Migration Flows: Measurement, Analysis and Modeling
Willekens, F.J.; White, Michael J.
2016-01-01
This chapter is an introduction to the study of migration flows. It starts with a review of major definition and measurement issues. Comparative studies of migration are particularly difficult because different countries define migration differently and measurement methods are not harmonized.
National and international graduate migration flows.
Mosca, Irene; Wright, Robert E
2010-01-01
This article examines the nature of national and international graduate migration flows in the UK. Migration equations are estimated with microdata from a matched dataset of Students and Destinations of Leavers from Higher Education, information collected by the Higher Education Statistical Agency. The probability of migrating is related to a set of observable characteristics using multinomial logit regression. The analysis suggests that migration is a selective process with graduates with certain characteristics having considerably higher probabilities of migrating, both to other regions of the UK and abroad.
A Missing Element in Migration Theories.
Massey, Douglas S
2015-09-01
From the mid-1950s through the mid1980s, migration between Mexico and the United States constituted a stable system whose contours were shaped by social and economic conditions well-theorized by prevailing models of migration. It evolved as a mostly circular movement of male workers going to a handful of U.S. states in response to changing conditions of labor supply and demand north and south of the border, relative wages prevailing in each nation, market failures and structural economic changes in Mexico, and the expansion of migrant networks following processes specified by neoclassical economics, segmented labor market theory, the new economics of labor migration, social capital theory, world systems theory, and theoretical models of state behavior. After 1986, however, the migration system was radically transformed, with the net rate of migration increasing sharply as movement shifted from a circular flow of male workers going a limited set of destinations to a nationwide population of settled families. This transformation stemmed from a dynamic process that occurred in the public arena to bring about an unprecedented militarization of the Mexico-U.S. border, and not because of shifts in social, economic, or political factors specified in prevailing theories. In this paper I draw on earlier work to describe that dynamic process and demonstrate its consequences, underscoring the need for greater theoretical attention to the self-interested actions of politicians, pundits, and bureaucrats who benefit from the social construction and political manufacture of immigration crises when none really exist.
The European Crisis and Migration to Germany: Expectations and the Diversion of Migration Flows
Brücker, Herbert; Bertoli, Simone; Fernández-Huertas Moraga, Jesús
2013-01-01
The European crisis has diverted migration flows away from countries affected by the recession towards Germany. The diversion process creates a challenge for traditional discrete-choice models that assume that only bilateral factors account for dyadic migration rates. This paper shows how taking into account the sequential nature of migration decisions leads to write the bilateral migration rate as a function of expectations about the evolution of economic conditions in alternative destinatio...
Migration of actinide elements in representative US soils
International Nuclear Information System (INIS)
Sheppard, J.C.; Campbell, M.J.; Kittrick, J.A.; Hardt, T.L.
1981-01-01
Diffusion data indicate the Am, Cm, and Np migrate 1.2, 0.8, and 26 centimeters, respectively, in a thousand years. Thus, excluding mass transport by moving water or wind, actinide elements, such as Cm, Am, and Np that find their way to the soil-squatic environment are relatively immobile. Measured diffusion coefficients, corrected for distribution between the aqueous and soil phases, tortuosity, negative absorption, and relative fluidity are in reasonable agreement with aqueous diffusion coefficients. However, agreement depends strongly on measurement method used to determine distribution ratios
Semiflexible polymer conformation, distribution and migration in microcapillary flows
International Nuclear Information System (INIS)
Chelakkot, Raghunath; Gompper, Gerhard; Winkler, Roland G
2011-01-01
The flow behavior of a semiflexible polymer in microchannels is studied using multiparticle collision dynamics, a particle-based hydrodynamic simulation technique. Conformations, distributions, and radial cross-streamline migration are investigated for various bending rigidities, with persistence lengths L p in the range 0.5 ≤ L p /L r ≤ 30. The flow behavior is governed by the competition between a hydrodynamic lift force and steric repulsion from the wall, which lead to migration away from the wall, and a locally varying flow induced orientation, which drives the polymer away from the channel center and towards the wall. The different dependences of these effects on the polymer bending rigidity and the flow velocity results in a complex dynamical behavior. However, a generic effect is the appearance of a maximum in the monomer and the center-of-mass distributions, which occurs at the channel center for small flow velocities, but moves off-center at higher velocities.
Interaction Between Flow Elements in Large Enclosures
DEFF Research Database (Denmark)
Heiselberg, Per
and if this influences the overall air flow pattern in the enclosure. The main emphasis has been put on the pathways of chilled free air jets and whether the convective flows from both distributed and concentrated heat sources affect the pathway of the jet and the air flow pattern in the enclosure as a function......In this paper experiments in a scale model are used as a first attempt to investigate how different flow elements such as supply air jets, thermal plumes and free convection flows interact with each other in a large enclosure, if the path of each individual flow element changes...... of the location of the heat source and as a function of the heat supplied by the source....
European Integration, Labour Market Dynamics and Migration Flows
Directory of Open Access Journals (Sweden)
Martinoia, Michela
2011-06-01
Full Text Available The paper has two objectives. Firstly, we wish to evaluate whether a greater economic integration has effects, and of what type, on migration flows from Central and Eastern Europe (New Member States of the EU, NMS towards the fifteen countries of the European Union (EU-15. Secondly, we wish to understand what effect the migration flows from the NMS have on the labour market of the receiving countries in the EU-15. The most suitable theoretical context that seems to summarise European labour market characteristics is that of the insider/outsider model by Layard, Nickell and Jackman (Layard et al., 1991. We have modified the above mentioned model by introducing two innovations. Firstly, we constructed three measures that act as a proxy for economic integration: the Intra Regional Trade Index (IRTI, Global Trade Index (GTI and Financial Market Integration (FMI. Then we placed the three indicators into the insider/outsider model to arrive at a modified version of Layard, Nickell and Jackman (Layard et al., 1991. The second innovative contribution was the introduction of an equation modelling migration flows. The creation of this equation is inspired by the neo-classical approach to migration theory (Harris-Todaro, 1970. The theoretical model, based on rational expectations, has been solved to find the equilibrium solution and the impact multipliers. We then carried out an empirical analysis, which involved estimating a Structural Vector Autoregression Model (SVAR. The aim of this estimation was to evaluate, on the one hand, the effect that greater European integration (a positive shock to the integration indicators has on migration flows, and, on the other, to measure the type of effect that migration flows could have on the labour market of the EU-15 countries, considered as a single entity. The results of our empirical evidence show that economic integration does generate significant effects on migration flows from the enlargement countries
Waste migration in shallow burial sites under unsaturated flow conditions
International Nuclear Information System (INIS)
Eicholz, G.G.; Whang, J.
1987-01-01
Unsaturated conditions prevail in many shallow-land burial sites, both in arid and humid regions. Unless a burial site is allowed to flood and possibly overflow, a realistic assessment of any migration scenario must take into account the conditions of unsaturated flow. These are more difficult to observe and to model, but introduce significant changes into projected rates of waste leaching and waste migration. Column tests have been performed using soils from the Southeastern coastal plain to observe the effects of varying degrees of ''unsaturation'' on the movement of radioactive tracers. The moisture content in the columns was controlled by maintaining various levels of hydrostatic suction on soil columns whose hydrodynamic characteristics had been determined carefully. Tracer tests, employing Cs-137, I-131 and Ba-133 were used to determine migration profiles and to follow their movement down the column for different suction values. A calculational model has been developed for unsaturated flow and seems to match the observations fairly well. It is evident that a full description of migration processes must take into account the reduced migration rates under unsaturated conditions and the hysteresis effects associated with wetting-drying cycles
Directory of Open Access Journals (Sweden)
M. A. Brovelli
2017-07-01
Full Text Available Recent years have seen a noticeable growth in migration flows from Africa and Middle East to Southern Europe, thus generating a remarkable increase of attention on media and public opinion, sometimes resulting in stereotypes and prejudices. Funded by the European Commission – Joint Research Centre through the MYGEOSS program, MIGRation pATtterns in Europe (MIGRATE aims at educating the citizens about migration fluxes in Europe using a gamification approach based on a trivia game. MIGRATE is completely developed with Free and Open Source Software. On the server-side Django is used to define the models that handle all the required data and tables are created in a PostgreSQL database. Questions and answers are sent in JSON format to the client, while the geospatial layers in GeoJSON format are rendered on the map interface using OpenLayers 3. Bootstrap, HTML5 and CSS3 are used for responsive design, while the jQuery library is used to ease the JavaScript programming. All the data sources used within MIGRATE are available as full and open access with no restrictions for reuse, except for the obligation to mention the source of the input data. Exploited data sources include OpenStreetMap for geospatial information, and UNHCR, IOM, Eurostat and The Migrant’s Files project for non-geospatial information. Overall, data shows how the users’ perceptions change while playing and that players’ awareness of migration-related problems increases with the number of games played. The source code of MIGRATE and the collected data are available respectively under the EU Public License (EUPL and the CC BY 4.0 license.
Rodriguez Chavez, E
1996-01-01
"The article argues that the rafters crisis of 1994 and the resulting migration agreements between the United States and Cuba in 1994 and 1995 were a radical turn in policies and migration flows between the two countries. The article also describes the general evolution of Cuban migration flows towards the U.S. from the 1984 bilateral agreement up to 1996. As a context, it describes the structural elements of recent Cuban emigration and the place Cubans occupy in the general immigration from Latin America and the Caribbean." (EXCERPT)
Boundary element method for internal axisymmetric flow
Directory of Open Access Journals (Sweden)
Gokhman Alexander
1999-01-01
Full Text Available We present an accurate fast method for the computation of potential internal axisymmetric flow based on the boundary element technique. We prove that the computed velocity field asymptotically satisfies reasonable boundary conditions at infinity for various types of inlet/exit. Computation of internal axisymmetric potential flow is an essential ingredient in the three-dimensional problem of computation of velocity fields in turbomachines. We include the results of a practical application of the method to the computation of flow in turbomachines of Kaplan and Francis types.
Migration Flows from the Perspective of Sending and Receiving Countries
DEFF Research Database (Denmark)
Pytlikova, Mariola
There are two specific phenomena that have had a large influence on the development in international migration during the last decades. First, while labor migration flows were dominating in the past, refugee immigrants and family reunion migrants from less developed non-Western countries have been......, the former communist countries have become a relatively new and large source of immigration. In my PhD thesis I analyze the recent developments in international migration by using a rich dataset, which I collected myself by contacting national statistical offices. I use state-of-art econometric tools in my...... area with the free movement of labor. The results of my analyses show that migrants respond strongly to the interregional differences in wages. On the other hand, the districts' unemployment rates do not seem to play an important role. Further, on average Czechs prefer to move to regions near...
Inertial migration of particles in Taylor-Couette flows
Majji, Madhu V.; Morris, Jeffrey F.
2018-03-01
An experimental study of inertial migration of neutrally buoyant particles in the circular Couette flow (CCF), Taylor vortex flow (TVF) and wavy vortex flow (WVF) is reported. This work considers a concentric cylinder Taylor-Couette device with a stationary outer cylinder and rotating inner cylinder. The device has a radius ratio of η = ri/ro = 0.877, where ri and ro are the inner and outer radii of the flow annulus. The ratio of the annular width between the cylinders (δ = ro - ri) and the particle diameter (dp) is α = δ/dp = 20. For η = 0.877, the flow of a Newtonian fluid undergoes transitions from CCF to TVF and TVF to WVF at Reynolds numbers Re = 120 and 151, respectively, and for the dilute suspensions studied here, these critical Reynolds numbers are almost unchanged. In CCF, particles were observed to migrate, due to the competition between the shear gradient of the flow and the wall interactions, to an equilibrium location near the middle of the annulus with an offset toward the inner cylinder. In TVF, the vortex motion causes the particles to be exposed to the shear gradient and wall interactions in a different manner, resulting in a circular equilibrium region in each vortex. The radius of this circular region grows with increase in Re. In WVF, the azimuthal waviness results in fairly well-distributed particles across the annulus.
International Nuclear Information System (INIS)
Ahmed, M.A.
