the same path as the bromide cloud, but a significant amount of their mass was adsorbed onto the aquifer sediments, and their rates of movement were retarded about 50 percent relative to the bromide movement. (Author) (5 figs., 23 refs.)
Souza, W.R.
1999-01-01
This report documents a graphical display post-processor (SutraPlot) for the U.S. Geological Survey Saturated-Unsaturated flow and solute or energy TRAnsport simulation model SUTRA, Version 2D3D.1. This version of SutraPlot is an upgrade to SutraPlot for the 2D-only SUTRA model (Souza, 1987). It has been modified to add 3D functionality, a graphical user interface (GUI), and enhanced graphic output options. Graphical options for 2D SUTRA (2-dimension) simulations include: drawing the 2D finite-element mesh, mesh boundary, and velocity vectors; plots of contours for pressure, saturation, concentration, and temperature within the model region; 2D finite-element based gridding and interpolation; and 2D gridded data export files. Graphical options for 3D SUTRA (3-dimension) simulations include: drawing the 3D finite-element mesh; plots of contours for pressure, saturation, concentration, and temperature in 2D sections of the 3D model region; 3D finite-element based gridding and interpolation; drawing selected regions of velocity vectors (projected on principal coordinate planes); and 3D gridded data export files. Installation instructions and a description of all graphic options are presented. A sample SUTRA problem is described and three step-by-step SutraPlot applications are provided. In addition, the methodology and numerical algorithms for the 2D and 3D finite-element based gridding and interpolation, developed for SutraPlot, are described. 1
RADIONUCLIDE TRANSPORT MODELS UNDER AMBIENT CONDITIONS
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.
Control and optimization of solute transport in a thin porous tube
Griffiths, I. M.; Howell, P. D.; Shipley, R. J.
2013-01-01
differentials upon the dispersive solute behaviour are investigated. The model is used to explore the control of solute transport across the membrane walls via the membrane permeability, and a parametric expression for the permeability required to generate a
Sn approach applied to the solution of transport equation
Lopes, J.P.
1973-09-01
In this work the origin of the Transport Theory is considered and the Transport Equation for the movement of the neutron in a system is established in its more general form, using the laws of nuclear physics. This equation is used as the starting point for development, under adequate assumptions, of simpler models that render the problem suitable for numerical solution. Representation of this model in different geometries is presented. The different processes of nuclear physics are introduced briefly and discussed. In addition, the boundary conditions for the different cases and a general procedure for the application of the Conservation Law are stated. The last chapter deals specifically with the S n method, its development, definitions and generalities. Computational schemes for obtaining the S n solution in spherical and cylindrical geometry, and convergence acceleration methods are also developed. (author)
Zhang, Guoxiang; Spycher, Nicolas; Xu, Tianfu; Sonnenthal, Eric; Steefel , Carl
2006-12-15
In this report, we present: -- The Pitzer ion-interactiontheory and models -- Input file requirements for using the TOUGHREACTPitzer ion-interaction model and associated databases -- Run-time errormessages -- Verification test cases and application examples. For themain code structure, features, overall solution methods, description ofinput/output files for parameters other than those specific to theimplemented Pitzer model, and error messages, see the TOUGHREACT User'sGuide (Xu et al., 2005). The TOUGHREACT Pitzer version runs on aDEC-alpha architecture CPU, under OSF1 V5.1, with Compaq Digital FortranCompiler. The compiler run-time libraries are required for execution aswell as compilation. The code also runs on Intel Pentium IV andhigher-version CPU-based machines with Compaq Visual Fortran Compiler orIntel Fortran Compiler (integrated with the Microsoft DevelopmentEnvironment). The minimum hardware configuration should include 1 GB RAMand 1 GB (2 GB recommended) of available disk space.
Faure, M H
1994-03-01
Understanding the mechanisms which control the transient transport of particles and radionuclides in natural and artificial porous media is a key problem for the assessment of safety of radioactive waste disposals. An experimental study has been performed to characterize the clayey particle mobility in porous media: a laboratory- made column, packed with an unconsolidated sand bentonite (5% weight) sample, is flushed with a salt solution. An original method of salinity gradient allowed us to show and to quantify some typical behaviours of this system: threshold effects in the peptization of particles, creation of preferential pathways, formation of immobile water zones induce solute-transfer limitation. The mathematical modelling accounts for a phenomenological law, where the distribution of particles between the stagnant water zone and the porous medium is a function of sodium chloride concentration. This distribution function is associated with a radionuclide adsorption model, and is included in a convective dispersive transport model with stagnant water zones. It allowed us to simulate the particle and solute transport when the salt environment is modified. The complete model has been validated with experiments involving cesium, calcium and neptunium in a sodium chloride gradient. (author). refs., figs., tabs.
Fernandes, Julio C.L.; Vilhena, Marco T.; Bodmann, Bardo E.J., E-mail: julio.lombaldo@ufrgs.br, E-mail: mtmbvilhena@gmail.com, E-mail: bardo.bodmann@ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Dept. de Matematica Pura e Aplicada; Dulla, Sandra; Ravetto, Piero, E-mail: sandra.dulla@polito.it, E-mail: piero.ravetto@polito.it [Dipartimento di Energia, Politecnico di Torino, Piemonte (Italy)
2015-07-01
In this work we generalize the solution of the one-dimensional neutron transport equation to a multi- group approach in planar geometry. The basic idea of this work consists in consider the hierarchical construction of a solution for a generic number G of energy groups, starting from a mono-energetic solution. The hierarchical method follows the reasoning of the decomposition method. More specifically, the additional terms from adding energy groups is incorporated into the recursive scheme as source terms. This procedure leads to an analytical representation for the solution with G energy groups. The recursion depth is related to the accuracy of the solution, that may be evaluated after each recursion step. The authors present a heuristic analysis of stability for the results. Numerical simulations for a specific example with four energy groups and a localized pulsed source. (author)
Water and solute transport across the peritoneal membrane.
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.
Bodin, Jacques
2015-03-01
In this study, new multi-dimensional time-domain random walk (TDRW) algorithms are derived from approximate one-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) analytical solutions of the advection-dispersion equation and from exact 1-D, 2-D, and 3-D analytical solutions of the pure-diffusion equation. These algorithms enable the calculation of both the time required for a particle to travel a specified distance in a homogeneous medium and the mass recovery at the observation point, which may be incomplete due to 2-D or 3-D transverse dispersion or diffusion. The method is extended to heterogeneous media, represented as a piecewise collection of homogeneous media. The particle motion is then decomposed along a series of intermediate checkpoints located on the medium interface boundaries. The accuracy of the multi-dimensional TDRW method is verified against (i) exact analytical solutions of solute transport in homogeneous media and (ii) finite-difference simulations in a synthetic 2-D heterogeneous medium of simple geometry. The results demonstrate that the method is ideally suited to purely diffusive transport and to advection-dispersion transport problems dominated by advection. Conversely, the method is not recommended for highly dispersive transport problems because the accuracy of the advection-dispersion TDRW algorithms degrades rapidly for a low Péclet number, consistent with the accuracy limit of the approximate analytical solutions. The proposed approach provides a unified methodology for deriving multi-dimensional time-domain particle equations and may be applicable to other mathematical transport models, provided that appropriate analytical solutions are available.
Fradin, J.
1958-12-03
This report presents a system aimed at sampling active solution from a specific transport container (SCRGR model) while transferring this solution with a maximum safety. The sampling principle is described (a flexible tube connected to the receiving container, with a needle at the other end which goes through a rubber membrane and enters a plunger tube). Its benefits are outlined (operator protection, reduction of contamination risk; only the rubber membrane is removed and replaced). Some manufacturing details are described concerning the membrane and the cover.
A stochastic solution of the advective transport equation with uncertainty
Williams, M.M.R.
1991-01-01
A model has been developed for calculating the transport of water-borne radionuclides through layers of porous materials, such as rock or clay. The model is based upon a purely advective transport equation, in which the fluid velocity is a random variable, thereby simulating dispersion in a more realistic manner than the ad hoc introduction of a dispersivity. In addition to a random velocity field, which is an observable physical phenomenon, allowance is made for uncertainty in our knowledge of the parameters which enter the equation, e.g. the retardation coefficient. This too, is assumed to be a random variable and contributes to the stochasticity of the resulting partial differential equation of transport. The stochastic differential equation can be solved analytically and then ensemble averages taken over the associated probability distribution of velocity and retardation coefficient. A method based upon a novel form of the central limit theorem of statistics is employed to obtain tractable solutions of a system consisting of many serial legs of varying properties. One interesting conclusion is that the total flux out of a medium is significantly underestimated by using the deterministic solution with an average transit time compared with that from the stochastically averaged solution. The theory is illustrated numerically for a number of physically relevant cases. (author) 8 figs., 4 tabs., 7 refs
Huan, Huan; Wang, Jinsheng; Lai, Desheng; Teng, Yanguo; Zhai, Yuanzheng
2015-05-01
Well vulnerability assessment is essential for groundwater source protection. A quantitative approach to assess well vulnerability in a well capture zone is presented, based on forward solute transport modeling. This method was applied to three groundwater source areas (Jiuzhan, Hadawan and Songyuanhada) in Jilin City, northeast China. The ratio of the maximum contaminant concentration at the well to the released concentration at the contamination source ( c max/ c 0) was determined as the well vulnerability indicator. The results indicated that well vulnerability was higher close to the pumping well. The well vulnerability in each groundwater source area was low. Compared with the other two source areas, the cone of depression at Jiuzhan resulted in higher spatial variability of c max/ c 0 and lower minimum c max/ c 0 by three orders of magnitude. Furthermore, a sensitivity analysis indicated that the denitrification rate in the aquifer was the most sensitive with respect to well vulnerability. A process to derive a NO3-N concentration at the pumping well is presented, based on determining the maximum nitrate loading limit to satisfy China's drinking-water quality standards. Finally, the advantages, disadvantages and prospects for improving the precision of this well vulnerability assessment approach are discussed.
Molinero Huguet, J
2001-07-01
This work deals with numerical modeling of groundwater flow, solute transport and chemical reactions through fractured media. These models have been developed within the framework of research activities founded by ENRESA , the Spanish Company for Nuclear Waste Management. This project is the result of a collaborative agreement between ENRESA and his equivalent Swedish Company (SKB) through the research project Task Force 5 of the Aspo Underground Laboratory. One of the objectives of this project is to assess quantitatively th hydrogeological and hydrochemical impact produced by the construction of a Deep Geological Repository in fractured granites. This is important because the new conditions altered construction impact will constitute the initial conditions for the repository closure stage. A second goo l of this work deals with testing the ability of current numerical tools to cope simultaneously with the complex hydrogeological and hydrochemical settlings, which are expected to take place in actual nuclear waste underground repositories constructed in crystalline fractured bed racks. This study has been undertaken through the performance of numerical models, which have subsequently been applied to simulate the hydrogeological and hydrochemical behavior of a granite massif, at a kilo metrical scale, during construction of the Aspo Hard Rock Underground Laboratory (Sweden). The Aspo Hard Rock Laboratory is a prototype, full-scale underground facility launched and operated by SKB. The main aim of the laboratory is to provide an opportunity for research, development and demonstration in a realistic rock environment down to the depth planned for the future deep repository. The framework of this underground facility provides a unique opportunity to attempt the objectives of the present dissertation. (Author)
Molinero Huguet, J.
2001-06-01
This work deals with numerical modeling of groundwater flow, solute transport and chemical reactions through fractured media. These models have been developed within the framework of research activities founded by ENRESA , the Spanish Company for Nuclear Waste Management. This project is the result of a collaborative agreement between ENRESA and his equivalent Swedish Company (SKB) through the research project Task Force 5 of the Aspo Underground Laboratory. One of the objectives of this project is to assess quantitatively th hydrogeological and hydrochemical impact produced by the construction of a Deep Geological Repository in fractured granites. This is important because the new conditions altered construction impact will constitute the initial conditions for the repository closure stage. A second goo l of this work deals with testing the ability of current numerical tools to cope simultaneously with the complex hydrogeological and hydrochemical settlings, which are expected to take place in actual nuclear waste underground repositories constructed in crystalline fractured bed racks. This study has been undertaken through the performance of numerical models, which have subsequently been applied to simulate the hydrogeological and hydrochemical behavior of a granite massif, at a kilo metrical scale, during construction of the Aspo Hard Rock Underground Laboratory (Sweden). The Aspo Hard Rock Laboratory is a prototype, full-scale underground facility launched and operated by SKB. The main aim of the laboratory is to provide an opportunity for research, development and demonstration in a realistic rock environment down to the depth planned for the future deep repository. The framework of this underground facility provides a unique opportunity to attempt the objectives of the present dissertation. (Author)
Travis, C.C.
1978-10-01
This report reviews selected literature related to the mathematical description of the transport of reactive solutes through soil. The primary areas of the literature reviewed are (1) mathematical models in current use for description of the adsorption-desorption interaction between the soil solution and the soil matrix and (2) analytic solutions of the differential equations describing the convective-dispersive transport of reactive solutes through soil
One-dimensional spatially dependent solute transport in semi ...
Initially porous domain is considered solute free and the input source condition is ... parameters for description of solute transport in porous media. ... flow assuming uniform initial concentration with first and third type boundary conditions. Aral.
Elert, M.; Svensson, Haakan [Kemakta Konsult AB, Stockholm (Sweden)
2001-05-01
The Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. In this report, the modelling work performed within Tasks 4E and 4F is evaluated, which comprised predictive modelling of the tracer tests (STT-1, STT-1b and STT-2) performed within the TRUE-1 project using sorbing and non-sorbing tracers. The tests were made between packed off boreholes penetrating a water-conducting geological feature with a simple structure (Feature A). Nine modelling teams representing eight organisations have performed predictive modelling of the tracer tests using different modelling approaches and models. The modelling groups were initially given data from the site characterisation, data from preliminary tracer tests performed with non-sorbing tracers and data on the experimental set-up of the sorbing tracer tests. Based on this information, model predictions were made of drawdown, tracer mass recovery and tracer breakthrough. For the predictions of the STT-1b and STT-2 tests results from previous tracer tests with sorbing tracer were also available. The predictions of the sorbing tracer breakthrough in the initial tracer test (STT-1) generally underestimated the breakthrough time, suggesting the need to include additional processes and evaluate the application of the laboratory data. As a result of model calibration and modification the predictions were considerably improved for the latter tracer tests (STT-1b and STT-2). Task 4E and 4F have proved to be very valuable in increasing the understanding of non-sorbing tracer transport in fractured rock. There is a general consensus on the major processes responsible for
A single continuum approximation of the solute transport in fractured porous media
Jeong, J.T.; Lee, K.J.
1992-01-01
Solute transport in fractured porous media is described by the single continuum model, i.e., equivalent porous medium model. In this model, one-dimensional solute transport in the fracture and two-dimensional solute transport in the porous rock matrix is considered. The network of fractures embedded in the porous rock matrix is idealized as two orthogonally intersecting families of equally spaced, parallel fractures directed at 45 o to the regional groundwater flow direction. Governing equations are solved by the finite element method, and an upstream weighting technique is used in order to prevent the oscillation of the solution in the case of highly advection dominated transport. Breakthrough curves, similar to those of the one-dimensional solute transport problem in ordinary porous media, are obtained as a function of time according to volume or flux averaging of the concentration profile across the width of the flow region. The equivalent parameters, i.e., porosity and overall coefficient of longitudinal dispersivity, are obtained by a trial-and-error method. Analyses for the non-sorbing solute transport case show that within the range of considered parameters, and except for the region very close to the source, application of the single continuum model in the idealized fracture system is sufficient for modeling solute transport in fractured porous media. This numerical scheme is shown to be applicable to a sorbing solute and radionuclide transport. (author)
Frick, U.
1995-01-01
The safety assessment of radioactive waste repositories is to provide confidence that the predictive models utilized are applicable for the specific repository systems. Nagra has carried out radionuclide migration experiments at the Grimsel underground test site (Switzerland) for testing of currently used methodologies, data bases, conceptual approaches and codes for modeling radionuclide transport through fractured host rocks. Specific objectives included: identification of the relevant transport processes, to test the extrapolation of laboratory sorption data to field conditions, and to demonstrate the applicability of currently used methodology for conceptualizing or building realistic transport models. Field tests and transport modeling work are complemented by an extensive laboratory program. The field experimental activities focused predominantly on establishing appropriate conditions for identifying relevant transport mechanisms on the scale of a few meters, aiming at full recovery of injected tracers, simple geometry and long-term stability of induced dipole flow fields. A relatively simple homogeneous, dual-porosity advection/diffusion model was built with input from a state of the art petrographic characterisation of the water conducting feature. It was possible to calibrate the model from conservative tracer breakthrough curves. (J.S.). 21 refs., 14 figs., 4 tabs
Two-point model for divertor transport
Galambos, J.D.; Peng, Y.K.M.
1984-04-01
Plasma transport along divertor field lines was investigated using a two-point model. This treatment requires considerably less effort to find solutions to the transport equations than previously used one-dimensional (1-D) models and is useful for studying general trends. It also can be a valuable tool for benchmarking more sophisticated models. The model was used to investigate the possibility of operating in the so-called high density, low temperature regime
Predictability of solute transport in diffusion-controlled hydrogeologic regimes
Gillham, R.W.; Cherry, J.A.
1983-01-01
Hydrogeologic regimes that are favourable for the subsurface management of low-level radioactive wastes must have transport properties that will limit the migration velocity of contaminants to some acceptably low value. Of equal importance, for the purpose of impact assessment and licensing, is the need to be able to predict, with a reasonable degree of certainty and over long time periods, what the migration velocity of the various contaminants of interest will be. This paper presents arguments to show that in addition to having favourable velocity characteristics, transport in saturated, diffusion-controlled hydrogeologic regimes is considerably more predictable than in the most common alternatives. The classical transport models for unsaturated, saturated-advection-controlled and saturated-diffusion-controlled environments are compared, with particular consideration being given to the difficulties associated with the characterization of the respective transport parameters. Results are presented which show that the diffusion of non-reactive solutes and solutes that react according to a constant partitioning ratio (K/sub d/) are highly predictable under laboratory conditions and that the diffusion coefficients for the reactive solutes can be determined with a reasonable degree of accuracy from independent measurements of bulk density, porosity, distribution coefficient and tortuosity. Field evidence is presented which shows that the distribution of environmental isotopes and chloride in thick clayey deposits is consistent with a diffusion-type transport process in these media. These results are particularly important in that they not only demonstrate the occurrence of diffusion-controlled hydrogeologic regimes, but they also demonstrate the predictability of the migration characteristics over very long time periods
Jensen, Mads Mønster; De Weerdt, K.; Johannesson, Björn
2015-01-01
Simulations of ion ingress in Portland cement mortar using a multi-species reactive mass transport model are compared with experimental test results. The model is an extended version of the Poisson–Nernst–Planck equations, accounting for chemical equilibrium. Saturated mortar samples were exposed...
A biomechanical triphasic approach to the transport of nondilute solutions in articular cartilage.
Abazari, Alireza; Elliott, Janet A W; Law, Garson K; McGann, Locksley E; Jomha, Nadr M
2009-12-16
Biomechanical models for biological tissues such as articular cartilage generally contain an ideal, dilute solution assumption. In this article, a biomechanical triphasic model of cartilage is described that includes nondilute treatment of concentrated solutions such as those applied in vitrification of biological tissues. The chemical potential equations of the triphasic model are modified and the transport equations are adjusted for the volume fraction and frictional coefficients of the solutes that are not negligible in such solutions. Four transport parameters, i.e., water permeability, solute permeability, diffusion coefficient of solute in solvent within the cartilage, and the cartilage stiffness modulus, are defined as four degrees of freedom for the model. Water and solute transport in cartilage were simulated using the model and predictions of average concentration increase and cartilage weight were fit to experimental data to obtain the values of the four transport parameters. As far as we know, this is the first study to formulate the solvent and solute transport equations of nondilute solutions in the cartilage matrix. It is shown that the values obtained for the transport parameters are within the ranges reported in the available literature, which confirms the proposed model approach.
Hydrophilic solute transport across the rat blood-brain barrier
Lucchesi, K.J.
1987-01-01
Brain capillary permeability-surface area products (PS) of hydrophilic solutes ranging in size from 180 to 5,500 Daltons were measured in rats according to the method of Ohno, Pettigrew and Rapoport. The distribution volume of 70 KD dextran at 10 minutes after i.v. injection was also measured to determine the residual volume of blood in brain tissue at the time of sacrifice. Small test solutes were injected in pairs in order to elucidate whether their transfer into the brain proceeds by diffusion through water- or lipid-filled channels or by vesicular transport. This issue was examined in rats whose blood-brain barrier (BBB) was presumed to be intact (untreated) and in rats that received intracarotid infusions to open the BBB (isosmotic salt (ISS) and hyperosmolar arabinose). Ohno PS values of 3 H-inulin and 14 C-L-glucose in untreated rats were found to decrease as the labelling time was lengthened. This was evidence that a rapidly equilibrating compartment exists between blood and brain that renders the Ohno two-compartment model inadequate for computing true transfer rate constants. When the data were reanalyzed using a multi-compartment graphical analysis, solutes with different molecular radii were found to enter the brain at approximately equal rates. Furthermore, unidirectional transport is likely to be initiated by solute adsorption to a glycocalyx coat on the luminal surface of brain capillary endothelium. Apparently, more inulin than L-glucose was adsorbed, which may account for its slightly faster transfer across the BBB. After rats were treated with intracarotid infusions of ISS or hyperosmolar arabinose, solute PS values were significantly increased, but the ratio of PS for each of the solute pairs approached that of their free-diffusion coefficients
Transport of Liquid Phase Organic Solutes in Liquid Crystalline Membranes
Han, Sangil
2010-01-01
Porous cellulose nitrate membranes were impregnated with 8CB and PCH5 LCs (liquid crystals) and separations of solutes dissolved in aqueous phases were performed while monitoring solute concentration via UV-VIS spectrometry. The diffusing organic solutes, which consist of one aromatic ring and various functional groups, were selected to exclude molecular size effects on the diffusion and sorption. We studied the effects on solute transport of solute intra-molecular hydrogen bonding and so...
Smooth solutions for the dyadic model
Barbato, David; Morandin, Francesco; Romito, Marco
2011-01-01
We consider the dyadic model, which is a toy model to test issues of well-posedness and blow-up for the Navier–Stokes and Euler equations. We prove well-posedness of positive solutions of the viscous problem in the relevant scaling range which corresponds to Navier–Stokes. Likewise we prove well-posedness for the inviscid problem (in a suitable regularity class) when the parameter corresponds to the strongest transport effect of the nonlinearity
Elert, M.
1999-05-01
The 'Aespoe task force on modelling of groundwater flow and transport of solutes' is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. In this report, the modelling work performed within Tasks 4C and 4D is evaluated, which comprised predictive modelling of the radially converging tracer tests and dipole tracer tests performed within the TRUE-1 tests using non-sorbing tracers. The tests were performed between packed off boreholes penetrating a water-conducting geological feature with a simple structure (Feature A). These tests are to a great extent preparatory steps for the subsequent tests with sorbing radioactive tracers. In Tasks 4E and 4F of the Aespoe Modelling Task Force predictive modelling of the sorbing tracer tests is performed. Eight modelling teams representing seven organisations have performed predictive modelling using different modelling approaches and models. The modelling groups were initially given data from the site characterisation and data on the experimental set-up of the tracer tests. Based on this information model predictions were performed of drawdown, tracer mass recovery and tracer breakthrough. The performed predictions shows that the concept of Feature A as a singular well-connected feature with limited connectivity to its surroundings is quite adequate for predictions of drawdown in boreholes and conservative tracer breakthrough. Reasonable estimates were obtained using relatively simple models. However, more elaborate models with calibration or conditioning of transmissivities and transport apertures are required for more accurate predictions. The general flow and transport processes are well understood, but the methodology to derive the
Elert, M. [Kemakta Konsult AB, Stockholm (Sweden)
1999-05-01
The `Aespoe task force on modelling of groundwater flow and transport of solutes` is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. In this report, the modelling work performed within Tasks 4C and 4D is evaluated, which comprised predictive modelling of the radially converging tracer tests and dipole tracer tests performed within the TRUE-1 tests using non-sorbing tracers. The tests were performed between packed off boreholes penetrating a water-conducting geological feature with a simple structure (Feature A). These tests are to a great extent preparatory steps for the subsequent tests with sorbing radioactive tracers. In Tasks 4E and 4F of the Aespoe Modelling Task Force predictive modelling of the sorbing tracer tests is performed. Eight modelling teams representing seven organisations have performed predictive modelling using different modelling approaches and models. The modelling groups were initially given data from the site characterisation and data on the experimental set-up of the tracer tests. Based on this information model predictions were performed of drawdown, tracer mass recovery and tracer breakthrough. The performed predictions shows that the concept of Feature A as a singular well-connected feature with limited connectivity to its surroundings is quite adequate for predictions of drawdown in boreholes and conservative tracer breakthrough. Reasonable estimates were obtained using relatively simple models. However, more elaborate models with calibration or conditioning of transmissivities and transport apertures are required for more accurate predictions. The general flow and transport processes are well understood, but the methodology to derive the
Engineering solutions of traffic safety problems of road transport
M. Bogdevičius
2004-02-01
Full Text Available The authors of this paper focus on the simulation of the motor vehicle movement (taking into consideration motor vehicle dynamics, motor vehicle hydraulic brake system influence on motor vehicle movement, interaction between its wheels with road pavements, road guardrail characteristics, interaction between motor vehicle and road guardrail on a certain road section and propose their specific solution of this problem. The presented results, illustrating the motor vehicle movement trajectories (motor vehicle braking and interaction between motor vehicle and road guardrail at various initial conditions and at various certain pavement surface of the road section under investigation and work of a motor vehicle hydraulic brake system. Taking into consideration the presented general mathematical model and computer aided test results it is possible to investigate various road transport traffic situations as well as to investigate various transport traffic safety problems.
Solute transport in fractured rock - applications to radionuclide waste repositories
Neretnieks, I.
1990-12-01
Flow and solute transport in fractured rocks has been intensively studied in the last decade. The increased interest is mainly due to the plans in many countries to site repositories for high level nuclear waste in deep geologic formations. All investigated crystalline rocks have been found to be fractured and most of the water flows in the fractures and fracture zones. The water transports dissolved species and radionuclides. It is thus of interest to be able to understand and to do predictive modelling of the flowrate of water, the flowpaths and the residence times of the water and of the nuclides. The dissolved species including the nuclides will interact with the surrounding rock in different ways and will in many cases be strongly retarded relative to the water velocity. Ionic species may be ion exchanged or sorbed in the mineral surfaces. Charges and neutral species may diffuse into the stagnant waters in the rock matrix and thus be withdrawn from the mobile water. These effects will be strongly dependent on how much rock surface is in contact with the flowing water. It has been found in a set of field experiments and by other observations that not all fractures conduct water. Furthermore it is found that conductive fractures only conduct the water in a small part of the fracture in what is called channels or preferential flowpaths. This report summarizes the present concepts of water flow and solute transport in fractured rocks. The data needs for predictive modelling are discussed and both field and laboratory measurement which have been used to obtain data are described. Several large scale field experiments which have been specially designed to study flow and tracer transport in crystalline rocks are described. In many of the field experients new techniques have been developed and used. (81 refs.) (author)
Jacek Waniewski
2016-01-01
Full Text Available During peritoneal dialysis (PD, the peritoneal membrane undergoes ageing processes that affect its function. Here we analyzed associations of patient age and dialysis vintage with parameters of peritoneal transport of fluid and solutes, directly measured and estimated based on the pore model, for individual patients. Thirty-three patients (15 females; age 60 (21–87 years; median time on PD 19 (3–100 months underwent sequential peritoneal equilibration test. Dialysis vintage and patient age did not correlate. Estimation of parameters of the two-pore model of peritoneal transport was performed. The estimated fluid transport parameters, including hydraulic permeability (LpS, fraction of ultrasmall pores (αu, osmotic conductance for glucose (OCG, and peritoneal absorption, were generally independent of solute transport parameters (diffusive mass transport parameters. Fluid transport parameters correlated whereas transport parameters for small solutes and proteins did not correlate with dialysis vintage and patient age. Although LpS and OCG were lower for older patients and those with long dialysis vintage, αu was higher. Thus, fluid transport parameters—rather than solute transport parameters—are linked to dialysis vintage and patient age and should therefore be included when monitoring processes linked to ageing of the peritoneal membrane.
Waniewski, Jacek; Antosiewicz, Stefan; Baczynski, Daniel; Poleszczuk, Jan; Pietribiasi, Mauro; Lindholm, Bengt; Wankowicz, Zofia
2016-01-01
During peritoneal dialysis (PD), the peritoneal membrane undergoes ageing processes that affect its function. Here we analyzed associations of patient age and dialysis vintage with parameters of peritoneal transport of fluid and solutes, directly measured and estimated based on the pore model, for individual patients. Thirty-three patients (15 females; age 60 (21–87) years; median time on PD 19 (3–100) months) underwent sequential peritoneal equilibration test. Dialysis vintage and patient age did not correlate. Estimation of parameters of the two-pore model of peritoneal transport was performed. The estimated fluid transport parameters, including hydraulic permeability (LpS), fraction of ultrasmall pores (α u), osmotic conductance for glucose (OCG), and peritoneal absorption, were generally independent of solute transport parameters (diffusive mass transport parameters). Fluid transport parameters correlated whereas transport parameters for small solutes and proteins did not correlate with dialysis vintage and patient age. Although LpS and OCG were lower for older patients and those with long dialysis vintage, αu was higher. Thus, fluid transport parameters—rather than solute transport parameters—are linked to dialysis vintage and patient age and should therefore be included when monitoring processes linked to ageing of the peritoneal membrane. PMID:26989432
Transport Visualization for Studying Mass Transfer and Solute Transport in Permeable Media
Roy Haggerty
2004-01-01
first such experiments that show mass transfer in porous media in great detail. Experimental and theoretical work in media with pore-scale heterogeneity showed the temporal scale-dependency of mass transfer. Extension of the work into reactive transport, where mass transfer is very important to mixing, suggests a number of promising research directions for constructing better models of reactive transport and provides the experimental tools to develop and test these models. In particular, it is important to determine how the different solute spreading mechanisms in heterogeneous conductivity fields affect the rate and spatial pattern of chemical reaction. The project was conducted collaboratively between Oregon State University, Sandia National Laboratories, and the Massachusetts Institute of Technology. While each institution is submitting a copy of this final report for administrative purposes, the report is the largely the same since the project was a joint effort. This final report will outline the results of work completed and summarize publications and presentations. Manuscripts published or in press are attached, and subsequent publications will follow once published
Effects of turbulent hyporheic mixing on reach-scale solute transport
Roche, K. R.; Li, A.; Packman, A. I.
2017-12-01
Turbulence rapidly mixes solutes and fine particles into coarse-grained streambeds. Both hyporheic exchange rates and spatial variability of hyporheic mixing are known to be controlled by turbulence, but it is unclear how turbulent mixing influences mass transport at the scale of stream reaches. We used a process-based particle-tracking model to simulate local- and reach-scale solute transport for a coarse-bed stream. Two vertical mixing profiles, one with a smooth transition from in-stream to hyporheic transport conditions and a second with enhanced turbulent transport at the sediment-water interface, were fit to steady-state subsurface concentration profiles observed in laboratory experiments. The mixing profile with enhanced interfacial transport better matched the observed concentration profiles and overall mass retention in the streambed. The best-fit mixing profiles were then used to simulate upscaled solute transport in a stream. Enhanced mixing coupled in-stream and hyporheic solute transport, causing solutes exchanged into the shallow subsurface to have travel times similar to the water column. This extended the exponential region of the in-stream solute breakthrough curve, and delayed the onset of the heavy power-law tailing induced by deeper and slower hyporheic porewater velocities. Slopes of observed power-law tails were greater than those predicted from stochastic transport theory, and also changed in time. In addition, rapid hyporheic transport velocities truncated the hyporheic residence time distribution by causing mass to exit the stream reach via subsurface advection, yielding strong exponential tempering in the in-stream breakthrough curves at the timescale of advective hyporheic transport through the reach. These results show that strong turbulent mixing across the sediment-water interface violates the conventional separation of surface and subsurface flows used in current models for solute transport in rivers. Instead, the full distribution of
Transport of Organic Solutes in Clay Formations
The research is a pilot investigation for the SERDP (Strategic Environmental Research and Development Program, DoD) founded project, Impact of Clay-DNAPL Interactions on Transport and Storage of Chlorinated Solvents in Low Permeability Zones, from 2010-2012. The report tries to s...
Radionuclide Transport Models Under Ambient Conditions
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
A variational solution of transport equation based on spherical geometry
Liu Hui; Zhang Ben'ai
2002-01-01
A variational method with differential forms gives better precision for numerical solution of transport critical problem based on spherical geometry, and its computation seems simple than other approximate methods
TRANSPORT OF SOLUTES IN THE FIELD AS AFFECTED BY IRRIGATION
Alessandro Comegna
2007-09-01
Full Text Available This study documents and compares the transport of a conservative solute in near saturated soil profiles under flood and sprinkler irrigation. The experiments were carried out on a clay Vertic-Usthortens soil located near Potenza (Italy. Two 2x2 m2 plots were clipped of their native grass vegetation. After spraying on the surface a Cl- pulse as KCl salt; water was applied in five increments over two months as flood irrigation on the first plot and as sprinkler irrigation on the second one. Chloride resident concentration Cr, was sampled by soil coring at four different days after chemical application. Cr(z,t profiles were analyzed by spatial moment method. The recovered mass of Cl- and location of center of mass were comparable for the two types of irrigation. The spread around the center of mass, however, was higher for the flood-irrigated plot. In the flood-irrigated plot, more mass leached below the depth of 90 cm. The velocity of the center of mass was consistently 10-20% larger than the piston displacement velocity. To evaluate the nature of transport, the Cr(z,t distributions were modelled using quasi-steady solution of convection-dispersion equation(CDE. At the scale of our experiments the profiles of Cl- resident concentration are well-simulated.
Solute transport across the articular surface of injured cartilage.
Chin, Hooi Chuan; Moeini, Mohammad; Quinn, Thomas M
2013-07-15
Solute transport through extracellular matrix (ECM) is important to physiology and contrast agent-based clinical imaging of articular cartilage. Mechanical injury is likely to have important effects on solute transport since it involves alteration of ECM structure. Therefore it is of interest to characterize effects of mechanical injury on solute transport in cartilage. Using cartilage explants injured by an established mechanical compression protocol, effective partition coefficients and diffusivities of solutes for transport across the articular surface were measured. A range of fluorescent solutes (fluorescein isothiocyanate, 4 and 40kDa dextrans, insulin, and chondroitin sulfate) and an X-ray contrast agent (sodium iodide) were used. Mechanical injury was associated with a significant increase in effective diffusivity versus uninjured explants for all solutes studied. On the other hand, mechanical injury had no effects on effective partition coefficients for most solutes tested, except for 40kDa dextran and chondroitin sulfate where small but significant changes in effective partition coefficient were observed in injured explants. Findings highlight enhanced diffusive transport across the articular surface of injured cartilage, which may have important implications for injury and repair situations. Results also support development of non-equilibrium methods for identification of focal cartilage lesions by contrast agent-based clinical imaging. Copyright © 2013 Elsevier Inc. All rights reserved.