2012-01-01
Vertical migration of pollutants through unsaturated zone is a complicated process and is affected by a number of factors like type of soil, its chemical properties, or organic matter content, in addition to climatic conditions and biological activity of microorganisms in soil. Soil properties that influence water movement through unsaturated zone are important for determining flow paths, reactions between soil and pollutants and the ultimate destination of these pollutants, and may improve the diagnosis of the potential pollution risk. Three soil cores were sampled to a depth up to 100 cm from cultivated clayey soil, sewage irrigated sandy soil and fertilized sandy soil. The samples were collected at intervals of 5 or 10 cm. The δ 13 C signature of the soil shifted significantly towards that of C 3 -type vegetation in soil cores. The general trend toward heavier 13 C enrichment with depth could be due to isotopic fractionation occurring during decomposition of soil organic matters. Increased δ 15 N with depth in the soil cores suggests that microbial mineralization, denitrification, or volatilization processes caused the enriched δ 15 N signatures. Decreasing nitrogen percent and nitrate values with depth also help support the idea of microbiological processes. The results indicate that concentrations of major and trace elements varied widely among the different soil types and decreased with depths in the studied soil profile. The accumulation pattern for these elements in the soil profiles follows the order: Co < Ni < Mo < Ag < Sr < V < Cu < Cr < Zn < Mn < B < Mg < Al < Fe. The relationships between element concentrations against ph and organic matter contents show antithetical relationships and suggest evidence that these elements arise from anthropogenic input. The results of this study show that there exists risk for the environment due to notable migration of pollutants through the unsaturated zone and that the migrations were also observed to be highly
Semiflexible polymer conformation, distribution and migration in microcapillary flows
Energy Technology Data Exchange (ETDEWEB)
Chelakkot, Raghunath; Gompper, Gerhard [Institut fuer Festkoerperforschung, Forschungszentrum Juelich, 52425 Juelich (Germany); Winkler, Roland G [Institute for Advanced Simulation, Forschungszentrum Juelich, 52425 Juelich (Germany)
2011-05-11
The flow behavior of a semiflexible polymer in microchannels is studied using multiparticle collision dynamics, a particle-based hydrodynamic simulation technique. Conformations, distributions, and radial cross-streamline migration are investigated for various bending rigidities, with persistence lengths L{sub p} in the range 0.5 {<=} L{sub p}/L{sub r} {<=} 30. The flow behavior is governed by the competition between a hydrodynamic lift force and steric repulsion from the wall, which lead to migration away from the wall, and a locally varying flow induced orientation, which drives the polymer away from the channel center and towards the wall. The different dependences of these effects on the polymer bending rigidity and the flow velocity results in a complex dynamical behavior. However, a generic effect is the appearance of a maximum in the monomer and the center-of-mass distributions, which occurs at the channel center for small flow velocities, but moves off-center at higher velocities.
International migration flows. Framework for understanding and current features.
Directory of Open Access Journals (Sweden)
Colectivo IOÉ
2016-10-01
Full Text Available The present article aims to outline a framework for the understanding of the present international migratory flows as well as to outline their main traits. In order to do this, we first group together the different migratory flows produced since the sixteenth century up to the mid seventies in the twentieth century, stopping then for a closer look at the present situation which register the impact of economic globalization, translating it into an increase of said flows and, above all, to their enormous diversification. To end, we make a brief balance of the present period and a critical evaluation on the meaning of one of the flows which attracts most attention, economic migrations south-north, because these are the ones which have the most impact on developed countries.
Finite element methods for incompressible flow problems
John, Volker
2016-01-01
This book explores finite element methods for incompressible flow problems: Stokes equations, stationary Navier-Stokes equations, and time-dependent Navier-Stokes equations. It focuses on numerical analysis, but also discusses the practical use of these methods and includes numerical illustrations. It also provides a comprehensive overview of analytical results for turbulence models. The proofs are presented step by step, allowing readers to more easily understand the analytical techniques.
Redox flow batteries having multiple electroactive elements
Energy Technology Data Exchange (ETDEWEB)
Wang, Wei; Li, Liyu; Yang, Zhenguo; Nie, Zimin
2018-05-01
Introducing multiple redox reactions with a suitable voltage range can improve the energy density of redox flow battery (RFB) systems. One example includes RFB systems utilizing multiple redox pairs in the positive half cell, the negative half cell, or in both. Such RFB systems can have a negative electrolyte, a positive electrolyte, and a membrane between the negative electrolyte and the positive electrolyte, in which at least two electrochemically active elements exist in the negative electrolyte, the positive electrolyte, or both.
Construction of the migration flows forecasting into Russian regions
Directory of Open Access Journals (Sweden)
Aleksandr Aleksandrovich Tarasyev
2013-06-01
Full Text Available This paper presents a dynamic model that can predict the dynamics of migration flows between source countries and host regions, as well as the dynamics of wage levels there. The model is constructed within the framework of neoclassical economics and human capital theory in continuous time. Thanks to liberalization of migration policy in Russia in 2007, the model could be successfully employed to Russian regions and the Commonwealth of Independent States (CIS, which have visa-free entry regulations with the Russian Federation. Employing the model on statistical data, we forecast the number and origin composition of foreign labor force from the CIS into Russian regions for 2010-2016. The purpose of our further research is to classify migrants by skills
Kenyon, Patricia M.
1993-01-01
Trace element concentrations and isotopic ratios are frequently used to study the behavior of high-temperature fluids in both metamorphic and igneous systems. Many theoretical formulations of the effects of fluid migration on trace elements have assumed instantaneous reequilibration between the migrating fluid and the solid material through which it is passing. This paper investigates the additional effects which arise when equilibration is not instantaneous due to a limited rate of diffusion in the solid, using an analytical steady state solution to a set of partial differential equations describing the exchange of trace elements between the fluid and the solid during the migration of the fluid.
International Nuclear Information System (INIS)
Soares, Eufemia Paez
2008-01-01
Over the past few years, problems related to food contamination by substances or elements that can be a risk to human health have became a concern, not only to government authorities, but to the general population as well. Within this context, plastic packaging can constitute a source of food contamination since plastic manufacturing processes involve the use of catalysts and different types of additives that may contain toxic elements. When food comes into contact with this packaging, components of the package may migrate to the food. In order to control the material used as food packaging, the National Health Surveillance Agency (ANVISA) in Brazil, has established boundary values of migrant substances and procedures to determine migration from plastic packagings to food. In this study the radiometric method was evaluated for element migration determination from plastic packaging to food simulating or to the food itself. This radiometric method consisted in irradiating plastic packaging samples with a thermal neutron flux from the IEA-R1 nuclear research reactor in order to produce radionuclides of elements present in the packagings. The irradiated plastic was then exposed to food simulant or food for element migration. Gamma ray spectrometry was used to measure radioactivity in the simulant or food in order to quantify the migration. The food simulating types and experimental conditions were established according to the ANVISA regulations. Element migration was studied for plastic packaging used for soft drinks, drinking water, milk, dairy products, juices and fatty foods. In the instrumental neutron activation analysis of these packagings the presence of As, Cd, Cr, Co and Sb II was verified. Results obtained from the migration experiments by the radiometric method indicated that Cd, Co, Cr and Sb present in these plastics migrated to the simulant or to the food. In some packagings, the migration of only some of these elements was observed. In these cases the
McNally, Colin P.; Nelson, Richard P.; Paardekooper, Sijme-Jan
2018-04-01
We examine the migration of low mass planets in laminar protoplanetary discs, threaded by large scale magnetic fields in the dead zone that drive radial gas flows. As shown in Paper I, a dynamical corotation torque arises due to the flow-induced asymmetric distortion of the corotation region and the evolving vortensity contrast between the librating horseshoe material and background disc flow. Using simulations of laminar torqued discs containing migrating planets, we demonstrate the existence of the four distinct migration regimes predicted in Paper I. In two regimes, the migration is approximately locked to the inward or outward radial gas flow, and in the other regimes the planet undergoes outward runaway migration that eventually settles to fast steady migration. In addition, we demonstrate torque and migration reversals induced by midplane magnetic stresses, with a bifurcation dependent on the disc surface density. We develop a model for fast migration, and show why the outward runaway saturates to a steady speed, and examine phenomenologically its termination due to changing local disc conditions. We also develop an analytical model for the corotation torque at late times that includes viscosity, for application to discs that sustain modest turbulence. Finally, we use the simulation results to develop torque prescriptions for inclusion in population synthesis models of planet formation.
Peng, Q.; Liang, Y.
2008-12-01
To better understand the melting processes beneath the mid-ocean ridge, we developed a simple model for trace element fractionation during concurrent melting and melt migration in an upwelling steady-state mantle column. Based on petrologic considerations, we divided the upwelling mantle into two regions: a double- lithology upper region where high permeability dunite channels are embedded in a lherzolite/harzburgite matrix, and a single-lithology lower region that consists of partially molten lherzolite. Melt generated in the single lithology region migrates upward through grain-scale diffuse porous flow, whereas melt in the lherzolite/harzburgite matrix in the double-lithology region is allowed to flow both vertically through the overlying matrix and horizontally into its neighboring dunite channels. There are three key dynamic parameters in our model: degree of melting experienced by the single lithology column (Fd), degree of melting experienced by the double lithology column (F), and a dimensionless melt suction rate (R) that measures the accumulated rate of melt extraction from the matrix to the channel relative to the accumulated rate of matrix melting. In terms of trace element fractionation, upwelling and melting in the single lithology column is equivalent to non-modal batch melting (R = 0), whereas melting and melt migration in the double lithology region is equivalent to a nonlinear combination of non-modal batch and fractional melting (0 abyssal peridotite, we showed, with the help of Monte Carlo simulations, that it is difficult to invert for all three dynamic parameters from a set of incompatible trace element data with confidence. However, given Fd, it is quite possible to constrain F and R from incompatible trace element abundances in residual peridotite. As an illustrative example, we used the simple melting model developed in this study and selected REE and Y abundance in diopside from abyssal peridotites to infer their melting and melt migration
International Nuclear Information System (INIS)
Soares, Eufemia Paez; Saiki, Mitiko; Wiebeck, Helio
2005-01-01
In the present study a radiometric method was established to determine the migration of elements from food plastic packagings to a simulated acetic acid solution. This radiometric method consisted of irradiating plastic samples with neutrons at IEA-R1 nuclear reactor for a period of 16 hours under a neutron flux of 10 12 n cm -2 s -1 and, then to expose them to the element migration into a simulated solution. The radioactivity of the activated elements transferred to the solutions was measured to evaluate the migration. The experimental conditions were: time of exposure of 10 days at 40 deg C and 3% acetic acid solution was used as simulated solution, according to the procedure established by the National Agency of Sanitary Monitoring (ANVISA). The migration study was applied for plastic samples from soft drink and juice packagings. The results obtained indicated the migration of elements Co, Cr and Sb. The advantage of this methodology was no need to analyse the blank of simulantes, as well as the use of high purity simulated solutions. Besides, the method allows to evaluate the migration of the elements into the food content instead of simulated solution. The detention limits indicated high sensitivity of the radiometric method. (author)
Application of INAA in monitoring vertical migration of elements in weathering zone
International Nuclear Information System (INIS)
Frana, J.; Mastalka, A.; Henes, J.
1983-01-01
The vertical migration of elements is studied in two types of Czechoslovak soils formed on loess. The INAA method is used to determine the total value of ca 40 elements in soils. Processed are relative errors of determination and the concentrations of elements to depths of 150 cm. Tables show the distribution of elements of rare earths according to genetic horizons, graphically presented is the vertical distribution of elements with concentrations exceeding 0.1 weight %. Soil enrichment or depletion with trace elements as compared with bedrock is shown on the examples of Co, Mn and Zn. (author)
Trace element and isotopic effects arising from magma migration beneath mid-ocean ridges
International Nuclear Information System (INIS)
Kenyon, P.M.
1990-01-01
The trace element concentrations and isotopic ratios in the magma erupted on mid-ocean ridges may differ from those in the source material due to physical effects such as porous flow dispersion, exchange of trace elements between the fluid and solid phases during magma migration, and convective mixing in magma chambers. These differences are in addition to those produced by better known processes such as fractional crystallization and partial melting. The effects of the three former processes are described. It is predicted that magma typically reaches the sub-ridge magma chambers with a spatial heterogeneity only slightly reduced from that of the source material, but with a subdued variation in time. Convective mixing then further reduces the spatial heterogeneity. Application of the results for convective mixing to a recent Fourier analysis of 87 Sr/ 86 Sr variations along the Mid-Atlantic Ridge suggests that the falloff in amplitude of variation observed with decreasing wavelength in the Mid-Atlantic Ridge data cannot be explained by convective mixing in magma chambers. Instead, it is postulated that this falloff is due to the mechanics of the production and/or the solid-state convective mixing of chemical and isotopic heterogeneities in the solid mantle. (orig.)
Trace Elements in Basalts From the Siqueiros Fracture Zone: Implications for Melt Migration Models
Pickle, R. C.; Forsyth, D. W.; Saal, A. E.; Nagle, A. N.; Perfit, M. R.
2008-12-01
Incompatible trace element (ITE) ratios in MORB from a variety of locations may provide insights into the melt migration process by constraining aggregated melt compositions predicted by mantle melting and flow models. By using actual plate geometries to create a 3-D thermodynamic mantle model, melt volumes and compositions at all depths and locations may be calculated and binned into cubes using the pHMELTS algorithm [Asimow et al., 2004]. These melts can be traced from each cube to the surface assuming several migration models, including a simplified pressure gradient model and one in which melt is guided upwards by a low permeability compacted layer. The ITE ratios of all melts arriving at the surface are summed, averaged, and compared to those of the actual sample compositions from the various MOR locales. The Siqueiros fracture zone at 8° 20' N on the East Pacific Rise (EPR) comprises 4 intra-transform spreading centers (ITSCs) across 140 km of offset between two longer spreading ridges, and is an excellent study region for several reasons. First, an abundance of MORB data is readily available, and the samples retrieved from ITSCs are unlikely to be aggregated in a long-lived magma chamber or affected by along-axis transport, so they represent melts extracted locally from the mantle. Additionally, samples at Siqueiros span a compositional range from depleted to normal MORB within the fracture zone yet have similar isotopic compositions to samples collected from the 9-10° EPR. This minimizes the effect of assuming a uniform source composition in our melting model despite a heterogeneous mantle, allowing us to consistently compare the actual lava composition with that predicted by our model. Finally, it has been demonstrated with preliminary migration models that incipient melts generated directly below an ITSC may not necessarily erupt at that ITSC but migrate laterally towards a nearby ridge due to enhanced pressure gradients. The close proximity of the
Evaluation of chemical elements migration from food packaging plastics into food
International Nuclear Information System (INIS)
Kamiya, Adriana M.; Fulfaro, Roberto; Saiki, Mitiko
2000-01-01
This work presents results of As, Cd, Co, Cr, Sb, Se, Sn, and Zn obtained in the analysis of plastics from food packing materials by instrumental neutron activation analysis. The radiometric method was also applied to evaluate the migration of Co and Sb from the plastic into the food simulant. The possible sources of the toxic elements in plastic materials and the advantages of radiometric method in the migration evaluation are discussed. (author)
Adsorption and migration of transplutonium elements in environmental systems
Energy Technology Data Exchange (ETDEWEB)
Balukova, V.D.; Kaymin, E.P.; Ushakov, S.I.
Behavior of long decay-time transuranium and transplutonium elements in natural systems was addressed. The most dangerous among them are /sup 238/Np, /sup 241/ /sup 243/Am, /sup 244/ /sup 245/ /sup 246/Cm, and /sup 239/ /sup 240/ /sup 242/ /sup 244/Pu. Their transportation through natural deposits is tightly connected with ground water movements. The principal parameters determining behavior of these radionuclides in ground formations are coefficients of isotope distribution between various phases, adsorption capacities of component minerals, effective porosity, filtration coefficients of the liquid, etc. These data are presented in tabular and graphic forms. In carbonate-bicarbonate ground waters containing silicate minerals, the content of radionuclides could be quickly decreased by hydrolysis and formation of insoluble precipitates. 2 references, 3 figures.
Zhang, Ling; Liu, Shuming; Liu, Wenjun
2014-02-01
Polymeric pipes, such as unplasticized polyvinyl chloride (uPVC) pipes, polypropylene random (PPR) pipes and polyethylene (PE) pipes are increasingly used for drinking water distribution lines. Plastic pipes may include some additives like metallic stabilizers and other antioxidants for the protection of the material during its production and use. Thus, some compounds can be released from those plastic pipes and cast a shadow on drinking water quality. This work develops a new procedure to investigate three types of polymer pipes (uPVC, PE and PPR) with respect to the migration of total organic carbon (TOC) into drinking water. The migration test was carried out in stagnant conditions with two types of migration processes, a continuous migration process and a successive migration process. These two types of migration processes are specially designed to mimic the conditions of different flow manners in drinking water pipelines, i.e., the situation of continuous stagnation with long hydraulic retention times and normal flow status with regular water renewing in drinking water networks. The experimental results showed that TOC release differed significantly with different plastic materials and under different flow manners. The order of materials with respect to the total amount of TOC migrating into drinking water was observed as PE > PPR > uPVC under both successive and continuous migration conditions. A higher amount of organic migration from PE and PPR pipes was likely to occur due to more organic antioxidants being used in pipe production. The results from the successive migration tests indicated the trend of the migration intensity of different pipe materials over time, while the results obtained from the continuous migration tests implied that under long stagnant conditions, the drinking water quality could deteriorate quickly with the consistent migration of organic compounds and the dramatic consumption of chlorine to a very low level. Higher amounts of TOC
Emerging migration flows in a changing climate in dryland Africa
Kniveton, Dominic R.; Smith, Christopher D.; Black, Richard
2012-06-01
Fears of the movement of large numbers of people as a result of changes in the environment were first voiced in the 1980s (ref. ). Nearly thirty years later the numbers likely to migrate as a result of the impacts of climate change are still, at best, guesswork. Owing to the high prevalence of rainfed agriculture, many livelihoods in sub-Saharan African drylands are particularly vulnerable to changes in climate. One commonly adopted response strategy used by populations to deal with the resulting livelihood stress is migration. Here, we use an agent-based model developed around the theory of planned behaviour to explore how climate and demographic change, defined by the ENSEMBLES project and the United Nations Statistics Division of the Department of Economic and Social Affairs, combine to influence migration within and from Burkina Faso. The emergent migration patterns modelled support framing the nexus of climate change and migration as a complex adaptive system. Using this conceptual framework, we show that the extent of climate-change-related migration is likely to be highly nonlinear and the extent of this nonlinearity is dependent on population growth; therefore supporting migration policy interventions based on both demographic and climate change adaptation.
International Nuclear Information System (INIS)
Soares, Eufemia Paez; Saki, Mitiko; Silva, Leonardo G.A.
2007-01-01
Brazilian plastic production for food packagings, in recent years, has grown in the same proportion as food consumption. Considering that the plastic manufacturing involves catalytic processes and the use of additives, when the foods are in direct contact with these materials, the components present in plastics may migrate to the food. The Brazilian Health Surveillance Agency (ANVISA) has established boundary-values of migrants as well as procedures to evaluate migration of elements and substances from plastic packaging to food. In this study elemental composition of poly (ethylene terephthalate) - PET - packaging and results of elemental migration were obtained. Instrumental Neutron Activation Analysis (INAA) was used to determine elemental concentrations in PET packagings and the radiometric method was applied for elemental migration determination. This radiometric method consisted of irradiating the PET samples with neutrons, followed by migration exposition and radioactivity measurement in food-simulated solution. Experimental conditions used for migration were 10 days exposure period at 40 deg C. Migration was evaluated for soft drink, juice and water PET packaging. The analytical results indicated that PET packagings contain Co and Sb and those elements are transferred to the simulated solutions. However, these migration results were lower than the maximum tolerance values established by ANVISA. The migration detection limits also indicated high sensitivity of the radiometric method. (author)
Management of migration flows in the European Union
Directory of Open Access Journals (Sweden)
Dana Larisa Drugă
2011-12-01
Full Text Available International migration can contribute to the economic growth of the European Union (EU as a whole, as well as provide resources for migrants and their home countries, and thus contribute to their development. It can be an opportunity, because it is a factor of human and economic exchange and enables people to achieve what they aspire to. However, there is a need to manage migration in a manner that takes account of Europe's reception capacity in terms of its labour market, housing and health, education and social services, while protecting migrants against possible exploitation by criminal networks.
A STUDY ON THE INTERNAL MIGRATION FLOWS IN TURKEY: LOWRY HYPOTHESIS
Directory of Open Access Journals (Sweden)
FERHAT TOPBAŞ
2013-06-01
Full Text Available The purpose of this study is to re-examine Lowry hypothesis that were examined for Turkey in period of 1965–1980 by Gedik (1992 and period of 1985–1990 by Yamak and Küçükkale (2001 by using The Census of Population 1975, 1980, 1985, 1990 and 2000 in Turkey. For this reason, the relationships between in-migration and out-migration and net migration have investigated with population size, net migration rate and per capita income factors. Analysis that involve in all provinces called general model is not considered in social, economic and urban development factors. In addition, estimated restriction models that are considered urban development are involved population, net migration rate and per capita income factors. In conclusion we have exposed comparatively relationship between internal migration flows and urban development frame of estimated models.
Finite element analysis of nonlinear creeping flows
International Nuclear Information System (INIS)
Loula, A.F.D.; Guerreiro, J.N.C.
1988-12-01
Steady-state creep problems with monotone constitutive laws are studied. Finite element approximations are constructed based on mixed Petrov-Galerkin formulations for constrained problems. Stability, convergence and a priori error estimates are proved for equal-order discontinuous stress and continuous velocity interpolations. Numerical results are presented confirming the rates of convergence predicted in the analysis and the good performance of this formulation. (author) [pt
Fine element (F.E.) modelling of hydrogen migration and blister formation in PHWR coolant channels
International Nuclear Information System (INIS)
Prasad, P.S.; Dutta, B.K.; Sinha, R.K.; Kushwaha, H.S.; Mahajan, S.C.; Kakodkar, A.
1995-01-01
The formation of a cold spot in pressure tube due to its contact with calandria tube of PHWR coolant results in the migration of Hydrogen in pressure tube towards contact zone from its surrounding material. A 3-D finite element code SPARSH is developed to model the hydrogen redistribution and consequent hydride blister formation due to thermal and Hydrogen concentration gradients. In the present paper, the details and performance of this code are presented. (author). 6 refs., 2 figs
Radiochemical approaches to the migration of elements from a radwaste repository
International Nuclear Information System (INIS)
Guillaumont, R.