Temporal moment analysis of solute transport in a coupled fracture ...
by considering an inlet boundary condition of constant continuous source in a single fracture. The effect of various fracture-skin parameters like porosity, thickness and ... Study on fluid flow and transport of solute through fractures has been an .... of solutes is happening normal to the direction of flow due to the free molecular.
Fluid and solute transport in a network of channels
Moreno, L.; Neretnieks, I.
1991-09-01
A three-dimensional channel network model is presented. The fluid flow and solute transport are assumed to take place through a network of connected channels. The channels are generated assuming that the conductances are lognormally distributed. The flow is calculated resolving the pressure distribution and the sole transport is calculated by using a particle tracking technique. The model includes diffusion into the rock matrix and sorption within the matrix in addition to advection along the channel network. Different approaches are used to describe the channel volume and its relation to the conductivity. To quantify the diffusion into the rock matrix the size of the flow wetted surface (contact surface between the channel and the rock) is needed in addition to the diffusion properties and the sorption capacity of the rock. Two different geometries were simulated: regional parallel flow and convergent flow toward a tunnel. In the generation of the channel network, it is found that its connectivity is reduced when the standard deviation in conductances is increased. For large standard deviations, the water conducting channels are found to be few. Standard deviations for the distribution of the effluent channel flowrates were calculated. Comparisons were made with experimental data from drifts and tunnels as well as boreholes as a means to validate the model. (au) (31 refs.)
Sanchez, Richard.
1980-11-01
This work is divided into two parts: the first part deals with the solution of complex two-dimensional transport problems, the second one (note CEA-N-2166) treats the critically mixed methods of resolution. A set of approximate solutions for the isotropic two-dimensional neutron transport problem has been developed using the interface current formalism. The method has been applied to regular lattices of rectangular cells containing a fuel pin, cladding, and water, or homogenized structural material. The cells are divided into zones that are homogeneous. A zone-wise flux expansion is used to formulate a direct collision probability problem within a cell. The coupling of the cells is effected by making extra assumptions on the currents entering and leaving the interfaces. Two codes have been written: CALLIOPE uses a cylindrical cell model and one or three terms for the flux expansion, and NAUSICAA uses a two-dimensional flux representation and does a truly two-dimensional calculation inside each cell. In both codes, one or three terms can be used to make a space-independent expansion of the angular fluxes entering and leaving each side of the cell. The accuracies and computing times achieved with the different approximations are illustrated by numerical studies on two benchmark problems and by calculations performed in the APOLLO multigroup code [fr
Jakob, Andreas; Mazurek, Martin; Heer, Walter
2003-03-01
Based on the results from detailed structural and petrological characterisation and on up-scaled laboratory values for sorption and diffusion, blind predictions were made for the STT1 dipole tracer test performed in the Swedish Äspö Hard Rock Laboratory. The tracers used were nonsorbing, such as uranine and tritiated water, weakly sorbing 22Na +, 85Sr 2+, 47Ca 2+and more strongly sorbing 86Rb +, 133Ba 2+, 137Cs +. Our model consists of two parts: (1) a flow part based on a 2D-streamtube formalism accounting for the natural background flow field and with an underlying homogeneous and isotropic transmissivity field and (2) a transport part in terms of the dual porosity medium approach which is linked to the flow part by the flow porosity. The calibration of the model was done using the data from one single uranine breakthrough (PDT3). The study clearly showed that matrix diffusion into a highly porous material, fault gouge, had to be included in our model evidenced by the characteristic shape of the breakthrough curve and in line with geological observations. After the disclosure of the measurements, it turned out that, in spite of the simplicity of our model, the prediction for the nonsorbing and weakly sorbing tracers was fairly good. The blind prediction for the more strongly sorbing tracers was in general less accurate. The reason for the good predictions is deemed to be the result of the choice of a model structure strongly based on geological observation. The breakthrough curves were inversely modelled to determine in situ values for the transport parameters and to draw consequences on the model structure applied. For good fits, only one additional fracture family in contact with cataclasite had to be taken into account, but no new transport mechanisms had to be invoked. The in situ values for the effective diffusion coefficient for fault gouge are a factor of 2-15 larger than the laboratory data. For cataclasite, both data sets have values comparable to
Sustainable freight transport in South Africa:Domestic intermodal solutions
Jan H. Havenga
2011-11-01
Full Text Available Due to the rapid deregulation of freight transport in South Africa two decades ago, and low historical investment in rail (with resultant poor service delivery, an integrated alternative to road and rail competition was never developed. High national freight logistics costs, significant road infrastructure challenges and environmental impact concerns of a road-dominated freight transport market have, however, fuelled renewed interest in intermodal transport solutions. In this article, a high-level business case for domestic intermodal solutions in South Africa is presented. The results demonstrate that building three intermodal terminals to connect the three major industrial hubs (i.e. Gauteng, Durban and Cape Town through an intermodal solution could reduce transport costs (including externalities for the identified 11.5 million tons of intermodalfriendly freight flows on the Cape and Natal corridors by 42% (including externalities.
Determination of chemical solute transport parameters effecting radiostrontium interbed sediments
Hemming, C.; Bunde, R.L.; Rosentreter, J.J.
1993-01-01
The extent to which radionuclides migrate in an aquifer system is a function of various physical, chemical, and biological processes. A measure of this migration rate is of primary concern when locating suitable storage sites for such species. Parameters including water-rock interactions, infiltration rates, chemical phase modification, and biochemical reactions all affect solute transport. While these different types of chemical reactions can influence solute transport in subsurface waters, distribution coefficients (Kd) can be send to effectively summarize the net chemical factors which dictate transport efficiency. This coefficient describes the partitioning of the solute between the solution and solid phase. Methodology used in determining and interpreting the distribution coefficient for radiostrontium in well characterized sediments will be presented
George J. Moridis
2001-01-01
In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive solute tracers through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the non-flowing matrix account for (a) diffusion, (b) surface diffusion, (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first-order chemical reactions. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of 3 H, 237 Np and 239 Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity
VS2DRTI: Simulating Heat and Reactive Solute Transport in Variably Saturated Porous Media.
Healy, Richard W; Haile, Sosina S; Parkhurst, David L; Charlton, Scott R
2018-01-29
Variably saturated groundwater flow, heat transport, and solute transport are important processes in environmental phenomena, such as the natural evolution of water chemistry of aquifers and streams, the storage of radioactive waste in a geologic repository, the contamination of water resources from acid-rock drainage, and the geologic sequestration of carbon dioxide. Up to now, our ability to simulate these processes simultaneously with fully coupled reactive transport models has been limited to complex and often difficult-to-use models. To address the need for a simple and easy-to-use model, the VS2DRTI software package has been developed for simulating water flow, heat transport, and reactive solute transport through variably saturated porous media. The underlying numerical model, VS2DRT, was created by coupling the flow and transport capabilities of the VS2DT and VS2DH models with the equilibrium and kinetic reaction capabilities of PhreeqcRM. Flow capabilities include two-dimensional, constant-density, variably saturated flow; transport capabilities include both heat and multicomponent solute transport; and the reaction capabilities are a complete implementation of geochemical reactions of PHREEQC. The graphical user interface includes a preprocessor for building simulations and a postprocessor for visual display of simulation results. To demonstrate the simulation of multiple processes, the model is applied to a hypothetical example of injection of heated waste water to an aquifer with temperature-dependent cation exchange. VS2DRTI is freely available public domain software. © 2018, National Ground Water Association.
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
Pouran, Behdad; Arbabi, Vahid; Zadpoor, Amir A; Weinans, Harrie
2016-12-01
The metabolic function of cartilage primarily depends on transport of solutes through diffusion mechanism. In the current study, we use contrast enhanced micro-computed tomography to determine equilibrium concentration of solutes through different cartilage zones and solute flux in the cartilage, using osteochondral plugs from equine femoral condyles. Diffusion experiments were performed with two solutes of different charge and approximately equal molecular weight, namely iodixanol (neutral) and ioxaglate (charge=-1) in order to isolate the effects of solute's charge on diffusion. Furthermore, solute concentrations as well as bath osmolality were changed to isolate the effects of steric hindrance on diffusion. Bath concentration and bath osmolality only had minor effects on the diffusion of the neutral solute through cartilage at the surface, middle and deep zones, indicating that the diffusion of the neutral solute was mainly Fickian. The negatively charged solute diffused considerably slower through cartilage than the neutral solute, indicating a large non-Fickian contribution in the diffusion of charged molecules. The numerical models determined maximum solute flux in the superficial zone up to a factor of 2.5 lower for the negatively charged solutes (charge=-1) as compared to the neutral solutes confirming the importance of charge-matrix interaction in diffusion of molecules across cartilage. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.
Schuff, M M; Gore, J P; Nauman, E A
2013-12-01
The treatment of cancerous tumors is dependent upon the delivery of therapeutics through the blood by means of the microcirculation. Differences in the vasculature of normal and malignant tissues have been recognized, but it is not fully understood how these differences affect transport and the applicability of existing mathematical models has been questioned at the microscale due to the complex rheology of blood and fluid exchange with the tissue. In addition to determining an appropriate set of governing equations it is necessary to specify appropriate model parameters based on physiological data. To this end, a two stage sensitivity analysis is described which makes it possible to determine the set of parameters most important to the model's calibration. In the first stage, the fluid flow equations are examined and a sensitivity analysis is used to evaluate the importance of 11 different model parameters. Of these, only four substantially influence the intravascular axial flow providing a tractable set that could be calibrated using red blood cell velocity data from the literature. The second stage also utilizes a sensitivity analysis to evaluate the importance of 14 model parameters on extravascular flux. Of these, six exhibit high sensitivity and are integrated into the model calibration using a response surface methodology and experimental intra- and extravascular accumulation data from the literature (Dreher et al. in J Natl Cancer Inst 98(5):335-344, 2006). The model exhibits good agreement with the experimental results for both the mean extravascular concentration and the penetration depth as a function of time for inert dextran over a wide range of molecular weights.
Multi-compartment Aerosol Transport Model
Hubbard, Joshua Allen; Santarpia, Joshua; Brotherton, Christopher M.; Omana, Michael Alexis; Rivera, Danielle; Lucero, Gabriel Anthony
2017-06-01
A simple aerosol transport model was developed for a multi-compartmented cleanroom. Each compartment was treated as a well-mixed volume with ventilating supply and return air. Gravitational settling, intercompartment transport, and leakage of exterior air into the system were included in the model. A set of first order, coupled, ordinary differential equations was derived from the conservation equations of aerosol mass and air mass. The system of ODEs was then solved in MATLAB using pre-existing numerical methods. The model was verified against cases of (1) constant inlet-duct concentration, and (2) exponentially decaying inlet-duct concentration. Numerical methods resulted in normalized error of less than 10 -9 when model solutions were compared to analytical solutions. The model was validated against experimental measurements from a single field test and showed good agreement in the shape and magnitude of the aerosol concentration profile with time.
McEwen, T.J.; Chapman, N.A.; Robinson, P.C.
1990-08-01
This report describes the data requirements for the codes that may be used in the modelling of groundwater flow and radionuclide transport during the assessment of a Nirex site for the deep disposal of low and intermediate level radioactive waste and also the site investigation methods that exist to supply the data for these codes. The data requirements for eight codes are reviewed, with most emphasis on three of the more significant codes, VANDAL, NAMMU and CHEMTARD. The largest part of the report describes and discusses the site investigation techniques and each technique is considered in terms of its ability to provide the data necessary to characterise the geological and hydrogeological environment around a potential repository. (author)
Stochastic models of intracellular transport
Bressloff, Paul C.
2013-01-09
The interior of a living cell is a crowded, heterogenuous, fluctuating environment. Hence, a major challenge in modeling intracellular transport is to analyze stochastic processes within complex environments. Broadly speaking, there are two basic mechanisms for intracellular transport: passive diffusion and motor-driven active transport. Diffusive transport can be formulated in terms of the motion of an overdamped Brownian particle. On the other hand, active transport requires chemical energy, usually in the form of adenosine triphosphate hydrolysis, and can be direction specific, allowing biomolecules to be transported long distances; this is particularly important in neurons due to their complex geometry. In this review a wide range of analytical methods and models of intracellular transport is presented. In the case of diffusive transport, narrow escape problems, diffusion to a small target, confined and single-file diffusion, homogenization theory, and fractional diffusion are considered. In the case of active transport, Brownian ratchets, random walk models, exclusion processes, random intermittent search processes, quasi-steady-state reduction methods, and mean-field approximations are considered. Applications include receptor trafficking, axonal transport, membrane diffusion, nuclear transport, protein-DNA interactions, virus trafficking, and the self-organization of subcellular structures. © 2013 American Physical Society.
Analysis of the Sodium Recirculation Theory of Solute Coupled Water Transport in Small Intestine
Larsen, E. H.; Sørensen, Jens Nørkær; Sørensen, J. B.
2002-01-01
Our previous mathematical model of solute-coupled water transport through the intestinal epithelium is extended for dealing with electrolytes rather than electroneutral solutes. A 3Na+-2K+ pump in the lateral membranes provides the energy-requiring step for driving transjunctional and translateral......, computations predict that the concentration differences between lis and bathing solutions are small for all three ions. Nevertheless, the diffusion fluxes of the ions out of lis significantly exceed their mass transports. It is concluded that isotonic transport requires recirculation of all three ions....... The computed sodium recirculation flux that is required for isotonic transport corresponds to that estimated in experiments on toad small intestine. This result is shown to be robust and independent of whether the apical entrance mechanism for the sodium ion is a channel, a SGLT1 transporter driving inward...
Analytical solution to the hybrid diffusion-transport equation
Nanneh, M.M.; Williams, M.M.R.
1986-01-01
A special integral equation was derived in previous work using a hybrid diffusion-transport theory method for calculating the flux distribution in slab lattices. In this paper an analytical solution of this equation has been carried out on a finite reactor lattice. The analytical results of disadvantage factors are shown to be accurate in comparison with the numerical results and accurate transport theory calculations. (author)
Modelling Ballast Water Transport
Jayakumar, S.; Babu, M.T.; Vethamony, P.
Ballast water discharges in the coastal environs have caused a great concern over the recent periods as they account for transporting marine organisms from one part of the world to the other. The movement of discharged ballast water as well...
Fluid flow and convective transport of solutes within the intervertebral disc.
Ferguson, Stephen J; Ito, Keita; Nolte, Lutz P
2004-02-01
Previous experimental and analytical studies of solute transport in the intervertebral disc have demonstrated that for small molecules diffusive transport alone fulfils the nutritional needs of disc cells. It has been often suggested that fluid flow into and within the disc may enhance the transport of larger molecules. The goal of the study was to predict the influence of load-induced interstitial fluid flow on mass transport in the intervertebral disc. An iterative procedure was used to predict the convective transport of physiologically relevant molecules within the disc. An axisymmetric, poroelastic finite-element structural model of the disc was developed. The diurnal loading was divided into discrete time steps. At each time step, the fluid flow within the disc due to compression or swelling was calculated. A sequentially coupled diffusion/convection model was then employed to calculate solute transport, with a constant concentration of solute being provided at the vascularised endplates and outer annulus. Loading was simulated for a complete diurnal cycle, and the relative convective and diffusive transport was compared for solutes with molecular weights ranging from 400 Da to 40 kDa. Consistent with previous studies, fluid flow did not enhance the transport of low-weight solutes. During swelling, interstitial fluid flow increased the unidirectional penetration of large solutes by approximately 100%. Due to the bi-directional temporal nature of disc loading, however, the net effect of convective transport over a full diurnal cycle was more limited (30% increase). Further study is required to determine the significance of large solutes and the timing of their delivery for disc physiology.
Winston, Richard B.; Voss, Clifford I.
2004-01-01
This report describes SutraGUI, a flexible graphical user-interface (GUI) that supports two-dimensional (2D) and three-dimensional (3D) simulation with the U.S. Geological Survey (USGS) SUTRA ground-water-flow and transport model (Voss and Provost, 2002). SutraGUI allows the user to create SUTRA ground-water models graphically. SutraGUI provides all of the graphical functionality required for setting up and running SUTRA simulations that range from basic to sophisticated, but it is also possible for advanced users to apply programmable features within Argus ONE to meet the unique demands of particular ground-water modeling projects. SutraGUI is a public-domain computer program designed to run with the proprietary Argus ONE? package, which provides 2D Geographic Information System (GIS) and meshing support. For 3D simulation, GIS and meshing support is provided by programming contained within SutraGUI. When preparing a 3D SUTRA model, the model and all of its features are viewed within Argus 1 in 2D projection. For 2D models, SutraGUI is only slightly changed in functionality from the previous 2D-only version (Voss and others, 1997) and it provides visualization of simulation results. In 3D, only model preparation is supported by SutraGUI, and 3D simulation results may be viewed in SutraPlot (Souza, 1999) or Model Viewer (Hsieh and Winston, 2002). A comprehensive online Help system is included in SutraGUI. For 3D SUTRA models, the 3D model domain is conceptualized as bounded on the top and bottom by 2D surfaces. The 3D domain may also contain internal surfaces extending across the model that divide the domain into tabular units, which can represent hydrogeologic strata or other features intended by the user. These surfaces can be non-planar and non-horizontal. The 3D mesh is defined by one or more 2D meshes at different elevations that coincide with these surfaces. If the nodes in the 3D mesh are vertically aligned, only a single 2D mesh is needed. For nonaligned
Colombant, Denis; Manheimer, Wallace
2010-01-01
Flux limitation and preheat are important processes in electron transport occurring in laser produced plasmas. The proper calculation of both of these has been a subject receiving much attention over the entire lifetime of the laser fusion project. Where nonlocal transport (instead of simple single flux limit) has been modeled, it has always been with what we denote the equivalent diffusion solution, namely treating the transport as only a diffusion process. We introduce here a new approach called the nonlocal source solution and show it is numerically viable for laser produced plasmas. It turns out that the equivalent diffusion solution generally underestimates preheat. Furthermore, the advance of the temperature front, and especially the preheat, can be held up by artificial 'thermal barriers'. The nonlocal source method of solution, on the other hand more accurately describes preheat and can stably calculate the solution for the temperature even if the heat flux is up the gradient.
New numerical method for solving the solute transport equation
Ross, B.; Koplik, C.M.
1978-01-01
The solute transport equation can be solved numerically by approximating the water flow field by a network of stream tubes and using a Green's function solution within each stream tube. Compared to previous methods, this approach permits greater computational efficiency and easier representation of small discontinuities, and the results are easier to interpret physically. The method has been used to study hypothetical sites for disposal of high-level radioactive waste
Efficient solution of a multi objective fuzzy transportation problem
Vidhya, V.; Ganesan, K.
2018-04-01
In this paper we present a methodology for the solution of multi-objective fuzzy transportation problem when all the cost and time coefficients are trapezoidal fuzzy numbers and the supply and demand are crisp numbers. Using a new fuzzy arithmetic on parametric form of trapezoidal fuzzy numbers and a new ranking method all efficient solutions are obtained. The proposed method is illustrated with an example.
Stable solutions of nonlocal electron heat transport equations
Prasad, M.K.; Kershaw, D.S.
1991-01-01
Electron heat transport equations with a nonlocal heat flux are in general ill-posed and intrinsically unstable, as proved by the present authors [Phys. Fluids B 1, 2430 (1989)]. A straightforward numerical solution of these equations will therefore lead to absurd results. It is shown here that by imposing a minimal set of constraints on the problem it is possible to arrive at a globally stable, consistent, and energy conserving numerical solution
Wang, W.; Oswald, S. E.; Munz, M.; Strasser, D.
2017-12-01
Bank filtration is widely used either as main- or pre-treatment process for water supply. The colmation of the river bottom as interface to groundwater plays a key role for hydraulic control of flow paths and location of several beneficial attenuation processes, such as pathogen filtration, mixing, biodegradation and sorption. Along the flow path, mixing happens between the `young' infiltrated water and ambient `old' groundwater. To clarify the mechanisms and their interaction, modelling is often used for analysing spatial and temporal distribution of the travelling time, quantifying mixing ratios, and estimating the biochemical reaction rates. As the most comprehensive tool, 2-D or 3-D spatially-explicit modelling is used in several studies, and for area with geological heterogeneity, the adaptation of different natural tracers could constrain the model in respect to model non-uniqueness and improve the interpretation of the flow field. In our study, we have evaluated the influence of a river excavation and bank reconstruction project on the groundwater-surface water exchange at a bank filtration site. With data from years of field site monitoring, we could include besides heads and temperature also the analysis of stable isotope data and ions to differentiate between infiltrated water and groundwater. Thus, we have set up a 3-D transient heat and mass transport groundwater model, taking the strong local geological heterogeneity into consideration, especially between river and water work wells. By transferring the effect of the river excavation into a changing hydraulic conductivity of the riverbed, model could be calibrated against both water head and temperature time-series observed. Finally, electrical conductivity dominated by river input was included as quasi-conservative tracer. The `triple' calibrated, transient model was then used to i) understand the flow field and quantify the long term changes in infiltration rate and distribution brought by the
Green transportation logistics: the quest for win-win solutions
measures and speed and route optimization; Sulphur emissions; Lifecycle emissions; Green rail transportation; Green air transportation; Green inland navigation and possible areas for further research. Throughout, the book pursues the goal of “win-win” solutions and analyzes the phenomenon of “push......This book examines the state of the art in green transportation logistics from the perspective of balancing environmental performance in the transportation supply chain while also satisfying traditional economic performance criteria. Part of the book is drawn from the recently completed European...... Union project Super Green, a three-year project intended to promote the development of European freight corridors in an environmentally friendly manner. Additional chapters cover both the methodological base and the application context of green transportation logistics. Individual chapters look...
Reactive solute transport in an asymmetrical fracture-rock matrix system
Zhou, Renjie; Zhan, Hongbin
2018-02-01
The understanding of reactive solute transport in a single fracture-rock matrix system is the foundation of studying transport behavior in the complex fractured porous media. When transport properties are asymmetrically distributed in the adjacent rock matrixes, reactive solute transport has to be considered as a coupled three-domain problem, which is more complex than the symmetric case with identical transport properties in the adjacent rock matrixes. This study deals with the transport problem in a single fracture-rock matrix system with asymmetrical distribution of transport properties in the rock matrixes. Mathematical models are developed for such a problem under the first-type and the third-type boundary conditions to analyze the spatio-temporal concentration and mass distribution in the fracture and rock matrix with the help of Laplace transform technique and de Hoog numerical inverse Laplace algorithm. The newly acquired solutions are then tested extensively against previous analytical and numerical solutions and are proven to be robust and accurate. Furthermore, a water flushing phase is imposed on the left boundary of system after a certain time. The diffusive mass exchange along the fracture/rock matrixes interfaces and the relative masses stored in each of three domains (fracture, upper rock matrix, and lower rock matrix) after the water flushing provide great insights of transport with asymmetric distribution of transport properties. This study has the following findings: 1) Asymmetric distribution of transport properties imposes greater controls on solute transport in the rock matrixes. However, transport in the fracture is mildly influenced. 2) The mass stored in the fracture responses quickly to water flushing, while the mass stored in the rock matrix is much less sensitive to the water flushing. 3) The diffusive mass exchange during the water flushing phase has similar patterns under symmetric and asymmetric cases. 4) The characteristic distance
Rockhold, M.L.
1993-02-01
A field-scale, unsaturated flow and solute transport experiment at the Las Cruces trench site in New Mexico was simulated as part of a ''blind'' modeling exercise to demonstrate the ability or inability of uncalibrated models to predict unsaturated flow and solute transport in spatially variable porous media. Simulations were conducted using a recently developed multiphase flow and transport simulator. Uniform and heterogeneous soil models were tested, and data from a previous experiment at the site were used with an inverse procedure to estimate water retention parameters. A spatial moment analysis was used to provide a quantitative basis for comparing the mean observed and simulated flow and transport behavior. The results of this study suggest that defensible predictions of waste migration and fate at low-level waste sites will ultimately require site-specific data for model calibration
The future of public transport in light of solutions for sustainable transport development
Kazimierz LEJDA
2017-06-01
Full Text Available The paper highlights possible directions in the development of sustainable public transport solutions. When appropriately identified and implemented, such solutions can contribute to improved quality of urban life by reducing the adverse effects of transport on human health and the natural environment. The paper also raises questions about implementing pedestrian traffic zones, expanding the level of cycling, and introducing a workable parking policy, congestion charges, electromobility and intelligent systems for road traffic management in conurbations.
Kong, Rong; Spanier, Jerome
2013-01-01
In this paper we develop novel extensions of collision and track length estimators for the complete space-angle solutions of radiative transport problems. We derive the relevant equations, prove that our new estimators are unbiased, and compare their performance with that of more conventional estimators. Such comparisons based on numerical solutions of simple one dimensional slab problems indicate the the potential superiority of the new estimators for a wide variety of more general transport problems
Scaling and predicting solute transport processes in streams
R. González-Pinzón; R. Haggerty; M. Dentz
2013-01-01
We investigated scaling of conservative solute transport using temporal moment analysis of 98 tracer experiments (384 breakthrough curves) conducted in 44 streams located on five continents. The experiments span 7 orders of magnitude in discharge (10-3 to 103 m3/s), span 5 orders of magnitude in...
Radionuclide Transport Models Under Ambient Conditions
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
Prolonged river water pollution due to variable-density flow and solute transport in the riverbed
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.
Win-Win transportation solutions price reforms with multiple benefits
Litman, T.
2001-01-01
Reform strategies in the transportation market, such as the Win-Win Transportation Solutions, can provide several economic, social and environmental benefits. The strategies are cost effective, technically feasible reforms based on market principles which help create a more equitable and efficient transportation system that supports sustainable economic development. The benefits they provide include reduced traffic congestion, road and parking facility savings, consumer savings, equity, safety and environmental protection. They also increase economic productivity. If fully implemented, they could reduce motor vehicle impacts by 15 to 30 per cent and could help achieve the Kyoto emission reduction targets. Examples of Win-Win strategies at the federal level include: (1) removal of subsidies to oil production and internalized costs, and (2) tax exempt employer provided transfer benefits. Examples of Win-Win strategies at the state/provincial level include: (1) distance-based vehicle insurance and registration fees, (2) least-coast transportation planning and funding, (3) revenue-neutral tax shifting, (4) road pricing, (5) reform motor carrier regulations for competition and efficiency, (6) local and regional transportation demand management programs, (7) more efficient land use, (8) more flexible zoning requirements, (9) parking cash out, (10) transportation management associations, (11) location-efficient housing and mortgages, (12) school and campus trip management, (13) car sharing, (14) non-motorized transport improvements, and (15) traffic calming. It was noted that any market reform that leads to more efficient use of existing transportation systems can provide better economic development benefits. 9 refs., 1 tab., 1 fig
Probabilistic transport models for fusion
Milligen, B.Ph. van; Carreras, B.A.; Lynch, V.E.; Sanchez, R.
2005-01-01
A generalization of diffusive (Fickian) transport is considered, in which particle motion is described by probability distributions. We design a simple model that includes a critical mechanism to switch between two transport channels, and show that it exhibits various interesting characteristics, suggesting that the ideas of probabilistic transport might provide a framework for the description of a range of unusual transport phenomena observed in fusion plasmas. The model produces power degradation and profile consistency, as well as a scaling of the confinement time with system size reminiscent of the gyro-Bohm/Bohm scalings observed in fusion plasmas, and rapid propagation of disturbances. In the present work we show how this model may also produce on-axis peaking of the profiles with off-axis fuelling. It is important to note that the fluid limit of a simple model like this, characterized by two transport channels, does not correspond to the usual (Fickian) transport models commonly used for modelling transport in fusion plasmas, and behaves in a fundamentally different way. (author)
Savovic, S.; Djordjevich, A.; Ristic, G.
2012-01-01
A theoretical evaluation of the properties and processes affecting the radon transport from subsurface soil into buildings is presented in this work. The solution of the relevant transport equation is obtained using the explicit finite difference method (EFDM). Results are compared with analytical steady-state solution reported in the literature. Good agreement is found. It is shown that EFDM is effective and accurate for solving the equation that describes radon diffusion, advection and decay during its transport from subsurface to buildings, which is especially important when arbitrary initial and boundary conditions are required. (authors)
Yang, Jianwen
2012-04-01
A general analytical solution is derived by using the Laplace transformation to describe transient reactive silica transport in a conceptualized 2-D system involving a set of parallel fractures embedded in an impermeable host rock matrix, taking into account of hydrodynamic dispersion and advection of silica transport along the fractures, molecular diffusion from each fracture to the intervening rock matrix, and dissolution of quartz. A special analytical solution is also developed by ignoring the longitudinal hydrodynamic dispersion term but remaining other conditions the same. The general and special solutions are in the form of a double infinite integral and a single infinite integral, respectively, and can be evaluated using Gauss-Legendre quadrature technique. A simple criterion is developed to determine under what conditions the general analytical solution can be approximated by the special analytical solution. It is proved analytically that the general solution always lags behind the special solution, unless a dimensionless parameter is less than a critical value. Several illustrative calculations are undertaken to demonstrate the effect of fracture spacing, fracture aperture and fluid flow rate on silica transport. The analytical solutions developed here can serve as a benchmark to validate numerical models that simulate reactive mass transport in fractured porous media.
Transport of organic solutes through amorphous teflon AF films.
Zhao, Hong; Zhang, Jie; Wu, Nianqiang; Zhang, Xu; Crowley, Katie; Weber, Stephen G
2005-11-02
Fluorous media have great potential for selective extraction (e.g., as applied to organic synthesis). Fluorous polymer films would have significant advantages in fluorous separations. Stable films of Teflon AF 2400 were cast from solution. Films appear defect-free (SEM; AFM). Rigid aromatic solutes are transported (from chloroform solution to chloroform receiving phase) in a size-dependent manner (log permeability is proportional to -0.0067 times critical volume). Benzene's permeability is about 2 orders of magnitude higher than in comparable gas-phase experiments. The films show selectivity for fluorinated solutes in comparison to the hydrogen-containing control. Transport rates are dependent on the solvent making up the source and receiving phases. The effect of solvent is, interestingly, not due to changes in partition ratio, but rather it is due to changes in the solute diffusion coefficient in the film. Solvents plasticize the films. A less volatile compound, -COOH-terminated poly(hexafluoropropylene oxide) (4), plasticizes the films (T(g) = -40 degrees C). Permeabilities are decreased in comparison to 4-free films apparently because of decreased diffusivity of solutes. The slope of dependence of log permeability on critical volume is not changed, however.
Simulation of transportation of low enriched uranium solutions
Hope, E.P.; Ades, M.J.
1996-01-01
A simulation of the transportation by truck of low enriched uranium solutions has been completed for NEPA purposes at the Savannah River Site. The analysis involves three distinct source terms, and establishes the radiological risks of shipment to three possible destinations. Additionally, loading accidents were analyzed to determine the radiological consequences of mishaps during handling and delivery. Source terms were developed from laboratory measurements of chemical samples from low enriched uranium feed materials being stored at SRS facilities, and from manufacturer data on transport containers. The transportation simulations were accomplished over the INTERNET using the DOE TRANSNET system at Sandia National Laboratory. The HIGHWAY 3.3 code was used to analyze routing scenarios, and the RADTRAN 4 code was used to analyze incident free and accident risks of transporting radiological materials. Loading accidents were assessed using the Savannah River Site AXAIR89Q and RELEASE 2 codes
Transport properties site descriptive model. Guidelines for evaluation and modelling
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
Modeling the highway transportation of spent fuel
Harrison, I.G.
1986-01-01
There will be a substantial increase in the number of spent fuel shipments on the nation's highway system in the next thirty years. Most of the spent fuel will be moving from reactors to a spent fuel repository. This study develops two models that evaluate the risk and cost of moving the spent fuel. The Minimum Total Transport Risk Model (MTTRM) seeks an efficient solution for this problem by finding the minimum risk path through the network and sending all the spent fuel shipments over this one path. The Equilibrium Transport Risk Model (ETRM) finds an equitable solution by distributing the shipments over a number of paths in the network. This model decreases the risk along individual paths, but increases society's risk because the spent fuel shipments are traveling over more links in the network. The study finds that there is a trade off between path risk and societal risk. As path risk declines, societal risk rises. The cost of shipping also increases as the number of paths expand. The cost and risk of shipping spent fuel from ten reactors to four potential repository sites are evaluated using the MTTRM. The temporary monitored retrievable storage (MRS) facility in Tennessee is found to be the minimum cost and minimum risk solution. When direct shipment to the permanent sites is considered, Deaf Smith, Texas is the least cost and least incident free transport risk location. Yucca Mountain, Nevada is the least risk location when the focus is placed on the potential consequences of an accident
Transport modelling for ergodic configurations
Runov, A.; Kasilov, S.V.; McTaggart, N.; Schneider, R.; Bonnin, X.; Zagorski, R.; Reiter, D.
2004-01-01
The effect of ergodization, either by additional coils like in TEXTOR-dynamic ergodic divertor (DED) or by intrinsic plasma effects like in W7-X, defines the need for transport models that are able to describe the ergodic configuration properly. A prerequisite for this is the concept of local magnetic coordinates allowing a correct discretization with minimized numerical errors. For these coordinates the appropriate full metric tensor has to be known. To study the transport in complex edge geometries (in particular for W7-X) two possible methods are used. First, a finite-difference discretization of the transport equations on a custom-tailored grid in local magnetic coordinates is used. This grid is generated by field-line tracing to guarantee an exact discretization of the dominant parallel transport (thus also minimizing the numerical diffusion problem). The perpendicular fluxes are then interpolated in a plane (a toroidal cut), where the interpolation problem for a quasi-isotropic system has to be solved by a constrained Delaunay triangulation (keeping the structural information for magnetic surfaces if they exist) and discretization. All toroidal terms are discretized by finite differences. Second, a Monte Carlo transport model originally developed for the modelling of the DED configuration of TEXTOR is used. A generalization and extension of this model was necessary to be able to handle W7-X. The model solves the transport equations with Monte Carlo techniques making use of mappings of local magnetic coordinates. The application of this technique to W7-X in a limiter-like configuration is presented. The decreasing dominance of parallel transport with respect to radial transport for electron heat, ion heat and particle transport results in increasingly steep profiles for the respective quantities within the islands. (author)
Conceptual and Numerical Models for UZ Flow and Transport
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
Solution of the transport equation with account for inelastic collisions
Kalashnikov, N.P.; Remizovich, V.S.; Ryazanov, M.I.