1993-01-01
Underground high-level or intermediary-level alpha radwaste repositories will contain tons to hundreds of tons of anthropogenic elements. It is predicted that the release of the elements into the far field will be mainly dependent upon the 'solubilities', sums of the concentrations of soluble species and colloidal/pseudo colloidal forms, of expected near field compounds. On the other hand, safety assessments, based on computation models of migration, show that elements in the discharged water into the biosphere will be at tracer level, or at least, at trace levels. Kinetic and thermodynamic aspects of the processes in which elements will be involved during their migration are discussed together with the change in their concentrations, over several orders of magnitude. It is shown that special attention must be given to predict the behaviour of the elements in the far field from what we know from classical chemistry, and that more experimental data must be obtained to improve the models. (author). 31 refs., 5 figs., 4 tabs
Silva, Kênia Lara; de Sena, Roseni Rosângela; Tavares, Tatiana Silva; Belga, Stephanie Marques Moura Franco; Maas, Lucas Wan Der
2016-01-01
Objective to analyze the migration of nurses in Brazil, describe the demographic characteristics of migrant nurses, the main migration flows, and establish relationships with the training process. Method a descriptive, exploratory study, based on 2010 Census data. The data were analyzed using descriptive statistics. Result there were 355,383 nurses in Brazil in 2010. Of these, 36,479 (10.3%) reported having moved compared to the year 2005: 18,073 (5.1%) for intrastate migration, 17,525 (4.8%) interstate migration, and 871 (0.2%) international migration. Females (86.3%), Caucasians (65.2%), and unmarried (48.3%) nurses prevailed in the population, without considerable variation between groups according to migration situation. The findings indicate that the migration flows are driven by the training process for states that concentrate a greater number of courses and positions in undergraduate and graduate studies, and the motivation of employment opportunity in regions of economic expansion in the country. Conclusion it is necessary to deepen the discussion on the movement of nurses in Brazil, their motivations, and international migration. PMID:27027681
Directory of Open Access Journals (Sweden)
Kênia Lara Silva
2016-01-01
Full Text Available Objective to analyze the migration of nurses in Brazil, describe the demographic characteristics of migrant nurses, the main migration flows, and establish relationships with the training process. Method a descriptive, exploratory study, based on 2010 Census data. The data were analyzed using descriptive statistics. Result there were 355,383 nurses in Brazil in 2010. Of these, 36,479 (10.3% reported having moved compared to the year 2005: 18,073 (5.1% for intrastate migration, 17,525 (4.8% interstate migration, and 871 (0.2% international migration. Females (86.3%, Caucasians (65.2%, and unmarried (48.3% nurses prevailed in the population, without considerable variation between groups according to migration situation. The findings indicate that the migration flows are driven by the training process for states that concentrate a greater number of courses and positions in undergraduate and graduate studies, and the motivation of employment opportunity in regions of economic expansion in the country. Conclusion it is necessary to deepen the discussion on the movement of nurses in Brazil, their motivations, and international migration.
Labor Market Determinants of Migration Flows in Europe
Directory of Open Access Journals (Sweden)
Elvira Nica
2015-01-01
Full Text Available Considerable research attention has focused on the labor market impacts of immigration, the operation and competitiveness of the European Union (EU labor market, and the expenditures and advantages of labor circulation for sending and receiving economies. The aim of the present study is to examine and evaluate the negative social consequences arising from the mobility of workers, the social and economic drivers of migration, and the effect of immigration on natives’ labor market results such as wages and employment.
Impacts and Risks of Migration and Refugee Flows in Africa
2012-03-12
sparsely forested hillsides. Such development not only accelerate deforestation and soil erosion, they also limit the water drainage capacity of...peace will indeed depend on addressing the underlying competition for water and fertile land,”12 Linking Migration, and Enviroment to Conflict13 The...An expanding population increases the demand on soils and intensifies deforestation as 17 inhabitants clear forest land for fuel wood and shelter
Common and Specific Features of Migration Flows In Russia, CIS and Far Abroad
Directory of Open Access Journals (Sweden)
Tamara Vladimirovna Kuprina
2015-06-01
Full Text Available The article discusses the features of migration flows in Russia, CIS and abroad in terms of transnationality and translocality. Special attention is paid to migration flows from Asia, depending on the gender perception. During the analysis, the preferences of migrants of different age groups are determined. It shows their desire for a more independent financial and professional life, relationship with family responsibilities, plans for the future. The data obtained by the method of continuous selection have led to the following conclusions: migration is a multidimensional phenomenon that requires multidisciplinary research; the heterogeneity of migration flows to the socio-cultural and gender features must be taken into account; the problem of illegal migration requires special solutions; in connection with the emigration of highly skilled professionals and immigration of low-skilled personnel, a professional important indicator of migratory replacement and attracting compatriots from abroad are important. The data obtained can be used for ethnic and cultural planning in order to improve production activities that affect the quality of solving of production tasks and programming adaptation of migrants as the significant impact of intangible factors on the development of society has been noted by economists for a long time. Thus, the economic sustainability requires new thinking based on socio-cultural sustainability determined by such global phenomena as international migration flows.
Particle migration and sorting in microbubble streaming flows
Thameem, Raqeeb; Hilgenfeldt, Sascha
2016-01-01
Ultrasonic driving of semicylindrical microbubbles generates strong streaming flows that are robust over a wide range of driving frequencies. We show that in microchannels, these streaming flow patterns can be combined with Poiseuille flows to achieve two distinctive, highly tunable methods for size-sensitive sorting and trapping of particles much smaller than the bubble itself. This method allows higher throughput than typical passive sorting techniques, since it does not require the inclusion of device features on the order of the particle size. We propose a simple mechanism, based on channel and flow geometry, which reliably describes and predicts the sorting behavior observed in experiment. It is also shown that an asymptotic theory that incorporates the device geometry and superimposed channel flow accurately models key flow features such as peak speeds and particle trajectories, provided it is appropriately modified to account for 3D effects caused by the axial confinement of the bubble. PMID:26958103
Kink structures induced in nickel-based single crystal superalloys by high-Z element migration
Energy Technology Data Exchange (ETDEWEB)
Sun, Fei; Zhang, Jianxin [Key Laboratory for Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Mao, Shengcheng [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Jiang, Ying [Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Feng, Qiang [National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Shen, Zhenju; Li, Jixue; Zhang, Ze [Center of Electron Microscopy and State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Han, Xiaodong [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China)
2015-01-05
Highlights: • Innovative kink structures generate at the γ/γ′ interfaces in the crept superalloy. • Clusters of heavy elements congregate at the apex of the kinks. • Dislocation core absorbs hexagonal structural high-Z elements. - Abstract: Here, we investigate a new type of kink structure that is found at γ/γ′ interfaces in nickel-based single crystal superalloys. We studied these structures at the atomic and elemental level using aberration corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The core of the dislocation absorbs high-Z elements (i.e., Co and Re) that adopt hexagonal arrangements, and it extrudes elements (i.e., Ni and Al) that adopt face centered cubic (fcc) structures. High-Z elements (i.e., Ta and W) and Cr, which is a low-Z element, are stabilized in body centered cubic (bcc) arrangements; Cr tends to behave like Re. High-Z elements, which migrate and adopt a hexagonal structure, induce kink formation at γ/γ′ interfaces. This process must be analyzed to fully understand the kinetics and dynamics of creep in nickel-based single crystal superalloys.
International Nuclear Information System (INIS)
Oh, Kyeongmin; Won, Seongyeon; Ju, Hyunchul
2015-01-01
Highlights: • Migration effects on crossover phenomena is examined. • Crossover and migration model is newly implemented. • Totally opposite crossover trend is observed with migration during charging. • During discharging, the crossover is enhanced due to migration. - ABSTRACT: According to the Nernst–Planck equation, the transport of charged species in porous electrodes is mainly driven by diffusion and migration. Although a number of all-vanadium redox flow battery (VRFB) models have been developed by several VRFB modeling groups, a comparative study of these two ion transport mechanisms has not been clearly reported in the literature. In this study, we develop a three-dimensional (3-D), transient VRFB model that rigorously accounts for both diffusion and migration mechanisms of charged species, including V 2+ , V 3+ , VO 2+ ,VO 2 + and H + . The VRFB model relies upon five principles of conservation: mass, momentum, species, electric charge, and thermal energy. Due to the general form of the conservation equations, both species migration effects on species transport and species diffusion effects on charge transport are considered in the source terms of the model equations. The model calculates species migration and diffusion fluxes through the membrane and compares their relative magnitudes under various charging and discharging stages. This paper clearly elucidates the role of species migration on vanadium crossover and the subsequent capacity losses, demonstrating that the present VRFB model is a valuable tool for optimizing the component design and operation of VRFBs.
Comparison of 3-D finite elements for incompressible fluid flow
International Nuclear Information System (INIS)
Robichaud, M.; Tanguy, P.A.
1985-01-01
In recent years, the finite element method applied to the solution of incompressible fluid flow has been in constant evolution. In the present state-of-the-art, 2-D problems are solved routinely and reliable results are obtained at a reasonable cost. In 3-D the finite element method is still undergoing active research and many methods have been proposed to solve the Navier-Stokes equations at 'low cost'. These methods have in common the choice of the element which has a trilinear velocity and a discontinuous constant pressure (Q1-PO). The prohibitive cost of 3-D finite element method in fluid flow is the reason for this choice: the Q1-PO is the simplest and the cheapest 3-D element. However, as mentioned in (5) and (6), it generates 'spurious' pressure modes phenomenon called checkerboarding. On regular mesh these spurious modes can be filtered but on distorted mesh the pressure solution is meaningless. (author)
International Nuclear Information System (INIS)
Vardzelashvili, N.S.; Areshidze, G.G.; Khutsaidze, A.L.
1982-01-01
Rock samples from different levels of stratigraphic section of the Digomi-Saburtatinsk depresion and underground thermal waters of the well for investigation into reguliarities of distribution, migration and deposition of uranium and associated elements were studied. Absence of correlation between the content elements under investigation and the depth of rock occurrence, their qranulometric and substantial composition was established. Concentration factors for Pb, Co, Cr over the whole section are more than one and for Ni, Mn, 6a, Ti, Zn, U, Th are less than one Th/U ratios enable to propose, that U in the hypergenesis zone is removed simultaneously with hydrophilic elements. Water-bearing complex of thermal waters occurs at 1200-3100 m in depth. Thermal waters are weakly mineralized alkalihydrosulphuric (oxygen-free) with low factor of water migration of U (0.001); uranium associated elements are absent. The present-day chemical conditions point to the fact, that U supply in rocks with thermal waters didn't take place
Pillatzki, A.E.; Neiger, R.D.; Chipps, S.R.; Higgins, K.F.; Thiex, N.; Afton, A.D.
2011-01-01
High concentrations of some hepatic elements might be contributing to the decline of the continental lesser scaup (Aythya affinis) population. We evaluated hepatic element concentrations of male and female lesser scaup collected from the upper Midwest (Iowa, Minnesota, North Dakota, and South Dakota) during the 2003 and 2004 spring migrations. We measured concentrations of 24 elements in livers of 117 lesser scaup. We found that only selenium concentrations were at levels (>3.0 ??g/g wet weight [ww)]) proposed to adversely affect reproduction. Approximately 49% of females (n = 61) had individual hepatic concentrations >3.0 ??g/g ww selenium (Se). Our observed hepatic concentration of Se was similar to that reported in lesser scaup collected from the mid-continental United States but less than Se concentrations reported from the Great Lakes region. We found that the liver cadmium (Cd) concentration for males was significantly higher than that for females. Gender differences in hepatic Cd concentrations have not been previously reported for lesser scaup, but Cd is known to have negative impacts on male reproduction. Our results indicate that lesser scaup migrating through the upper Midwest in spring have elevated Se levels and that males carry a significantly greater Cd burden than females. Moreover, elemental concentrations might be high enough to affect reproduction in both male and female lesser scaup, but controlled laboratory studies are needed to adequately assess the effects of Se and Cd on lesser scaup reproduction. ?? 2010 Springer Science+Business Media, LLC.
Basics elements for modelling the dynamics of cell migration in cell culture
International Nuclear Information System (INIS)
FarIas, Ro; Vidal, Cs; Rapacioli, M; Flores, V
2007-01-01
This paper introduces some basic elements for modelling the dynamics of cell migration activity over a bi-dimensional substratum. A square matrix, representing the substratum, is implemented in order to generate virtual cells with an initial random uniform distribution, with the ability to freely move within the matrix and to interact with each others by mean of adhesive forces. Two different conditions were examined: A) cells can freely move and after contacting with another cell they both completely inhibit their migration; B) cells that come into contact have the ability to rotate respect to each other without losing their contacts and retaining the ability to move together but at a slower rate, being the decrease in the rate of movement proportional to the number of contacting cells. The dynamics of the migration process in these two conditions was evaluated by recording the evolution of several parameters as a function of time. Minor modifications in some parameters (mobility, intensity of cell-cell and cell-substratum adhesiveness) significantly change the dynamics and the final result of the virtual migrating cells
Selection and network effects - Migration flows into OECD countries 1990-2000
DEFF Research Database (Denmark)
Pedersen, Peder J.; Pytlikova, Mariola; Smith, Nina
2008-01-01
This paper presents empirical evidence on immigration flows into the OECD countries during the period 1990-2000. Our results indicate that network effects are strong, but vary between different groups of welfare states and between countries according to the type of immigration policy being applie...... a major influence on the observed migration patterns until now. This may partly be explained by restrictive migration policies which may have dampened the potential selection effects....
A study of long-term (103-104Yr) elemental migration in saturated clays and sediments
International Nuclear Information System (INIS)
Mac Kenzie, A.B.; Scott, R.D.; Ridgway, I.M.; Mc Kinley, I.G.; West, J.M.
1986-01-01
This report presents the results of a project to investigate the use of elemental profiles in Scottisch sediments resulting from the Flandrian marine transgression as a natural analogue of radionuclide migration through argillaceous material. The work was carried out within Research Area no. 5 of the CEC project MIRAGE ''Natural Geological Migration Systems''
Migration Flow and Its Impact on Tuberculosis Notification in Portugal.
Dias, Ana; Gaio, Rita; Sousa, Pedro; Gomes, Marta; Oliveira, Olena; Duarte, Raquel
2018-01-01
Tuberculosis notification in Portugal has decreased in the last few years. As a consequence of the economic crisis, emigration has increased and immigration has decreased. Immigrants are a risk group for tuberculosis. Most emigrants are 20-44 years old and belong to the age group most affected by tuberculosis. To describe the decrease in tuberculosis notification in Portugal over the last years from a demographical point of view. Mathematical analysis was performed to quantify the effect of the migration movements (separately and simultaneously) on tuberculosis notification in Portugal from 2008 to 2014. We calculated the estimated tuberculosis notification for each year during the period of study: 1) fixing immigration rate and tuberculosis rate in immigrants at 2008 values; 2) fixing emigration rate and tuberculosis rate in emigrants at 2008 values; 3) fixing both phenomenons at 2008 values. The differences between the observed and the estimated numbers were small (≤0.5 cases/100000 inhabitants). Impact of the migration movements on tuberculosis notification rate does not seem to be significant when analyzed for each phenomenon individually and simultaneously, by our model. This might mean that we have to concentrate our efforts in other risk factors for tuberculosis. Copyright © 2017 SEPAR. Publicado por Elsevier España, S.L.U. All rights reserved.
AC power flow importance measures considering multi-element failures
International Nuclear Information System (INIS)
Li, Jian; Dueñas-Osorio, Leonardo; Chen, Changkun; Shi, Congling
2017-01-01
Quantifying the criticality of individual components of power systems is essential for overall reliability and management. This paper proposes an AC-based power flow element importance measure, while considering multi-element failures. The measure relies on a proposed AC-based cascading failure model, which captures branch overflow, bus load shedding, and branch failures, via AC power flow and optimal power flow analyses. Taking the IEEE 30, 57 and 118-bus power systems as case studies, we find that N-3 analyses are sufficient to measure the importance of a bus or branch. It is observed that for a substation bus, its importance is statistically proportional to its power demand, but this trend is not observed for power plant buses. While comparing with other reliability, functionality, and topology-based importance measures popular today, we find that a DC power flow model, although better correlated with the benchmark AC model as a whole, still fails to locate some critical elements. This is due to the focus of DC-based models on real power that ignores reactive power. The proposed importance measure is aimed to inform decision makers about key components in complex systems, while improving cascading failure prevention, system backup setting, and overall resilience. - Highlights: • We propose a novel importance measure based on joint failures and AC power flow. • A cascading failure model considers both AC power flow and optimal power flow. • We find that N-3 analyses are sufficient to measure the importance of an element. • Power demand impacts the importance of substations but less so that of generators. • DC models fail to identify some key elements, despite correlating with AC models.
Modelling of flow and contaminant migration in single rock fractures
International Nuclear Information System (INIS)
Dahlblom, P.; Joensson, L.
1990-03-01
The report deals with flow and hydrodynamic dispersion of a nonreactive contaminant in a single, irregularly shaped fracture. The main purpose of the report is to describe the basis and development of a computational 'tool' for simulating the aperture geometry of a single fracture and the detailed flow in it. On the basis of this flow information further properties of the fracture can be studied. Some initial application to dispersion of a nonreactive contaminant are thus discussed. The spatial pattern of variation of the fracture aperture is considered as a two-dimensional stochastic process. A method for simulation of such a process is described. The stochastic properties can be chosen arbitrarily. It is assumed that the fracture aperture belongs to a log-normal distribution. For calculation of the flow pattern, the Navier-Stokes equations are simplified to describe low velocity and steady-state flow. These equations, and the continuity equation are integrated in the direction across the fracture plane. A stream function, which describes the integrated flow in the fracture, is defined. A second order partial differential equation, with respect to the stream function, is established and solved by the finite difference method. Isolines for the stream function define boundaries between channels with equal flow rates. The travel time for each channel can be calculated to achieve a measure of the dispersion. The impact of the aperture distribution on the ratio between the mass balance fracture aperture and the cubic law fracture aperture is shown by simple examples. (28 figs., 1 tab., 22 refs.)
Bending the urban flow: a construction-migration strategy.
Shaw, R P
1980-01-01
The excess rate of migration to urban centers is a problem affecting over 50 developing countries and 18 developed ones (68% of the world's population). Policies that rely on compulsion or disincentives have mostly failed because they do not deal with the cause of the problem. This paper proposes a strategy of increasing or decreasing the rate of housing construction in different urban areas as a means of stimulating or reducing migration to those areas; in most developing areas priority is given to residential construction in already congested metropolitan areas. 5 assumptions are the basis for this approach: 1) migrants tend to gravitate to the most powerful growth poles; 2) residential construction is a leading sector of regional and urban economies; 3) the encouragement of construction activity will make itself felt indirectly via its effect on construction-related employment; 4) rates of residential construction may be manipulated through government policy affecting the cost of materials, availability of loans, level of unionization, and price of housing; and 5) residential construction is amenable to quick policy action. The central idea of the strategy is that an increase in residential construction will exercise a pull on migrants, increasing job opportunities, raising incomes, lowering housing costs, and improving the chances of home ownership. This idea has been verified by various projects in Hong Kong, Ghana, Venezuela, Brazil, Bahrain, Mexico, Colombia, Poland, USSR, and the UK. In Bahrain low-income housing programs have been used to relocate Bahraini nationals in new outlying suburbs and to promote population growth in rural villages. In Mexico self-help and low-income housing programs have helped to redirect migrants headed for small towns toward smaller communities. There is also evidence to show that building construction has the potential to expand and contribute to economic growth. Some problems of implementation might be finding an adequate
Mathematical aspects of finite element methods for incompressible viscous flows
Gunzburger, M. D.
1986-01-01
Mathematical aspects of finite element methods are surveyed for incompressible viscous flows, concentrating on the steady primitive variable formulation. The discretization of a weak formulation of the Navier-Stokes equations are addressed, then the stability condition is considered, the satisfaction of which insures the stability of the approximation. Specific choices of finite element spaces for the velocity and pressure are then discussed. Finally, the connection between different weak formulations and a variety of boundary conditions is explored.
A finite element method for flow problems in blast loading
International Nuclear Information System (INIS)
Forestier, A.; Lepareux, M.
1984-06-01
This paper presents a numerical method which describes fast dynamic problems in flow transient situations as in nuclear plants. A finite element formulation has been chosen; it is described by a preprocessor in CASTEM system: GIBI code. For these typical flow problems, an A.L.E. formulation for physical equations is used. So, some applications are presented: the well known problem of shock tube, the same one in 2D case and a last application to hydrogen detonation
From east to west. Enlargement and migration flows
Directory of Open Access Journals (Sweden)
Ruth Ferrero
2014-11-01
Full Text Available The end of the Cold produced migratory flows of an economic type in the direction East-West Although the exchange and movement of populations in Europe is nothing new, what was new was the change in the underlying philosophy. The change of paradigm from a world with two opposing poles to one with an hegemonic power, shattered all the schemes that until then were taken for granted. Since the fall of the Berlin wall the issue was no longer to take in political refugies coming from the soviet block, butrather to regulate the flows coming from those countries in more and more numbers. In this paper we try to reconstruct the history of the development of control of the migratory flows coming from Central and Easter Europe towards the European Union before,during and after the enlowgement processes which have taken place in 2004 and 2007.
Migration and Adult Language Learning: Global Flows and Local Transpositions
Burns, Anne; Roberts, Celia
2010-01-01
In the 21st century, global flows politically, socially, economically, and environmentally are creating widespread movements of people around the world and giving rise to increased resettlements of immigrants and refugees internationally. The reality in most countries worldwide is that contemporary populations are multifaceted, multicultural,…
Origin and migration of trace elements in the surface sediments of Majuro Atoll, Marshall Islands.
Ito, Lisa; Omori, Takayuki; Yoneda, Minoru; Yamaguchi, Toru; Kobayashi, Ryuta; Takahashi, Yoshio
2018-07-01
The sediments of Majuro Atoll, Marshall Islands, consist of bioclastic materials, including foraminifera and coral debris. The sedimentary depth profiles of elements showed that various elements including zinc (Zn) and copper (Cu) were enriched in the upper layers of the islands of Majuro Atoll. Carbon-14 dating revealed that the sedimentation of the upper layer was completed before 1670 and 542 cal BP in Laura and Calalen, respectively. The enriched elements could be categorized by their origins: (a) terrestrial elements transported as dust (aluminum (Al) and rare earth elements (REEs)); (b) anthropogenic elements (Zn and Cu); and (c) elements supplied by seabirds (phosphorus (P)). From the results of the total amount of Al supplied to sediments for ca. 2000 years, Al in Majuro Atoll was suggested to be airborne origin. The enrichment factors of the elements normalized to Al concentration of continental crust showed that REEs were also transported as dust, while Zn and Cu were mainly of anthropogenic origin. The speciation analysis by X-ray absorption near-edge structure (XANES) showed the presence of Zn-Cu alloys originated from industrial products. It was also revealed that Zn was enriched in the surface due to anthropogenic emission after urbanization on Majuro Atoll and fixed by carbonate and phosphate at the upper layer, which inhibits migration of Zn into the deeper layer and its release to the groundwater and costal water. Hence, the fixation of heavy metals at the surface prevents their exposure to aquatic organisms and residents via fresh groundwater in the island. Copyright © 2018 Elsevier Ltd. All rights reserved.
Leading tip drives soma translocation via forward F-actin flow during neuronal migration.
He, Min; Zhang, Zheng-hong; Guan, Chen-bing; Xia, Di; Yuan, Xiao-bing
2010-08-11
Neuronal migration involves coordinated extension of the leading process and translocation of the soma, but the relative contribution of different subcellular regions, including the leading process and cell rear, in driving soma translocation remains unclear. By local manipulation of cytoskeletal components in restricted regions of cultured neurons, we examined the molecular machinery underlying the generation of traction force for soma translocation during neuronal migration. In actively migrating cerebellar granule cells in culture, a growth cone (GC)-like structure at the leading tip exhibits high dynamics, and severing the tip or disrupting its dynamics suppressed soma translocation within minutes. Soma translocation was also suppressed by local disruption of F-actin along the leading process but not at the soma, whereas disrupting microtubules along the leading process or at the soma accelerated soma translocation. Fluorescent speckle microscopy using GFP-alpha-actinin showed that a forward F-actin flow along the leading process correlated with and was required for soma translocation, and such F-actin flow depended on myosin II activity. In migrating neurons, myosin II activity was high at the leading tip but low at the soma, and increasing or decreasing this front-to-rear difference accelerated or impeded soma advance. Thus, the tip of the leading process actively pulls the soma forward during neuronal migration through a myosin II-dependent forward F-actin flow along the leading process.
Experimental study of water flow in nuclear fuel elements
International Nuclear Information System (INIS)
Rodrigues, Lorena Escriche; Rezende, Hugo Cesar; Mattos, Joao Roberto Loureiro de; Barros Filho, Jose Afonso; Santos, Andre Augusto Campagnole dos
2013-01-01
This work aims to develop an experimental methodology for investigating the water flow through rod bundles after spacer grids of nuclear fuel elements of PWR type reactors. Speed profiles, with the device LDV (Laser Doppler Velocimetry), and the pressure drop between two sockets located before and after the spacer grid, using pressure transducers were measured
International Nuclear Information System (INIS)
Michel, H.