1980-01-01
The theory of charged particle scattering in a matter with account for inelastic collisions is considered. In ''directly-forward'' approximation the transport equation at the absence of elastic collisions is obtained. The solution of the transport equation is made without and with account for fluctuation of energy losses. Formulas for path-energy relation are given. Energy spectrum and distribution of fast charged particles with respect to paths are studied. The problem of quantum mechanical approach to the theory of multiple scattering of fast charged particles in a matter is discussed briefly
Analytical solutions of a fractional diffusion-advection equation for solar cosmic-ray transport
Litvinenko, Yuri E.; Effenberger, Frederic
2014-01-01
Motivated by recent applications of superdiffusive transport models to shock-accelerated particle distributions in the heliosphere, we analytically solve a one-dimensional fractional diffusion-advection equation for the particle density. We derive an exact Fourier transform solution, simplify it in a weak diffusion approximation, and compare the new solution with previously available analytical results and with a semi-numerical solution based on a Fourier series expansion. We apply the results to the problem of describing the transport of energetic particles, accelerated at a traveling heliospheric shock. Our analysis shows that significant errors may result from assuming an infinite initial distance between the shock and the observer. We argue that the shock travel time should be a parameter of a realistic superdiffusive transport model.
Hydrogeochemistry and simulated solute transport, Piceance Basin, northwestern Colorado
Robson, S.G.; Saulnier, G.J.
1981-01-01
Oil-shale mining activities in Piceance basin in northwestern Colorado could adversely affect the ground- and surface-water quality in the basin. This study of the hydrology and geochemistry of the area used ground-water solute-transport-modeling techniques to investigate the possible impact of the mines on water quality. Maps of the extent and structure of the aquifer were prepared and show that a saturated thickness of 2,000 feet occurs in the northeast part of the basin. Ground-water recharge in the upland areas in the east, south, and west parts of the basin moves down into deeper zones in the aquifer and laterally to the discharge areas along Piceance and Yellow Creeks. The saline zone and the unsaturated zone provide the majority of the dissolved solids found in the ground water. Precipitation, ion-exchange, and oxidation-reduction reactions are also occuring in the aquifer. Model simulations of ground-water pumpage in tracts C-a and C-b indicate that the altered direction of ground-water movement near the pumped mines will cause an improvement in ground-water quality near the mines and a degradation of water quality downgradient from the tracts. Model simulations of mine leaching in tract C-a and C-b indicate that equal rates of mine leaching in the tracts will produce much different effects on the water quality in the basin. Tract C-a, by virtue of its remote location from perennial streams, will primarily degrade the ground-water quality over a large area to the northeast of the tract. Tract C-b, by contrast, will primarily degrade the surface-water quality in Piceance Creek, with only localized effects on the ground-water quality. (USGS)
Solute carrier transporters: potential targets for digestive system neoplasms.
Xie, Jing; Zhu, Xiao Yan; Liu, Lu Ming; Meng, Zhi Qiang
2018-01-01
Digestive system neoplasms are the leading causes of cancer-related death all over the world. Solute carrier (SLC) superfamily is composed of a series of transporters that are ubiquitously expressed in organs and tissues of digestive systems and mediate specific uptake of small molecule substrates in facilitative manner. Given the important role of SLC proteins in maintaining normal functions of digestive system, dysregulation of these protein in digestive system neoplasms may deliver biological and clinical significance that deserves systemic studies. In this review, we critically summarized the recent advances in understanding the role of SLC proteins in digestive system neoplasms. We highlighted that several SLC subfamilies, including metal ion transporters, transporters of glucose and other sugars, transporters of urea, neurotransmitters and biogenic amines, ammonium and choline, inorganic cation/anion transporters, transporters of nucleotide, amino acid and oligopeptide organic anion transporters, transporters of vitamins and cofactors and mitochondrial carrier, may play important roles in mediating the initiation, progression, metastasis, and chemoresistance of digestive system neoplasms. Proteins in these SLC subfamilies may also have diagnostic and prognostic values to particular cancer types. Differential expression of SLC proteins in tumors of digestive system was analyzed by extracting data from human cancer database, which revealed that the roles of SLC proteins may either be dependent on the substrates they transport or be tissue specific. In addition, small molecule modulators that pharmacologically regulate the functions of SLC proteins were discussed for their possible application in the treatment of digestive system neoplasms. This review highlighted the potential of SLC family proteins as drug target for the treatment of digestive system neoplasms.
Mass transfer processes and field-scale transport of organic solutes
Brusseau, M.L.
1990-01-01
The influence of mass transfer processes, such as sorption/desorption and mass transfer between immiscible liquids and water, on the transport of organic solutes is discussed. Rate-limited sorption of organic solutes caused by a diffusion-constrained mechanism is shown to be significant under laboratory conditions. The significance of the impact of nonequilibrium sorption on field-scale transport is scale dependent. The impact of organic liquids on mass transfer and transport of organic solutes depends upon the nature of the solute and the nature and form of the organic liquid. For example, while retardation of nonionic solutes is decreased in mixed-solvent systems, (i.e. systems comprised of water and a miscible organic liquid or an immiscible liquid present in concentrations below phase separation), the retardation of organic acids may, in some cases, increase with addition of a cosolvent. While the presence of an immiscible liquid existing as a mobile phase will reduce retention of organic solutes, the presence of residual saturation of an immiscible liquid can significantly increase retention. A model is presented that incorporates the effects of retention resulting from residual saturation, as well as nonequilibrium sorption, on the transport of organic solutes. (Author) (70 refs., 3 figs.)
Torok, J.; Buckley, L.P.; Woods, B.L.
1989-01-01
Laboratory-scale lysimeter experiments were performed with simulated waste forms placed in candidate buffer materials which have been chosen for a low-level radioactive waste repository. Radionuclide releases into the effluent water and radionuclide capture by the buffer material were determined. The results could not be explained by traditional solution transport mechanisms, and transport by particles released from the waste form and/or transport by buffer particles were suspected as the dominant mechanism for radionuclide release from the lysimeters. To elucidate the relative contribution of particle and solution transport, the waste forms were replaced by a wafer of neutron-activated buffer soaked with selected soluble isotopes. Particle transport was determined by the movement of gamma-emitting neutron-activation products through the lysimeter. Solution transport was quantified by comparing the migration of soluble radionuclides relative to the transport of neutron activation products. The new approach for monitoring radionuclide migration in soil is presented. It facilitates the determination of most of the fundamental coefficients required to model the transport process
Continuous time random walk analysis of solute transport in fractured porous media
Cortis, Andrea; Cortis, Andrea; Birkholzer, Jens
2008-06-01
The objective of this work is to discuss solute transport phenomena in fractured porous media, where the macroscopic transport of contaminants in the highly permeable interconnected fractures can be strongly affected by solute exchange with the porous rock matrix. We are interested in a wide range of rock types, with matrix hydraulic conductivities varying from almost impermeable (e.g., granites) to somewhat permeable (e.g., porous sandstones). In the first case, molecular diffusion is the only transport process causing the transfer of contaminants between the fractures and the matrix blocks. In the second case, additional solute transfer occurs as a result of a combination of advective and dispersive transport mechanisms, with considerable impact on the macroscopic transport behavior. We start our study by conducting numerical tracer experiments employing a discrete (microscopic) representation of fractures and matrix. Using the discrete simulations as a surrogate for the 'correct' transport behavior, we then evaluate the accuracy of macroscopic (continuum) approaches in comparison with the discrete results. However, instead of using dual-continuum models, which are quite often used to account for this type of heterogeneity, we develop a macroscopic model based on the Continuous Time Random Walk (CTRW) framework, which characterizes the interaction between the fractured and porous rock domains by using a probability distribution function of residence times. A parametric study of how CTRW parameters evolve is presented, describing transport as a function of the hydraulic conductivity ratio between fractured and porous domains.
Non-cooperative and cooperative solutions of government subsidy on public transportation
Husniah Hennie
2018-01-01
Full Text Available The paper deals with two models of government subsidy given to a public transport operator: (i the subsidy for buying bus from an appointed public transport manufacturer, and (ii the subsidy for reimbursing reduced ticket price for passengers. The models are developed to determine the maximum profit for both the public transport operator and the manufacturer. Since we consider two parties – the public transport operator and the manufacturer of the bus, then we use game theoretical approach by considering non-cooperative and cooperative solutions. Furthermore, since the bus is repairable we consider virtual age to model the preventive maintenance and we consider minimal repair to model the corrective maintenance. We analyse both type of subsidy models and give some numerical examples which show the effects of different subsidies to the profit of operator and manufacturer. The result of the numerical examples indicates that reducing ticket price would give a higher profit both to the operator and the manufacturer.
Developments in tokamak transport modeling
Houlberg, W.A.; Attenberger; Lao, L.L.
1981-01-01
A variety of numerical methods for solving the time-dependent fluid transport equations for tokamak plasmas is presented. Among the problems discussed are techniques for solving the sometimes very stiff parabolic equations for particle and energy flow, treating convection-dominated energy transport that leads to large cell Reynolds numbers, optimizing the flow of a code to reduce the time spent updating the particle and energy source terms, coupling the one-dimensional (1-D) flux-surface-averaged fluid transport equations to solutions of the 2-D Grad-Shafranov equation for the plasma geometry, handling extremely fast transient problems such as internal MHD disruptions and pellet injection, and processing the output to summarize the physics parameters over the potential operating regime for reactors. Emphasis is placed on computational efficiency in both computer time and storage requirements
Geological entropy and solute transport in heterogeneous porous media
Bianchi, Marco; Pedretti, Daniele
2017-06-01
We propose a novel approach to link solute transport behavior to the physical heterogeneity of the aquifer, which we fully characterize with two measurable parameters: the variance of the log K values (σY2), and a new indicator (HR) that integrates multiple properties of the K field into a global measure of spatial disorder or geological entropy. From the results of a detailed numerical experiment considering solute transport in K fields representing realistic distributions of hydrofacies in alluvial aquifers, we identify empirical relationship between the two parameters and the first three central moments of the distributions of arrival times of solute particles at a selected control plane. The analysis of experimental data indicates that the mean and the variance of the solutes arrival times tend to increase with spatial disorder (i.e., HR increasing), while highly skewed distributions are observed in more orderly structures (i.e., HR decreasing) or at higher σY2. We found that simple closed-form empirical expressions of the bivariate dependency of skewness on HR and σY2 can be used to predict the emergence of non-Fickian transport in K fields considering a range of structures and heterogeneity levels, some of which based on documented real aquifers. The accuracy of these predictions and in general the results from this study indicate that a description of the global variability and structure of the K field in terms of variance and geological entropy offers a valid and broadly applicable approach for the interpretation and prediction of transport in heterogeneous porous media.
Limit Theorems and Their Relation to Solute Transport in Simulated Fractured Media
Reeves, D. M.; Benson, D. A.; Meerschaert, M. M.
2003-12-01
Solute particles that travel through fracture networks are subject to wide velocity variations along a restricted set of directions. This may result in super-Fickian dispersion along a few primary scaling directions. The fractional advection-dispersion equation (FADE), a modification of the original advection-dispersion equation in which a fractional derivative replaces the integer-order dispersion term, has the ability to model rapid, non-Gaussian solute transport. The FADE assumes that solute particle motions converge to either α -stable or operator stable densities, which are modeled by spatial fractional derivatives. In multiple dimensions, the multi-fractional dispersion derivative dictates the order and weight of differentiation in all directions, which correspond to the statistics of large particle motions in all directions. This study numerically investigates the presence of super- Fickian solute transport through simulated two-dimensional fracture networks. An ensemble of networks is gen
An Experimental Study on Solute Transport in One-Dimensional Clay Soil Columns
Muhammad Zaheer
2017-01-01
Full Text Available Solute transport in low-permeability media such as clay has not been studied carefully up to present, and we are often unclear what the proper governing law is for describing the transport process in such media. In this study, we composed and analyzed the breakthrough curve (BTC data and the development of leaching in one-dimensional solute transport experiments in low-permeability homogeneous and saturated media at small scale, to identify key parameters controlling the transport process. Sodium chloride (NaCl was chosen to be the tracer. A number of tracer tests were conducted to inspect the transport process under different conditions. The observed velocity-time behavior for different columns indicated the decline of soil permeability when switching from tracer introducing to tracer flushing. The modeling approaches considered were the Advection-Dispersion Equation (ADE, Two-Region Model (TRM, Continuous Time Random Walk (CTRW, and Fractional Advection-Dispersion Equation (FADE. It was found that all the models can fit the transport process very well; however, ADE and TRM were somewhat unable to characterize the transport behavior in leaching. The CTRW and FADE models were better in capturing the full evaluation of tracer-breakthrough curve and late-time tailing in leaching.
A three-dimensional neutron transport benchmark solution
Ganapol, B.D.; Kornreich, D.E.
1993-01-01
For one-group neutron transport theory in one dimension, several powerful analytical techniques have been developed to solve the neutron transport equation, including Caseology, Wiener-Hopf factorization, and Fourier and Laplace transform methods. In addition, after a Fourier transform in the transverse plane and formulation of a pseudo problem, two-dimensional (2-D) and three-dimensional (3-D) problems can be solved using the techniques specifically developed for the one-dimensional (1-D) case. Numerical evaluation of the resulting expressions requiring an inversion in the transverse plane have been successful for 2-D problems but becomes exceedingly difficult in the 3-D case. In this paper, we show that by using the symmetry along the beam direction, a 2-D problem can be transformed into a 3-D problem in an infinite medium. The numerical solution to the 3-D problem is then demonstrated. Thus, a true 3-D transport benchmark solution can be obtained from a well-established numerical solution to a 2-D problem
Joekar-Niasar, V.
2013-01-25
Upscaling electroosmosis in porous media is a challenge due to the complexity and scale-dependent nonlinearities of this coupled phenomenon. "Pore-network modeling" for upscaling electroosmosis from pore scale to Darcy scale can be considered as a promising approach. However, this method requires analytical solutions for flow and transport at pore scale. This study concentrates on the development of analytical solutions of flow and transport in a single rectangular channel under combined effects of electrohydrodynamic forces. These relations will be used in future works for pore-network modeling. The analytical solutions are valid for all regimes of overlapping electrical double layers and have the potential to be extended to nonlinear Boltzmann distribution. The innovative aspects of this study are (a) contribution of overlapping of electrical double layers to the Stokes flow as well as Nernst-Planck transport has been carefully included in the analytical solutions. (b) All important transport mechanisms including advection, diffusion, and electromigration have been included in the analytical solutions. (c) Fully algebraic relations developed in this study can be easily employed to upscale electroosmosis to Darcy scale using pore-network modeling. © 2013 Springer Science+Business Media Dordrecht.
Joekar-Niasar, V.; Schotting, R.; Leijnse, A.
2013-01-01
Upscaling electroosmosis in porous media is a challenge due to the complexity and scale-dependent nonlinearities of this coupled phenomenon. "Pore-network modeling" for upscaling electroosmosis from pore scale to Darcy scale can be considered as a promising approach. However, this method requires analytical solutions for flow and transport at pore scale. This study concentrates on the development of analytical solutions of flow and transport in a single rectangular channel under combined effects of electrohydrodynamic forces. These relations will be used in future works for pore-network modeling. The analytical solutions are valid for all regimes of overlapping electrical double layers and have the potential to be extended to nonlinear Boltzmann distribution. The innovative aspects of this study are (a) contribution of overlapping of electrical double layers to the Stokes flow as well as Nernst-Planck transport has been carefully included in the analytical solutions. (b) All important transport mechanisms including advection, diffusion, and electromigration have been included in the analytical solutions. (c) Fully algebraic relations developed in this study can be easily employed to upscale electroosmosis to Darcy scale using pore-network modeling. © 2013 Springer Science+Business Media Dordrecht.
Modeling of capacitated transportation systems for integral scheduling
Ebben, Mark; van der Heijden, Matthijs C.; Hurink, Johann L.; Schutten, Johannes M.J.
2003-01-01
Motivated by a planned automated cargo transportation network, we consider transportation problems in which the finite capacity of resources has to be taken into account. We present a flexible modeling methodology which allows to construct, evaluate, and improve feasible solutions. The modeling is
Modeling of capacitated transportation systems for integral scheduling
Ebben, Mark; van der Heijden, Matthijs C.; Hurink, Johann L.; Schutten, Johannes M.J.
2003-01-01
Motivated by a planned automated cargo transportation network, we consider transportation problems in which the finite capacity of resources has to be taken nto account. We present a flexible modeling methodology which allows to construct, evaluate, and improve feasible solutions. The modeling is
Modelling of Transport Projects Uncertainties
Salling, Kim Bang; Leleur, Steen
2009-01-01
This paper proposes a new way of handling the uncertainties present in transport decision making based on infrastructure appraisals. The paper suggests to combine the principle of Optimism Bias, which depicts the historical tendency of overestimating transport related benefits and underestimating...... to supplement Optimism Bias and the associated Reference Class Forecasting (RCF) technique with a new technique that makes use of a scenario-grid. We tentatively introduce and refer to this as Reference Scenario Forecasting (RSF). The final RSF output from the CBA-DK model consists of a set of scenario......-based graphs which function as risk-related decision support for the appraised transport infrastructure project....
Modelling dust transport in tokamaks
Martin, J.D.; Martin, J.D.; Bacharis, M.; Coppins, M.; Counsell, G.F.; Allen, J.E.; Counsell, G.F.
2008-01-01
The DTOKS code, which models dust transport through tokamak plasmas, is described. The floating potential and charge of a dust grain in a plasma and the fluxes of energy to and from it are calculated. From this model, the temperature of the dust grain can be estimated. A plasma background is supplied by a standard tokamak edge modelling code (B2SOLPS5.0), and dust transport through MAST (the Mega-Amp Spherical Tokamak) and ITER plasmas is presented. We conclude that micron-radius tungsten dust can reach the separatrix in ITER. (authors)
Methods for testing transport models
Singer, C.; Cox, D.
1991-01-01
Substantial progress has been made over the past year on six aspects of the work supported by this grant. As a result, we have in hand for the first time a fairly complete set of transport models and improved statistical methods for testing them against large databases. We also have initial results of such tests. These results indicate that careful application of presently available transport theories can reasonably well produce a remarkably wide variety of tokamak data
Solvable Model for Dynamic Mass Transport in Disordered Geophysical Media
Marder, M.; Eftekhari, Behzad; Patzek, Tadeusz
2018-01-01
We present an analytically solvable model for transport in geophysical materials on large length and time scales. It describes the flow of gas to a complicated absorbing boundary over long periods of time. We find a solution to this model using Green's function techniques, and apply the solution to three absorbing networks of increasing complexity.
Solvable Model for Dynamic Mass Transport in Disordered Geophysical Media
Marder, M.
2018-03-29
We present an analytically solvable model for transport in geophysical materials on large length and time scales. It describes the flow of gas to a complicated absorbing boundary over long periods of time. We find a solution to this model using Green\\'s function techniques, and apply the solution to three absorbing networks of increasing complexity.
Brine transport in porous media self-similar solutions
C.J. van Duijn (Hans); L.A. Peletier (Bert); R.J. Schotting (Ruud)
1996-01-01
textabstractIn this paper we analyze a model for brine transport in porous media, which includes a mass balance for the fluid, a mass balance for salt, Darcy's law and an equation of state, which relates the fluid density to the salt mass fraction. This model incorporates the effect of local volume
Effects of sorption and temperature on solute transport in unsaturated steady flow
Fuentes, H.R.; Polzer, W.L.; Essington, E.H.
1986-01-01
It is known that temperature affects physical and chemical processes and that these processes may alter the transport of solutes in the environment. Laboratory column studies were performed in unsaturated flow conditions with a composite pulse containing iodide, cobalt, cesium and strontium each at 10 -3 M. The experiments were performed with Bandelier Tuff and produced breakthrough curves that indicate significant changes in transport due to a temperature change from 25 0 C to 5 0 C for nonconservative solutes. Also, the interpretation of the temperature and sorption data suggest that the differences in transport between 5 0 C and 25 0 C for nonconservative solutes may be predicted in a qualitative manner from batch equilibrium and nonequilibrium sorption data and the theory of sorption used in deriving the modified Freundlich isotherm equation. These effects should be of concern in modeling and management of spills and waste disposal within this range of environmental temperatures
Semianalytical Solutions for Transport in Aquifer and Fractured Clay Matrix System
A three-dimensional mathematical model that describes transport of contaminant in a horizontal aquifer with simultaneous diffusion into a fractured clay formation is proposed. A group of analytical solutions is derived based on specific initial and boundary conditions as well as ...
Koohbor, Behshad; Fahs, Marwan; Ataie-Ashtiani, Behzad; Simmons, Craig T.; Younes, Anis
2018-05-01
Existing closed-form solutions of contaminant transport problems are limited by the mathematically convenient assumption of uniform flow. These solutions cannot be used to investigate contaminant transport in coastal aquifers where seawater intrusion induces a variable velocity field. An adaptation of the Fourier-Galerkin method is introduced to obtain semi-analytical solutions for contaminant transport in a confined coastal aquifer in which the saltwater wedge is in equilibrium with a freshwater discharge flow. Two scenarios dealing with contaminant leakage from the aquifer top surface and contaminant migration from a source at the landward boundary are considered. Robust implementation of the Fourier-Galerkin method is developed to efficiently solve the coupled flow, salt and contaminant transport equations. Various illustrative examples are generated and the semi-analytical solutions are compared against an in-house numerical code. The Fourier series are used to evaluate relevant metrics characterizing contaminant transport such as the discharge flux to the sea, amount of contaminant persisting in the groundwater and solute flux from the source. These metrics represent quantitative data for numerical code validation and are relevant to understand the effect of seawater intrusion on contaminant transport. It is observed that, for the surface contamination scenario, seawater intrusion limits the spread of the contaminant but intensifies the contaminant discharge to the sea. For the landward contamination scenario, moderate seawater intrusion affects only the spatial distribution of the contaminant plume while extreme seawater intrusion can increase the contaminant discharge to the sea. The developed semi-analytical solution presents an efficient tool for the verification of numerical models. It provides a clear interpretation of the contaminant transport processes in coastal aquifers subject to seawater intrusion. For practical usage in further studies, the full
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.
Symposium on unsaturated flow and transport modeling
Arnold, E.M.; Gee, G.W.; Nelson, R.W.
1982-09-01
This document records the proceedings of a symposium on flow and transport processes in partially saturated groundwater systems, conducted at the Battelle Seattle Research Center on March 22-24, 1982. The symposium was sponsored by the US Nuclear Regulatory Commission for the purpose of assessing the state-of-the-art of flow and transport modeling for use in licensing low-level nuclear waste repositories in partially saturated zones. The first day of the symposium centered around research in flow through partially saturated systems. Papers were presented with the opportunity for questions following each presentation. In addition, after all the talks, a formal panel discussion was held during which written questions were addressed to the panel of the days speakers. The second day of the Symposium was devoted to solute and contaminant transport in partially saturated media in an identical format. Individual papers are abstracted
Symposium on unsaturated flow and transport modeling
Arnold, E.M.; Gee, G.W.; Nelson, R.W. (eds.)
1982-09-01
This document records the proceedings of a symposium on flow and transport processes in partially saturated groundwater systems, conducted at the Battelle Seattle Research Center on March 22-24, 1982. The symposium was sponsored by the US Nuclear Regulatory Commission for the purpose of assessing the state-of-the-art of flow and transport modeling for use in licensing low-level nuclear waste repositories in partially saturated zones. The first day of the symposium centered around research in flow through partially saturated systems. Papers were presented with the opportunity for questions following each presentation. In addition, after all the talks, a formal panel discussion was held during which written questions were addressed to the panel of the days speakers. The second day of the Symposium was devoted to solute and contaminant transport in partially saturated media in an identical format. Individual papers are abstracted.
Singha, Kamini; Li, Li; Day-Lewis, Frederick D.; Regberg, Aaron B.
2012-01-01
The concept of a nonreactive or conservative tracer, commonly invoked in investigations of solute transport, requires additional study in the context of electrical geophysical monitoring. Tracers that are commonly considered conservative may undergo reactive processes, such as ion exchange, thus changing the aqueous composition of the system. As a result, the measured electrical conductivity may reflect not only solute transport but also reactive processes. We have evaluated the impacts of ion exchange reactions, rate-limited mass transfer, and surface conduction on quantifying tracer mass, mean arrival time, and temporal variance in laboratory-scale column experiments. Numerical examples showed that (1) ion exchange can lead to resistivity-estimated tracer mass, velocity, and dispersivity that may be inaccurate; (2) mass transfer leads to an overestimate in the mobile tracer mass and an underestimate in velocity when using electrical methods; and (3) surface conductance does not notably affect estimated moments when high-concentration tracers are used, although this phenomenon may be important at low concentrations or in sediments with high and/or spatially variable cation-exchange capacity. In all cases, colocated groundwater concentration measurements are of high importance for interpreting geophysical data with respect to the controlling transport processes of interest.
Monte Carlo methods for flux expansion solutions of transport problems
Spanier, J.
1999-01-01
Adaptive Monte Carlo methods, based on the use of either correlated sampling or importance sampling, to obtain global solutions to certain transport problems have recently been described. The resulting learning algorithms are capable of achieving geometric convergence when applied to the estimation of a finite number of coefficients in a flux expansion representation of the global solution. However, because of the nonphysical nature of the random walk simulations needed to perform importance sampling, conventional transport estimators and source sampling techniques require modification to be used successfully in conjunction with such flux expansion methods. It is shown how these problems can be overcome. First, the traditional path length estimators in wide use in particle transport simulations are generalized to include rather general detector functions (which, in this application, are the individual basis functions chosen for the flus expansion). Second, it is shown how to sample from the signed probabilities that arise as source density functions in these applications, without destroying the zero variance property needed to ensure geometric convergence to zero error
Reactive transport models and simulation with ALLIANCES
Leterrier, N.; Deville, E.; Bary, B.; Trotignon, L.; Hedde, T.; Cochepin, B.; Stora, E.
2009-01-01
Many chemical processes influence the evolution of nuclear waste storage. As a result, simulations based only upon transport and hydraulic processes fail to describe adequately some industrial scenarios. We need to take into account complex chemical models (mass action laws, kinetics...) which are highly non-linear. In order to simulate the coupling of these chemical reactions with transport, we use a classical Sequential Iterative Approach (SIA), with a fixed point algorithm, within the mainframe of the ALLIANCES platform. This approach allows us to use the various transport and chemical modules available in ALLIANCES, via an operator-splitting method based upon the structure of the chemical system. We present five different applications of reactive transport simulations in the context of nuclear waste storage: 1. A 2D simulation of the lixiviation by rain water of an underground polluted zone high in uranium oxide; 2. The degradation of the steel envelope of a package in contact with clay. Corrosion of the steel creates corrosion products and the altered package becomes a porous medium. We follow the degradation front through kinetic reactions and the coupling with transport; 3. The degradation of a cement-based material by the injection of an aqueous solution of zinc and sulphate ions. In addition to the reactive transport coupling, we take into account in this case the hydraulic retroaction of the porosity variation on the Darcy velocity; 4. The decalcification of a concrete beam in an underground storage structure. In this case, in addition to the reactive transport simulation, we take into account the interaction between chemical degradation and the mechanical forces (cracks...), and the retroactive influence on the structure changes on transport; 5. The degradation of the steel envelope of a package in contact with a clay material under a temperature gradient. In this case the reactive transport simulation is entirely directed by the temperature changes and
A Finite-Difference Solution of Solute Transport through a Membrane Bioreactor
B. Godongwana
2015-01-01
Full Text Available The current paper presents a theoretical analysis of the transport of solutes through a fixed-film membrane bioreactor (MBR, immobilised with an active biocatalyst. The dimensionless convection-diffusion equation with variable coefficients was solved analytically and numerically for concentration profiles of the solutes through the MBR. The analytical solution makes use of regular perturbation and accounts for radial convective flow as well as axial diffusion of the substrate species. The Michaelis-Menten (or Monod rate equation was assumed for the sink term, and the perturbation was extended up to second-order. In the analytical solution only the first-order limit of the Michaelis-Menten equation was considered; hence the linearized equation was solved. In the numerical solution, however, this restriction was lifted. The solution of the nonlinear, elliptic, partial differential equation was based on an implicit finite-difference method (FDM. An upwind scheme was employed for numerical stability. The resulting algebraic equations were solved simultaneously using the multivariate Newton-Raphson iteration method. The solution allows for the evaluation of the effect on the concentration profiles of (i the radial and axial convective velocity, (ii the convective mass transfer rates, (iii the reaction rates, (iv the fraction retentate, and (v the aspect ratio.
Influence of pore structure on solute transport in degraded and undegraded fen peat soils
C. Kleimeier
2017-10-01
Full Text Available In peat soils, decomposition and degradation reduce the proportion of large pores by breaking down plant debris into smaller fragments and infilling inter-particle pore spaces. This affects water flow and solute migration which, in turn, influence reactive transport processes and biogeochemical functions. In this study we conducted flow-through reactor experiments to investigate the interplay between pore structure and solute transport in samples of undegraded and degraded peat collected in Canada and Germany, respectively. The pore size distributions and transport parameters were characterised using the breakthrough curve and two-region non-equilibrium transport model analyses for a non-reactive solute. The results of transport characterisation showed a higher fraction of immobile pores in the degraded peat with higher diffusive exchanges of solutes between the mobile and immobile pores associated with the dual-porosity structure. The rates of steady-state potential nitrate reduction were compared with pore fractions and exchange coefficients to investigate the influence of pore structure on the rates of nitrate reduction. The results indicated that the degraded peat has potential to provide the necessary boundary conditions to support nitrate removal and serves as a favourable substrate for denitrification, due to the nature of its pore structure and its lower organic carbon content compared to undegraded peat.
Fukutsuka, Tomokazu; Koyamada, Kohei; Maruyama, Shohei; Miyazaki, Kohei; Abe, Takeshi
2016-01-01
Highlights: • Ion transport in organic electrolyte solution in macro- and meso-pores was focused. • Anodic nanoporous alumina membrane was used as a porous material. • The specific ion conductivities drastically decreased in macro- and meso-pores. - Abstract: For the development of high energy density lithium-ion batteries with the high rate performance, the enhancement of the ion transport in the electrolyte solutions impregnated in the porous electrodes is a key. To study the ion transport in porous electrodes, anodic nanoporous alumina (APA) self-standing membranes with macro- or meso-pores were used as model porous materials. These membranes had nearly spherical pore channels of discrete 20–68 nm in diameters. By using the geometric shape of the pores, we attempted to evaluate the specific ion conductivities of the organic electrolyte solution dissolving lithium salt simply. AC impedance spectroscopy measurement of a four-electrode cell with membranes showed one depressed semi-circle in the Nyquist plots and this semi-circle can be assigned as the ion transport resistance in the pores. The specific ion conductivities evaluated from the ion transport resistances and the geometric parameters showed very small values, even in the macro-pores, as compared with that of the bulk electrolyte solution.
Soil properties and preferential solute transport at the field scale
Koestel, J K; Minh, Luong Nhat; Nørgaard, Trine
An important fraction of water flow and solute transport through soil takes place through preferential flow paths. Although this had been already observed in the nineteenth century, it had been forgotten by the scientific community until it was rediscovered during the 1970s. The awareness...... of the relevance of preferential flow was broadly re-established in the community by the early 1990s. However, since then, the notion remains widespread among soil scientists that the occurrence and strength of preferential flow cannot be predicted from measurable proxy variables such as soil properties or land...
Solute carrier transporters: potential targets for digestive system neoplasms
Xie, Jing; Zhu, Xiao Yan; Liu, Lu Ming; Meng, Zhi Qiang
2018-01-01
Jing Xie,1,2 Xiao Yan Zhu,1,2 Lu Ming Liu,1,2 Zhi Qiang Meng1,2 1Department of Integrative Oncology, Fudan University Shanghai Cancer Center, 2Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, People’s Republic of China Abstract: Digestive system neoplasms are the leading causes of cancer-related death all over the world. Solute carrier (SLC) superfamily is composed of a series of transporters that are ubiquitously expressed in organs and tissues o...
On the Solution of the Neutron Transport Equation
Depken, S
1962-12-15
The neutron transport equation has occupied the attention of many authors since Placzek, Wick and others made their first attempts to solve it, Even in the simple case of energy independent cross-sections, and disregarding the motion of the scattering nucleons, it is difficult to find a solution in an analytical form which is easily surveyable and fitted for numerical calculations. In Part I of this paper some new viewpoints will be introduced which enable the solution to be presented in its simplest possible form. Part II is devoted to an investigation of some functions introduced in Part I. In Part III the results are applied to the case of large energy lethargy, and the validity of derived formulas is discussed.
Nakka, B W; Chan, T
1994-12-01
A deterministic particle-tracking code (TRACK3D) has been developed to compute convective flow paths of conservative (nonreactive) contaminants through porous geological media. TRACK3D requires the groundwater velocity distribution, which, in our applications, results from flow simulations using AECL`s MOTIF code. The MOTIF finite-element code solves the transient and steady-state coupled equations of groundwater flow, solute transport and heat transport in fractured/porous media. With few modifications, TRACK3D can be used to analyse the velocity distributions calculated by other finite-element or finite-difference flow codes. This report describes the assumptions, limitations, organization, operation and applications of the TRACK3D code, and provides a comprehensive user`s manual.
Implementation of Solute Transport in the Vadose Zone into the `HYDRUS Package for MODFLOW'
Simunek, J.; Beegum, S.; Szymkiewicz, A.; Sudheer, K. P.
2017-12-01
The 'HYDRUS package for MODFLOW' was developed by Seo et al. (2007) and Twarakavi et al. (2008) to simultaneously evaluate transient water flow in both unsaturated and saturated zones. The package, which is based on the HYDRUS-1D model (Šimůnek et al., 2016) simulating unsaturated water flow in the vadose zone, was incorporated into MODFLOW (Harbaugh et al., 2000) simulating saturated groundwater flow. The HYDRUS package in the coupled model can be used to represent the effects of various unsaturated zone processes, including infiltration, evaporation, root water uptake, capillary rise, and recharge in homogeneous or layered soil profiles. The coupled model is effective in addressing spatially-variable saturated-unsaturated hydrological processes at the regional scale, allowing for complex layering in the unsaturated zone, spatially and temporarily variable water fluxes at the soil surface and in the root zone, and with alternating recharge and discharge fluxes (Twarakavi et al., 2008). One of the major limitations of the coupled model was that it could not be used to simulate at the same time solute transport. However, solute transport is highly dependent on water table fluctuations due to temporal and spatial variations in groundwater recharge. This is an important concern when the coupled model is used for analyzing groundwater contamination due to transport through the unsaturated zone. The objective of this study is to integrate the solute transport model (the solute transport part of HYDRUS-1D for the unsaturated zone and MT3DMS (Zheng and Wang, 1999; Zheng, 2009) for the saturated zone) into an existing coupled water flow model. The unsaturated zone component of the coupled model can consider solute transport involving many biogeochemical processes and reactions, including first-order degradation, volatilization, linear or nonlinear sorption, one-site kinetic sorption, two-site sorption, and two-kinetic sites sorption (Šimůnek and van Genuchten, 2008
Used Fuel Logistics: Decades of Experience with transportation and Interim storage solutions
Orban, G.; Shelton, C.