1999-01-01
The nuclear tests carried out in the atmosphere in the Sixties, the accidents and in particular that to the power station of Chernobyl in 1986, were at the origin of the dispersion of a significant quantity of transuranic elements and fission products. The study of a lake system, such that of the Blelham Tarn in Great Britain, presented in this memory, can bring interesting answers to the problems of management of the environment. The determination of the radionuclides in sediment cores made it possible not only to establish the history of the depositions and consequently the origin of the radionuclides, but also to evaluate the various transfers which took place according to the parameters of the site and the properties of the elements. The studied transuranic elements are plutonium 238, 239-240, americium 241 and neptunium 237. Alpha emitting radionuclides, their determination requires complex radiochemical separations. A method was worked out to successively separate the three radioelements by using a same chromatographic column. Cesium 137 is the studied fission product, its determination is done by direct Gamma spectrometry. Lead 210, natural radionuclide, whose atmospheric flow can be supposed constant. makes it possible to obtain a chronology of the various events. The detailed vertical study of sediment cores showed that the accumulation mode of the studied elements is the same one and that the methods of dating converge. The cesium, more mobile than transuranic elements in the atmosphere, was detected in the 1963 and 1986 fallout whereas an activity out of transuranic elements appears only for the 1963 fallout. The activity of the 1963 cesium fallout is of the same order of magnitude as that of 1986. The calculation of the diffusion coefficients of the elements in the sediments shows an increased migration of cesium compared to transuranic elements. An inventory on the whole of the lake made it possible to note that the atmospheric fallout constitute the
Corona, T; Iglesias, M; Anticó, E
2014-06-18
The inorganic elements potentially migrating from cork to a food simulant [a hydroalcoholic solution containing 12 and 20% (v/v) ethanol] have been determined by means of inductively coupled plasma (ICP) with atomic emission and mass spectrometric detection. The experimental instrumental conditions were evaluated in depth, taking into account spectroscopic and nonspectroscopic interference caused by the presence of ethanol and other components in the sample. We report concentrations ranging from 4 μg kg(-1) for Cd to 28000 μg kg(-1) for Al in the food simulant (concentrations given in kilograms of cork). The values found for Ba, Mn, Fe, Cu, and Zn have been compared with the guideline values stated in EU Regulation 10/2011. In all cases, cork met the general safety criteria applicable to food contact material. Finally, we have proposed water as an alternative to the hydroalcoholic solution to simplify quantification of the tested elements using ICP techniques.
Coupling nonlinear Stokes and Darcy flow using mortar finite elements
Ervin, Vincent J.
2011-11-01
We study a system composed of a nonlinear Stokes flow in one subdomain coupled with a nonlinear porous medium flow in another subdomain. Special attention is paid to the mathematical consequence of the shear-dependent fluid viscosity for the Stokes flow and the velocity-dependent effective viscosity for the Darcy flow. Motivated by the physical setting, we consider the case where only flow rates are specified on the inflow and outflow boundaries in both subdomains. We recast the coupled Stokes-Darcy system as a reduced matching problem on the interface using a mortar space approach. We prove a number of properties of the nonlinear interface operator associated with the reduced problem, which directly yield the existence, uniqueness and regularity of a variational solution to the system. We further propose and analyze a numerical algorithm based on mortar finite elements for the interface problem and conforming finite elements for the subdomain problems. Optimal a priori error estimates are established for the interface and subdomain problems, and a number of compatibility conditions for the finite element spaces used are discussed. Numerical simulations are presented to illustrate the algorithm and to compare two treatments of the defective boundary conditions. © 2010 Published by Elsevier B.V. on behalf of IMACS.
Linked migration systems: immigration and internal labor flows in the United States.
R. Walker; M. Ellis; R. Barff
1992-01-01
We investigate the relationship between immigration and internal labor movements in the US. Wedding the literatures on immigration and internal migration, we develop a mobility model linking these various flows on the basis of occupational status of worker, producction and institutional relations in the economy, and economic restructuring.
Can otolith elemental chemistry retrospectively track migrations in fully marine fishes?
Sturrock, A M; Trueman, C N; Darnaude, A M; Hunter, E
2012-07-01
scope of migration studies. Among the otolith elements that routinely occur above instrument detection limits, Ba, Mn and Li were deemed the most likely to prove reliable geographic markers in marine species. © 2012 The Authors. Journal of Fish Biology © 2012 The Fisheries Society of the British Isles.
Groundwater flow and tritium migration from the SRS Old Burial Ground to Fourmile Branch
International Nuclear Information System (INIS)
Flach, G.P.; Hamm, L.L.; Harris, M.K.
1996-04-01
The objectives of this investigation are twofold. The initial goal is to devise and demonstrate a technique for directly incorporating fine-scale lithologic data into heterogeneous hydraulic conductivity fields, for improved groundwater flow and contaminant transport model accuracy. The ultimate goal is to rigorously simulate past and future tritium migration from the SRS Old Burial Ground towards Fourmile Branch, to better understand the effects of various remediation alternatives such as no action and capping. Large-scale variability in hydraulic conductivity is usually the main influence on field-scale groundwater flow patterns and dispersive transport, following the relative locations of recharge and discharge areas. Incorporating realistic hydraulic conductivity heterogeneity into flow and transport models is paramount to accurate simulations, particularly for contaminant migration. Sediment lithologic descriptions and geophysical logs typically offer finer spatial resolution, and therefore more potential information about heterogeneity, than other site characterization data
Finite element approximation to a model problem of transonic flow
International Nuclear Information System (INIS)
Tangmanee, S.
1986-12-01
A model problem of transonic flow ''the Tricomi equation'' in Ω is contained in IR 2 bounded by the rectangular-curve boundary is posed in the form of symmetric positive differential equations. The finite element method is then applied. When the triangulation of Ω-bar is made of quadrilaterals and the approximation space is the Lagrange polynomial, we get the error estimates. 14 refs, 1 fig
International Nuclear Information System (INIS)
Trotignon, L.; Bienvenu, P.; Rose, J.; Bulle, C.; Crouzet, N.; Khoury, H.
2005-01-01
Full text of publication follows: The site of Maqarin (Jordan), in which natural cements occur as a result of the combustion metamorphism of a bio-micrite, is studied since 1989 as a natural analogue for the long term evolution of a cementitious repository environment [1]. In order to better understand and simulate observed elemental migrations along high pH groundwater plumes, laboratory scale column experiments were conducted in which crushed materials (cement, bio-micrite) collected on site were submitted to leaching by deionized water or Ca(OH) 2 equilibrated solutions. The evolution of pH and major elements was monitored in leachates (Ca, SO 4 , Si, Al) during the experiments. Simulations of the experiments were attempted using the reactive transport code Hytec (Ecole des Mines de Paris and Pole Geochimie Transport). The column experiments presented here contribute to a better understanding of the evolution of hyper-alkaline waters in Maqarin. They suggest several key parameters to be taken into account in the modelling of such systems: - the rate limited precipitation of CSH phases; - the pH dependence of ettringite dissolution (and probably precipitation); - the competition in the availability of Al and Si from the bio-micrite, showing to be a critical issue for modeling the alkaline perturbation Further experiments and modeling of this type is needed to understand how (and how fast) Maqarin groundwaters acquire their high pH. Such information will be useful to better bracket the extent of precipitation of secondary CSH phases in the near field of a repository. [1] Khoury H.N., Salameh E., Clark I.D., Fritz P., Bajjali W., Milodowski A.E., Cave M.R. and Alexander W.R. 1992. A natural analogue of high pH cement pore waters from the Maqarin area of northern Jordan. I: Introduction to the site. J. Geochem. Explor. 46: 117-132. (authors)
International Nuclear Information System (INIS)
Strickert, R.; Friedman, A.M.; Fried, S.
1979-04-01
A computer program (ARDISC, the Argonne Dispersion Code) is described which simulates the migration of nuclides in porous media and includes first order kinetic effects on the retention constants. The code allows for different absorption and desorption rates and solves the coupled migration equations by arithmetic reiterations. Input data needed are the absorption and desorption rates, equilibrium surface absorption coefficients, flow rates and volumes, and media porosities
Use of X-ray fluorescence analysis in studying vertical element migration in weathering zone
International Nuclear Information System (INIS)
Houdkova, Z.; Hally, J.
1980-01-01
The vertical migration of elements was studied in a model area of the Zelivka river basin. The VRS 2 Zeiss GDR analyzer, connected to automatic processor KSR 4 100, were used for the study of concentration variations. Soil samples were taken from bore holes drilled to a depth of the solid bedrock (0 to 6 m). The contents of SiO 2 , Al 2 O 3 , Fe 2 O 3 , K 2 O, CaO, TiO 2 , P 2 O 5 and MnO were determined in concentration ranges from 10 -2 to 10 1 %. The method was tested in comparative measurements against conventional methods of chemical analysis. (author)
DEFF Research Database (Denmark)
Hays, Graeme C.; Christensen, Asbjørn; Fossette, Sabrina
2014-01-01
The optimum path to follow when subjected to cross flows was first considered over 80 years ago by the German mathematician Ernst Zermelo, in the context of a boat being displaced by ocean currents, and has become known as the ‘Zermelo navigation problem’. However, the ability of migrating animals...... to solve this problem has received limited consideration, even though wind and ocean currents cause the lateral displacement of flyers and swimmers, respectively, particularly during long-distance journeys of 1000s of kilometres. Here, we examine this problem by combining long-distance, open-ocean marine...... not follow the optimum (Zermelo's) route. Even though adult marine turtles regularly complete incredible long-distance migrations, these vertebrates primarily rely on course corrections when entering neritic waters during the final stages of migration. Our work introduces a new perspective in the analysis...
Cooling flow measurement in fuel elements of the RA-6
International Nuclear Information System (INIS)
Brollo, F; Silin, N
2009-01-01
Under the UBERA6 project for the core change and power increase of the RA-6 reactor, the total coolant flow was increased to meet the requirements imposed by the new operating conditions. The flow through the fuel elements is an important parameter and is difficult to determine due to the geometric complexity of the core. To ensure safe operation of the reactor, adequate safety margins must be kept for all operating conditions. In the present work we performed the direct measurement of the cooling flow rate of a fuel in the reactor core, for which we used a turbine flowmeter built specifically for this use. This helped to confirm previous results obtained during the launch, made by an indirect method based on measuring the pressure difference of the core. The turbine flowmeter was chosen due to its robustness, ease of operation and low disturbance of the input stream to the fuel. We describe the calibration of this instrument and the results of flow measurements made on some of the RA6 reactor fuel elements under conditions of zero power. [es
Lateral migration of a microdroplet under optical forces in a uniform flow
International Nuclear Information System (INIS)
Cho, Hyunjun; Chang, Cheong Bong; Jung, Jin Ho; Sung, Hyung Jin
2014-01-01
The behavior of a microdroplet in a uniform flow and subjected to a vertical optical force applied by a loosely focused Gaussian laser beam was studied numerically. The lattice Boltzmann method was applied to obtain the two-phase flow field, and the dynamic ray tracing method was adopted to calculate the optical force. The optical forces acting on the spherical droplets agreed well with the analytical values. The numerically predicted droplet migration distances agreed well with the experimentally obtained values. Simulations of the various flow and optical parameters showed that the droplet migration distance nondimensionalized by the droplet radius is proportional to the S number (z d /r p = 0.377S), which is the ratio of the optical force to the viscous drag. The effect of the surface tension was also examined. These results indicated that the surface tension influenced the droplet migration distance to a lesser degree than the flow and optical parameters. The results of the present work hold for the refractive indices of the mean fluid and the droplet being 1.33 and 1.59, respectively
Directory of Open Access Journals (Sweden)
Tom J Coulthard
Full Text Available Human migration north through Africa is contentious. This paper uses a novel palaeohydrological and hydraulic modelling approach to test the hypothesis that under wetter climates c.100,000 years ago major river systems ran north across the Sahara to the Mediterranean, creating viable migration routes. We confirm that three of these now buried palaeo river systems could have been active at the key time of human migration across the Sahara. Unexpectedly, it is the most western of these three rivers, the Irharhar river, that represents the most likely route for human migration. The Irharhar river flows directly south to north, uniquely linking the mountain areas experiencing monsoon climates at these times to temperate Mediterranean environments where food and resources would have been abundant. The findings have major implications for our understanding of how humans migrated north through Africa, for the first time providing a quantitative perspective on the probabilities that these routes were viable for human habitation at these times.
E.U. VERSUS O.E.C.D. - MIGRATION FLOW UNDER THE LABOUR TAXATION IMPACT
Directory of Open Access Journals (Sweden)
LAZAR PAULA
2015-07-01
Full Text Available In a world governed by the freedom of movement, production factors – capital, labour and consumption – can “run” from on territory to another bringing along positive and negative effects, just as well. Labour, the second in line of “run away” production factors, has a great impact upon a state economy generating sustainable growth or increasing budgetary revenues This paper presents for a period of 7 years, for both European (UE-28 and international (OECD level, the migration flow under the labour taxation impact (it is well known that more than 75% of the migration flow is work force related. The authors found that even if both areas are attracting labour force the reasons for doing that are completely different – while for the OECD member states and non-EU member states there will always be the “occident fascination” in the Europeans are “voting with their feet”.
GPU-accelerated element-free reverse-time migration with Gauss points partition
Zhou, Zhen; Jia, Xiaofeng; Qiang, Xiaodong
2018-06-01
An element-free method (EFM) has been demonstrated successfully in elasticity, heat conduction and fatigue crack growth problems. We present the theory of EFM and its numerical applications in seismic modelling and reverse time migration (RTM). Compared with the finite difference method and the finite element method, the EFM has unique advantages: (1) independence of grids in computation and (2) lower expense and more flexibility (because only the information of the nodes and the boundary of the concerned area is required). However, in EFM, due to improper computation and storage of some large sparse matrices, such as the mass matrix and the stiffness matrix, the method is difficult to apply to seismic modelling and RTM for a large velocity model. To solve the problem of storage and computation efficiency, we propose a concept of Gauss points partition and utilise the graphics processing unit to improve the computational efficiency. We employ the compressed sparse row format to compress the intermediate large sparse matrices and attempt to simplify the operations by solving the linear equations with CULA solver. To improve the computation efficiency further, we introduce the concept of the lumped mass matrix. Numerical experiments indicate that the proposed method is accurate and more efficient than the regular EFM.
Inertia-driven particle migration and mixing in a wall-bounded laminar suspension flow
Energy Technology Data Exchange (ETDEWEB)
Loisel, V.; Abbas, M., E-mail: micheline.abbas@ensiacet.fr; Masbernat, O. [Université de Toulouse INPT-UPS: Laboratoire de Génie Chimique and CNRS, Fédération de Recherche FERMaT, Toulouse (France); Climent, E. [Université de Toulouse INPT-UPS: Institut de Mécanique des Fluides de Toulouse and CNRS, Fédération de Recherche FERMaT, Toulouse (France)
2015-12-15
Laminar pressure-driven suspension flows are studied in the situation of neutrally buoyant particles at finite Reynolds number. The numerical method is validated for homogeneous particle distribution (no lateral migration across the channel): the increase of particle slip velocities and particle stress with inertia and concentration is in agreement with former works in the literature. In the case of a two-phase channel flow with freely moving particles, migration towards the channel walls due to the Segré-Silberberg effect is observed, leading to the development of a non-uniform concentration profile in the wall-normal direction (the concentration peaks in the wall region and tends towards zero in the channel core). The particle accumulation in the region of highest shear favors the shear-induced particle interactions and agitation, the profile of which appears to be correlated to the concentration profile. A 1D model predicting particle agitation, based on the kinetic theory of granular flows in the quenched state regime when Stokes number St = O(1) and from numerical simulations when St < 1, fails to reproduce the agitation profile in the wall normal direction. Instead, the existence of secondary flows is clearly evidenced by long time simulations. These are composed of a succession of contra-rotating structures, correlated with the development of concentration waves in the transverse direction. The mechanism proposed to explain the onset of this transverse instability is based on the development of a lift force induced by spanwise gradient of the axial velocity fluctuations. The establishment of the concentration profile in the wall-normal direction therefore results from the combination of the mean flow Segré-Silberberg induced migration, which tends to stratify the suspension and secondary flows which tend to mix the particles over the channel cross section.
Inertia-driven particle migration and mixing in a wall-bounded laminar suspension flow
International Nuclear Information System (INIS)
Loisel, V.; Abbas, M.; Masbernat, O.; Climent, E.
2015-01-01
Laminar pressure-driven suspension flows are studied in the situation of neutrally buoyant particles at finite Reynolds number. The numerical method is validated for homogeneous particle distribution (no lateral migration across the channel): the increase of particle slip velocities and particle stress with inertia and concentration is in agreement with former works in the literature. In the case of a two-phase channel flow with freely moving particles, migration towards the channel walls due to the Segré-Silberberg effect is observed, leading to the development of a non-uniform concentration profile in the wall-normal direction (the concentration peaks in the wall region and tends towards zero in the channel core). The particle accumulation in the region of highest shear favors the shear-induced particle interactions and agitation, the profile of which appears to be correlated to the concentration profile. A 1D model predicting particle agitation, based on the kinetic theory of granular flows in the quenched state regime when Stokes number St = O(1) and from numerical simulations when St < 1, fails to reproduce the agitation profile in the wall normal direction. Instead, the existence of secondary flows is clearly evidenced by long time simulations. These are composed of a succession of contra-rotating structures, correlated with the development of concentration waves in the transverse direction. The mechanism proposed to explain the onset of this transverse instability is based on the development of a lift force induced by spanwise gradient of the axial velocity fluctuations. The establishment of the concentration profile in the wall-normal direction therefore results from the combination of the mean flow Segré-Silberberg induced migration, which tends to stratify the suspension and secondary flows which tend to mix the particles over the channel cross section
μ-PIV measurements of the ensemble flow fields surrounding a migrating semi-infinite bubble.
Yamaguchi, Eiichiro; Smith, Bradford J; Gaver, Donald P
2009-08-01
Microscale particle image velocimetry (μ-PIV) measurements of ensemble flow fields surrounding a steadily-migrating semi-infinite bubble through the novel adaptation of a computer controlled linear motor flow control system. The system was programmed to generate a square wave velocity input in order to produce accurate constant bubble propagation repeatedly and effectively through a fused glass capillary tube. We present a novel technique for re-positioning of the coordinate axis to the bubble tip frame of reference in each instantaneous field through the analysis of the sudden change of standard deviation of centerline velocity profiles across the bubble interface. Ensemble averages were then computed in this bubble tip frame of reference. Combined fluid systems of water/air, glycerol/air, and glycerol/Si-oil were used to investigate flows comparable to computational simulations described in Smith and Gaver (2008) and to past experimental observations of interfacial shape. Fluorescent particle images were also analyzed to measure the residual film thickness trailing behind the bubble. The flow fields and film thickness agree very well with the computational simulations as well as existing experimental and analytical results. Particle accumulation and migration associated with the flow patterns near the bubble tip after long experimental durations are discussed as potential sources of error in the experimental method.
μ-PIV measurements of the ensemble flow fields surrounding a migrating semi-infinite bubble
Yamaguchi, Eiichiro; Smith, Bradford J.; Gaver, Donald P.
2012-01-01
Microscale particle image velocimetry (μ-PIV) measurements of ensemble flow fields surrounding a steadily-migrating semi-infinite bubble through the novel adaptation of a computer controlled linear motor flow control system. The system was programmed to generate a square wave velocity input in order to produce accurate constant bubble propagation repeatedly and effectively through a fused glass capillary tube. We present a novel technique for re-positioning of the coordinate axis to the bubble tip frame of reference in each instantaneous field through the analysis of the sudden change of standard deviation of centerline velocity profiles across the bubble interface. Ensemble averages were then computed in this bubble tip frame of reference. Combined fluid systems of water/air, glycerol/air, and glycerol/Si-oil were used to investigate flows comparable to computational simulations described in Smith and Gaver (2008) and to past experimental observations of interfacial shape. Fluorescent particle images were also analyzed to measure the residual film thickness trailing behind the bubble. The flow fields and film thickness agree very well with the computational simulations as well as existing experimental and analytical results. Particle accumulation and migration associated with the flow patterns near the bubble tip after long experimental durations are discussed as potential sources of error in the experimental method. PMID:23049158
DEFF Research Database (Denmark)
Pytlikova, Mariola; Pedersen, Peder J.
We look at migration flows from 8 Central and Eastern European Countries (CEECs) to 5 Nordic countries over the years 1985 - 2005 and we can exploit a natural experiment that arose from the fact that while Sweden opened its labour market from the day one of the 2004 EU enlargement, the other Nordic...... countries chose a transition period in relation to the "new" EU members. We employ a differences-in-differences estimator in our analysis. The results show that the estimated effect of the opening of Swedish labour market in 2004 on migration is insignificantly different from zero. Further, we...... are interested in the overall effect of the "EU entry" on migration. Therefore we look at migration flows from CEECs during the first round EU enlargement towards CEECs in 2004 and compare them with migration flows from Bulgaria and Romania. We again used a DD estimator in our analysis. The estimated effect...
Natural analogue study on trace element migration in geological formation at Horonobe area, Japan
International Nuclear Information System (INIS)
Iwatsuki, Teruki; Ishii, Eiichi; Mizuno, Takashi; Honda, T.
2010-01-01
Usefulness of natural analog to study radionuclide transport models for deep geological repositories for high-level and long lived radioactive wastes is widely recognized. As the groundwater flow in the Horonobe area, Hokkaido, Japan is known to be stationary with neutral pH value and of reductive nature for a long-term, the authors began natural analog study by observing atomic distribution of such trace elements as rare earths, uranium, and thorium in carbonate nodules and veins of uranium minerals from several selected faults (Wakkanai F., Ketoi F., etc) in the area with the use of XED, XRF, and ICP-MS. The results give important information as to the maintainability of the rocks for trace elements and help to provide confidence in the safety assessment in the long term. (S. Ohno)
FEWA: a Finite Element model of Water flow through Aquifers
International Nuclear Information System (INIS)
Yeh, G.T.; Huff, D.D.
1983-11-01
This report documents the implementation and demonstration of a Finite Element model of Water flow through Aquifers (FEWA). The particular features of FEWA are its versatility and flexibility to deal with as many real-world problems as possible. Point as well as distributed sources/sinks are included to represent recharges/pumpings and rainfall infiltrations. All sources/sinks can be transient or steady state. Prescribed hydraulic head on the Dirichlet boundaries and fluxes on Neumann or Cauchy boundaries can be time-dependent or constant. Source/sink strength over each element and node, hydraulic head at each Dirichlet boundary node, and flux at each boundary segment can vary independently of each other. Either completely confined or completely unconfined aquifers, or partially confined and partially unconfined aquifers can be dealt with effectively. Discretization of a compound region with very irregular curved boundaries is made easy by including both quadrilateral and triangular elements in the formulation. Large-field problems can be solved efficiently by including a pointwise iterative solution strategy as an optional alternative to the direct elimination solution method for the matrix equation approximating the partial differential equation of groundwater flow. FEWA also includes transient flow through confining leaky aquifers lying above and/or below the aquifer of interest. The model is verified against three simple cases to which analytical solutions are available. It is then demonstrated by two examples of how the model can be applied to heterogeneous and anisotropic aquifers with transient boundary conditions, time-dependent sources/sinks, and confining aquitards for a confined aquifer of variable thickness and for a free surface problem in an unconfined aquifer, respectively. 20 references, 25 figures, 8 tables
FEWA: a Finite Element model of Water flow through Aquifers
Energy Technology Data Exchange (ETDEWEB)
Yeh, G.T.; Huff, D.D.