2015-07-01
Used fuel inventories are growing worldwide. While some countries have opted for a closed cycle with recycling, numerous countries must expand their interim storage solutions as implementation of permanent repositories is taking more time than foreseen. In both cases transportation capabilities will have to be developed. AREVA TN has an unparalleled expertise with transportation of used fuel. For more than 50 years AREVA TN has safely shipped more than 7,000 used fuel transport casks. The transportation model that was initially developed in the 1970s has been adapted and enhanced over the years to meet more restrictive regulatory requirements and evolving customer needs, and to address public concerns. The numerous “lessons learned” have offered data and guidance that have allowed for also efficient and consistent improvement over the decades. AREVA TN has also an extensive experience with interim dry storage solutions in many countries on-site but also is working with partners to developed consolidated interim storage facility. Both expertise with storage and transportation contribute to safe, secure and smooth continuity of the operations. This paper will describe decades of experience with a very successful transportation program as well as interim storage solutions. (Author)
Modelling of Transport Projects Uncertainties
Salling, Kim Bang; Leleur, Steen
2012-01-01
This paper proposes a new way of handling the uncertainties present in transport decision making based on infrastructure appraisals. The paper suggests to combine the principle of Optimism Bias, which depicts the historical tendency of overestimating transport related benefits and underestimating...... to supplement Optimism Bias and the associated Reference Class Forecasting (RCF) technique with a new technique that makes use of a scenario-grid. We tentatively introduce and refer to this as Reference Scenario Forecasting (RSF). The final RSF output from the CBA-DK model consists of a set of scenario......-based graphs which functions as risk-related decision support for the appraised transport infrastructure project. The presentation of RSF is demonstrated by using an appraisal case concerning a new airfield in the capital of Greenland, Nuuk....
Control and optimization of solute transport in a thin porous tube
Griffiths, I. M.
2013-03-01
Predicting the distribution of solutes or particles in flows within porous-walled tubes is essential to inform the design of devices that rely on cross-flow filtration, such as those used in water purification, irrigation devices, field-flow fractionation, and hollow-fibre bioreactors for tissue-engineering applications. Motivated by these applications, a radially averaged model for fluid and solute transport in a tube with thin porous walls is derived by developing the classical ideas of Taylor dispersion. The model includes solute diffusion and advection via both radial and axial flow components, and the advection, diffusion, and uptake coefficients in the averaged equation are explicitly derived. The effect of wall permeability, slip, and pressure differentials upon the dispersive solute behaviour are investigated. The model is used to explore the control of solute transport across the membrane walls via the membrane permeability, and a parametric expression for the permeability required to generate a given solute distribution is derived. The theory is applied to the specific example of a hollow-fibre membrane bioreactor, where a uniform delivery of nutrient across the membrane walls to the extra-capillary space is required to promote spatially uniform cell growth. © 2013 American Institute of Physics.
Analysis of solute transport in plants using positron emission tomography
Partelova, D.
2016-01-01
In the first part of the work, geometrically and radiochemically characterized standards (phantoms) imitating the plant tissues and allowing the exact quantification of visualised radioindicator in plant tissues were designed and prepared within the study of visual and analytical characteristics of used positron emission tomograph (microPET system) commercially developed for animal objects at visualization of thin objects. Individual experiments carried out by exposure of excised leaves of tobacco (Nicotiana tabacum L.) or radish (Raphanus sativus L.) in solutions of 2-deoxy-2-fluoro-D-glucose labelled with positron emitter 18 F (2-[ 18 F]FDG) containing 10-, 100-, or 1000-times higher concentrations of D-glucose (c glu ) in comparison with the original 2-[ 18 F]FDG solution showed that the significant changes in visualisation of 2-[ 18 F]FDG distribution as well as in chemical portion of 2-[ 18 F]FDG within the leaf blade were observed as result of increased c glu . In the experiments with the whole plants of tobacco or radish exposed in 2-[ 18 F]FDG solution through the root system, only minimal translocation of 18 F radioactivity into the above-ground parts of plants, also in the case of increased c glu , was observed, which suggest the role of root system as a selective barrier of 2-[ 18 F]FDG transport from roots to the above-ground parts. On the basis of mentioned knowledge and analytical approaches (application of prepared phantoms), the dynamic study of 2-[ 18 F]FDG uptake and transport within the excised leaf of tobacco or whole radish plant was carried out. The description of these processes was realized through the 3D PET images and through the quantification of 2-[ 18 F]FDG distribution within the chosen regions of interest from the point of view of accumulated 18 F radioactivity (in Bq) or amount of D-glucose (in μg) as well. Application of methods of multivariate analysis allows to found the similarities between studied objects mainly from the point
Understanding transport barriers through modelling
Rozhansky, V
2004-01-01
Models of radial electric field formation are discussed and compared with the results of numerical simulations from fluid transport codes and Monte Carlo codes. A comparison of the fluid and Monte Carlo codes is presented. A conclusion is arrived at that all the simulations do not predict any bifurcation of the electric field, i.e. no bifurcation of poloidal rotation from low to high Mach number values is obtained. In most of the simulations, the radial electric field is close to the neoclassical electric field. The deviation from neoclassical electric field at the separatrix due to the existence of a transitional viscous layer is discussed. Scalings for the shear of the poloidal rotation are checked versus simulation results. It is demonstrated that assuming the critical shear to be of the order of 10 5 s -1 , it is possible to obtain a L-H transition power scaling close to that observed in the experiment. The dependence of the threshold on the magnetic field direction, pellet injection, aspect ratio and other factors are discussed on the basis of existing simulations. Transport codes where transport coefficients depend on the turbulence level and scenario simulations of L-H transition are analysed. However, the details of gyrofluid and gyrokinetic modelling should be discussed elsewhere. Simulations of internal transport barrier (ITB) formation are discussed as well as factors responsible for ITB formation
Santos, Juliana; Künne, Annika; Kralisch, Sven; Fink, Manfred; Brenning, Alexander
2016-04-01
The Muriaé River basin in SE Brazil has been experiencing an increasing pressure on water resources, due to the population growth of the Rio de Janeiro urban area connected with the growth of the industrial and agricultural sector. This leads to water scarcity, riverine forest degradation, soil erosion and water quality problems among other impacts. Additionally the region has been suffering with seasonal precipitation variations leading to extreme events such as droughts, floods and landslides. Climate projections for the near future indicate a high inter-annual variability of rainfall with an increase in the frequency and intensity of heavy rainfall events combined with a statistically significant increase in the duration of dry periods and a reduced duration of wet periods. This may lead to increased soil erosion during the wet season, while the longer dry periods may reduce the vegetation cover, leaving the soil even more exposed and vulnerable to soil erosion. In consequence, it is crucial to understand how climate affects the interaction between the timing of extreme rainfall events, hydrological processes, vegetation growth, soil cover and soil erosion. In this context, physically-based hydrological modelling can contribute to a better understanding of spatial-temporal process dynamics in the Earth's system and support Integrated Water Resourses Management (IWRM) and adaptation strategies. The study area is the Muriaé river basin which has an area of approx. 8000 km² in Minas Gerais and Rio de Janeiro States. The basin is representative of a region of domain of hillslopes areas with the predominancy of pasture for livestock production. This study will present some of the relevant analyses which have been carried out on data (climate and streamflow) prior to using them for hydrological modelling, including consistency checks, homogeneity, pattern and statistical analyses, or annual and seasonal trends detection. Several inconsistencies on the raw data were
Methods for testing transport models
Singer, C.; Cox, D.
1993-01-01
This report documents progress to date under a three-year contract for developing ''Methods for Testing Transport Models.'' The work described includes (1) choice of best methods for producing ''code emulators'' for analysis of very large global energy confinement databases, (2) recent applications of stratified regressions for treating individual measurement errors as well as calibration/modeling errors randomly distributed across various tokamaks, (3) Bayesian methods for utilizing prior information due to previous empirical and/or theoretical analyses, (4) extension of code emulator methodology to profile data, (5) application of nonlinear least squares estimators to simulation of profile data, (6) development of more sophisticated statistical methods for handling profile data, (7) acquisition of a much larger experimental database, and (8) extensive exploratory simulation work on a large variety of discharges using recently improved models for transport theories and boundary conditions. From all of this work, it has been possible to define a complete methodology for testing new sets of reference transport models against much larger multi-institutional databases
Water flow and solute transport in floating fen root mats
Stofberg, Sija F.; EATM van der Zee, Sjoerd
2015-04-01
be very similar and likely functionally related. Our experimental field data were used for modelling water flow and solute transport in floating fens, using HYDRUS 2D. Fluctuations of surface water and root mat, as well as geometry and unsaturated zone parameters can have a major influence on groundwater fluctuations and the exchange between rain and surface water and the water in the root mats. In combination with the duration of salt pulses in surface water, and sensitivity of fen plants to salinity (Stofberg et al. 2014, submitted), risks for rare plants can be anticipated.
Stochastic models of intracellular transport
Bressloff, Paul C.; Newby, Jay M.
2013-01-01
mechanisms for intracellular transport: passive diffusion and motor-driven active transport. Diffusive transport can be formulated in terms of the motion of an overdamped Brownian particle. On the other hand, active transport requires chemical energy, usually
Modeling in transport phenomena a conceptual approach
Tosun, Ismail
2007-01-01
Modeling in Transport Phenomena, Second Edition presents and clearly explains with example problems the basic concepts and their applications to fluid flow, heat transfer, mass transfer, chemical reaction engineering and thermodynamics. A balanced approach is presented between analysis and synthesis, students will understand how to use the solution in engineering analysis. Systematic derivations of the equations and the physical significance of each term are given in detail, for students to easily understand and follow up the material. There is a strong incentive in science and engineering to
Coupling of transport and geochemical models
Noy, D.J.
1985-01-01
This contract stipulated separate pieces of work to consider mass transport in the far-field of a repository, and more detailed geochemical modelling of the groundwater in the near-field. It was envisaged that the far-field problem would be tackled by numerical solutions to the classical advection-diffusion equation obtained by the finite element method. For the near-field problem the feasibility of coupling existing geochemical equilibrium codes to the three dimensional groundwater flow codes was to be investigated. This report is divided into two sections with one part devoted to each aspect of this contract. (author)
Mihaela, Istrate; Alexandru, Boroiu; Viorel, Nicolae; Ionel, Vieru
2017-10-01
One of the major problems facing the Pitesti city is the road congestion that occurs in the central area of the city during the peak hours. With all the measures taken in recent years - the widening of road arteries, increasing the number of parking spaces, the creation of overground road passages - it is obvious that the problem can only be solved by a new philosophy regarding urban mobility: it is no longer possible to continue through solutions to increase the accessibility of the central area of the city, but it is necessary, on the contrary, to promote a policy of discouraging the penetration of vehicles in the city center, coupled with a policy of improving the connection between urban public transport and county public transport. This new approach is also proposed in the new Urban Mobility Plan of Pitesti city, under development. The most convincing argument for the necessity of this new orientation in the Pitesti city mobility plan is based on the analysis of the current situation of passenger transport on the territory of Pitesti city: the analysis of “public transport versus private transport” reveals a very low occupancy rate for cars and the fact that the road surface required for a passenger (the dynamic area) is much higher in the case of private transport than in the case of public transport. Measurements of passenger flows and vehicle flows on the 6 penetration ways in the city have been made and the calculations clearly demonstrate the benefits of an urban public transport system connected by “transshipment buses” to be made at the edge of the city, to the county public transport system. In terms of inter-county transport, it will continue to be connected to the urban public transport system by existing bus Station, within the city: South Bus Station and North Bus Station. The usefulness of the paper is that it identifies the solutions for sustainable mobility in Pitesti city and proposes concrete solutions for the development of the
Variational multiscale models for charge transport.
Wei, Guo-Wei; Zheng, Qiong; Chen, Zhan; Xia, Kelin
2012-01-01
This work presents a few variational multiscale models for charge transport in complex physical, chemical and biological systems and engineering devices, such as fuel cells, solar cells, battery cells, nanofluidics, transistors and ion channels. An essential ingredient of the present models, introduced in an earlier paper (Bulletin of Mathematical Biology, 72, 1562-1622, 2010), is the use of differential geometry theory of surfaces as a natural means to geometrically separate the macroscopic domain from the microscopic domain, meanwhile, dynamically couple discrete and continuum descriptions. Our main strategy is to construct the total energy functional of a charge transport system to encompass the polar and nonpolar free energies of solvation, and chemical potential related energy. By using the Euler-Lagrange variation, coupled Laplace-Beltrami and Poisson-Nernst-Planck (LB-PNP) equations are derived. The solution of the LB-PNP equations leads to the minimization of the total free energy, and explicit profiles of electrostatic potential and densities of charge species. To further reduce the computational complexity, the Boltzmann distribution obtained from the Poisson-Boltzmann (PB) equation is utilized to represent the densities of certain charge species so as to avoid the computationally expensive solution of some Nernst-Planck (NP) equations. Consequently, the coupled Laplace-Beltrami and Poisson-Boltzmann-Nernst-Planck (LB-PBNP) equations are proposed for charge transport in heterogeneous systems. A major emphasis of the present formulation is the consistency between equilibrium LB-PB theory and non-equilibrium LB-PNP theory at equilibrium. Another major emphasis is the capability of the reduced LB-PBNP model to fully recover the prediction of the LB-PNP model at non-equilibrium settings. To account for the fluid impact on the charge transport, we derive coupled Laplace-Beltrami, Poisson-Nernst-Planck and Navier-Stokes equations from the variational principle
Variational multiscale models for charge transport
Wei, Guo-Wei; Zheng, Qiong; Chen, Zhan; Xia, Kelin
2012-01-01
This work presents a few variational multiscale models for charge transport in complex physical, chemical and biological systems and engineering devices, such as fuel cells, solar cells, battery cells, nanofluidics, transistors and ion channels. An essential ingredient of the present models, introduced in an earlier paper (Bulletin of Mathematical Biology, 72, 1562-1622, 2010), is the use of differential geometry theory of surfaces as a natural means to geometrically separate the macroscopic domain from the microscopic domain, meanwhile, dynamically couple discrete and continuum descriptions. Our main strategy is to construct the total energy functional of a charge transport system to encompass the polar and nonpolar free energies of solvation, and chemical potential related energy. By using the Euler-Lagrange variation, coupled Laplace-Beltrami and Poisson-Nernst-Planck (LB-PNP) equations are derived. The solution of the LB-PNP equations leads to the minimization of the total free energy, and explicit profiles of electrostatic potential and densities of charge species. To further reduce the computational complexity, the Boltzmann distribution obtained from the Poisson-Boltzmann (PB) equation is utilized to represent the densities of certain charge species so as to avoid the computationally expensive solution of some Nernst-Planck (NP) equations. Consequently, the coupled Laplace-Beltrami and Poisson-Boltzmann-Nernst-Planck (LB-PBNP) equations are proposed for charge transport in heterogeneous systems. A major emphasis of the present formulation is the consistency between equilibrium LB-PB theory and non-equilibrium LB-PNP theory at equilibrium. Another major emphasis is the capability of the reduced LB-PBNP model to fully recover the prediction of the LB-PNP model at non-equilibrium settings. To account for the fluid impact on the charge transport, we derive coupled Laplace-Beltrami, Poisson-Nernst-Planck and Navier-Stokes equations from the variational principle
Water flow and solute transport through fractured rock
Bourke, P.J.; Kingdon, R.D.; Bolt, J.E.; Pascoe, D.M.; Watkins, V.M.B.
1991-01-01
In densely fractured slate at the Nirex research site in Cornwall, the positions, orientations and hydraulic conductivities of the 380 fractures intersecting a drill hole between 9 and 50 m depths have been individually measured. These data have been used: - to determine the dimensions of statistically representative volumes of the sheetwork of fractures; - to predict; using discrete flowpath modelling and the NAPSAC code; the total flows into the fractures when large numbers are simultaneously pressurised along various lengths of the hole; Corresponding measurements, which proved the modelling and validated the code to factor of two accuracy, are reported. Possibilities accounting for this factor are noted for experimental investigation, and continuing, more extensive inter-hole flow and transport measurements are outlined. The application of this experimental and theoretical approach for calculating radionuclide transport in less densely fractured rock suitable for waste disposal is discussed. 7 figs., 9 refs
Fractional diffusion models of nonlocal transport
Castillo-Negrete, D. del
2006-01-01
A class of nonlocal models based on the use of fractional derivatives (FDs) is proposed to describe nondiffusive transport in magnetically confined plasmas. FDs are integro-differential operators that incorporate in a unified framework asymmetric non-Fickian transport, non-Markovian ('memory') effects, and nondiffusive scaling. To overcome the limitations of fractional models in unbounded domains, we use regularized FDs that allow the incorporation of finite-size domain effects, boundary conditions, and variable diffusivities. We present an α-weighted explicit/implicit numerical integration scheme based on the Grunwald-Letnikov representation of the regularized fractional diffusion operator in flux conserving form. In sharp contrast with the standard diffusive model, the strong nonlocality of fractional diffusion leads to a linear in time response for a decaying pulse at short times. In addition, an anomalous fractional pinch is observed, accompanied by the development of an uphill transport region where the 'effective' diffusivity becomes negative. The fractional flux is in general asymmetric and, for steady states, it has a negative (toward the core) component that enhances confinement and a positive component that increases toward the edge and leads to poor confinement. The model exhibits the characteristic anomalous scaling of the confinement time, τ, with the system's size, L, τ∼L α , of low-confinement mode plasma where 1<α<2 is the order of the FD operator. Numerical solutions of the model with an off-axis source show that the fractional inward transport gives rise to profile peaking reminiscent of what is observed in tokamak discharges with auxiliary off-axis heating. Also, cold-pulse perturbations to steady sates in the model exhibit fast, nondiffusive propagation phenomena that resemble perturbative experiments
Advanced transport modeling of toroidal plasmas with transport barriers
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)
Baik, Min Hoon
1994-02-01
In this study, adsorption and transport models were developed to analyze the effect of chelating agents on the adsorption and subsurface transport of radioactive solutes. The effect of chelating agents on the adsorption of radioactive solutes was analyzed by developing an adsorption model based upon the extended concept of distribution coefficient reflecting the presence of chelating agents. Also, a batch adsorption experiment was conducted in order to validate the developed adsorption model and to investigate the effect of chelating agent on the adsorption of radioactive metal solutes. In this experiment, a Cobalt(II)/EDTA/Bentonite system was considered as a representative chelation/adsorption system. It was found from the results that the presence of chelating agents significantly reduced the adsorbing capacity of geologic media such as clay minerals and soils. Thus it was concluded that the presence of chelating agents even in a small amount could contribute to the mobilization of radioactive solutes from radioactive waste burial sites by reducing the adsorbing capacity of geologic media. The effect of chelating agents on the transport of radioactive solutes in subsurface porous media was analyzed by formulating an advective-dispersive transport model which incorporated chelate formation, adsorption, decay, and degradations and by introducing the concept of a tenad. Particularly the governing equation for the tenad of radioactive solutes, M, was presented as a linear partial differential form by introducing the extended distribution coefficient, K D . The calculated results from the model showed that the transport rate of the chelated radionuclides was much greater than that of the free ionic radionuclides. This much faster transport of the chelated radionuclides was found to be due to the lower retardation factor of the chelated radionuclides than the free ionic radionuclides. The effect of parameters on the transport of radioactive solutes was also analyzed
Solution to the monoenergetic time-dependent neutron transport equation with a time-varying source
Ganapol, B.D.
1986-01-01
Even though fundamental time-dependent neutron transport problems have existed since the inception of neutron transport theory, it has only been recently that a reliable numerical solution to one of the basic problems has been obtained. Experience in generating numerical solutions to time-dependent transport equations has indicated that the multiple collision formulation is the most versatile numerical technique for model problems. The formulation coupled with a moment reconstruction of each collided flux component has led to benchmark-quality (four- to five-digit accuracy) numerical evaluation of the neutron flux in plane infinite geometry for any degree of scattering anisotropy and for both pulsed isotropic and beam sources. As will be shown in this presentation, this solution can serve as a Green's function, thus extending the previous results to more complicated source situations. Here we will be concerned with a time-varying source at the center of an infinite medium. If accurate, such solutions have both pedagogical and practical uses as benchmarks against which other more approximate solutions designed for a wider class of problems can be compared
CFEST Coupled Flow, Energy & Solute Transport Version CFEST005 User’s Guide
Freedman, Vicky L.; Chen, Yousu; Gilca, Alex; Cole, Charles R.; Gupta, Sumant K.
2006-07-20
The CFEST (Coupled Flow, Energy, and Solute Transport) simulator described in this User’s Guide is a three-dimensional finite-element model used to evaluate groundwater flow and solute mass transport. Confined and unconfined aquifer systems, as well as constant and variable density fluid flows can be represented with CFEST. For unconfined aquifers, the model uses a moving boundary for the water table, deforming the numerical mesh so that the uppermost nodes are always at the water table. For solute transport, changes in concentra¬tion of a single dissolved chemical constituent are computed for advective and hydrodynamic transport, linear sorption represented by a retardation factor, and radioactive decay. Although several thermal parameters described in this User’s Guide are required inputs, thermal transport has not yet been fully implemented in the simulator. Once fully implemented, transport of thermal energy in the groundwater and solid matrix of the aquifer can also be used to model aquifer thermal regimes. The CFEST simulator is written in the FORTRAN 77 language, following American National Standards Institute (ANSI) standards. Execution of the CFEST simulator is controlled through three required text input files. These input file use a structured format of associated groups of input data. Example input data lines are presented for each file type, as well as a description of the structured FORTRAN data format. Detailed descriptions of all input requirements, output options, and program structure and execution are provided in this User’s Guide. Required inputs for auxillary CFEST utilities that aide in post-processing data are also described. Global variables are defined for those with access to the source code. Although CFEST is a proprietary code (CFEST, Inc., Irvine, CA), the Pacific Northwest National Laboratory retains permission to maintain its own source, and to distribute executables to Hanford subcontractors.
Multigroup adjoint transport solution using the method of cyclic characteristics
Assawaroongruengchot, M.; Marleau, G.
2005-01-01
The adjoint transport solution algorithm based on the method of cyclic characteristics (MOCC) is developed for the heterogeneous 2-dimensional geometries. The adjoint characteristics equation associated with a cyclic tracking line is formulated, then a closed form for adjoint angular flux can be determined. The acceleration techniques are implemented using the group-reduction and group-splitting techniques. To demonstrate the efficacy of the algorithm, the calculations are performed on the 17*17 PWR and Watanabe-Maynard benchmark problems. Comparisons of adjoint flux and k eff results obtained by MOCC and collision probability (CP) methods are performed. The mathematical relationship between pseudo-adjoint flux obtained by CP method and adjoint flux by MOCC method is presented. It appears that the pseudo-adjoint flux by CP method is equivalent to the adjoint flux by MOCC method and that the MOCC method requires lower computing time than the CP method for a single adjoint flux calculation
Multigroup adjoint transport solution using the method of cyclic characteristics
Assawaroongruengchot, M.; Marleau, G. [Ecole Polytechnique de Montreal, Institut de Genie Nucleaire, Montreal, Quebec (Canada)
2005-07-01
The adjoint transport solution algorithm based on the method of cyclic characteristics (MOCC) is developed for the heterogeneous 2-dimensional geometries. The adjoint characteristics equation associated with a cyclic tracking line is formulated, then a closed form for adjoint angular flux can be determined. The acceleration techniques are implemented using the group-reduction and group-splitting techniques. To demonstrate the efficacy of the algorithm, the calculations are performed on the 17*17 PWR and Watanabe-Maynard benchmark problems. Comparisons of adjoint flux and k{sub eff} results obtained by MOCC and collision probability (CP) methods are performed. The mathematical relationship between pseudo-adjoint flux obtained by CP method and adjoint flux by MOCC method is presented. It appears that the pseudo-adjoint flux by CP method is equivalent to the adjoint flux by MOCC method and that the MOCC method requires lower computing time than the CP method for a single adjoint flux calculation.
The quasi-diffusive approximation in transport theory: Local solutions
Celaschi, M.; Montagnini, B.
1995-01-01
The one velocity, plane geometry integral neutron transport equation is transformed into a system of two equations, one of them being the equation of continuity and the other a generalized Fick's law, in which the usual diffusion coefficient is replaced by a self-adjoint integral operator. As the kernel of this operator is very close to the Green function of a diffusion equation, an approximate inversion by means of a second order differential operator allows to transform these equations into a purely differential system which is shown to be equivalent, in the simplest case, to a diffusion-like equation. The method, the principles of which have been exposed in a previous paper, is here extended and applied to a variety of problems. If the inversion is properly performed, the quasi-diffusive solutions turn out to be quite accurate, even in the vicinity of the interface between different material regions, where elementary diffusion theory usually fails. 16 refs., 3 tabs
Approximate solution to neutron transport equation with linear anisotropic scattering
Coppa, G.; Ravetto, P.; Sumini, M.
1983-01-01
A method to obtain an approximate solution to the transport equation, when both sources and collisions show a linearly anisotropic behavior, is outlined and the possible implications for numerical calculations in applied neutronics as well as shielding evaluations are investigated. The form of the differential system of equations taken by the method is quite handy and looks simpler and more manageable than any other today available technique. To go deeper into the efficiency of the method, some typical calculations concerning critical dimension of multiplying systems are then performed and the results are compared with the ones coming from the classical Ssub(N) approximations. The outcome of such calculations leads us to think of interesting developments of the method which could be quite useful in alternative to other today widespread approximate procedures, for any geometry, but especially for curved ones. (author)
Engineering charge transport by heterostructuring solution-processed semiconductors
Voznyy, Oleksandr; Sutherland, Brandon R.; Ip, Alexander H.; Zhitomirsky, David; Sargent, Edward H.
2017-06-01
Solution-processed semiconductor devices are increasingly exploiting heterostructuring — an approach in which two or more materials with different energy landscapes are integrated into a composite system. Heterostructured materials offer an additional degree of freedom to control charge transport and recombination for more efficient optoelectronic devices. By exploiting energetic asymmetry, rationally engineered heterostructured materials can overcome weaknesses, augment strengths and introduce emergent physical phenomena that are otherwise inaccessible to single-material systems. These systems see benefit and application in two distinct branches of charge-carrier manipulation. First, they influence the balance between excitons and free charges to enhance electron extraction in solar cells and photodetectors. Second, they promote radiative recombination by spatially confining electrons and holes, which increases the quantum efficiency of light-emitting diodes. In this Review, we discuss advances in the design and composition of heterostructured materials, consider their implementation in semiconductor devices and examine unexplored paths for future advancement in the field.
Coupling of solute transport and cell expansion in pea stems
Schmalstig, J. G.; Cosgrove, D. J.
1990-01-01
As cells expand and are displaced through the elongation zone of the epicotyl of etiolated pea (Pisum sativum L. var Alaska) seedlings, there is little net dilution of the cell sap, implying a coordination between cell expansion and solute uptake from the phloem. Using [14C] sucrose as a phloem tracer (applied to the hypogeous cotyledons), the pattern of label accumulation along the stem closely matched the growth rate pattern: high accumulation in the growing zone, little accumulation in nongrowing regions. Several results suggest that a major portion of phloem contents enters elongating cells through the symplast. We propose that the coordination between phloem transport and cell expansion is accomplished via regulatory pathways affecting both plasmodesmata conductivity and cell expansion.
Study of reactive solutes transport and PAH migration in unsaturated soils
Gujisaite, V.; Simonnot, M.O.; Gujisaite, V.; Morel, J.L.; Ouvrard, S.; Simonnot, M.O.; Gaudet, J.P.
2005-01-01
Experimental studies about solute transport in soil have most of the time been conducted under saturated conditions, whereas studies with unsaturated media are usually limited to hydrodynamic analysis. Those are mainly concerning the prediction of water flow, which is the main vector for the transport of contaminants in soil. Only a few studies have made the link between unsaturated flow and physical, chemical and biological interactions, which are controlling the availability of pollutants. However, the presence of a gaseous phase in soil can modify not only the movement of soil solution, but also chemical interactions and exchanges between soil aggregates and solution. Study of reactive solute transport in the vadose zone seems thus to be a necessary stage to predict contaminant fate in natural soils, for risk assessment as well as for the design of effective processes for the remediation of contaminated soils. This question is the main objective of the present work developed in the frame of our French Scientific Interest Group Industrial Wastelands called 'GISFI' (www.gisfi.prd.fr), based around a scientific and technological project dedicated to acquisition of knowledge for sustainable requalification of degraded sites polluted by past industrial activities. We will focus here on Polycyclic Aromatic Hydrocarbons (PAH), which are among the most widely discussed environmental contaminants because of their toxicity for human health and ecosystems. They are present in large quantities in soils polluted by former industrial activities, especially in relation to the coal extraction, exploitation and treatment. An experimental system has been specifically designed at the laboratory scale to carry out experiments under controlled conditions, with an unsaturated steady-state flow. The first experiments are performed on model soils, in order to investigate unsaturated steady-state flow in relation to interactions mechanisms. We have thus chosen to use a sandy
Marcus M. Corrêa
2006-03-01
Full Text Available As equações diferenciais do movimento de água e do transporte de soluto em solo não saturado, considerando-se a existência de extração pela planta, foram resolvidas utilizando a técnica diferenças finitas. Para a implementação do modelo desenvolveu-se um programa em linguagem Delphi, denominado SIMASS-C - SImulação do Movimento de Água e Soluto no Solo, considerando-se a presença de Cultura. O modelo fornece, em diferentes tempos, os valores de umidade, do potencial matricial, do fluxo da água e da concentração de soluto ao longo do perfil do solo. Obtém-se, ainda, como resultados de saída, o crescimento e a densidade das raízes, o índice de área foliar e a evapotranspiração da cultura. Para testar o modelo desenvolvido conduziu-se um experimento em casa de vegetação, onde 42 colunas de solo foram montadas em tubo de PVC rígido. Em cada coluna, a cultura do milho foi semeada e durante 30 dias após a germinação, a umidade do solo e o desenvolvimento da cultura foram monitorados. Os resultados experimentais mostraram, ao nível de probabilidade de 90%, que o modelo SIMASS-C foi preciso em simular o transporte de água no solo.The differential equations that govern the water flow and the solute transport in an unsaturated soil, considering the water extraction by plants were solved using the finite difference method. A computer model named SIMASS-C (Simulation of the water and solute transport in the soil considering water extraction was developed using Delphi language. The model allows to calculate the water content, matric potential, water flux and solute concentration through the soil profile. Besides that, the model output gives the growth and the density of the roots, the leaf area index and the crop evapotranspiration. To test the model, an experiment was conducted in a green house using 42 soil columns made of PVC tubes. In each column, corn was seeded and during 30 days after the emergence the soil water
The use of non-dimensional representation of the solute transport equations
Laurens, J.-M.
1988-07-01
This report presents the results obtained in a pilot investigation into the use of non-dimensional representations of the solute transport equations, so as to improve the efficiency of the PRA codes used by the DoE and its contractors. A reduced set of parameters was obtained for a single layer transport model. As expected, the response was shown to be highly sensitive on the new parameters. A faster convergence of the system was observed when the sampling technique used was changed to take into account the properties of the new parameters, such that uniform coverage of the reduced parameter hyperspace was achieved. (author)
Biological transportation networks: Modeling and simulation
Albi, Giacomo; Artina, Marco; Foransier, Massimo; Markowich, Peter A.
2015-01-01
We present a model for biological network formation originally introduced by Cai and Hu [Adaptation and optimization of biological transport networks, Phys. Rev. Lett. 111 (2013) 138701]. The modeling of fluid transportation (e.g., leaf venation
Improved parallel solution techniques for the integral transport matrix method
Zerr, R. Joseph, E-mail: rjz116@psu.edu [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA (United States); Azmy, Yousry Y., E-mail: yyazmy@ncsu.edu [Department of Nuclear Engineering, North Carolina State University, Burlington Engineering Laboratories, Raleigh, NC (United States)
2011-07-01
Alternative solution strategies to the parallel block Jacobi (PBJ) method for the solution of the global problem with the integral transport matrix method operators have been designed and tested. The most straightforward improvement to the Jacobi iterative method is the Gauss-Seidel alternative. The parallel red-black Gauss-Seidel (PGS) algorithm can improve on the number of iterations and reduce work per iteration by applying an alternating red-black color-set to the subdomains and assigning multiple sub-domains per processor. A parallel GMRES(m) method was implemented as an alternative to stationary iterations. Computational results show that the PGS method can improve on the PBJ method execution time by up to 10´ when eight sub-domains per processor are used. However, compared to traditional source iterations with diffusion synthetic acceleration, it is still approximately an order of magnitude slower. The best-performing cases are optically thick because sub-domains decouple, yielding faster convergence. Further tests revealed that 64 sub-domains per processor was the best performing level of sub-domain division. An acceleration technique that improves the convergence rate would greatly improve the ITMM. The GMRES(m) method with a diagonal block pre conditioner consumes approximately the same time as the PBJ solver but could be improved by an as yet undeveloped, more efficient pre conditioner. (author)
Improved parallel solution techniques for the integral transport matrix method
Zerr, R. Joseph; Azmy, Yousry Y.
2011-01-01
Alternative solution strategies to the parallel block Jacobi (PBJ) method for the solution of the global problem with the integral transport matrix method operators have been designed and tested. The most straightforward improvement to the Jacobi iterative method is the Gauss-Seidel alternative. The parallel red-black Gauss-Seidel (PGS) algorithm can improve on the number of iterations and reduce work per iteration by applying an alternating red-black color-set to the subdomains and assigning multiple sub-domains per processor. A parallel GMRES(m) method was implemented as an alternative to stationary iterations. Computational results show that the PGS method can improve on the PBJ method execution time by up to 10´ when eight sub-domains per processor are used. However, compared to traditional source iterations with diffusion synthetic acceleration, it is still approximately an order of magnitude slower. The best-performing cases are optically thick because sub-domains decouple, yielding faster convergence. Further tests revealed that 64 sub-domains per processor was the best performing level of sub-domain division. An acceleration technique that improves the convergence rate would greatly improve the ITMM. The GMRES(m) method with a diagonal block pre conditioner consumes approximately the same time as the PBJ solver but could be improved by an as yet undeveloped, more efficient pre conditioner. (author)
Water flow and solute transport through fractured rock
Bolt, J.E.; Bourke, P.J.; Pascoe, D.M.; Watkins, V.M.B.; Kingdon, R.D.
1990-09-01
In densely fractured slate at the Nirex research site in Cornwall, the positions, orientations and hydraulic conductivities of the 380 fractures intersecting a drill hole between 9 and 50 m depth have been individually measured. These data have been used: to determine the dimensions of statistically representative volumes of the network of fractures and to predict, using discrete flow path modelling and the NAPSAC code, the total flows into the fractures when large numbers are simultaneously pressurised along various lengths of the hole. Corresponding measurements, which validated the NAPSAC code to factor of two accuracy for the Cornish site, are reported. Possibilities accounting for this factor are noted for experimental investigation, and continuing, more extensive, inter hole flow and transport measurements are outlined. The application of this experimental and theoretical approach for calculating radionuclide transport in less densely fractured rock suitable for waste disposal is discussed. (Author)
Hydro-dynamic Solute Transport under Two-Phase Flow Conditions.
Karadimitriou, Nikolaos K; Joekar-Niasar, Vahid; Brizuela, Omar Godinez
2017-07-26
There are abundant examples of natural, engineering and industrial applications, in which "solute transport" and "mixing" in porous media occur under multiphase flow conditions. Current state-of-the-art understanding and modelling of such processes are established based on flawed and non-representative models. Moreover, there is no direct experimental result to show the true hydrodynamics of transport and mixing under multiphase flow conditions while the saturation topology is being kept constant for a number of flow rates. With the use of a custom-made microscope, and under well-controlled flow boundary conditions, we visualized directly the transport of a tracer in a Reservoir-on-Chip (RoC) micromodel filled with two immiscible fluids. This study provides novel insights into the saturation-dependency of transport and mixing in porous media. To our knowledge, this is the first reported pore-scale experiment in which the saturation topology, relative permeability, and tortuosity were kept constant and transport was studied under different dynamic conditions in a wide range of saturation. The critical role of two-phase hydrodynamic properties on non-Fickian transport and saturation-dependency of dispersion are discussed, which highlight the major flaws in parametrization of existing models.
Global stability and exact solution of an arbitrary-solute nonlinear cellular mass transport system.
Benson, James D
2014-12-01
The prediction of the cellular state as a function of extracellular concentrations and temperatures has been of interest to physiologists for nearly a century. One of the most widely used models in the field is one where mass flux is linearly proportional to the concentration difference across the membrane. These fluxes define a nonlinear differential equation system for the intracellular state, which when coupled with appropriate initial conditions, define the intracellular state as a function of the extracellular concentrations of both permeating and nonpermeating solutes. Here we take advantage of a reparametrization scheme to extend existing stability results to a more general setting and to a develop analytical solutions to this model for an arbitrary number of extracellular solutes. Copyright © 2014 Elsevier Inc. All rights reserved.
SÁVIO LEANDRO BERTOLI
2016-07-01
Full Text Available In the engineering courses the field of Transport Phenomena is of significant importance and it is in several disciplines relating to Fluid Mechanics, Heat and Mass Transfer. In these disciplines, problems involving these phenomena are mathematically formulated and analytical solutions are obtained whenever possible. The aim of this paper is to emphasize the possibility of extending aspects of the teaching-learning in this area by a method based on time scales and limit solutions. Thus, aspects relative to the phenomenology naturally arise during the definition of the scales and / or by determining the limit solutions. Aspects concerning the phenomenology of the limit problems are easily incorporated into the proposed development, which contributes significantly to the understanding of physics inherent in the mathematical modeling of each limiting case studied. Finally the study aims to disseminate the use of the limit solutions and of the time scales in the general fields of engineering.
Leung, Juliana Y.; Srinivasan, Sanjay
2016-09-01
Modeling transport process at large scale requires proper scale-up of subsurface heterogeneity and an understanding of its interaction with the underlying transport mechanisms. A technique based on volume averaging is applied to quantitatively assess the scaling characteristics of effective mass transfer coefficient in heterogeneous reservoir models. The effective mass transfer coefficient represents the combined contribution from diffusion and dispersion to the transport of non-reactive solute particles within a fluid phase. Although treatment of transport problems with the volume averaging technique has been published in the past, application to geological systems exhibiting realistic spatial variability remains a challenge. Previously, the authors developed a new procedure where results from a fine-scale numerical flow simulation reflecting the full physics of the transport process albeit over a sub-volume of the reservoir are integrated with the volume averaging technique to provide effective description of transport properties. The procedure is extended such that spatial averaging is performed at the local-heterogeneity scale. In this paper, the transport of a passive (non-reactive) solute is simulated on multiple reservoir models exhibiting different patterns of heterogeneities, and the scaling behavior of effective mass transfer coefficient (Keff) is examined and compared. One such set of models exhibit power-law (fractal) characteristics, and the variability of dispersion and Keff with scale is in good agreement with analytical expressions described in the literature. This work offers an insight into the impacts of heterogeneity on the scaling of effective transport parameters. A key finding is that spatial heterogeneity models with similar univariate and bivariate statistics may exhibit different scaling characteristics because of the influence of higher order statistics. More mixing is observed in the channelized models with higher-order continuity. It
FASTREACT – An efficient numerical framework for the solution of reactive transport problems
Trinchero, Paolo; Molinero, Jorge; Román-Ross, Gabriela; Berglund, Sten; Selroos, Jan-Olof
2014-01-01
Highlights: • We present a tool for the efficient solution of reactive transport problems. • The tool is used to simulate radionuclide transport in a two-dimensional medium. • The results are successfully compared with those obtained using an Eulerian approach. • A large-scale application example is also solved. • The results show that the proposed tool can efficiently solve large-scale models. - Abstract: In the framework of safety assessment studies for geological disposal, large scale reactive transport models are powerful inter-disciplinary tools aiming at supporting regulatory decision making as well as providing input to repository engineering activities. Important aspects of these kinds of models are their often very large temporal and spatial modelling scales and the need to integrate different non-linear processes (e.g., mineral dissolution and precipitation, adsorption and desorption, microbial reactions and redox transformations). It turns out that these types of models may be computationally highly demanding. In this work, we present a Lagrangian-based framework, denoted as FASTREACT, that aims at solving multi-component-reactive transport problems with a computationally efficient approach allowing complex modelling problems to be solved in large spatial and temporal scales. The tool has been applied to simulate radionuclide migration in a synthetic heterogeneous transmissivity field and the results have been successfully compared with those obtained using a standard Eulerian approach. Finally, the same geochemical model has been coupled to an ensemble of realistic three-dimensional transport pathways to simulate the migration of a set of radionuclides from a hypothetical repository for spent nuclear fuel to the surface. The results of this modelling exercise, which includes key processes such as the exchange of mass between the conductive fractures and the matrix, show that FASTREACT can efficiently solve large-scale reactive transport models
Modelling of radon transport in porous media
van der Graaf, E.R.; de Meijer, R.J.; Katase, A; Shimo, M
1998-01-01
This paper aims to describe the state of the art of modelling radon transport in soil on basis of multiphase radon transport equations. Emphasis is given to methods to obtain a consistent set of input parameters needed For such models. Model-measurement comparisons with the KVI radon transport
Modeling spin magnetization transport in a spatially varying magnetic field
Picone, Rico A.R.; Garbini, Joseph L.; Sidles, John A.
2015-01-01
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]). - Highlights: • A framework for modeling the transport of conserved magnetic and thermodynamic quantities in any spatial configuration. • A thermodynamically grounded model of spin magnetization transport valid in new regimes, including high-polarization. • Analysis of the separative quality of
Modeling spin magnetization transport in a spatially varying magnetic field
Picone, Rico A.R., E-mail: rpicone@stmartin.edu [Department of Mechanical Engineering, University of Washington, Seattle (United States); Garbini, Joseph L. [Department of Mechanical Engineering, University of Washington, Seattle (United States); Sidles, John A. [Department of Orthopædics, University of Washington, Seattle (United States)
2015-01-15
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]). - Highlights: • A framework for modeling the transport of conserved magnetic and thermodynamic quantities in any spatial configuration. • A thermodynamically grounded model of spin magnetization transport valid in new regimes, including high-polarization. • Analysis of the separative quality of
Larsen, E.H.; Møbjerg, N.; Sørensen, Jens Nørkær
2006-01-01
transport similar to rat proximal tubule. Na+ recirculation is required for truly isotonic transport. The tonicity of the absorbate and the recirculation flux depend critically on ion permeabilities of interspace basement membrane. Conclusion: Our model based on solute-solvent coupling in lateral space......Aim: By mathematical modelling, we analyse conditions for near-isotonic and isotonic transport by mammalian kidney proximal tubule. Methods: The model comprises compliant lateral intercellular space (lis) and cells, and infinitely large luminal and peritubular compartments with diffusible species......: Na+, K+, Cl and an intracellular non-diffusible anion. Unknown model variables are solute concentrations, electrical potentials, volumes and hydrostatic pressures in cell and lis, and transepithelial potential. We used data mainly from rat proximal tubule to model epithelial cells and interspace...
Directions in Radiation Transport Modelling
P Nicholas Smith
2016-12-01
More exciting advances are on the horizon to increase the power of simulation tools. The advent of high performance computers is allowing bigger, higher fidelity models to be created, if the challenges of parallelization and memory management can be met. 3D whole core transport modelling is becoming possible. Uncertainty quantification is improving with large benefits to be gained from more accurate, less pessimistic estimates of uncertainty. Advanced graphical displays allow the user to assimilate and make sense of the vast amounts of data produced by modern modelling tools. Numerical solvers are being developed that use goal-based adaptivity to adjust the nodalisation of the system to provide the optimum scheme to achieve the user requested accuracy on the results, thus removing the need to perform costly convergence studies in space and angle etc. More use is being made of multi-physics methods in which radiation transport is coupled with other phenomena, such as thermal-hydraulics, structural response, fuel performance and/or chemistry in order to better understand their interplay in reactor cores.
Steirer, K. Xerxes; Berry, Joseph J.; Chesin, Jordan P.; Lloyd, Matthew T.; Widjonarko, Nicodemus Edwin; Miedaner, Alexander; Curtis, Calvin J.; Ginley, David S.; Olson, Dana C.
2017-01-10
A method for the application of solution processed metal oxide hole transport layers in organic photovoltaic devices and related organic electronics devices is disclosed. The metal oxide may be derived from a metal-organic precursor enabling solution processing of an amorphous, p-type metal oxide. An organic photovoltaic device having solution processed, metal oxide, thin-film hole transport layer.
Chen, C.S.; Yates, S.R.
1989-01-01
In dealing with problems related to land-based nuclear waste management, a number of analytical and approximate solutions were developed to quantify radionuclide transport through fractures contained in the porous formation. It has been reported that by treating the radioactive decay constant as the appropriate first-order rate constant, these solutions can also be used to study injection problems of a similar nature subject to first-order chemical or biological reactions. The fracture is idealized by a pair of parallel, smooth plates separated by an aperture of constant thickness. Groundwater was assumed to be immobile in the underlying and overlying porous formations due to their low permeabilities. However, the injected radionuclides were able to move from the fracture into the porous matrix by molecular diffusion (the matrix diffusion) due to possible concentration gradients across the interface between the fracture and the porous matrix. Calculation of the transient solutions is not straightforward, and the paper documents a contained Fortran program, which computes the Stehfest inversion, the Airy functions, and gives the concentration distributions in the fracture as well as in the porous matrix for both transient and steady-state cases
Pseudoclassical fermionic model and classical solutions
Smailagic, A.
1981-08-01
We study classical limit of fermionic fields seen as Grassmann variables and deduce the proper quantization prescription using Dirac's method for constrained systems and investigate quantum meaning of classical solutions for the Thirring model. (author)
Den Buijs, Jorn Op; Dragomir-Daescu, Dan; Ritman, Erik L
2009-08-01
Nutrient supply and waste removal in porous tissue engineering scaffolds decrease from the periphery to the center, leading to limited depth of ingrowth of new tissue into the scaffold. However, as many tissues experience cyclic physiological strains, this may provide a mechanism to enhance solute transport in vivo before vascularization of the scaffold. The hypothesis of this study was that pore cross-sectional geometry and interconnectivity are of major importance for the effectiveness of cyclic deformation-induced solute transport. Transparent elastic polyurethane scaffolds, with computer-programmed design of pore networks in the form of interconnected channels, were fabricated using a 3D printing and injection molding technique. The scaffold pores were loaded with a colored tracer for optical contrast, cyclically compressed with deformations of 10 and 15% of the original undeformed height at 1.0 Hz. Digital imaging was used to quantify the spatial distribution of the tracer concentration within the pores. Numerical simulations of a fluid-structure interaction model of deformation-induced solute transport were compared to the experimental data. The results of experiments and modeling agreed well and showed that pore interconnectivity heavily influences deformation-induced solute transport. Pore cross-sectional geometry appears to be of less relative importance in interconnected pore networks. Validated computer models of solute transport can be used to design optimal scaffold pore geometries that will enhance the convective transport of nutrients inside the scaffold and the removal of waste, thus improving the cell survivability deep inside the scaffold.
Up-gradient transport in a probabilistic transport model
Gavnholt, J.; Juul Rasmussen, J.; Garcia, O.E.
2005-01-01
The transport of particles or heat against the driving gradient is studied by employing a probabilistic transport model with a characteristic particle step length that depends on the local concentration or heat gradient. When this gradient is larger than a prescribed critical value, the standard....... These results supplement recent works by van Milligen [Phys. Plasmas 11, 3787 (2004)], which applied Levy distributed step sizes in the case of supercritical gradients to obtain the up-gradient transport. (c) 2005 American Institute of Physics....
Zhang, Hua; Harter, Thomas; Sivakumar, Bellie
2006-06-01
Facies-based geostatistical models have become important tools for analyzing flow and mass transport processes in heterogeneous aquifers. Yet little is known about the relationship between these latter processes and the parameters of facies-based geostatistical models. In this study, we examine the transport of a nonpoint source solute normal (perpendicular) to the major bedding plane of an alluvial aquifer medium that contains multiple geologic facies, including interconnected, high-conductivity (coarse textured) facies. We also evaluate the dependence of the transport behavior on the parameters of the constitutive facies model. A facies-based Markov chain geostatistical model is used to quantify the spatial variability of the aquifer system's hydrostratigraphy. It is integrated with a groundwater flow model and a random walk particle transport model to estimate the solute traveltime probability density function (pdf) for solute flux from the water table to the bottom boundary (the production horizon) of the aquifer. The cases examined include two-, three-, and four-facies models, with mean length anisotropy ratios for horizontal to vertical facies, ek, from 25:1 to 300:1 and with a wide range of facies volume proportions (e.g., from 5 to 95% coarse-textured facies). Predictions of traveltime pdfs are found to be significantly affected by the number of hydrostratigraphic facies identified in the aquifer. Those predictions of traveltime pdfs also are affected by the proportions of coarse-textured sediments, the mean length of the facies (particularly the ratio of length to thickness of coarse materials), and, to a lesser degree, the juxtapositional preference among the hydrostratigraphic facies. In transport normal to the sedimentary bedding plane, traveltime is not lognormally distributed as is often assumed. Also, macrodispersive behavior (variance of the traveltime) is found not to be a unique function of the conductivity variance. For the parameter range
Reactive solute transport in streams: A surface complexation approach for trace metal sorption
Runkel, Robert L.; Kimball, Briant A.; McKnight, Diane M.; Bencala, Kenneth E.
1999-01-01
A model for trace metals that considers in-stream transport, metal oxide precipitation-dissolution, and pH-dependent sorption is presented. Linkage between a surface complexation submodel and the stream transport equations provides a framework for modeling sorption onto static and/or dynamic surfaces. A static surface (e.g., an iron- oxide-coated streambed) is defined as a surface with a temporally constant solid concentration. Limited contact between solutes in the water column and the static surface is considered using a pseudokinetic approach. A dynamic surface (e.g., freshly precipitated metal oxides) has a temporally variable solid concentration and is in equilibrium with the water column. Transport and deposition of solute mass sorbed to the dynamic surface is represented in the stream transport equations that include precipitate settling. The model is applied to a pH-modification experiment in an acid mine drainage stream. Dissolved copper concentrations were depressed for a 3 hour period in response to the experimentally elevated pH. After passage of the pH front, copper was desorbed, and dissolved concentrations returned to ambient levels. Copper sorption is modeled by considering sorption to aged hydrous ferric oxide (HFO) on the streambed (static surface) and freshly precipitated HFO in the water column (dynamic surface). Comparison of parameter estimates with reported values suggests that naturally formed iron oxides may be more effective in removing trace metals than synthetic oxides used in laboratory studies. The model's ability to simulate pH, metal oxide precipitation-dissolution, and pH-dependent sorption provides a means of evaluating the complex interactions between trace metal chemistry and hydrologic transport at the field scale.
DRAGON solutions to the 3D transport benchmark over a range in parameter space
Martin, Nicolas; Hebert, Alain; Marleau, Guy
2010-01-01
DRAGON solutions to the 'NEA suite of benchmarks for 3D transport methods and codes over a range in parameter space' are discussed in this paper. A description of the benchmark is first provided, followed by a detailed review of the different computational models used in the lattice code DRAGON. Two numerical methods were selected for generating the required quantities for the 729 configurations of this benchmark. First, S N calculations were performed using fully symmetric angular quadratures and high-order diamond differencing for spatial discretization. To compare S N results with those of another deterministic method, the method of characteristics (MoC) was also considered for this benchmark. Comparisons between reference solutions, S N and MoC results illustrate the advantages and drawbacks of each methods for this 3-D transport problem.
Dou, Z.
2017-12-01
In this study, the influence of multi-scale roughness on transport behavior of the passive solute through the self-affine fracture was investigated. The single self-affine fracture was constructed by the successive random additions (SRA) and the fracture roughness was decomposed into two different scales (i.e. large-scale primary roughness and small-scale secondary roughness) by the Wavelet analysis technique. The fluid flow in fractures, which was characterized by the Forchheimer's law, showed the non-linear flow behaviors such as eddies and tortuous streamlines. The results indicated that the small-scale secondary roughness was primarily responsible for the non-linear flow behaviors. The direct simulations of asymptotic passive solute transport represented the Non-Fickian transport characteristics (i.e. early arrivals and long tails) in breakthrough curves (BTCs) and residence time distributions (RTDs) with and without consideration of the secondary roughness. Analysis of multiscale BTCs and RTDs showed that the small-scale secondary roughness played a significant role in enhancing the Non-Fickian transport characteristics. We found that removing small-scale secondary roughness led to the lengthening arrival and shortening tail. The peak concentration in BTCs decreased as the secondary roughness was removed, implying that the secondary could also enhance the solute dilution. The estimated BTCs by the Fickian advection-dispersion equation (ADE) yielded errors which decreased with the small-scale secondary roughness being removed. The mobile-immobile model (MIM) was alternatively implemented to characterize the Non-Fickian transport. We found that the MIM was more capable of estimating Non-Fickian BTCs. The small-scale secondary roughness resulted in the decreasing mobile domain fraction and the increasing mass exchange rate between immobile and mobile domains. The estimated parameters from the MIM could provide insight into the inherent mechanism of roughness
Product Lifecycle Management and the Quest for Sustainable Space Transportation Solutions
Caruso, Pamela W.
2009-01-01
This viewgraph presentation reviews NASA Marshall's effort to sustain space transportation solutions through product lines that include: 1) Propulsion and Transportation Systems; 2) Life Support Systems; and 3) and Earth and Space Science Spacecraft Systems, and Operations.
Parameter optimization for surface flux transport models
Whitbread, T.; Yeates, A. R.; Muñoz-Jaramillo, A.; Petrie, G. J. D.
2017-11-01
Accurate prediction of solar activity calls for precise calibration of solar cycle models. Consequently we aim to find optimal parameters for models which describe the physical processes on the solar surface, which in turn act as proxies for what occurs in the interior and provide source terms for coronal models. We use a genetic algorithm to optimize surface flux transport models using National Solar Observatory (NSO) magnetogram data for Solar Cycle 23. This is applied to both a 1D model that inserts new magnetic flux in the form of idealized bipolar magnetic regions, and also to a 2D model that assimilates specific shapes of real active regions. The genetic algorithm searches for parameter sets (meridional flow speed and profile, supergranular diffusivity, initial magnetic field, and radial decay time) that produce the best fit between observed and simulated butterfly diagrams, weighted by a latitude-dependent error structure which reflects uncertainty in observations. Due to the easily adaptable nature of the 2D model, the optimization process is repeated for Cycles 21, 22, and 24 in order to analyse cycle-to-cycle variation of the optimal solution. We find that the ranges and optimal solutions for the various regimes are in reasonable agreement with results from the literature, both theoretical and observational. The optimal meridional flow profiles for each regime are almost entirely within observational bounds determined by magnetic feature tracking, with the 2D model being able to accommodate the mean observed profile more successfully. Differences between models appear to be important in deciding values for the diffusive and decay terms. In like fashion, differences in the behaviours of different solar cycles lead to contrasts in parameters defining the meridional flow and initial field strength.
Parkhurst, David L.; Kipp, Kenneth L.; Charlton, Scott R.
2010-01-01
The computer program PHAST (PHREEQC And HST3D) simulates multicomponent, reactive solute transport in three-dimensional saturated groundwater flow systems. PHAST is a versatile groundwater flow and solute-transport simulator with capabilities to model a wide range of equilibrium and kinetic geochemical reactions. The flow and transport calculations are based on a modified version of HST3D that is restricted to constant fluid density and constant temperature. The geochemical reactions are simulated with the geochemical model PHREEQC, which is embedded in PHAST. Major enhancements in PHAST Version 2 allow spatial data to be defined in a combination of map and grid coordinate systems, independent of a specific model grid (without node-by-node input). At run time, aquifer properties are interpolated from the spatial data to the model grid; regridding requires only redefinition of the grid without modification of the spatial data. PHAST is applicable to the study of natural and contaminated groundwater systems at a variety of scales ranging from laboratory experiments to local and regional field scales. PHAST can be used in studies of migration of nutrients, inorganic and organic contaminants, and radionuclides; in projects such as aquifer storage and recovery or engineered remediation; and in investigations of the natural rock/water interactions in aquifers. PHAST is not appropriate for unsaturated-zone flow, multiphase flow, or density-dependent flow. A variety of boundary conditions are available in PHAST to simulate flow and transport, including specified-head, flux (specified-flux), and leaky (head-dependent) conditions, as well as the special cases of rivers, drains, and wells. Chemical reactions in PHAST include (1) homogeneous equilibria using an ion-association or Pitzer specific interaction thermodynamic model; (2) heterogeneous equilibria between the aqueous solution and minerals, ion exchange sites, surface complexation sites, solid solutions, and gases; and
Effects of Pisha sandstone content on solute transport in a sandy soil.
Zhen, Qing; Zheng, Jiyong; He, Honghua; Han, Fengpeng; Zhang, Xingchang
2016-02-01
In sandy soil, water, nutrients and even pollutants are easily leaching to deeper layers. The objective of this study was to assess the effects of Pisha sandstone on soil solute transport in a sandy soil. The miscible displacement technique was used to obtain breakthrough curves (BTCs) of Br(-) as an inert non-adsorbed tracer and Na(+) as an adsorbed tracer. The incorporation of Pisha sandstone into sandy soil was able to prevent the early breakthrough of both tracers by decreasing the saturated hydraulic conductivity compared to the controlled sandy soil column, and the impeding effects increased with Pisha sandstone content. The BTCs of Br(-) were accurately described by both the convection-dispersion equation (CDE) and the two-region model (T-R), and the T-R model fitted the experimental data slightly better than the CDE. The two-site nonequilibrium model (T-S) accurately fit the Na(+) transport data. Pisha sandstone impeded the breakthrough of Na(+) not only by decreasing the saturated hydraulic conductivity but also by increasing the adsorption capacity of the soil. The measured CEC values of Pisha sandstone were up to 11 times larger than those of the sandy soil. The retardation factors (R) determined by the T-S model increased with increasing Pisha sandstone content, and the partition coefficient (K(d)) showed a similar trend to R. According to the results of this study, Pisha sandstone can successfully impede solute transport in a sandy soil column. Copyright © 2015 Elsevier Ltd. All rights reserved.
The quantum Rabi model: solution and dynamics
Xie, Qiongtao; Zhong, Honghua; Lee, Chaohong; Batchelor, Murray T
2017-01-01
This article presents a review of recent developments on various aspects of the quantum Rabi model. Particular emphasis is given on the exact analytic solution obtained in terms of confluent Heun functions. The analytic solutions for various generalisations of the quantum Rabi model are also discussed. Results are also reviewed on the level statistics and the dynamics of the quantum Rabi model. The article concludes with an introductory overview of several experimental realisations of the quantum Rabi model. An outlook towards future developments is also given. (topical review)
Finite element based composite solution for neutron transport problems
Mirza, A.N.; Mirza, N.M.
1995-01-01
A finite element treatment for solving neutron transport problems is presented. The employs region-wise discontinuous finite elements for the spatial representation of the neutron angular flux, while spherical harmonics are used for directional dependence. Composite solutions has been obtained by using different orders of angular approximations in different parts of a system. The method has been successfully implemented for one dimensional slab and two dimensional rectangular geometry problems. An overall reduction in the number of nodal coefficients (more than 60% in some cases as compared to conventional schemes) has been achieved without loss of accuracy with better utilization of computational resources. The method also provides an efficient way of handling physically difficult situations such as treatment of voids in duct problems and sharply changing angular flux. It is observed that a great wealth of information about the spatial and directional dependence of the angular flux is obtained much more quickly as compared to Monte Carlo method, where most of the information in restricted to the locality of immediate interest. (author)
New constructive solutions for building of transport construction facilities
Babayev Vladimir
2017-01-01
Full Text Available New structural systems for civil and transport engineering were examined. The basis for the formation of the proposed reinforced concrete structures is the ideology of reducing its dead weight, with a given bearing capacity, the realization of which is accomplished by burial during concreting large-sized liners of a given shape and manufactured from lightweight, inexpensive composite materials. The process of erecting these systems is presented in two forms: for flat structures - using self-tightening concrete, and for curvilinear ones - by using shotcrete technologies. The second direction is presented by steel-reinforced concrete structures. These structural systems were created on the basis of innovative component and methods of rationalization of parameters. The basis of the above methods is a compiler which includes the finite element method, adaptive evolution method and special iterative procedures. Experimental verification of structural solutions and formation procedures for suggested systems was performed. Comparison between theoretical and experimental data is given. Suggested systems were implemented in a number of building companies.
Colloid transport in porous media: impact of hyper-saline solutions.
Magal, Einat; Weisbrod, Noam; Yechieli, Yoseph; Walker, Sharon L; Yakirevich, Alexander
2011-05-01
The transport of colloids suspended in natural saline solutions with a wide range of ionic strengths, up to that of Dead Sea brines (10(0.9) M) was explored. Migration of microspheres through saturated sand columns of different sizes was studied in laboratory experiments and simulated with mathematical models. Colloid transport was found to be related to the solution salinity as expected. The relative concentration of colloids at the columns outlet decreased (after 2-3 pore volumes) as the solution ionic strength increased until a critical value was reached (ionic strength > 10(-1.8) M) and then remained constant above this level of salinity. The colloids were found to be mobile even in the extremely saline brines of the Dead Sea. At such high ionic strength no energetic barrier to colloid attachment was presumed to exist and colloid deposition was expected to be a favorable process. However, even at these salinity levels, colloid attachment was not complete and the transport of ∼ 30% of the colloids through the 30-cm long columns was detected. To further explore the deposition of colloids on sand surfaces in Dead Sea brines, transport was studied using 7-cm long columns through which hundreds of pore volumes were introduced. The resulting breakthrough curves exhibited a bimodal shape whereby the relative concentration (C/C(0)) of colloids at the outlet rose to a value of 0.8, and it remained relatively constant (for the ∼ 18 pore volumes during which the colloid suspension was flushed through the column) and then the relative concentration increased to a value of one. The bimodal nature of the breakthrough suggests different rates of colloid attachment. Colloid transport processes were successfully modeled using the limited entrapment model, which assumes that the colloid attachment rate is dependent on the concentration of the attached colloids. Application of this model provided confirmation of the colloid aggregation and their accelerated attachment during
Mechanisms to explain the reverse perivascular transport of solutes out of the brain.
Schley, D; Carare-Nnadi, R; Please, C P; Perry, V H; Weller, R O
2006-02-21
Experimental studies and observations in the human brain indicate that interstitial fluid and solutes, such as amyloid-beta (Abeta), are eliminated from grey matter of the brain along pericapillary and periarterial pathways. It is unclear, however, what constitutes the motive force for such transport within blood vessel walls, which is in the opposite direction to blood flow. In this paper the potential for global pressure differences to achieve such transport are considered. A mathematical model is constructed in order to test the hypothesis that perivascular drainage of interstitial fluid and solutes out of brain tissue is driven by pulsations of the blood vessel walls. Here it is assumed that drainage occurs through a thin layer between astrocytes and endothelial cells or between smooth muscle cells. The model suggests that, during each pulse cycle, there are periods when fluid and solutes are driven along perivascular spaces in the reverse direction to the flow of blood. It is shown that successful drainage may depend upon some attachment of solutes to the lining of the perivascular space, in order to produce a valve-like effect, although an alternative without this requirement is also postulated. Reduction in pulse amplitude, as in ageing cerebral vessels, would prolong the attachment time, encourage precipitation of Abeta peptides in vessel walls, and impair elimination of Abeta from the brain. These factors may play a role in the pathogenesis of cerebral amyloid angiopathy and in the accumulation of Abeta in the brain in Alzheimer's disease.
Technology in rural transportation. Simple solution #6, traveler information on the internet
1997-01-01
This application was identified as a promising rural Intelligent Transportation Systems (ITS) solution under a project sponsored by the Federal Highway Administration (FHWA) and the ENTERPRISE program. This summary describes the solution as well as o...
Solute transport with periodic input point source in one-dimensional ...
JOY
groundwater flow velocity is considered proportional to multiple of temporal function and ζ th ... One-dimensional solute transport through porous media with or without .... solute free. ... the periodic concentration at source of the boundary i.e.,. 0.
Semianalytical solutions of radioactive or reactive tracer transport in layered fractured media
Moridis, G.J.; Bodvarsson, G.S.
2001-01-01
In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive tracers (solutes or colloids) through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the matrix account for (a) diffusion, (b) surface diffusion (for solutes only), (c) mass transfer between the mobile and immobile water fractions, (d) linear kinetic or equilibrium physical, chemical, or combined solute sorption or colloid filtration, and (e) radioactive decay or first order chemical reactions. Any number of radioactive decay daughter products (or products of a linear, first-order reaction chain) can be tracked. The tracer-transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Additionally, the colloid transport equations account for straining and velocity adjustments related to the colloidal size. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of 3 H, 237 Np and 239 Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity. 239 Pu colloid transport problems in multilayered systems indicate significant colloid accumulations at straining interfaces but much faster transport of the colloid than the corresponding strongly sorbing solute species
Luiz Fernando C. de Oliveira
2000-04-01
Full Text Available Desenvolveu-se um modelo matemático para simulação do transporte de soluto no solo e no escoamento superficial. As equações diferenciais que regem os processos de transporte são resolvidas numericamente, pelo método das diferenças finitas. Para se avaliar o desempenho do modelo proposto, montou-se um experimento em nível de campo, constituído de nove parcelas, nas quais foram aplicadas três lâminas de irrigação com diferentes intensidades de precipitação; antes e após a aplicação da irrigação foram retiradas amostras de solo, para a obtenção dos perfis de umidade e, no final da parcela, coletou-se a vazão escoada superficialmente, pelo método direto. Os resultados simulados pelo modelo foram comparados com os experimentais, através do erro relativo médio. O modelo desenvolvido mostrou-se adequado para se descrever os processos de movimento de água no solo e escoamento superficial, apresentando comportamento semelhante aos das observações experimentais, podendo ser utilizado para simular esses processos, desde que os parâmetros de entrada do modelo sejam representativos.A mathematical model was developed to simulate solute transport in both soil and in surface runoff. The differential equations that govern the transport processes are numerically solved through the finite difference method. For the evaluation of the proposed model a field experiment was planned with nine plots under three irrigation levels with different rainfall intensities. Soil was sampled before and after irrigation to obtain moisture content profiles. At the end of the plot runoff flow was collected by the direct method. The model-simulated results were compared with the experimental data through the mean relative error. The developed model was found to describe adequately water movement and surface runoff, showing a behavior similar to experimental observations, making possible the utilization of the model to simulate these processes, if the
Liu, Wen; Lund, Henrik; Mathiesen, Brian Vad
2013-01-01
Transport is one of the most challenge sectors when addressing energy security and climate change due to its high reliance on oil products and lack of the alternative fuels. This paper explores the ability of three transport strategies to contribute to the development of a sustainable transport in China. With this purpose in mind, a Chinese transport model has been created and three current transport strategies which are high speed railway (HSR), urban rail transit (URT) and electric vehicle (EV) were evaluated together with a reference transport system in 2020. As conservative results, 13% of the energy saving and 12% of the CO 2 emission reduction can be attained by accomplishing three strategies compared with the reference transport system. However, the energy demand of transport in 2020 with the implementation of three strategies will be about 1.7 times as much as today. The three strategies show the potential of drawing the transport demand to the more energy efficient vehicles; however, more initiatives are needed if the sustainable transport is the long term objective, such as the solutions to stabilise the private vehicle demands, to continuously improve the vehicle efficiency and to boost the alternative fuels produced from the renewable energy sources. - Highlights: • A Chinese transport model was created and three transport strategies were evaluated • Transport is the biggest driver of the oil demand in China not the industry • The energy demand of transport in 2020 will be twice as much as today • Strategies contribute 13% energy saving and 12% CO 2 emission reduction • More initiatives are needed if a sustainable transport is the long-term objective
Modelling the Transport Process in Marine Container Technology
Serđo Kos
2003-01-01
Full Text Available The paper introduces a mathematical problem that occursin marine container technology when programming the transportof a beforehand established number of ISO containers effectedby a full container ship from several ports of departure toseveral ports of destination at the minimum distance (time innavigation or at minimum transport costs. The application ofthe proposed model may have an effect on cost reduction incontainer transport thereby improving the operation process inmarine transport technology. The model has been tested by usinga numerical example with real data. In particular, it describesthe application of the dual variables in the analysis ofoptimum solution.
Transport of neutral solute across articular cartilage: the role of zonal diffusivities.
Arbabi, V; Pouran, B; Weinans, H; Zadpoor, A A
2015-07-01
Transport of solutes through diffusion is an important metabolic mechanism for the avascular cartilage tissue. Three types of interconnected physical phenomena, namely mechanical, electrical, and chemical, are all involved in the physics of transport in cartilage. In this study, we use a carefully designed experimental-computational setup to separate the effects of mechanical and chemical factors from those of electrical charges. Axial diffusion of a neutral solute Iodixanol into cartilage was monitored using calibrated microcomputed tomography micro-CT images for up to 48 hr. A biphasic-solute computational model was fitted to the experimental data to determine the diffusion coefficients of cartilage. Cartilage was modeled either using one single diffusion coefficient (single-zone model) or using three diffusion coefficients corresponding to superficial, middle, and deep cartilage zones (multizone model). It was observed that the single-zone model cannot capture the entire concentration-time curve and under-predicts the near-equilibrium concentration values, whereas the multizone model could very well match the experimental data. The diffusion coefficient of the superficial zone was found to be at least one order of magnitude larger than that of the middle zone. Since neutral solutes were used, glycosaminoglycan (GAG) content cannot be the primary reason behind such large differences between the diffusion coefficients of the different cartilage zones. It is therefore concluded that other features of the different cartilage zones such as water content and the organization (orientation) of collagen fibers may be enough to cause large differences in diffusion coefficients through the cartilage thickness.
Geiger, S.; Cortis, A.; Birkholzer, J.T.
2010-04-01
Solute transport in fractured porous media is typically 'non-Fickian'; that is, it is characterized by early breakthrough and long tailing and by nonlinear growth of the Green function-centered second moment. This behavior is due to the effects of (1) multirate diffusion occurring between the highly permeable fracture network and the low-permeability rock matrix, (2) a wide range of advection rates in the fractures and, possibly, the matrix as well, and (3) a range of path lengths. As a consequence, prediction of solute transport processes at the macroscale represents a formidable challenge. Classical dual-porosity (or mobile-immobile) approaches in conjunction with an advection-dispersion equation and macroscopic dispersivity commonly fail to predict breakthrough of fractured porous media accurately. It was recently demonstrated that the continuous time random walk (CTRW) method can be used as a generalized upscaling approach. Here we extend this work and use results from high-resolution finite element-finite volume-based simulations of solute transport in an outcrop analogue of a naturally fractured reservoir to calibrate the CTRW method by extracting a distribution of retention times. This procedure allows us to predict breakthrough at other model locations accurately and to gain significant insight into the nature of the fracture-matrix interaction in naturally fractured porous reservoirs with geologically realistic fracture geometries.
Applied Integer Programming Modeling and Solution
Chen, Der-San; Dang, Yu
2011-01-01
An accessible treatment of the modeling and solution of integer programming problems, featuring modern applications and software In order to fully comprehend the algorithms associated with integer programming, it is important to understand not only how algorithms work, but also why they work. Applied Integer Programming features a unique emphasis on this point, focusing on problem modeling and solution using commercial software. Taking an application-oriented approach, this book addresses the art and science of mathematical modeling related to the mixed integer programming (MIP) framework and
Representing solute transport through the multi-barrier disposal system by simplified concepts
Poteri, A.; Nordman, H.; Pulkkanen, V-M.; Kekaelaeinen, P.; Hautojaervi, A.
2012-02-01
The repository system chosen in Finland for spent nuclear fuel is composed of multiple successive transport barriers. If a waste canister is leaking, this multi-barrier system retards and limits the release rates of radionuclides into the biosphere. Analysis of radionuclide migration in the previous performance assessments has largely been based on numerical modelling of the repository system. The simplified analytical approach introduced here provides a tool to analyse the performance of the whole system using simplified representations of the individual transport barriers. This approach is based on the main characteristics of the individual barriers and on the generic nature of the coupling between successive barriers. In the case of underground repository the mass transfer between successive transport barriers is strongly restricted by the interfaces between barriers leading to well-mixed conditions in these barriers. The approach here simplifies the barrier system so that it can be described with a very simple compartment model, where each barrier is represented by a single, or in the case of buffer, by not more than two compartments. This system of compartments could be solved in analogy with a radioactive decay chain. The model of well mixed compartments lends itself to a very descriptive way to represent and analyse the barrier system because the relative efficiency of the different barriers in hindering transport of solutes can be parameterised by the solutes half-times in the corresponding compartments. In a real repository system there will also be a delay between the start of the inflow and the start of the outflow from the barrier. This delay can be important for the release rates of the short lived and sorbing radionuclides, and it was also included in the simplified representation of the barrier system. In a geological multi-barrier system, spreading of the outflowing release pulse is often governed by the typical behaviour of one transport barrier
Representing solute transport through the multi-barrier disposal system by simplified concepts
Poteri, A.; Nordman, H.; Pulkkanen, V-M. [VTT Technical Research Centre of Finland, Espoo (Finland); Kekaelaeinen, P. [Jyvaeskylae Univ. (Finland). Dept. pf Physics; Hautojaervi, A.
2012-02-15
The repository system chosen in Finland for spent nuclear fuel is composed of multiple successive transport barriers. If a waste canister is leaking, this multi-barrier system retards and limits the release rates of radionuclides into the biosphere. Analysis of radionuclide migration in the previous performance assessments has largely been based on numerical modelling of the repository system. The simplified analytical approach introduced here provides a tool to analyse the performance of the whole system using simplified representations of the individual transport barriers. This approach is based on the main characteristics of the individual barriers and on the generic nature of the coupling between successive barriers. In the case of underground repository the mass transfer between successive transport barriers is strongly restricted by the interfaces between barriers leading to well-mixed conditions in these barriers. The approach here simplifies the barrier system so that it can be described with a very simple compartment model, where each barrier is represented by a single, or in the case of buffer, by not more than two compartments. This system of compartments could be solved in analogy with a radioactive decay chain. The model of well mixed compartments lends itself to a very descriptive way to represent and analyse the barrier system because the relative efficiency of the different barriers in hindering transport of solutes can be parameterised by the solutes half-times in the corresponding compartments. In a real repository system there will also be a delay between the start of the inflow and the start of the outflow from the barrier. This delay can be important for the release rates of the short lived and sorbing radionuclides, and it was also included in the simplified representation of the barrier system. In a geological multi-barrier system, spreading of the outflowing release pulse is often governed by the typical behaviour of one transport barrier
Scaffolding Mathematical Modelling with a Solution Plan
Schukajlow, Stanislaw; Kolter, Jana; Blum, Werner
2015-01-01
In the study presented in this paper, we examined the possibility to scaffold mathematical modelling with strategies. The strategies were prompted using an instrument called "solution plan" as a scaffold. The effects of this step by step instrument on mathematical modelling competency and on self-reported strategies were tested using…
Thermally Cross-Linkable Hole Transport Materials for Solution Processed Phosphorescent OLEDs
Kim, Beom Seok; Kim, Ohyoung; Chin, Byung Doo; Lee, Chil Won
2018-04-01
Materials for unique fabrication of a solution-processed, multi-layered organic light-emitting diode (OLED) were developed. Preparation of a hole transport layer with a thermally cross-linkable chemical structure, which can be processed to form a thin film and then transformed into an insoluble film by using an amine-alcohol condensation reaction with heat treatment, was investigated. Functional groups, such as triplenylamine linked with phenylcarbazole or biphenyl, were employed in the chemical structure of the hole transport layer in order to maintain high triplet energy properties. When phenylcarbazole or biphenyl compounds continuously react with triphenylamine under acid catalysis, a chemically stable thin film material with desirable energy-level properties for a blue OLED could be obtained. The prepared hole transport materials showed excellent surface roughness and thermal stability in comparison with the commercial reference material. On the solution-processed model hole transport layer, we fabricated a device with a blue phosphorescent OLED by using sequential vacuum deposition. The maximum external quantum, 19.3%, was improved by more than 40% over devices with the commercial reference material (11.4%).
Sonnenborg, Torben Obel; Engesgaard, Peter Knudegaard; Rosbjerg, Dan
1996-01-01
An application of an inverse flow and transport model to a contaminated aquifer is presented. The objective of the study is to identify physical and nonreactive flow and transport parameters through an optimization approach. The approach can be classified as a statistical procedure, where a flow...... to steady state versus transient flow conditions and to the amount of hydraulic and solute data used is investigated. The flow parameters, transmissivity and leakage factor, are estimated simultaneously with the transport parameters: source strength, porosity, and longitudinal dispersivity. This paper...
SATURATED ZONE FLOW AND TRANSPORT MODEL ABSTRACTION
B.W. ARNOLD
2004-01-01
The purpose of the saturated zone (SZ) flow and transport model abstraction task is to provide radionuclide-transport simulation results for use in the total system performance assessment (TSPA) for license application (LA) calculations. This task includes assessment of uncertainty in parameters that pertain to both groundwater flow and radionuclide transport in the models used for this purpose. This model report documents the following: (1) The SZ transport abstraction model, which consists of a set of radionuclide breakthrough curves at the accessible environment for use in the TSPA-LA simulations of radionuclide releases into the biosphere. These radionuclide breakthrough curves contain information on radionuclide-transport times through the SZ. (2) The SZ one-dimensional (I-D) transport model, which is incorporated in the TSPA-LA model to simulate the transport, decay, and ingrowth of radionuclide decay chains in the SZ. (3) The analysis of uncertainty in groundwater-flow and radionuclide-transport input parameters for the SZ transport abstraction model and the SZ 1-D transport model. (4) The analysis of the background concentration of alpha-emitting species in the groundwater of the SZ
Capillary-Driven Solute Transport and Precipitation in Porous Media during Dry-Out
Ott, Holger; Andrew, Matthew; Blunt, Martin; Snippe, Jeroen
2014-05-01
The injection of dry or under-saturated gases or supercritical (SC) fluids into water bearing formations might lead to a formation dry-out in the vicinity of the injection well. The dry-out is caused by the evaporation/dissolution of formation water into the injected fluid and the subsequent transport of dissolved water in the injected fluid away from the injection well. Dry-out results in precipitation from solutes of the formation brine and consequently leads to a reduction of the rock's pore space (porosity) and eventually to a reduction of permeability near the injection well, or even to the loss of injectivity. Recently evidence has been found that the complexity of the pore space and the respective capillary driven solute transport plays a key role. While no effective-permeability (Keff) reduction was observed in a single-porosity sandstone, multi porosity carbonate rocks responded to precipitation with a strong reduction of Keff. The reason for the different response of Keff to salt precipitation is suspected to be in the exact location of the precipitate (solid salt) in the pore space. In this study, we investigate dry-out and salt precipitation due to supercritical CO2 injection in single and multi-porosity systems under near well-bore conditions. We image fluid saturation changes by means of μCT scanning during desaturation. We are able to observe capillary driven transport of the brine phase and the respective transport of solutes on the rock's pore scale. Finally we have access to the precipitated solid-salt phase and their distribution. The results can proof the thought models behind permeability porosity relationships K(φ) for injectivity modeling. The topic and the mechanisms we show are of general interest for drying processes in porous material such as soils and paper.
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
Transport Choice Modeling for the Evaluation of New Transport Policies
Ander Pijoan
2018-04-01
Full Text Available Quantifying the impact of the application of sustainable transport policies is essential in order to mitigate effects of greenhouse gas emissions produced by the transport sector. One of the most common approaches used for this purpose is that of traffic modelling and simulation, which consists of emulating the operation of an entire road network. This article presents the results of fitting 8 well known data science methods for transport choice modelling, the area in which more research is needed. The models have been trained with information from Biscay province in Spain in order to match as many of its commuters as possible. Results show that the best models correctly forecast more than 51% of the trips recorded. Finally, the results have been validated with a second data set from the Silesian Voivodeship in Poland, showing that all models indeed maintain their forecasting ability.
Hyporheic less-mobile porosity and solute transport in porous media
MahmoodPoorDehkordy, F.; Briggs, M. A.; Day-Lewis, F. D.; Scruggs, C.; Singha, K.; Zarnetske, J. P.; Lane, J. W., Jr.; Bagtzoglou, A. C.
2017-12-01
Solute transport and reactive processes are strongly influenced by hydrodynamic exchange with the hyporheic zone. Contaminant transport and redox zonation in the hyporheic zone and near-stream aquifer can be impacted by the exchange between mobile and less-mobile porosity zones in heterogeneous porous media. Less-mobile porosity zones can be created by fine materials with tight pore throats (e.g. clay, organics) and in larger, well-connected pores down gradient of flow obstructions (e.g. sand behind cobbles). Whereas fluid sampling is primarily responsive to the more-mobile domain, tracking solute tracer dynamics by geoelectrical methods provides direct information about both more- and less-mobile zones. During tracer injection through porous media of varied pore connectivity, a lag between fluid and bulk electrical conductivity is observed, creating a hysteresis loop when plotted in conductivity space. Thus, the combination of simultaneous fluid and bulk electrical conductivity measurements enables a much improved quantification of less-mobile solute dynamics compared to traditional fluid-only sampling approaches. We have demonstrated the less-mobile porosity exchange in laboratory-scale column experiments verified by simulation models. The experimental approach has also been applied to streambed sediments in column and reach-scale field experiments and verified using numerical simulation. Properties of the resultant hysteresis loops can be used to estimate exchange parameters of less-mobile porosity. Our integrated approach combining field experiments, laboratory experiments, and numerical modeling provides new insights into the effect of less-mobile porosity on solute transport in the hyporheic zone.
Logistics and Transport - a conceptual model
Jespersen, Per Homann; Drewes, Lise
2004-01-01
This paper describes how the freight transport sector is influenced by logistical principles of production and distribution. It introduces new ways of understanding freight transport as an integrated part of the changing trends of mobility. By introducing a conceptual model for understanding...... the interaction between logistics and transport, it points at ways to over-come inherent methodological difficulties when studying this relation...
Parkhurst, David L.; Kipp, Kenneth L.; Engesgaard, Peter; Charlton, Scott R.
2004-01-01
The computer program PHAST simulates multi-component, reactive solute transport in three-dimensional saturated ground-water flow systems. PHAST is a versatile ground-water flow and solute-transport simulator with capabilities to model a wide range of equilibrium and kinetic geochemical reactions. The flow and transport calculations are based on a modified version of HST3D that is restricted to constant fluid density and constant temperature. The geochemical reactions are simulated with the geochemical model PHREEQC, which is embedded in PHAST. PHAST is applicable to the study of natural and contaminated ground-water systems at a variety of scales ranging from laboratory experiments to local and regional field scales. PHAST can be used in studies of migration of nutrients, inorganic and organic contaminants, and radionuclides; in projects such as aquifer storage and recovery or engineered remediation; and in investigations of the natural rock-water interactions in aquifers. PHAST is not appropriate for unsaturated-zone flow, multiphase flow, density-dependent flow, or waters with high ionic strengths. A variety of boundary conditions are available in PHAST to simulate flow and transport, including specified-head, flux, and leaky conditions, as well as the special cases of rivers and wells. Chemical reactions in PHAST include (1) homogeneous equilibria using an ion-association thermodynamic model; (2) heterogeneous equilibria between the aqueous solution and minerals, gases, surface complexation sites, ion exchange sites, and solid solutions; and (3) kinetic reactions with rates that are a function of solution composition. The aqueous model (elements, chemical reactions, and equilibrium constants), minerals, gases, exchangers, surfaces, and rate expressions may be defined or modified by the user. A number of options are available to save results of simulations to output files. The data may be saved in three formats: a format suitable for viewing with a text editor; a
Coal supply and transportation model (CSTM)
1991-11-01
The Coal Supply and Transportation Model (CSTM) forecasts annual coal supply and distribution to domestic and foreign markets. The model describes US coal production, national and international coal transportation industries. The objective of this work is to provide a technical description of the current version of the model
Tariff Model for Combined Transport
Velimir Kolar
2002-11-01
Full Text Available By analysing the cwTen.t situation on the Croatian transportationmarket, and considering all parameters needed forthe development of combined transport, measures are suggestedin order to improve and stimulate its development. Oneof the first measures is the standardisation and introduction ofunique tariffs for combined transport, and then government incentivefor the organisation and development of combinedtransport means and equipment. A significant role in thisshould be set on adequately defined transport policy.
Schot, P.P.
1991-01-01
This thesis deals with solute transport by groundwater flow and the way in which solute transport is affected by human activities. This in relation to wetland ecosystems. Wetlands in the eastern part of the Vecht river plain in The Netherlands are historically renown for their great variety of
Biological transportation networks: Modeling and simulation
Albi, Giacomo
2015-09-15
We present a model for biological network formation originally introduced by Cai and Hu [Adaptation and optimization of biological transport networks, Phys. Rev. Lett. 111 (2013) 138701]. The modeling of fluid transportation (e.g., leaf venation and angiogenesis) and ion transportation networks (e.g., neural networks) is explained in detail and basic analytical features like the gradient flow structure of the fluid transportation network model and the impact of the model parameters on the geometry and topology of network formation are analyzed. We also present a numerical finite-element based discretization scheme and discuss sample cases of network formation simulations.
Classical solutions of some field theoretic models
Zakrzewski, W.J.
1982-01-01
In recent years much attention has been paid to simpler fields theories, so chosen that they possess several properties of nonabelian gauge theories. They preserve the conformal invariance of the action and one can define the topological charge for them. They possess nontrivial solutions to the equations of motion. The perturbation theory based on the fluctuations around each solution is characterized by asymptotic freedom. A model called CP sup(n-1) is presented and some models which are its natural generalizations are discussed. (M.F.W.)
Mathematical Model of Ion Transport in Electrodialysis Process
F.S. Rohman
2010-10-01
Full Text Available Mathematical models of ion transport in electrodialysis process is reviewed and their basics concept is discussed. Three scales of ion transport reviewed are: 1 ion transport in the membrane, where two approaches are used, the irreversible thermodynamics and modeling of the membrane material; 2 ion transport in a three-layer system composed of a membrane with two adjoining diffusion layers; and 3 coupling with hydraulic flow system in an electrodialysis 2D and 3D cell, where the differential equation of convectivediffusion is used. Most of the work carried out in the past implemented NP equations since relatively easily coupled with other equations describing hydrodynamic conditions and ion transport in the surrounding solutions, chemical reactions in the solutions and the membrane, boundary and other conditions. However, it is limited to point ionic transport in homogenous and uniformly - grainy phases of structure. © 2008 BCREC UNDIP. All rights reserved.[Received: 21 January 2008, Accepted: 10 March 2008][How to Cite: F.S. Rohman, N. Aziz (2008. Mathematical Model of Ion Transport in Electrodialysis Process. Bulletin of Chemical Reaction Engineering and Catalysis, 3(1-3: 3-8. doi:10.9767/bcrec.3.1-3.7122.3-8][How to Link/DOI: http://dx.doi.org/10.9767/bcrec.3.1-3.7122.3-8 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/7122 ]
Colloid transport in model fracture filling materials
Wold, S.; Garcia-Garcia, S.; Jonsson, M.
2010-12-01
Colloid transport in model fracture filling materials Susanna Wold*, Sandra García-García and Mats Jonsson KTH Chemical Science and Engineering Royal Institute of Technology, SE-100 44 Stockholm, Sweden *Corresponding author: E-mail: wold@kth.se Phone: +46 8 790 6295 In colloid transport in water-bearing fractures, the retardation depends on interactions with the fracture surface by sorption or filtration. These mechanisms are difficult to separate. A rougher surface will give a larger area available for sorption, and also when a particle is physically hindered, it approaches the surface and enables further sorption. Sorption can be explained by electrostatics were the strongest sorption on minerals always is observed at pH below pHpzc (Filby et al., 2008). The adhesion of colloids to mineral surfaces is related to the surface roughness according to a recent study (Darbha et al., 2010). There is a large variation in the characteristics of water-bearing fractures in bedrock in terms of aperture distribution, flow velocity, surface roughness, mineral distributions, presence of fracture filling material, and biological and organic material, which is hard to implement in modeling. The aim of this work was to study the transport of negatively charged colloids in model fracture filling material in relation to flow, porosity, mineral type, colloid size, and surface charge distribution. In addition, the impact on transport of colloids of mixing model fracture filling materials with different retention and immobilization capacities, determined by batch sorption experiments, was investigated. The transport of Na-montmorillonite colloids and well-defined negatively charged latex microspheres of 50, 100, and 200 nm diameter were studied in either columns containing quartz or quartz mixed with biotite. The ionic strength in the solution was exclusively 0.001 and pH 6 or 8.5. The flow rates used were 0.002, 0.03, and 0.6 mL min-1. Sorption of the colloids on the model fracture
Model for radionuclide transport in running waters
Jonsson, Karin; Elert, Mark [Kemakta Konsult AB, Stockholm (Sweden)
2005-11-15
, however, the approximation of equilibrium chemistry is assumed to be sufficient for order of magnitude predictions when a constant inflow of radionuclides is considered. A first sensitivity analysis of the model is performed in which different model parameters have been varied. At the time for the model development, almost no detailed site-specific information about e.g. channel geometry or sediment characteristics were available. Simulations were therefore performed for a hypothetical case, where the ranges of possible parameter values was based on literature information, generalizations from other stream systems and some site-specific information such as large-scale information of the morphology at the present sites. For order of magnitude predictions of the concentration or amount of radionuclides in the different parts of the stream ecosystem, a yearly mean value of the water flow was assumed to be sufficient. Therefore, the further sensitivity analyses were performed for constant flow conditions. The sensitivity analyses indicated that the main retention along the stream is due to uptake within the sediment. Initially, the uptake will cause a retardation of the solute transport. The sediment capacity is however limited and after saturation, the outflow of radionuclides in the longitudinal direction will be completely determined by the inflow to the system. The time for reaching this equilibrium and the equilibrium concentration in the sediment varies however with different conditions and radionuclides, e.g. due to sorption characteristics, sedimentation velocity and advective velocity within the sediment. The degree of variation caused by different factors is, however, different. In the simulations performed in this study, the time for reaching equilibrium ranges from less than a year to a couple of hundred years. For predictions of the dose to humans, the accumulated amount in the sediment should also be considered and not only the concentration in the stream water
Model for radionuclide transport in running waters
Jonsson, Karin; Elert, Mark
2005-11-01
, however, the approximation of equilibrium chemistry is assumed to be sufficient for order of magnitude predictions when a constant inflow of radionuclides is considered. A first sensitivity analysis of the model is performed in which different model parameters have been varied. At the time for the model development, almost no detailed site-specific information about e.g. channel geometry or sediment characteristics were available. Simulations were therefore performed for a hypothetical case, where the ranges of possible parameter values was based on literature information, generalizations from other stream systems and some site-specific information such as large-scale information of the morphology at the present sites. For order of magnitude predictions of the concentration or amount of radionuclides in the different parts of the stream ecosystem, a yearly mean value of the water flow was assumed to be sufficient. Therefore, the further sensitivity analyses were performed for constant flow conditions. The sensitivity analyses indicated that the main retention along the stream is due to uptake within the sediment. Initially, the uptake will cause a retardation of the solute transport. The sediment capacity is however limited and after saturation, the outflow of radionuclides in the longitudinal direction will be completely determined by the inflow to the system. The time for reaching this equilibrium and the equilibrium concentration in the sediment varies however with different conditions and radionuclides, e.g. due to sorption characteristics, sedimentation velocity and advective velocity within the sediment. The degree of variation caused by different factors is, however, different. In the simulations performed in this study, the time for reaching equilibrium ranges from less than a year to a couple of hundred years. For predictions of the dose to humans, the accumulated amount in the sediment should also be considered and not only the concentration in the stream water
Jahshan, S.N.; Wemple, C.A.; Ganapol, B.D.
1993-01-01
A comparison of the numerical solutions of the transport equation describing the steady neutron slowing down in an infinite medium with constant cross sections is made with stochastic solutions obtained from tracking successive neutron histories in the same medium. The transport equation solution is obtained using a numerical Laplace transform inversion algorithm. The basis for the algorithm is an evaluation of the Bromwich integral without analytical continuation. Neither the transport nor the stochastic solution is limited in the number of scattering species allowed. The medium may contain an absorption component as well. (orig.)
Uncertainty calculation in transport models and forecasts
Manzo, Stefano; Prato, Carlo Giacomo
Transport projects and policy evaluations are often based on transport model output, i.e. traffic flows and derived effects. However, literature has shown that there is often a considerable difference between forecasted and observed traffic flows. This difference causes misallocation of (public...... implemented by using an approach based on stochastic techniques (Monte Carlo simulation and Bootstrap re-sampling) or scenario analysis combined with model sensitivity tests. Two transport models are used as case studies: the Næstved model and the Danish National Transport Model. 3 The first paper...... in a four-stage transport model related to different variable distributions (to be used in a Monte Carlo simulation procedure), assignment procedures and levels of congestion, at both the link and the network level. The analysis used as case study the Næstved model, referring to the Danish town of Næstved2...
Cremer, Clemens; Neuweiler, Insa; Bechtold, Michel; Vanderborght, Jan
2016-04-01
behavior depends on the magnitude of the flow rates and hydraulic conductivity curves of the materials. Based on the unsaturated hydraulic conductivity at the intersection point of conductivity curves, we are able to define an estimate of flow rates at which the dynamic of the upper boundary condition significantly alters preferential flow paths through the system. If flow rates are low, with regard to the materials hydraulic conductivity at the intersection point, the influence of dynamic boundary conditions is small. If flow rates are in the range of the unsaturated hydraulic conductivity at intersection, solute is trapped in the fine material during upwards transport, which results in a more pronounced tailing. For flow rates exceeding the intersection conductivity, a redistribution at the soil surface can occur. References: Bechtold, M., S. Haber-Pohlmeier, J. Vanderborght, A. Pohlmeier, T.P.A. Ferré and H. Veerecken. 2011a. Near-surface solute redistribution during evaporation. Geophys. Res. Lett., 38, L17404, doi:10.1029/2011GL048147. Bechtold, M., J. Vanderborght, O. Ippisch and H. Vereecken. 2011b. Efficient random walk particle tracking algorithm for advective dispersive transport in media with discontinuous dispersion coefficients and water contents. Water Resour. Res., 47, W10526, doi: 10.1029/2010WR010267. Ippisch O., H.-J. Vogel and P. Bastian. 2006. Validity limits fort he van Genuchten-Mualem model and implications for parameter estimation and numerical simulation. Adv. Water Resour., 29, 1780-1789, doi: 10.1016/j.advwateres.2005.12.011. Lehmann, P. and D. Or. 2009. Evaporation and capillary coupling across vertical textural contrasts in porous media. Phys. Rev. E, 80, 046318, doi:10.1103/PhysRevE.80.046318.
Muna, Joseph T.; Prescott, Kevin
2011-08-01
Traditionally, freight transport and telematics solutions that exploit the GPS capabilities of in- vehicle devices to provide innovative Location Based Services (LBS) including track and trace transport systems have been the preserve of a select cluster of transport operators and organisations with the financial resources to develop the requisite custom software and hardware on which they are deployed. The average cost of outfitting a typical transport vehicle or truck with the latest Intelligent Transport System (ITS) increases the cost of the vehicle by anything from a couple to several thousand Euros, depending on the complexity and completeness of the solution. Though this does not generally deter large fleet transport owners since they typically get Return on Investment (ROI) based on economies of scale, it presents a barrier for the smaller independent entities that constitute the majority of freight transport operators [1].The North Sea Freight Intelligent Transport Solution (NS FRITS), a project co-funded by the European Commission Interreg IVB North Sea Region Programme, aims to make acquisition of such transport solutions easier for those organisations that cannot afford the expensive, bespoke systems used by their larger competitors.The project addresses transport security threats by developing a system capable of informing major actors along the freight logistics supply chain, of changing circumstances within the region's major transport corridors and between transport modes. The project also addresses issues of freight volumes, inter-modality, congestion and eco-mobility [2].
Fluid flow and convective transport of solutes within the intervertebral disc
Ferguson, S.J.; Ito, K.; Nolte, L.P.
2004-01-01
Previous experimental and analytical studies of solute transport in the intervertebral disc have demonstrated that for small molecules diffusive transport alone fulfils the nutritional needs of disc cells. It has been often suggested that fluid flow into and within the disc may enhance the transport
Ranathunge, Kosala; Kim, Yangmin X; Wassmann, Friedrich; Kreszies, Tino; Zeisler, Viktoria; Schreiber, Lukas
2017-03-01
Roots have complex anatomical structures, and certain localized cell layers develop suberized apoplastic barriers. The size and tightness of these barriers depend on the growth conditions and on the age of the root. Such complex anatomical structures result in a composite water and solute transport in roots. Development of apoplastic barriers along barley seminal roots was detected using various staining methods, and the suberin amounts in the apical and basal zones were analysed using gas chromatography-mass spectometry (GC-MS). The hydraulic conductivity of roots ( Lp r ) and of cortical cells ( Lp c ) was measured using root and cell pressure probes. When grown in hydroponics, barley roots did not form an exodermis, even at their basal zones. However, they developed an endodermis. Endodermal Casparian bands first appeared as 'dots' as early as at 20 mm from the apex, whereas a patchy suberin lamellae appeared at 60 mm. The endodermal suberin accounted for the total suberin of the roots. The absolute amount in the basal zone was significantly higher than in the apical zone, which was inversely proportional to the Lp r . Comparison of Lp r and Lp c suggested that cell to cell pathways dominate for water transport in roots. However, the calculation of Lp r from Lp c showed that at least 26 % of water transport occurs through the apoplast. Roots had different solute permeabilities ( P sr ) and reflection coefficients ( σ sr ) for the solutes used. The σ sr was below unity for the solutes, which have virtually zero permeability for semi-permeable membranes. Suberized endodermis significantly reduces Lp r of seminal roots. The water and solute transport across barley roots is composite in nature and they do not behave like ideal osmometers. The composite transport model should be extended by adding components arranged in series (cortex, endodermis) in addition to the currently included components arranged in parallel (apoplastic, cell to cell pathways). © The
Compacton solutions and multiple compacton solutions for a continuum Toda lattice model
Fan Xinghua; Tian Lixin
2006-01-01
Some special solutions of the Toda lattice model with a transversal degree of freedom are obtained. With the aid of Mathematica and Wu elimination method, more explicit solitary wave solutions, including compacton solutions, multiple compacton solutions, peakon solutions, as well as periodic solutions are found in this paper
A transport model with color confinement
Loh, S.
1997-01-01
First the mostly important properties of QCD are dealt with. It is made plausible, how the QCD vacuum generates a screening of color charges and is by this responsible for the quark confinement in color singlets. in the following the behaviour of classical color charges and color fields is studied and it is concluded that by this approximation, the neglection of quantum-mechanical fluctuation, the quark confinement cannot be explained, because the mean-field approximation leads to a screening of the color charges. Motivated by this result the Friedberg-Lee soliton model is presented, in which the the color confinement and all further nonperturbative QCD effects are phenomenologically modelled by means of a scalar field. Thereafter a derivation of the transport equations for quarks in the framework of the Wigner-function is presented. An extension of the equation to the Friedberg-Lee model is explained. As results the ground-state properties of the model are studied. Mesonic and baryonic ground-state solutions (soliton solutions) of the equations are constructed, whereby the constituents are both light quarks and heavy quarks. Furthermore the color coupling constant of QCD is fixed by means of the string tension by dynamical separation of the quarks of the meson. The flux tubes formed dynamically in this way are applied, in order to study the interaction of two strings and to calculate a string-string potential. Excited states of the meson (isovectorial modes) are presented as well as the influence of the color confinement on the quark motion. Finally the dynamical formation and the break-up of a string by the production of light and heavy quark pairs is described
New diffusion-like solutions of one-speed transport equations in spherical geometry
Sahni, D.C.
1988-01-01
Stationary, one-speed, spherically symmetric transport equations are considered in a conservative medium. Closed-form expressions are obtained for the angular flux ψ(r, μ) that yield a total flux varying as 1/r by using Sonine transforms. Properties of this solution are studied and it is shown that the solution can not be identified as a diffusion mode solution of the transport equation. Limitations of the Sonine transform technique are noted. (author)
Numerical Modeling for the Solute Uptake from Groundwater by Plants-Plant Uptake Package
El-Sayed, Amr A.
2006-01-01
A numerical model is presented to describe solute transport in groundwater coupled to sorption by plant roots, translocation into plant stems, and finally evapotranspiration. The conceptual model takes into account both Root Concentration Factor, RCF, and Transpiration Stream Concentration Factor, TSCF for chemicals which are a function of Kow. A similar technique used to simulate the solute transport in groundwater to simulate sorption and plant uptake is used. The mathematical equation is s...
Fibrin structural and diffusional analysis suggests that fibers are permeable to solute transport.
Leonidakis, Kimon Alexandros; Bhattacharya, Pinaki; Patterson, Jennifer; Vos, Bart E; Koenderink, Gijsje H; Vermant, Jan; Lambrechts, Dennis; Roeffaers, Maarten; Van Oosterwyck, Hans
2017-01-01
Fibrin hydrogels are promising carrier materials in tissue engineering. They are biocompatible and easy to prepare, they can bind growth factors and they can be prepared from a patient's own blood. While fibrin structure and mechanics have been extensively studied, not much is known about the relation between structure and diffusivity of solutes within the network. This is particularly relevant for solutes with a size similar to that of growth factors. A novel methodological approach has been used in this study to retrieve quantitative structural characteristics of fibrin hydrogels, by combining two complementary techniques, namely confocal fluorescence microscopy with a fiber extraction algorithm and turbidity measurements. Bulk rheological measurements were conducted to determine the impact of fibrin hydrogel structure on mechanical properties. From these measurements it can be concluded that variations in the fibrin hydrogel structure have a large impact on the rheological response of the hydrogels (up to two orders of magnitude difference in storage modulus) but only a moderate influence on the diffusivity of dextran solutes (up to 25% difference). By analyzing the diffusivity measurements by means of the Ogston diffusion model we further provide evidence that individual fibrin fibers can be semi-permeable to solute transport, depending on the average distance between individual protofibrils. This can be important for reducing mass transport limitations, for modulating fibrinolysis and for growth factor binding, which are all relevant for tissue engineering. Fibrin is a natural biopolymer that has drawn much interest as a biomimetic carrier in tissue engineering applications. We hereby use a novel combined approach for the structural characterization of fibrin networks based on optical microscopy and light scattering methods that can also be applied to other fibrillar hydrogels, like collagen. Furthermore, our findings on the relation between solute transport
Solutions to the relativistic precession model
Ingram, A.; Motta, S.
2014-01-01
The relativistic precession model (RPM) can be used to obtain a precise measurement of the mass and spin of a black hole when the appropriate set of quasi-periodic oscillations is detected in the power-density spectrum of an accreting black hole. However, in previous studies, the solution of the RPM
Finite medium Green's function solutions to nuclide transport in porous media
Oston, S.G.
1979-01-01
Current analytical techniques for predicting the transport of nuclides in porous materials center on the Green's function approach - i.e., determining the response characteristics of a geologic pathway to an impulse function input. To data, the analyses all have set the boundary conditions needed to solve the 1-D transport equation as though each pathway were infinite in length. The purpose of this work is to critically examine the effect that this infinite pathway assumption has on Green's function models of nuclide transport in porous media. The work described herein has directly attacked the more difficult problem of obtaining suitable Green's functions for finite pathways whose dimensions, in fact, may not be much greater than the diffusion length. Two different finite media Green's functions describing the nuclide mass flux have been determined, depending on whether the pathway is terminated by a high or a low flow resistance at the outlet end. Pulse shapes and peak amplitudes have been computed for each Green's function over a wide range of geohydrologic parameters. These results have been compared to both infinite and semi-infinite medium solutions. It was found that predicted pulse shapes are quite sensitive to selection of a Green's function model for short pathways only. For long pathways all models tend toward a symmetric Gaussian flux-time history at the outlet. Thus, the results of our previous waste transport studies using the infinite pathway assumption are still generally valid because they always included at least one long pathway. It was also found that finite medium models offer some unique computational advantages for evaluating nuclide transport in a series of connecting pathways
Shan, C.; Javandel, I.
1996-05-01
Analytical solutions are developed for modeling solute transport in a vertical section of a homogeneous aquifer. Part 1 of the series presents a simplified analytical solution for cases in which a constant-concentration source is located at the top (or the bottom) of the aquifer. The following transport mechanisms have been considered: advection (in the horizontal direction), transverse dispersion (in the vertical direction), adsorption, and biodegradation. In the simplified solution, however, longitudinal dispersion is assumed to be relatively insignificant with respect to advection, and has been neglected. Example calculations are given to show the movement of the contamination front, the development of concentration profiles, the mass transfer rate, and an application to determine the vertical dispersivity. The analytical solution developed in this study can be a useful tool in designing an appropriate monitoring system and an effective groundwater remediation method
Fiori, A.; Zarlenga, A.; Jankovic, I.; Dagan, G.
2017-12-01
Natural gradient steady flow of mean velocity U takes place in heterogeneous aquifers of random logconductivity Y = lnK , characterized by the normal univariate PDF f(Y) and autocorrelation ρY, of variance σY2 and horizontal integral scale I. Solute transport is quantified by the Breakthrough Curve (BTC) M at planes at distance x from the injection plane. The study builds on the extensive 3D numerical simulations of flow and transport of Jankovic et al. (2017) for different conductivity structures. The present study further explores the predictive capabilities of the Advection Dispersion Equation (ADE), with macrodispersivity αL given by the First Order Approximation (FOA), by checking in a quantitative manner its applicability. After a discussion on the suitable boundary conditions for ADE, we find that the ADE-FOA solution is a sufficiently accurate predictor for applications, the many other sources of uncertainty prevailing in practice notwithstanding. We checked by least squares and by comparison of travel time of quantiles of M that indeed the analytical Inverse Gaussian M with αL =σY2 I , is able to fit well the bulk of the simulated BTCs. It tends to underestimate the late arrival time of the thin and persistent tail. The tail is better reproduced by the semi-analytical MIMSCA model, which also allows for a physical explanation of the success of the Inverse Gaussian solution. Examination of the pertinent longitudinal mass distribution shows that it is different from the commonly used Gaussian one in the analysis of field experiments, and it captures the main features of the plume measurements of the MADE experiment. The results strengthen the confidence in the applicability of the ADE and the FOA to predicting longitudinal spreading in solute transport through heterogeneous aquifers of stationary random structure.
Solute transport and storage mechanisms in wetlands of the Everglades, south Florida
Harvey, Judson W.; Saiers, James E.; Newlin, Jessica T.
2005-01-01
Solute transport and storage processes in wetlands play an important role in biogeochemical cycling and in wetland water quality functions. In the wetlands of the Everglades, there are few data or guidelines to characterize transport through the heterogeneous flow environment. Our goal was to conduct a tracer study to help quantify solute exchange between the relatively fast flowing water in the open part of the water column and much more slowly moving water in thick floating vegetation and in the pore water of the underlying peat. We performed a tracer experiment that consisted of a constant‐rate injection of a sodium bromide (NaBr) solution for 22 hours into a 3 m wide, open‐ended flume channel in Everglades National Park. Arrival of the bromide tracer was monitored at an array of surface water and subsurface samplers for 48 hours at a distance of 6.8 m downstream of the injection. A one‐dimensional transport model was used in combination with an optimization code to identify the values of transport parameters that best explained the tracer observations. Parameters included dimensions and mass transfer coefficients describing exchange with both short (hours) and longer (tens of hours) storage zones as well as the average rates of advection and longitudinal dispersion in the open part of the water column (referred to as the “main flow zone”). Comparison with a more detailed set of tracer measurements tested how well the model's storage zones approximated the average characteristics of tracer movement into and out of the layer of thick floating vegetation and the pore water in the underlying peat. The rate at which the relatively fast moving water in the open water column was exchanged with slowly moving water in the layer of floating vegetation and in sediment pore water amounted to 50 and 3% h−1, respectively. Storage processes decreased the depth‐averaged velocity of surface water by 50% relative to the water velocity in the open part of the water
Jarsjoe, Jerker; Destouni, Georgia; Persson, Klas; Prieto, Carmen (Dept. of Physical Geography, Quaternary Geology, Stockholm Univ., Stockholm (Sweden))
2007-12-15
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
A Mercury Model of Atmospheric Transport
Christensen, Alex B. [Oregon State Univ., Corvallis, OR (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chodash, Perry A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Procassini, R. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2018-01-19
Using the particle transport code Mercury, accurate models were built of the two sources used in Operation BREN, a series of radiation experiments performed by the United States during the 1960s. In the future, these models will be used to validate Mercury’s ability to simulate atmospheric transport.
The european Trans-Tools transport model
Rooijen, T. van; Burgess, A.
2008-01-01
The paper presents the use of ArcGIS in the Transtools Transport Model, TRANS-TOOLS, created by an international consortium for the European Commission. The model describe passenger as well as freight transport in Europe with all medium and long distance modes (cars, vans, trucks, train, inland
Dileptons from transport and hydrodynamical models
Huovinen, P.; Koch, V.
2000-01-01
Transport and hydrodynamical models used to describe the expansion stage of a heavy-ion collision at the CERN SPS give different dilepton spectrum even if they are tuned to reproduce the observed hadron spectra. To understand the origin of this difference we compare the dilepton emission from transport and hydrodynamical models using similar initial states in both models. We find that the requirement of pion number conservation in a hydrodynamical model does not change the dilepton emission. Also the mass distribution from the transport model indicates faster cooling and longer lifetime of the fireball
Sediment and solute transport in a mountainous watershed in Valle del Cauca, Colombia
Guzman, Christian; Hoyos Villada, Fanny; Morales Vargas, Amalia; Rivera, Baudelino; Da Silva, Mayesse; Moreno Padilla, Pedro; Steenhuis, Tammo
2015-04-01
Sediment samples and solute concentrations were measured from the La Vega micro watershed in the southwestern region of the Colombian Andes. A main goal of this study was to improve prediction of soil surface and soil nutrient changes, based on field measurements, within small basin of the Aguaclara watershed network receiving different types of conservation measures. Two modeling approaches for stream discharge and sediment transport predictions were used with one of these based on infiltration-excess and the other on saturation-excess runoff. These streams are a part of a recent initiative from a water fund established by Asobolo, Asocaña, and Cenicaña in collaboration with the Natural Capital Project to improve conservation efforts and monitor their effects. On-site soil depth changes, groundwater depth measurements, and soil nutrient concentrations were also monitored to provide more information about changes within this mountainous watershed during one part of the yearly rainy season. This information is being coupled closely with the outlet sediment concentration and solute concentration patterns to discern correlations between scales. Lateral transects in the upper, middle, and lower part of the hillsides in the La Vega micro watershed showed differences in soil nutrient status and soil surface depth changes. The model based on saturation-excess, semi-distributed hydrology was able to reproduce discharge and sediment transport rates as well as the initially used infiltration excess model indicating available options for comparison of conservation changes in the future.
The Importance of Protons in Reactive Transport Modeling
McNeece, C. J.; Hesse, M. A.
2014-12-01
The importance of pH in aqueous chemistry is evident; yet, its role in reactive transport is complex. Consider a column flow experiment through silica glass beads. Take the column to be saturated and flowing with solution of a distinct pH. An instantaneous change in the influent solution pH can yield a breakthrough curve with both a rarefaction and shock component (composite wave). This behavior is unique among aqueous ions in transport and is more complex than intuition would tell. Analysis of the hyperbolic limit of this physical system can explain these first order transport phenomenon. This analysis shows that transport behavior is heavily dependent on the shape of the adsorption isotherm. Hence it is clear that accurate surface chemistry models are important in reactive transport. The proton adsorption isotherm has nonconstant concavity due to the proton's ability to partition into hydroxide. An eigenvalue analysis shows that an inflection point in the adsorption isotherm allows the development of composite waves. We use electrostatic surface complexation models to calculate realistic proton adsorption isotherms. Surface characteristics such as specific surface area, and surface site density were determined experimentally. We validate the model by comparison against silica glass bead flow through experiments. When coupled to surface complexation models, the transport equation captures the timing and behavior of breakthrough curves markedly better than with commonly used Langmuir assumptions. Furthermore, we use the adsorption isotherm to predict, a priori, the transport behavior of protons across pH composition space. Expansion of the model to multicomponent systems shows that proton adsorption can force composite waves to develop in the breakthrough curves of ions that would not otherwise exhibit such behavior. Given the abundance of reactive surfaces in nature and the nonlinearity of chemical systems, we conclude that building a greater understanding of
Pore connectivity effects on solute transport in rocks
Hu, Qinhong; Ewing, Robert P.
2001-01-01
Retardation of nuclear contaminants in rock matrices can lead to long retention times, allowing substantial radionuclide decay prior to eventual release. Imbibition and diffusion into the rock matrix can move contaminants away from an active fracture, thereby contributing to their retardation. However, diffusive transport in some rocks may behave anomalously because of their sparsely connected porespace, in contrast to diffusion in rocks with denser pore connections. We examined imbibition of weakly sorbing tracers into welded tuff and Indiana sandstone, and water imbibition into metagraywacke and Berea sandstone. Tuff samples were initially equilibrated to 12% and 76% water (v/v) within controlled humidity chambers, while the other rocks were air-dried. For imbibition, one face was exposed to water, with or without tracer, and uptake was measured over time. Following imbibition, tracer concentration measurements were made at fine (1 mm) increments. Three anomalous results were observed: (1) Indiana sandstone and metagraywacke showed mass of imbibed water scaling as time 0.26 , while tuff and Berea sandstone showed the more classical scaling with time 0.5 ; (2) tracer movement into dry (2% initial saturation) Indiana sandstone showed a dispersion pattern similar to that expected during tracer movement into moist (76% initial saturation) tuff; and (3) tracer concentrations at the inlet face of the tuff sample were approximately twice those deeper inside the sample. The experiment was then modeled using random walk methods on a 3-D lattice with different values of pore coordination. Network model simulations that used a pore coordination of 1.49 for Indiana sandstone and 1.56 for metagraywacke showed similar temporal scaling, a result of their porespace being close to the percolation threshold. Tracer concentration profiles in Indiana sandstone and tuff were closely matched by simulations that used pore coordinations of 1.49 and 1.68, respectively, because of how low
Pore Connectivity Effects on Solute Transport in Rocks
Oinhong Hu
2001-01-01
Retardation of nuclear contaminants in rock matrices can lead to long retention times, allowing substantial radionuclide decay prior to eventual release. Imbibition and diffusion into the rock matrix can move contaminants away from an active fracture, thereby contributing to their retardation. However, diffusive transport in some rocks may behave anomalously because of their sparsely connected porespace, in contrast to diffusion in rocks with denser pore connections. We examined imbibition of weakly sorbing tracers into welded tuff and Indiana sandstone, and water imbibition into metagraywacke and Berea sandstone. Tuff samples were initially equilibrated to 12% and 76% water (v/v) within controlled humidity chambers, while the other rocks were air-dried. For imbibition, one face was exposed to water, with or without tracer, and uptake was measured over time. Following imbibition, tracer concentration measurements were made at fine (1 mm) increments. Three anomalous results were observed: (1) Indiana sandstone and metagraywacke showed mass of imbibed water scaling as time 0.26 , while tuff and Berea sandstone showed the more classical scaling with time 0.05 ; (2) tracer movement into dry (2% initial saturation) Indiana sandstone showed a dispersion pattern similar to that expected during tracer movement into moist (76% initial saturation) tuft and (3) tracer concentrations at the inlet face of the tuff sample were approximately twice those deeper inside the sample. The experiment was then modeled using random walk methods on a 3-D lattice with different values of pore coordination. Network model simulations that used a pore coordination of 1.49 for Indiana sandstone and 1.56 for metagraywacke showed similar temporal scaling, a result of their porespace being close to the percolation threshold. Tracer concentration profiles in Indiana sandstone and tuff were closely matched by simulations that used pore coordinations of 1.49 and 1.68, respectively, because of how low
One-dimensional spatially dependent solute transport in semi ...
Space dependent retardation factor is also taken. The nature of porous media and solute pollutant are considered chemically non-reactive. Initially porous domain is considered solute free and the input source condition is considered uniformly continuous. A new transformation is introduced to solve the advection dispersion ...
3D neutron transport modelization
Warin, X.
1996-12-01
Some nodal methods to solve the transport equation in 3D are presented. Two nodal methods presented at an OCDE congress are described: a first one is a low degree one called RTN0; a second one is a high degree one called BDM1. The two methods can be made faster with a totally consistent DSA. Some results of parallelization show that: 98% of the time is spent in sweeps; transport sweeps are easily parallelized. (K.A.)
3D neutron transport modelization
Warin, X.
1996-12-01
Some nodal methods to solve the transport equation in 3D are presented. Two nodal methods presented at an OCDE congress are described: a first one is a low degree one called RTN0; a second one is a high degree one called BDM1. The two methods can be made faster with a totally consistent DSA. Some results of parallelization show that: 98% of the time is spent in sweeps; transport sweeps are easily parallelized. (K.A.). 10 refs.
Modeling spin magnetization transport in a spatially varying magnetic field
Picone, Rico A. R.; Garbini, Joseph L.; Sidles, John A.
2015-01-01
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield (1975) [1]. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment (Degen et al., 2009 [2]; Kuehn et al., 2008 [3]; Sidles et al., 2003 [4]; Dougherty et al., 2000 [5]). A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation (Fenske, 1932 [6]).
Water, solute and heat transport in the soil: the Australian connection
Knight, John
2016-04-01
The interest of Peter Raats in water, solute and heat transport in the soil has led to scientific and/or personal interactions with several Australian scientists such as John Philip, David Smiles, Greg Davis and John Knight. Along with John Philip and Robin Wooding, Peter was an early user of the Gardner (1958) linearised model of soil water flow, which brought him into competition with John Philip. I will discuss some of Peter's solutions relevant to infiltration from line and point sources, cavities and basins. A visit to Canberra, Australia in the early 1980s led to joint work on soil water flow, and on combined water and solute movement with David Smiles and others. In 1983 Peter was on the PhD committee for Greg Davis at the University of Wollongong, and some of the methods in his thesis 'Mathematical modelling of rate-limiting mechanisms of pyritic oxidation in overburden dumps' were later used by Peter's student Sjoerd van der Zee. David Smiles and Peter wrote a survey article 'Hydrology of swelling clay soils' in 2005. In the last decade Peter has been investigating the history of groundwater and vadose zone hydrology, and recently he and I have been bringing to light the largely forgotten work of Lewis Fry Richardson on finite difference solution of the heat equation, drainage theory, soil physics, and the soil-plant-atmosphere continuum.
Yuan, Wei; Li, Guanglei; Gil, Eun Seok; Lowe, Tao Lu; Fu, Bingmei M
2010-04-01
Charge carried by the surface glycocalyx layer (SGL) of the cerebral endothelium has been shown to significantly modulate the permeability of the blood-brain barrier (BBB) to charged solutes in vivo. The cultured monolayer of bEnd3, an immortalized mouse cerebral endothelial cell line, is becoming a popular in vitro BBB model due to its easy growth and maintenance of many BBB characteristics over repeated passages. To test whether the SGL of bEnd3 monolayer carries similar charge as that in the intact BBB and quantify this charge, which can be characterized by the SGL thickness (L(f)) and charge density (C(mf)), we measured the solute permeability of bEnd3 monolayer to neutral solutes and to solutes with similar size but opposite charges: negatively charged alpha-lactalbumin (-11) and positively charged ribonuclease (+3). Combining the measured permeability data with a transport model across the cell monolayer, we predicted the L(f) and the C(mf) of bEnd3 monolayer, which is approximately 160 nm and approximately 25 mEq/L, respectively. We also investigated whether orosomucoid, a plasma glycoprotein modulating the charge of the intact BBB, alters the charge of bEnd3 monolayer. We found that 1 mg/mL orosomucoid would increase SGL charge density of bEnd3 monolayer to approximately 2-fold of its control value.
Optimal transportation networks models and theory
Bernot, Marc; Morel, Jean-Michel
2009-01-01
The transportation problem can be formalized as the problem of finding the optimal way to transport a given measure into another with the same mass. In contrast to the Monge-Kantorovitch problem, recent approaches model the branched structure of such supply networks as minima of an energy functional whose essential feature is to favour wide roads. Such a branched structure is observable in ground transportation networks, in draining and irrigation systems, in electrical power supply systems and in natural counterparts such as blood vessels or the branches of trees. These lectures provide mathematical proof of several existence, structure and regularity properties empirically observed in transportation networks. The link with previous discrete physical models of irrigation and erosion models in geomorphology and with discrete telecommunication and transportation models is discussed. It will be mathematically proven that the majority fit in the simple model sketched in this volume.
M. M. Potsane
2014-01-01
Full Text Available The transport of chemicals through soils to the groundwater or precipitation at the soils surfaces leads to degradation of these resources. Serious consequences may be suffered in the long run. In this paper, we consider macroscopic deterministic models describing contaminant transport in saturated soils under uniform radial water flow backgrounds. The arising convection-dispersion equation given in terms of the stream functions is analyzed using classical Lie point symmetries. A number of exotic Lie point symmetries are admitted. Group invariant solutions are classified according to the elements of the one-dimensional optimal systems. We analyzed the group invariant solutions which satisfy the physical boundary conditions.
UrbanTransport Solution An Experience From Prague
unique firstlady
Based on the result of the research ... associated with road transport like its impact on environment ..... Prague is utilizing a variety of marketing strategies used for many years in ... at strategic metro stations providing customers with maps , time ...
Solution approach for a large scale personnel transport system for a large company in Latin America
Garzón-Garnica, Eduardo-Arturo; Caballero-Morales, Santiago-Omar; Martínez-Flores, José-Luis
2017-07-01
The present paper focuses on the modelling and solution of a large-scale personnel transportation system in Mexico where many routes and vehicles are currently used to service 525 points. The routing system proposed can be applied to many cities in the Latin-American region. Design/methodology/approach: This system was modelled as a VRP model considering the use of real-world transit times, and the fact that routes start at the farthest point from the destination center. Experiments were performed on different sized sets of service points. As the size of the instances was increased, the performance of the heuristic method was assessed in comparison with the results of an exact algorithm, the results remaining very close between both. When the size of the instance was full-scale and the exact algorithm took too much time to solve the problem, then the heuristic algorithm provided a feasible solution. Supported by the validation with smaller scale instances, where the difference between both solutions was close to a 6%, the full –scale solution obtained with the heuristic algorithm was considered to be within that same range. Findings: The proposed modelling and solving method provided a solution that would produce significant savings in the daily operation of the routes. Originality/value: The urban distribution of the cities in Latin America is unique to other regions in the world. The general layout of the large cities in this region includes a small town center, usually antique, and a somewhat disordered outer region. The lack of a vehicle-centered urban planning poses distinct challenges for vehicle routing problems in the region. The use of a heuristic VRP combined with the results of an exact VRP, allowed the obtention of an improved routing plan specific to the requirements of the region.
Solution approach for a large scale personnel transport system for a large company in Latin America
Garzón-Garnica, Eduardo-Arturo; Caballero-Morales, Santiago-Omar; Martínez-Flores, José-Luis
2017-01-01
The present paper focuses on the modelling and solution of a large-scale personnel transportation system in Mexico where many routes and vehicles are currently used to service 525 points. The routing system proposed can be applied to many cities in the Latin-American region. Design/methodology/approach: This system was modelled as a VRP model considering the use of real-world transit times, and the fact that routes start at the farthest point from the destination center. Experiments were performed on different sized sets of service points. As the size of the instances was increased, the performance of the heuristic method was assessed in comparison with the results of an exact algorithm, the results remaining very close between both. When the size of the instance was full-scale and the exact algorithm took too much time to solve the problem, then the heuristic algorithm provided a feasible solution. Supported by the validation with smaller scale instances, where the difference between both solutions was close to a 6%, the full –scale solution obtained with the heuristic algorithm was considered to be within that same range. Findings: The proposed modelling and solving method provided a solution that would produce significant savings in the daily operation of the routes. Originality/value: The urban distribution of the cities in Latin America is unique to other regions in the world. The general layout of the large cities in this region includes a small town center, usually antique, and a somewhat disordered outer region. The lack of a vehicle-centered urban planning poses distinct challenges for vehicle routing problems in the region. The use of a heuristic VRP combined with the results of an exact VRP, allowed the obtention of an improved routing plan specific to the requirements of the region.
Solution approach for a large scale personnel transport system for a large company in Latin America
Eduardo-Arturo Garzón-Garnica
2017-10-01
Full Text Available Purpose: The present paper focuses on the modelling and solution of a large-scale personnel transportation system in Mexico where many routes and vehicles are currently used to service 525 points. The routing system proposed can be applied to many cities in the Latin-American region. Design/methodology/approach: This system was modelled as a VRP model considering the use of real-world transit times, and the fact that routes start at the farthest point from the destination center. Experiments were performed on different sized sets of service points. As the size of the instances was increased, the performance of the heuristic method was assessed in comparison with the results of an exact algorithm, the results remaining very close between both. When the size of the instance was full-scale and the exact algorithm took too much time to solve the problem, then the heuristic algorithm provided a feasible solution. Supported by the validation with smaller scale instances, where the difference between both solutions was close to a 6%, the full –scale solution obtained with the heuristic algorithm was considered to be within that same range. Findings: The proposed modelling and solving method provided a solution that would produce significant savings in the daily operation of the routes. Originality/value: The urban distribution of the cities in Latin America is unique to other regions in the world. The general layout of the large cities in this region includes a small town center, usually antique, and a somewhat disordered outer region. The lack of a vehicle-centered urban planning poses distinct challenges for vehicle routing problems in the region. The use of a heuristic VRP combined with the results of an exact VRP, allowed the obtention of an improved routing plan specific to the requirements of the region.
Tao, Wanghai; Wang, Quanjiu; Lin, Henry
2018-03-01
Soil and water loss from farmland causes land degradation and water pollution, thus continued efforts are needed to establish mathematical model for quantitative analysis of relevant processes and mechanisms. In this study, an approximate analytical solution has been developed for overland flow model and sediment transport model, offering a simple and effective means to predict overland flow and erosion under natural rainfall conditions. In the overland flow model, the flow regime was considered to be transitional with the value of parameter β (in the kinematic wave model) approximately two. The change rate of unit discharge with distance was assumed to be constant and equal to the runoff rate at the outlet of the plane. The excess rainfall was considered to be constant under uniform rainfall conditions. The overland flow model developed can be further applied to natural rainfall conditions by treating excess rainfall intensity as constant over a small time interval. For the sediment model, the recommended values of the runoff erosion calibration constant (cr) and the splash erosion calibration constant (cf) have been given in this study so that it is easier to use the model. These recommended values are 0.15 and 0.12, respectively. Comparisons with observed results were carried out to validate the proposed analytical solution. The results showed that the approximate analytical solution developed in this paper closely matches the observed data, thus providing an alternative method of predicting runoff generation and sediment yield, and offering a more convenient method of analyzing the quantitative relationships between variables. Furthermore, the model developed in this study can be used as a theoretical basis for developing runoff and erosion control methods.
Using Flux Information at Surface Water Boundaries to Improve a Groundwater Flow and Transport Model
Genereux, David
2000-01-01
We investigated the performance of a groundwater flow and solute transport model when different combinations of hydraulic head, seepage flux, and chloride concentration data were used in calibration of the model...
Model Comparison for Electron Thermal Transport
Moses, Gregory; Chenhall, Jeffrey; Cao, Duc; Delettrez, Jacques
2015-11-01
Four electron thermal transport models are compared for their ability to accurately and efficiently model non-local behavior in ICF simulations. Goncharov's transport model has accurately predicted shock timing in implosion simulations but is computationally slow and limited to 1D. The iSNB (implicit Schurtz Nicolai Busquet electron thermal transport method of Cao et al. uses multigroup diffusion to speed up the calculation. Chenhall has expanded upon the iSNB diffusion model to a higher order simplified P3 approximation and a Monte Carlo transport model, to bridge the gap between the iSNB and Goncharov models while maintaining computational efficiency. Comparisons of the above models for several test problems will be presented. This work was supported by Sandia National Laboratory - Albuquerque and the University of Rochester Laboratory for Laser Energetics.
Masiello, E.
2006-01-01
The principal goal of this manuscript is devoted to the investigation of a new type of heterogeneous mesh adapted to the shape of the fuel pins (fuel-clad-moderator). The new heterogeneous mesh guarantees the spatial modelling of the pin-cell with a minimum of regions. Two methods are investigated for the spatial discretization of the transport equation: the discontinuous finite element method and the method of characteristics for structured cells. These methods together with the new representation of the pin-cell result in an appreciable reduction of calculation points. They allow an exact modelling of the fuel pin-cell without spatial homogenization. A new synthetic acceleration technique based on an angular multigrid is also presented for the speed up of the inner iterations. These methods are good candidates for transport calculations for a nuclear reactor core. A second objective of this work is the application of method of characteristics for non-structured geometries to the study of double heterogeneity problem. The letters is characterized by fuel material with a stochastic dispersion of heterogeneous grains, and until now was solved with a model based on collision probabilities. We propose a new statistical model based on renewal-Markovian theory, which makes possible to take into account the stochastic nature of the problem and to avoid the approximations of the collision probability model. The numerical solution of this model is guaranteed by the method of characteristics. (author)
Flow and solute transport in backfilled tunnel and collapsed backfill - possible extension of Comp32
Neretnieks, Ivars
2006-09-01
In the Swedish deep geological final repository for spent fuel the tunnels will be filled with a backfill with low permeability. However, some flow may take place in the backfill. Nuclides released from a leaking canister could diffuse up to the flowing water in the backfill and be transported downstream in the tunnel. At an intersection of the tunnel with a fracture zone the contaminated water might flow out into the zone.This report addresses the transport mechanisms and rate of transport from a leaking canister up through the buffer and backfill in the deposition hole, further into the backfill in the tunnel and the transport along the tunnel. Spreading by diffusion in the buffer and backfill as well as retardation of sorbing nuclides is accounted for.The transport mechanisms and rates of transport are described and some simple models with analytical solutions are used to quantify the processes. These simple solutions are used to gain insights into when different transport mechanisms are important. The simple solutions are used to simulate a base case example where a non-sorbing nuclide (iodide) and a sorbing nuclide (radium) move in the backfill by diffusion and by advective flow. The simple sample calculations show that it would take thousands of years for iodide to move 20 m along the tunnel and that a release pulse would spread out considerably over time. The sorbing nuclide 226 Ra with a half life of 1,600 years would be strongly retarded by sorption and would decay to insignificance during its migration along the tunnel. The consequences of a collapse of backfill leaving a channel above the backfill is also studied by a simple analytical model that accounts for water flowing in the collapsed part of the backfill at the ceiling of the tunnel. A nuclide that diffuses up to the flowing channel will flow with the ('rapidly' flowing) water but will be retarded by diffusion down into the backfill again. This down diffusion retards the nuclide migration
Flow and solute transport in backfilled tunnel and collapsed backfill - possible extension of Comp32
Neretnieks, Ivars [Royal Inst. of Technology, Stockholm (Sweden). Dept. of Chemical Engineering and Technology
2006-09-15
In the Swedish deep geological final repository for spent fuel the tunnels will be filled with a backfill with low permeability. However, some flow may take place in the backfill. Nuclides released from a leaking canister could diffuse up to the flowing water in the backfill and be transported downstream in the tunnel. At an intersection of the tunnel with a fracture zone the contaminated water might flow out into the zone.This report addresses the transport mechanisms and rate of transport from a leaking canister up through the buffer and backfill in the deposition hole, further into the backfill in the tunnel and the transport along the tunnel. Spreading by diffusion in the buffer and backfill as well as retardation of sorbing nuclides is accounted for.The transport mechanisms and rates of transport are described and some simple models with analytical solutions are used to quantify the processes. These simple solutions are used to gain insights into when different transport mechanisms are important. The simple solutions are used to simulate a base case example where a non-sorbing nuclide (iodide) and a sorbing nuclide (radium) move in the backfill by diffusion and by advective flow. The simple sample calculations show that it would take thousands of years for iodide to move 20 m along the tunnel and that a release pulse would spread out considerably over time. The sorbing nuclide {sup 226}Ra with a half life of 1,600 years would be strongly retarded by sorption and would decay to insignificance during its migration along the tunnel. The consequences of a collapse of backfill leaving a channel above the backfill is also studied by a simple analytical model that accounts for water flowing in the collapsed part of the backfill at the ceiling of the tunnel. A nuclide that diffuses up to the flowing channel will flow with the ('rapidly' flowing) water but will be retarded by diffusion down into the backfill again. This down diffusion retards the nuclide
Modeling pollutant transport using a meshless-lagrangian particle model
Carrington, D.B.; Pepper, D.W.
2002-01-01
A combined meshless-Lagrangian particle transport model is used to predict pollutant transport over irregular terrain. The numerical model for initializing the velocity field is based on a meshless approach utilizing multiquadrics established by Kansa. The Lagrangian particle transport technique uses a random walk procedure to depict the advection and dispersion of pollutants over any type of surface, including street and city canyons
Application of preconditioned GMRES to the numerical solution of the neutron transport equation
Patton, B.W.; Holloway, J.P.
2002-01-01
The generalized minimal residual (GMRES) method with right preconditioning is examined as an alternative to both standard and accelerated transport sweeps for the iterative solution of the diamond differenced discrete ordinates neutron transport equation. Incomplete factorization (ILU) type preconditioners are used to determine their effectiveness in accelerating GMRES for this application. ILU(τ), which requires the specification of a dropping criteria τ, proves to be a good choice for the types of problems examined in this paper. The combination of ILU(τ) and GMRES is compared with both DSA and unaccelerated transport sweeps for several model problems. It is found that the computational workload of the ILU(τ)-GMRES combination scales nonlinearly with the number of energy groups and quadrature order, making this technique most effective for problems with a small number of groups and discrete ordinates. However, the cost of preconditioner construction can be amortized over several calculations with different source and/or boundary values. Preconditioners built upon standard transport sweep algorithms are also evaluated as to their effectiveness in accelerating the convergence of GMRES. These preconditioners show better scaling with such problem parameters as the scattering ratio, the number of discrete ordinates, and the number of spatial meshes. These sweeps based preconditioners can also be cast in a matrix free form that greatly reduces storage requirements
Recirculating cooling water solute depletion models
Price, W.T.
1990-01-01
Chromates have been used for years to inhibit copper corrosion in the plant Recirculating Cooling Water (RCW) system. However, chromates have become an environmental problem in recent years both in the chromate removal plant (X-616) operation and from cooling tower drift. In response to this concern, PORTS is replacing chromates with Betz Dianodic II, a combination of phosphates, BZT, and a dispersant. This changeover started with the X-326 system in 1989. In order to control chemical concentrations in X-326 and in systems linked to it, we needed to be able to predict solute concentrations in advance of the changeover. Failure to predict and control these concentrations can result in wasted chemicals, equipment fouling, or increased corrosion. Consequently, Systems Analysis developed two solute concentration models. The first simulation represents the X-326 RCW system by itself; and models the depletion of a solute once the feed has stopped. The second simulation represents the X-326, X-330, and the X-333 systems linked together by blowdown. This second simulation represents the concentration of a solute in all three systems simultaneously. 4 figs
Coarse-Grained Modeling of Polyelectrolyte Solutions
Denton, Alan R.; May, Sylvio
2014-03-01
Ionic mixtures, such as electrolyte and polyelectrolyte solutions, have attracted much attention recently for their rich and challenging combination of electrostatic and non-electrostatic interparticle forces and their practical importance, from battery technologies to biological systems. Hydration of ions in aqueous solutions is known to entail ion-specific effects, including variable solubility of organic molecules, as manifested in the classic Hofmeister series for salting-in and salting-out of proteins. The physical mechanism by which the solvent (water) mediates effective interactions between ions, however, is still poorly understood. Starting from a microscopic model of a polyelectrolyte solution, we apply a perturbation theory to derive a coarse-grained model of ions interacting through both long-range electrostatic and short-range solvent-induced pair potentials. Taking these effective interactions as input to molecular dynamics simulations, we calculate structural and thermodynamic properties of aqueous ionic solutions. This work was supported by the National Science Foundation under Grant No. DMR-1106331.
Modeling of coupled geochemical and transport processes: An overview
Carnahan, C.L.
1989-10-01
Early coupled models associated with fluid flow and solute transport have been limited by assumed conditions of constant temperature, fully saturated fluid flow, and constant pore fluid velocity. Developments including coupling of chemical reactions to variable fields of temperature and fluid flow have generated new requirements for experimental data. As the capabilities of coupled models expand, needs are created for experimental data to be used for both input and validation. 25 refs
Light-driven solute transport in Halobacterium halobium
Lanyi, J. K.
1979-01-01
The cell membrane of Halobacterium halobium exhibits differential regions which contain crystalline arrays of a single kind of protein, termed bacteriorhodopsin. This bacterial retinal-protein complex resembles the visual pigment and, after the absorption of protons, translocates H(+) across the cell membrane, leading to an electrochemical gradient for protons between the inside and the outside of the cell. Thus, light is an alternate source of energy in these bacteria, in addition to terminal oxidation. The paper deals with work on light-driven transport in H. halobium with cell envelope vesicles. The discussion covers light-driven movements of H(+), Na(+), and K(+); light-driven amino acid transport; and apparent allosteric control of amino acid transport. The scheme of energy coupling in H. halobium vesicles appears simple, its quantitative details are quite complex and reveal regulatory phenomena. More knowledge is required of the way the coupling components are regulated by the ion gradients present.
Cui, Yi-an; Liu, Lanbo; Zhu, Xiaoxiong
2017-08-01
Monitoring the extent and evolution of contaminant plumes in local and regional groundwater systems from existing landfills is critical in contamination control and remediation. The self-potential survey is an efficient and economical nondestructive geophysical technique that can be used to investigate underground contaminant plumes. Based on the unscented transform, we have built a Kalman filtering cycle to conduct time-lapse data assimilation for monitoring the transport of solute based on the solute transport experiment using a bench-scale physical model. The data assimilation was formed by modeling the evolution based on the random walk model and observation correcting based on the self-potential forward. Thus, monitoring self-potential data can be inverted by the data assimilation technique. As a result, we can reconstruct the dynamic process of the contaminant plume instead of using traditional frame-to-frame static inversion, which may cause inversion artifacts. The data assimilation inversion algorithm was evaluated through noise-added synthetic time-lapse self-potential data. The result of the numerical experiment shows validity, accuracy and tolerance to the noise of the dynamic inversion. To validate the proposed algorithm, we conducted a scaled-down sandbox self-potential observation experiment to generate time-lapse data that closely mimics the real-world contaminant monitoring setup. The results of physical experiments support the idea that the data assimilation method is a potentially useful approach for characterizing the transport of contamination plumes using the unscented Kalman filter (UKF) data assimilation technique applied to field time-lapse self-potential data.
Centrifuge modelling of contaminant transport processes
Culligan, P. J.; Savvidou, C.; Barry, D. A.
1996-01-01
Over the past decade, research workers have started to investigate problems of subsurface contaminant transport through physical modelling on a geotechnical centrifuge. A major advantage of this apparatus is its ability to model complex natural systems in a controlled laboratory environment In this paper, we discusses the principles and scaling laws related to the centrifugal modelling of contaminant transport, and presents four examples of recent work that has bee...
A Sediment Transport Model for Sewers
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...
Coupled models in porous media: reactive transport and fractures
Amir, L.
2008-12-01
This thesis deals with numerical simulation of coupled models for flow and transport in porous media. We present a new method for coupling chemical reactions and transport by using a Newton-Krylov method, and we also present a model of flow in fractured media, based on a domain decomposition method that takes into account the case of intersecting fractures. This study is composed of three parts: the first part contains an analysis, and implementation, of various numerical methods for discretizing advection-diffusion problems, in particular by using operator splitting methods. The second part is concerned with a fully coupled method for modeling transport and chemistry problems. The coupled transport-chemistry model is described, after discretization in time, by a system of nonlinear equations. The size of the system, namely the number of grid points times the number a chemical species, precludes a direct solution of the linear system. To alleviate this difficulty, we solve the system by a Newton-Krylov method, so as to avoid forming and factoring the Jacobian matrix. In the last part, we present a model of flow in 3D for intersecting fractures, by using a domain decomposition method. The fractures are treated as interfaces between sub-domains. We show existence and uniqueness of the solution, and we validate the model by numerical tests. (author)
The influence of mass transfer on solute transport in column experiments with an aggregated soil
Roberts, Paul V.; Goltz, Mark N.; Summers, R. Scott; Crittenden, John C.; Nkedi-Kizza, Peter
1987-06-01
The spreading of concentration fronts in dynamic column experiments conducted with a porous, aggregated soil is analyzed by means of a previously documented transport model (DFPSDM) that accounts for longitudinal dispersion, external mass transfer in the boundary layer surrounding the aggregate particles, and diffusion in the intra-aggregate pores. The data are drawn from a previous report on the transport of tritiated water, chloride, and calcium ion in a column filled with Ione soil having an average aggregate particle diameter of 0.34 cm, at pore water velocities from 3 to 143 cm/h. The parameters for dispersion, external mass transfer, and internal diffusion were predicted for the experimental conditions by means of generalized correlations, independent of the column data. The predicted degree of solute front-spreading agreed well with the experimental observations. Consistent with the aggregate porosity of 45%, the tortuosity factor for internal pore diffusion was approximately equal to 2. Quantitative criteria for the spreading influence of the three mechanisms are evaluated with respect to the column data. Hydrodynamic dispersion is thought to have governed the front shape in the experiments at low velocity, and internal pore diffusion is believed to have dominated at high velocity; the external mass transfer resistance played a minor role under all conditions. A transport model such as DFPSDM is useful for interpreting column data with regard to the mechanisms controlling concentration front dynamics, but care must be exercised to avoid confounding the effects of the relevant processes.
Modeling the Quiet Time Outflow Solution in the Polar Cap
Glocer, Alex
2011-01-01
We use the Polar Wind Outflow Model (PWOM) to study the geomagnetically quiet conditions in the polar cap during solar maximum, The PWOM solves the gyrotropic transport equations for O(+), H(+), and He(+) along several magnetic field lines in the polar region in order to reconstruct the full 3D solution. We directly compare our simulation results to the data based empirical model of Kitamura et al. [2011] of electron density, which is based on 63 months of Akebono satellite observations. The modeled ion and electron temperatures are also compared with a statistical compilation of quiet time data obtained by the EISCAT Svalbard Radar (ESR) and Intercosmos Satellites (Kitamura et al. [2011]). The data and model agree reasonably well. This study shows that photoelectrons play an important role in explaining the differences between sunlit and dark results, ion composition, as well as ion and electron temperatures of the quiet time polar wind solution. Moreover, these results provide validation of the PWOM's ability to model the quiet time ((background" solution.
UrbanTransport Solution An Experience From Prague | Jeremiah ...
This paper examines the urban transport problems in Prague in Czech Republic. Based on the result of the research conducted, it was found that with the collapsed of Communism in Czech Republic, there was an upsurge in the use of private cars which was not possible during communism because the law does not ...
Solute transport through porous media using asymptotic dispersivity
ber of processes and porous media properties including convective transport .... existence of regions within the porous medium in which there is minimum advective flow. .... concentration at x = L. The initial and the exit boundary conditions can be .... rial was cleaned, washed and dried to ensure that the material free from ...
Modeling electrokinetic transport in phenol contaminated soils
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.)
Cellular automaton model of coupled mass transport and chemical reactions
Karapiperis, T.
1994-01-01
Mass transport, coupled with chemical reactions, is modelled as a cellular automaton in which solute molecules perform a random walk on a lattice and react according to a local probabilistic rule. Assuming molecular chaos and a smooth density function, we obtain the standard reaction-transport equations in the continuum limit. The model is applied to the reactions a + b ↔c and a + b →c, where we observe interesting macroscopic effects resulting from microscopic fluctuations and spatial correlations between molecules. We also simulate autocatalytic reaction schemes displaying spontaneous formation of spatial concentration patterns. Finally, we propose and discuss the limitations of a simple model for mineral-solute interaction. (author) 5 figs., 20 refs
Martin Gregory T
2004-11-01
Full Text Available Abstract Background Investigation of bioheat transfer problems requires the evaluation of temporal and spatial distributions of temperature. This class of problems has been traditionally addressed using the Pennes bioheat equation. Transport of heat by conduction, and by temperature-dependent, spatially heterogeneous blood perfusion is modeled here using a transport lattice approach. Methods We represent heat transport processes by using a lattice that represents the Pennes bioheat equation in perfused tissues, and diffusion in nonperfused regions. The three layer skin model has a nonperfused viable epidermis, and deeper regions of dermis and subcutaneous tissue with perfusion that is constant or temperature-dependent. Two cases are considered: (1 surface contact heating and (2 spatially distributed heating. The model is relevant to the prediction of the transient and steady state temperature rise for different methods of power deposition within the skin. Accumulated thermal damage is estimated by using an Arrhenius type rate equation at locations where viable tissue temperature exceeds 42°C. Prediction of spatial temperature distributions is also illustrated with a two-dimensional model of skin created from a histological image. Results The transport lattice approach was validated by comparison with an analytical solution for a slab with homogeneous thermal properties and spatially distributed uniform sink held at constant temperatures at the ends. For typical transcutaneous blood gas sensing conditions the estimated damage is small, even with prolonged skin contact to a 45°C surface. Spatial heterogeneity in skin thermal properties leads to a non-uniform temperature distribution during a 10 GHz electromagnetic field exposure. A realistic two-dimensional model of the skin shows that tissue heterogeneity does not lead to a significant local temperature increase when heated by a hot wire tip. Conclusions The heat transport system model of the
Cho, Kyu-Hyang; Do, Jun-Young; Park, Jong-Won; Yoon, Kyung-Woo; Kim, Yong-Lim
2013-01-01
Several studies have reported benefits for human peritoneal mesothelial cell function of a neutral-pH dialysate low in glucose degradation products (GDPs). However, the effects of low-GDP solution on ultrafiltration (UF), transport of solutes, and control of body water remain elusive. We therefore investigated the effect of low-GDP solution on UF, solute transport, and control of body water. Among 79 new continuous ambulatory peritoneal dialysis (CAPD) patients, 60 completed a 12-month protocol (28 in a lactate-based high-GDP solution group, 32 in a lactate-based low-GDP solution group). Clinical indices--including 24-hour UF volume (UFV), 24-hour urine volume (UV), residual renal function, and dialysis adequacy--were measured at months 1, 6, and 12. At months 1, 6, and 12, UFV, glucose absorption, 4-hour dialysate-to-plasma (D/P) creatinine, and 1-hour D/P Na(+) were assessed during a modified 4.25% peritoneal equilibration test (PET). Body composition by bioelectric impedance analysis was measured at months 1 and 12 in 26 CAPD patients. Daily UFV was lower in the low-GDP group. Despite similar solute transport and aquaporin function, the low-GDP group also showed lower UFV and higher glucose absorption during the PET. Factors associated with UFV during the PET were lactate-based high-GDP solution and 1-hour D/P Na(+). No differences in volume status and obesity at month 12 were observed, and improvements in hypervolemia were equal in both groups. Compared with the high-GDP group, the low-GDP group had a lower UFV during a PET and a lower daily UFV during the first year after peritoneal dialysis initiation. Although the low-GDP group had a lower daily UFV, no difficulties in controlling edema were encountered.
Modeling biogechemical reactive transport in a fracture zone
Molinero, Jorge; Samper, Javier; Yang, Chan Bing, and Zhang, Guoxiang; Guoxiang, Zhang
2005-01-14
A coupled model of groundwater flow, reactive solute transport and microbial processes for a fracture zone of the Aspo site at Sweden is presented. This is the model of the so-called Redox Zone Experiment aimed at evaluating the effects of tunnel construction on the geochemical conditions prevailing in a fracture granite. It is found that a model accounting for microbially-mediated geochemical processes is able to reproduce the unexpected measured increasing trends of dissolved sulfate and bicarbonate. The model is also useful for testing hypotheses regarding the role of microbial processes and evaluating the sensitivity of model results to changes in biochemical parameters.
Modeling biogeochemical reactive transport in a fracture zone
Molinero, Jorge; Samper, Javier; Yang, Chan Bing; Zhang, Guoxiang; Guoxiang, Zhang
2005-01-01
A coupled model of groundwater flow, reactive solute transport and microbial processes for a fracture zone of the Aspo site at Sweden is presented. This is the model of the so-called Redox Zone Experiment aimed at evaluating the effects of tunnel construction on the geochemical conditions prevailing in a fracture granite. It is found that a model accounting for microbially-mediated geochemical processes is able to reproduce the unexpected measured increasing trends of dissolved sulfate and bicarbonate. The model is also useful for testing hypotheses regarding the role of microbial processes and evaluating the sensitivity of model results to changes in biochemical parameters
2010-01-01
Based on the results from this research, MoDOT can confidently state that the diverging diamond was the right transportation solution for the Interstate 44 and Route 13 intersection. The overall results show: Most Springfield area residents were ...
Gureghian, A.B.
1979-01-01
A mathematical model of ground water transport through an aquifer is presented. The solute of interest is a metal tracer or radioactive material which may undergo decay through a sorbing unconfined aquifer. The subject is developed under the following headings: flow equation, solute equation, boundary conditions, finite element formulation, element formulation, solution scheme (flow equation, solute equation), results and discussions, water movement in a ditch drained aquifer under transient state, water and solute movement in a homogeneous and unsaturated soil, transport of 226 Ra in nonhomogeneous aquifer, tailings pond lined, and tailings pond unlined. It is concluded that this mathematical model may have a wide variety of applications. The uranium milling industry may find it useful to evaluate the hydrogeological suitability of their disposal sites. It may prove suited for the design of clay disposal ponds destined to hold hazardous liquids. It may also provide a means of estimating the long-term impact of radionuclides or other pollutants on the quality of ground water. 31 references, 9 figures, 3 tables
Brain washing : Transport of cerebral extracellular fluids and solutes
Bedussi, B.
2017-01-01
Regulation of extracellular volume and fluid composition provides a robust microenvironment for brain cells. In peripheral tissue, fluid surplus and solutes are removed from the interstitium via drainage into lymphatic channels. Since the central nervous system lacks a proper lymphatic vasculature,
Solute transport in a well under slow-purge and no-purge conditions
Plummer, M. A.; Britt, S. L.; Martin-Hayden, J. M.
2010-12-01
than when vertical flow velocities are assumed uniform. The second study was conducted to explain results of a recent laboratory experiment (Britt, 2005) that indicated that vertical transport of solute in a well, perpendicular to the groundwater flow direction, can be much faster than horizontal advection and that a solute may also mix rapidly in the direction opposite its net buoyant force. We replicate much of the vertical mixing simply by incorporating the Boussinesq approximation in the incompressible Navier Stokes equations, and offer several possible explanations for the latter behavior. The third study examines the thermally driven free convection in a well through comparison of numerical model simulations with detailed temperature measurements from inside and outside a pipe installed in shallow groundwater. Such studies are useful because the dimensionless numbers that indicate when onset of free convection should occur do not provide information about the scale or magnitude of that convection, and thus do not aid in estimating effects on solute redistribution. Finally, we discuss the implications of these results for interpretation of groundwater sampling data and provide recommendations for passive and low-flow groundwater sampling methods.
TLC scheme for numerical solution of the transport equation on equilateral triangular meshes
Walters, W.F.
1983-01-01
A new triangular linear characteristic TLC scheme for numerically solving the transport equation on equilateral triangular meshes has been developed. This scheme uses the analytic solution of the transport equation in the triangle as its basis. The data on edges of the triangle are assumed linear as is the source representation. A characteristic approach or nodal approach is used to obtain the analytic solution. Test problems indicate that the new TLC is superior to the widely used DITRI scheme for accuracy
Concept Layout Model of Transportation Terminals
Li-ya Yao
2012-01-01
Full Text Available Transportation terminal is the key node in transport systems. Efficient terminals can improve operation of passenger transportation networks, adjust the layout of public transportation networks, provide a passenger guidance system, and regulate the development of commercial forms, as well as optimize the assembly and distribution of modern logistic modes, among others. This study aims to clarify the relationship between the function and the structure of transportation terminals and establish the function layout design. The mapping mechanism of demand, function, and structure was analyzed, and a quantitative relationship between function and structure was obtained from a design perspective. Passenger demand and terminal structure were decomposed into several demand units and structural elements following the principle of reverse engineering. The relationship maps between these two kinds of elements were then analyzed. Function-oriented concept layout model of transportation terminals was established using the previous method. Thus, a technique in planning and design of transportation structures was proposed. Meaningful results were obtained from the optimization of transportation terminal facilities, which guide the design of the functional layout of transportation terminals and improve the development of urban passenger transportation systems.
A transportronic solution to the problem of interorbital transportation
Brown, William C.
1992-01-01
An all-electronic transportation system described by the term 'transportronics' is examined as a means of solving the current problem of the high cost of transporting material from low-Earth orbit (LEO) to geostationary orbit (GEO). In this transportation system, low cost electric energy at the surface of the Earth is efficiently converted into microwave power which is then efficiently formed into a narrow beam which is kept incident upon the orbital transfer vehicles (OTV's) by electronic tracking. The incident beam is efficiently captured and converted into DC power by a device which has a very high ratio of DC power output to its mass. Because the mass of the electric thruster is also low, the resulting acceleration is unprecedented for electric-propelled vehicles. However, the performance of the system in terms of transit times from LEO to GEO is penalized by the short time of contact between the beam and the vehicle in low-Earth orbits. This makes it necessary to place the Earth based transmitters and the vehicles in the equatorial plane thus introducing many geopolitical factors. Technically, however, such a system as described in the report may out-perform any other approach to transportation in the LEO to GEO regime. The report describes and analyzes all portions of the beamed microwave power transmission system in considerable detail. An economic analysis of the operating and capital costs is made with the aid of a reference system capable of placing about 130,000 kilograms of payload into GEO each year. More mature states of the system are then examined, to a level in which 60,000 metric tons per year could be placed into GEO.
Hamamoto, S.; Arihara, M.; Kawamoto, K.; Nishimura, T.; Komatsu, T.; Moldrup, P.
2014-12-01
Subsurface warming driven by global warming, urban heat islands, and increasing use of shallow geothermal heating and cooling systems such as the ground source heat pump, potentially causes changes in subsurface mass transport. Therefore, understanding temperature dependency of the solute transport characteristics is essential to accurately assess environmental risks due to increased subsurface temperature. In this study, one-dimensional solute transport experiments were conducted in soil columns under temperature control to investigate effects of temperature on solute transport parameters, such as solute dispersion and diffusion coefficients, hydraulic conductivity, and retardation factor. Toyoura sand, Kaolin clay, and intact loamy soils were used in the experiments. Intact loamy soils were taken during a deep well boring at the Arakawa Lowland in Saitama Prefecture, Japan. In the transport experiments, the core sample with 5-cm diameter and 4-cm height was first isotropically consolidated, whereafter 0.01M KCl solution was injected to the sample from the bottom. The concentrations of K+ and Cl- in the effluents were analyzed by an ion chromatograph to obtain solute breakthrough curves. The solute transport parameters were calculated from the breakthrough curves. The experiments were conducted under different temperature conditions (15, 25, and 40 oC). The retardation factor for the intact loamy soils decreased with increasing temperature, while water permeability increased due to reduced viscosity of water at higher temperature. Opposite, the effect of temperature on solute dispersivity for the intact loamy soils was insignificant. The effects of soil texture on the temperature dependency of the solute transport characteristics will be further investigated from comparison of results from differently-textured samples.
Highway and interline transportation routing models
Joy, D.S.; Johnson, P.E.
1994-01-01
The potential impacts associated with the transportation of hazardous materials are important issues to shippers, carriers, and the general public. Since transportation routes are a central characteristic in most of these issues, the prediction of likely routes is the first step toward the resolution of these issues. In addition, US Department of Transportation requirements (HM-164) mandate specific routes for shipments of highway controlled quantities of radioactive materials. In response to these needs, two routing models have been developed at Oak Ridge National Laboratory under the sponsorship of the U.S. Department of Energy (DOE). These models have been designated by DOE's Office of Environmental Restoration and Waste Management, Transportation Management Division (DOE/EM) as the official DOE routing models. Both models, HIGHWAY and INTERLINE, are described
Modelling anisotropic water transport in polymer composite ...
Parameters for Fickian diffusion and polymer relaxation models were determined by .... Water transport process of resin and polymer composite specimens at ..... simulation. ... Kwon Y W and Bang H 1997 Finite element method using matlab.
Mathematical modeling plasma transport in tokamaks
Quiang, Ji [Univ. of Illinois, Urbana-Champaign, IL (United States)
1997-01-01
In this work, the author applied a systematic calibration, validation and application procedure based on the methodology of mathematical modeling to international thermonuclear experimental reactor (ITER) ignition studies. The multi-mode plasma transport model used here includes a linear combination of drift wave branch and ballooning branch instabilities with two a priori uncertain constants to account for anomalous plasma transport in tokamaks. A Bayesian parameter estimation method is used including experimental calibration error/model offsets and error bar rescaling factors to determine the two uncertain constants in the transport model with quantitative confidence level estimates for the calibrated parameters, which gives two saturation levels of instabilities. This method is first tested using a gyroBohm multi-mode transport model with a pair of DIII-D discharge experimental data, and then applied to calibrating a nominal multi-mode transport model against a broad database using twelve discharges from seven different tokamaks. The calibrated transport model is then validated on five discharges from JT-60 with no adjustable constants. The results are in a good agreement with experimental data. Finally, the resulting class of multi-mode tokamak plasma transport models is applied to the transport analysis of the ignition probability in a next generation machine, ITER. A reference simulation of basic ITER engineering design activity (EDA) parameters shows that a self-sustained thermonuclear burn with 1.5 GW output power can be achieved provided that impurity control makes radiative losses sufficiently small at an average plasma density of 1.2 X 10^{20}/m^{3} with 50 MW auxiliary heating. The ignition probability of ITER for the EDA parameters, can be formally as high as 99.9% in the present context. The same probability for concept design activity (CDA) parameters of ITER, which has smaller size and lower current, is only 62.6%.
Mathematical modeling plasma transport in tokamaks
Quiang, Ji
1995-01-01
In this work, the author applied a systematic calibration, validation and application procedure based on the methodology of mathematical modeling to international thermonuclear experimental reactor (ITER) ignition studies. The multi-mode plasma transport model used here includes a linear combination of drift wave branch and ballooning branch instabilities with two a priori uncertain constants to account for anomalous plasma transport in tokamaks. A Bayesian parameter estimation method is used including experimental calibration error/model offsets and error bar rescaling factors to determine the two uncertain constants in the transport model with quantitative confidence level estimates for the calibrated parameters, which gives two saturation levels of instabilities. This method is first tested using a gyroBohm multi-mode transport model with a pair of DIII-D discharge experimental data, and then applied to calibrating a nominal multi-mode transport model against a broad database using twelve discharges from seven different tokamaks. The calibrated transport model is then validated on five discharges from JT-60 with no adjustable constants. The results are in a good agreement with experimental data. Finally, the resulting class of multi-mode tokamak plasma transport models is applied to the transport analysis of the ignition probability in a next generation machine, ITER. A reference simulation of basic ITER engineering design activity (EDA) parameters shows that a self-sustained thermonuclear burn with 1.5 GW output power can be achieved provided that impurity control makes radiative losses sufficiently small at an average plasma density of 1.2 X 10 20 /m 3 with 50 MW auxiliary heating. The ignition probability of ITER for the EDA parameters, can be formally as high as 99.9% in the present context. The same probability for concept design activity (CDA) parameters of ITER, which has smaller size and lower current, is only 62.6%
Weak solutions to interdiffusion models with Vegard rule
Sapa, Lucjan; BoŻek, Bogusław; Danielewski, Marek
2018-01-01
In this work we consider the diffusional transport in an r-component solid solution. The one and multidimensional models are expressed by the nonlinear systems of strongly coupled differential equations with the initial and the nonlinear coupled boundary conditions. They are obtained from the local mass conservation law for fluxes which are a sum of the diffusional and Darken drift terms, together with the Vegard rule. The considered boundary conditions allow the physical system to be not only closed but also open. The theorems on existence, uniqueness and properties of global weak solutions in the one-dimensional case are formulated. The agreement between the theoretical results, numerical simulations and experimental data in the one-dimensional case is shown.
Core2D. A code for non-isothermal water flow and reactive solute transport. Users manual version 2
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
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)
Core 2D. A code for non-isothermal water flow and reactive solute transport. Users manual version 2
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)
Computer-based modelling and optimization in transportation
Rossi, Riccardo
2014-01-01
This volume brings together works resulting from research carried out by members of the EURO Working Group on Transportation (EWGT) and presented during meetings and workshops organized by the Group under the patronage of the Association of European Operational Research Societies in 2012 and 2013. The main targets of the EWGT include providing a forum to share research information and experience, encouraging joint research and the development of both theoretical methods and applications, and promoting cooperation among the many institutions and organizations which are leaders at national level in the field of transportation and logistics. The primary fields of interest concern operational research methods, mathematical models and computation algorithms, to solve and sustain solutions to problems mainly faced by public administrations, city authorities, public transport companies, service providers and logistic operators. Related areas of interest are: land use and transportation planning, traffic control and ...
Stochastic model of radioiodine transport
Schwarz, G.; Hoffman, F.O.
1980-01-01
A research project has been underway at the Oak Ridge National Laboratory with the objective to evaluate dose assessment models and to determine the uncertainty associated with the model predictions. This has resulted in the application of methods to propagate uncertainties through models. Some techniques and results related to this problem are discussed
The Governor's Challenge: "Building a Stronger Virginia Today": Transportation Visions and Solutions
Baker, Susan
2008-01-01
Using STM(Science, Technology, Engineering, Math) education, this emerging workforce will have the chance to creatively solve one of Virginia's biggest challenges: TRANSPORTATION. - Students will be asked to develop alternative transportation systems for the state. This competition will enable teams to work with business mentors to design creative solutions for regional gridlocks and develop other transportation systems to more easily and expediently reach all parts of the Commonwealth.
Exact solutions for some discrete models of the Boltzmann equation
Cabannes, H.; Hong Tiem, D.
1987-01-01
For the simplest of the discrete models of the Boltzmann equation: the Broadwell model, exact solutions have been obtained by Cornille in the form of bisolitons. In the present Note, we build exact solutions for more complex models [fr
Reactive transport in a partially molten system with binary solid solution
Jordan, J.; Hesse, M. A.
2017-12-01
Melt extraction from the Earth's mantle through high-porosity channels is required to explain the composition of the oceanic crust. Feedbacks from reactive melt transport are thought to localize melt into a network of high-porosity channels. Recent studies invoke lithological heterogeneities in the Earth's mantle to seed the localization of partial melts. Therefore, it is necessary to understand the reaction fronts that form as melt flows across the lithological interface of a heterogeneity and the background mantle. Simplified melting models of such systems aide in the interpretation and formulation of larger scale mantle models. Motivated by the aforementioned facts, we present a chromatographic analysis of reactive melt transport across lithological boundaries, using theory for hyperbolic conservation laws. This is an extension of well-known linear trace element chromatography to the coupling of major elements and energy transport. Our analysis allows the prediction of the feedbacks that arise in reactive melt transport due to melting, freezing, dissolution and precipitation for frontal reactions. This study considers the simplified case of a rigid, partially molten porous medium with binary solid solution. As melt traverses a lithological contact-modeled as a Riemann problem-a rich set of features arise, including a reacted zone between an advancing reaction front and partial chemical preservation of the initial contact. Reactive instabilities observed in this study originate at the lithological interface rather than along a chemical gradient as in most studies of mantle dynamics. We present a regime diagram that predicts where reaction fronts become unstable, thereby allowing melt localization into high-porosity channels through reactive instabilities. After constructing the regime diagram, we test the one-dimensional hyperbolic theory against two-dimensional numerical experiments. The one-dimensional hyperbolic theory is sufficient for predicting the
New solution for transport and industrial noise protection through reflective noise barriers
Kralov Ivan
2017-01-01
Full Text Available A new solution for protection of transportation and industrial noise through reflective noise barriers is proposed and investigated in this study. The new solution combines the advantages of the known barriers and has its own advantages in addition. The preliminary results show a very good level of noise reduction for this type of barriers.
Large time behaviour of oscillatory nonlinear solute transport in porous media
Duijn, van C.J.; Zee, van der S.E.A.T.M.
2018-01-01
Oscillations in flow occur under many different situations in natural porous media, due to tidal, daily or seasonal patterns. In this paper, we investigate how such oscillations in flow affect the transport of an initially sharp solute front, if the solute undergoes nonlinear sorption and,
Tang, Yi.
1991-01-01
A computational procedure was developed in this study to provide flexibility needed in the application of three-dimensional groundwater flow and dissolved multicomponent solute transport simulations. In the first part of this study, analytical solutions were proposed for the dissolved single-component solute transport problem. These closed form solutions were developed for homogeneous but stratified porous media. This analytical model took into account two-dimensional diffusion-advection in the main aquifer layer and one-dimensional diffusion-advection in the adjacent aquitards, as well as first order radioactive decay and linear adsorption isotherm in both aquifer and aquitards. The associated analytical solutions for solute concentration distributions in the aquifer and aquitards were obtained using Laplace Transformation and Method of Separation of Variables techniques. Next, in order to analyze the problem numerically, a quasi-three-dimensional finite element algorithm was developed based on the multilayer aquifer concept. In this phase, advection, dispersion, adsorption and first order multi-species chemical reaction terms were included to the analysis. Employing this model, without restriction on groundwater flow pattern in the multilayer aquifer system, one may analyze the complex behavior of the groundwater flow and solute movement pattern in the system. These numerical models may be utilized as calibration tools in site characterization studies, or as predictive models during the initial stages of a typical site investigation study. Through application to several test and field problems, the usefulness, accuracy and efficiency of the proposed models were demonstrated. Comparison of results with analytical solution, experimental data and other numerical methods were also discussed
Zhang, Kejiang; Achari, Gopal; Li, Hua
2009-11-03
Traditionally, uncertainty in parameters are represented as probabilistic distributions and incorporated into groundwater flow and contaminant transport models. With the advent of newer uncertainty theories, it is now understood that stochastic methods cannot properly represent non random uncertainties. In the groundwater flow and contaminant transport equations, uncertainty in some parameters may be random, whereas those of others may be non random. The objective of this paper is to develop a fuzzy-stochastic partial differential equation (FSPDE) model to simulate conditions where both random and non random uncertainties are involved in groundwater flow and solute transport. Three potential solution techniques namely, (a) transforming a probability distribution to a possibility distribution (Method I) then a FSPDE becomes a fuzzy partial differential equation (FPDE), (b) transforming a possibility distribution to a probability distribution (Method II) and then a FSPDE becomes a stochastic partial differential equation (SPDE), and (c) the combination of Monte Carlo methods and FPDE solution techniques (Method III) are proposed and compared. The effects of these three methods on the predictive results are investigated by using two case studies. The results show that the predictions obtained from Method II is a specific case of that got from Method I. When an exact probabilistic result is needed, Method II is suggested. As the loss or gain of information during a probability-possibility (or vice versa) transformation cannot be quantified, their influences on the predictive results is not known. Thus, Method III should probably be preferred for risk assessments.
Majdalani, Samer; Guinot, Vincent; Delenne, Carole; Gebran, Hicham
2018-06-01
This paper is devoted to theoretical and experimental investigations of solute dispersion in heterogeneous porous media. Dispersion in heterogenous porous media has been reported to be scale-dependent, a likely indication that the proposed dispersion models are incompletely formulated. A high quality experimental data set of breakthrough curves in periodic model heterogeneous porous media is presented. In contrast with most previously published experiments, the present experiments involve numerous replicates. This allows the statistical variability of experimental data to be accounted for. Several models are benchmarked against the data set: the Fickian-based advection-dispersion, mobile-immobile, multirate, multiple region advection dispersion models, and a newly proposed transport model based on pure advection. A salient property of the latter model is that its solutions exhibit a ballistic behaviour for small times, while tending to the Fickian behaviour for large time scales. Model performance is assessed using a novel objective function accounting for the statistical variability of the experimental data set, while putting equal emphasis on both small and large time scale behaviours. Besides being as accurate as the other models, the new purely advective model has the advantages that (i) it does not exhibit the undesirable effects associated with the usual Fickian operator (namely the infinite solute front propagation speed), and (ii) it allows dispersive transport to be simulated on every heterogeneity scale using scale-independent parameters.
Analytical modelling of hydrogen transport in reactor containments
Manno, V.P.
1983-09-01
A versatile computational model of hydrogen transport in nuclear plant containment buildings is developed. The background and significance of hydrogen-related nuclear safety issues are discussed. A computer program is constructed that embodies the analytical models. The thermofluid dynamic formulation spans a wide applicability range from rapid two-phase blowdown transients to slow incompressible hydrogen injection. Detailed ancillary models of molecular and turbulent diffusion, mixture transport properties, multi-phase multicomponent thermodynamics and heat sink modelling are addressed. The numerical solution of the continuum equations emphasizes both accuracy and efficiency in the employment of relatively coarse discretization and long time steps. Reducing undesirable numerical diffusion is addressed. Problem geometry options include lumped parameter zones, one dimensional meshs, two dimensional Cartesian or axisymmetric coordinate systems and three dimensional Cartesian or cylindrical regions. An efficient lumped nodal model is included for simulation of events in which spatial resolution is not significant. Several validation calculations are reported
Model for cadmium transport and distribution in CHO cells
Hayden, T.L.; Turner, J.E.; Williams, M.W.; Cook, J.S.; Hsie, A.W.
1982-01-01
A compartmental model is developed to study the transport and distribution of cadmium in Chinese hamster ovary (CHO) cells. Of central importance to the model is the role played by sequestering components which bind free Cd/sup 2 +/ ions. The most important of these is a low-molecular-weight protein, metallothionein, which is produced by the cells in response to an increase in the cellular concentration of Cd/sup 2 +/. Monte Carlo techniques are used to generate a stochastic model based on existing experimental data describing the intracellular transport of cadmium between different compartments. This approach provides an alternative to the usual numerical solution of differential-delay equations that arise in deterministic models. Our model suggests subcellular structures which may be responsible for the accumulation of cadmium and, hence, could account for cadmium detoxification. 4 figures, 1 table.
Coupling Solute and Fine Particle Transport with Sand Bed Morphodynamics within a Field Experiment
Phillips, C. B.; Ortiz, C. P.; Schumer, R.; Jerolmack, D. J.; Packman, A. I.
2017-12-01
Fine suspended particles are typically considered to pass through streams and rivers as wash load without interacting with the bed, however experiments have demonstrated that hyporheic flow causes advective exchange of fine particles with the stream bed, yielding accumulation of fine particle deposits within the bed. Ultimately, understanding river morphodynamics and ecosystem dynamics requires coupling both fine particle and solute transport with bed morphodynamics. To better understand the coupling between these processes we analyze a novel dataset from a controlled field experiment conducted on Clear Run, a 2nd order sand bed stream located within the North Carolina coastal plain. Data include concentrations of continuously injected conservative solutes and fine particulate tracers measured at various depths within the stream bed, overhead time lapse images of bed forms, stream discharge, and geomorphological surveys of the stream. We use image analysis of bed morphodynamics to assess exchange, retention, and remobilization of solutes and fine particles during constant discharge and a short duration experimental flood. From the images, we extract a time series of bedform elevations and scour depths for the duration of the experiment. The high-resolution timeseries of bed elevation enables us to assess coupling of bed morphodynamics with both the solute and fine particle flux during steady state mobile bedforms prior to the flood and to changing bedforms during the flood. These data allow the application of a stochastic modeling framework relating bed elevation fluctuations to fine particle residence times. This combined experimental and modeling approach ultimately informs our ability to predict not only the fate of fine particulate matter but also associated nutrient and carbon dynamics within streams and rivers.
Investigating the effect of compression on solute transport through degrading municipal solid waste
Woodman, N.D., E-mail: n.d.woodman@soton.ac.uk; Rees-White, T.C.; Stringfellow, A.M.; Beaven, R.P.; Hudson, A.P.
2014-11-15
Highlights: • The influence of compression on MSW flushing was evaluated using 13 tracer tests. • Compression has little effect on solute diffusion times in MSW. • Lithium tracer was conservative in non-degrading waste but not in degrading waste. • Bromide tracer was conservative, but deuterium was not. - Abstract: The effect of applied compression on the nature of liquid flow and hence the movement of contaminants within municipal solid waste was examined by means of thirteen tracer tests conducted on five separate waste samples. The conservative nature of bromide, lithium and deuterium tracers was evaluated and linked to the presence of degradation in the sample. Lithium and deuterium tracers were non-conservative in the presence of degradation, whereas the bromide remained effectively conservative under all conditions. Solute diffusion times into and out of less mobile blocks of waste were compared for each test under the assumption of dominantly dual-porosity flow. Despite the fact that hydraulic conductivity changed strongly with applied stress, the block diffusion times were found to be much less sensitive to compression. A simple conceptual model, whereby flow is dominated by sub-parallel low permeability obstructions which define predominantly horizontally aligned less mobile zones, is able to explain this result. Compression tends to narrow the gap between the obstructions, but not significantly alter the horizontal length scale. Irrespective of knowledge of the true flow pattern, these results show that simple models of solute flushing from landfill which do not include depth dependent changes in solute transport parameters are justified.
Dopamine transporter SPECT imaging of the peroral addicts of compound codeine phosphate solution
Sun Taotao; Hu Shu; Jia Shaowei; Chen Qing; Fan Rong
2010-01-01
Objective: To study the damage to striatum in patients perorally addicted to compound codeine phosphate solution by using the brain dopamine transporter SPECT imaging. Methods: Patients perorally addicted to compound codeine phosphate solution (n = 29) and addicted to heroin (n = 27), as well as healthy volunteers (n = 31) were included in the study. Each of them underwent dopamine transporter (DAT) SPECT imaging with 99 Tc m -2β-[N, N'-bis-( 2- mercaptoethyl ) ethylenediamino] methyl, 3β-(4-chlorophenyl)tropane ( 99 Tc m -TRODAT-1). The striatum volume (V, cm 3 ), mass (m, g) and radioactivity ratio (Ra) of striatum to whole brain were calculated using physio-mathematical modeling method. Results: Bilateral striatum of healthy volunteers showed typical 'panda eyes' pattern and the distribution of DAT was uniform and symmetrical. Bila