1983-11-01
This report documents the implementation and demonstration of a Finite Element model of Water flow through Aquifers (FEWA). The particular features of FEWA are its versatility and flexibility to deal with as many real-world problems as possible. Point as well as distributed sources/sinks are included to represent recharges/pumpings and rainfall infiltrations. All sources/sinks can be transient or steady state. Prescribed hydraulic head on the Dirichlet boundaries and fluxes on Neumann or Cauchy boundaries can be time-dependent or constant. Source/sink strength over each element and node, hydraulic head at each Dirichlet boundary node, and flux at each boundary segment can vary independently of each other. Either completely confined or completely unconfined aquifers, or partially confined and partially unconfined aquifers can be dealt with effectively. Discretization of a compound region with very irregular curved boundaries is made easy by including both quadrilateral and triangular elements in the formulation. Large-field problems can be solved efficiently by including a pointwise iterative solution strategy as an optional alternative to the direct elimination solution method for the matrix equation approximating the partial differential equation of groundwater flow. FEWA also includes transient flow through confining leaky aquifers lying above and/or below the aquifer of interest. The model is verified against three simple cases to which analytical solutions are available. It is then demonstrated by two examples of how the model can be applied to heterogeneous and anisotropic aquifers with transient boundary conditions, time-dependent sources/sinks, and confining aquitards for a confined aquifer of variable thickness and for a free surface problem in an unconfined aquifer, respectively. 20 references, 25 figures, 8 tables.
A finite-elements method for turbulent flow analysis
International Nuclear Information System (INIS)
Autret, A.
1986-03-01
The work discussed here covers turbulent flow calculations using GALERKIN's finite-element method. Turbulence effects on the mean field are taken into account by the k-epsilon model with two evolution equations: one for the kinetic energy of the turbulence, and one for the energy dissipation rate. The wall zone is covered by wall laws, and by REICHARDT's law in particular. A law is advanced for the epsilon input profile, and a numerical solution is proposed for the physically aberrant values of k and epsilon generated by the model. Single-equation models are reviewed comparatively with the k-epsilon model. A comparison between calculated and analytical solutions or calculated and experimental results is presented for decreasing turbulence behind a grid, for the flow between parallel flat plates with three REYNOLDS numbers, and for backward facing step. This part contains graphs and curves corresponding to results of the calculations presented in part one [fr
Time-dependent particle migration and margination in the pressure-driven channel flow of blood
Qi, Qin M.; Shaqfeh, Eric S. G.
2018-03-01
We present a theory to describe the time evolution of the red blood cell (RBC) and platelet concentration distributions in pressure-driven flow through a straight channel. This model is based on our previous theory for the steady-state distributions [Qi and Shaqfeh, Phys. Rev. Fluids 2, 093102 (2017), 10.1103/PhysRevFluids.2.093102] and captures the flow-induced nonuniformity of the concentrations of RBCs and platelets in the cross-flow direction. Starting with a uniform concentration, RBCs migrate away from the channel walls due to a shear-induced lift force and eventually reach steady state due to shear-induced diffusion, i.e., hydrodynamic "collisions" with other RBCs. On the other hand, platelets exit the cell-laden region due to RBC-platelet interactions and enter the cell-free layer, resulting in margination. To validate the theory, we also perform boundary integral simulations of blood flow in microchannels and directly compare various measureables between theory and simulation. The timescales associated with RBC migration and platelet margination are discussed in the context of the simulation and theory, and their importance in the function of microfluidic devices as well as the vascular network are elucidated. Due to the varying shear rate in pressure-driven flow and the wall-induced RBC lift, we report a separation of timescales for the transport in the near-wall region and in the bulk region. We also relate the transient problem to the axial variation of migration and margination, and we demonstrate how the relevant timescales can be used to predict corresponding entrance lengths. Our theory can serve as a fast and convenient alternative to large-scale simulations of these phenomena.
Finite element analysis of turbulent flow in fast reactor fuel subassembly elementary flow cell
International Nuclear Information System (INIS)
Muehlbauer, P.
1987-03-01
The method is described of calculating fully developed longitudinal steady-state turbulent flow of an incompressible fluid through an infinite bundle of parallel smooth rods, based on the finite element method and one-equation turbulence model. Theoretical calculation results are compared with experimental results. (author). 5 figs., 3 refs
International Nuclear Information System (INIS)
Klotz, D.; Wolf, M.
2001-01-01
Humic acid transport of 152 in non-binding loose sediments of different grain sizes was investigated using a groundwater of the tertiary lignite of Northern Germany with a high humic acid concentration. The migration experiments were carried out in flow columns at natural filter flow rates and natural flow lengths [de
DEFF Research Database (Denmark)
Spangenberg, J.; Roussel, N.; Hattel, J.H.
2012-01-01
In this paper, we describe and compare the various physical phenomena which potentially lead to flow induced particle migration in concrete. We show that, in the case of industrial casting of concrete, gravity induced particle migration dominates all other potential sources of heterogeneities ind...
Parallel genetic algorithms with migration for the hybrid flow shop scheduling problem
Directory of Open Access Journals (Sweden)
K. Belkadi
2006-01-01
Full Text Available This paper addresses scheduling problems in hybrid flow shop-like systems with a migration parallel genetic algorithm (PGA_MIG. This parallel genetic algorithm model allows genetic diversity by the application of selection and reproduction mechanisms nearer to nature. The space structure of the population is modified by dividing it into disjoined subpopulations. From time to time, individuals are exchanged between the different subpopulations (migration. Influence of parameters and dedicated strategies are studied. These parameters are the number of independent subpopulations, the interconnection topology between subpopulations, the choice/replacement strategy of the migrant individuals, and the migration frequency. A comparison between the sequential and parallel version of genetic algorithm (GA is provided. This comparison relates to the quality of the solution and the execution time of the two versions. The efficiency of the parallel model highly depends on the parameters and especially on the migration frequency. In the same way this parallel model gives a significant improvement of computational time if it is implemented on a parallel architecture which offers an acceptable number of processors (as many processors as subpopulations.
An adaptative finite element method for turbulent flow simulations
International Nuclear Information System (INIS)
Arnoux-Guisse, F.; Bonnin, O.; Leal de Sousa, L.; Nicolas, G.
1995-05-01
After outlining the space and time discretization methods used in the N3S thermal hydraulic code developed at EDF/NHL, we describe the possibilities of the peripheral version, the Adaptative Mesh, which comprises two separate parts: the error indicator computation and the development of a module subdividing elements usable by the solid dynamics code ASTER and the electromagnetism code TRIFOU also developed by R and DD. The error indicators implemented in N3S are described. They consist of a projection indicator quantifying the space error in laminar or turbulent flow calculations and a Navier-Stokes residue indicator calculated on each element. The method for subdivision of triangles into four sub-triangles and tetrahedra into eight sub-tetrahedra is then presented with its advantages and drawbacks. It is illustrated by examples showing the efficiency of the module. The last concerns the 2 D case of flow behind a backward-facing step. (authors). 9 refs., 5 figs., 1 tab
Prohaska, T.; Irrgeher, J.; Zitek, A.; Teschler Nicola, M.
2010-12-01
Strontium - named after the small Scottish town Strontian - as such is an element with little popularity. Firstly described by Martin Heinrich Klaproth in 1798, the metal is used in metallurgy to some extent whereas its compounds are interesting in glass industries, electronics and pyrotechnics. The element has chemical similarity to Ca and makes up 1/60 of the earth’s amount of the latter. Nonetheless, it is its isotopic composition which makes Sr so interesting for a large number of scientists. The natural composition of the four naturally occurring isotopes (84Sr, 86Sr 87Sr and 88Sr) varies in nature due to the radioactive decay of 87Rb to 87Sr. Thus, it was early recognized as geochronometer especially in Ca rich matrices. With increasing precision of applied methodology, the natural variation of the 87Sr/86Sr isotope ratio (analyzed at first mainly by thermal ionization mass spectrometry (TIMS)) became more and more popular in provenance studies. The natural variation of the ratio is mainly determined by the geological age and the original composition of the rock and can be used therefore as fingerprint of the local geology. The ratio is transferred with no significant fractionation via the water into plants and finally via the food chain into animal and human tissues (especially bones and teeth). As the element is chemically similar to Ca, it appears in most matrices. The use for provenance studies is supported by the fact that the long half life (4.8 x 1010 years) does not lead to an alteration during the time scales which are investigated (from recent samples to human or animal skeletal remains which date back up to 30.000 BC). The uniqueness of the system besides the natural variation is defined by the ubiquity in nature and the relatively high (and thus measurable) elemental concentration in most tissues. It was finally the advent of multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) which augmented the number of applications
FLASH: A finite element computer code for variably saturated flow
International Nuclear Information System (INIS)
Baca, R.G.; Magnuson, S.O.
1992-05-01
A numerical model was developed for use in performance assessment studies at the INEL. The numerical model, referred to as the FLASH computer code, is designed to simulate two-dimensional fluid flow in fractured-porous media. The code is specifically designed to model variably saturated flow in an arid site vadose zone and saturated flow in an unconfined aquifer. In addition, the code also has the capability to simulate heat conduction in the vadose zone. This report presents the following: description of the conceptual frame-work and mathematical theory; derivations of the finite element techniques and algorithms; computational examples that illustrate the capability of the code; and input instructions for the general use of the code. The FLASH computer code is aimed at providing environmental scientists at the INEL with a predictive tool for the subsurface water pathway. This numerical model is expected to be widely used in performance assessments for: (1) the Remedial Investigation/Feasibility Study process and (2) compliance studies required by the US Department of Energy Order 5820.2A
A finite-elements method for turbulent flow analysis
International Nuclear Information System (INIS)
Autret, A.
1986-03-01
The work discussed here covers turbulent flow calculations using GALERKIN's finite-element method. In our specific case, we have to deal with monophasic incompressible flow in Boussinesq approximation in the normal operating conditions of a primary circuit of nuclear power plant. Turbulence effects on the mean field are taken into account by the k-epsilon model with two evolution equations: one for the kinetic energy of the turbulence, and one for the energy dissipation rate. The wall zone is covered by wall laws, and by REICHARDT's law in particular. A Law is advanced for the epsilon input profile, and a numerical solution is proposed for the physically aberrant values of k and epsilon generated by the model. Single-equation models are reviewed comparatively with the k-epsilon model. A comparison between calculated and analytical solutions or calculated and experimental results is presented for decreasing turbulence behind a grid, for the flow between parallel flat plates with three REYNOLDS numbers, and for backward facing step [fr
International Nuclear Information System (INIS)
Thompson, D.; Parry, S.J.; Benzing, R.
1997-01-01
A new radiotracer method has been developed to measure the migration of trace elements from food contact packaging into four standard food simulants; acetic acid, ethanol, olive oil, deionised water. A sample of material is irradiated in a thermal neutron flux of 10 16 n x m -2 x s -1 to activate the trace elements and produce a range of radionuclides. The samples is then placed in the food simulant and the migration of the radionuclides is monitored by performing γ-ray spectrometry on a sample of the simulant. Any radionuclides measured must be due entirely to the migration of the elements present in the plastic, since the simulant itself is not radioactive. Preliminary studies have shown that detection limits of around 0.2 μg x dm -2 (0.002 mg/kg) can be achieved for antimony in a sample of polyethylene terephthalate. This method can now been extended to measure migration into real foods. This will highlight any differences between the standard simulants currently used and real foods. Since the method only involves irradiation of the packaging material any food matrix can be studied. (author)
Kawai, T.
Among the topics discussed are the application of FEM to nonlinear free surface flow, Navier-Stokes shallow water wave equations, incompressible viscous flows and weather prediction, the mathematical analysis and characteristics of FEM, penalty function FEM, convective, viscous, and high Reynolds number FEM analyses, the solution of time-dependent, three-dimensional and incompressible Navier-Stokes equations, turbulent boundary layer flow, FEM modeling of environmental problems over complex terrain, and FEM's application to thermal convection problems and to the flow of polymeric materials in injection molding processes. Also covered are FEMs for compressible flows, including boundary layer flows and transonic flows, hybrid element approaches for wave hydrodynamic loadings, FEM acoustic field analyses, and FEM treatment of free surface flow, shallow water flow, seepage flow, and sediment transport. Boundary element methods and FEM computational technique topics are also discussed. For individual items see A84-25834 to A84-25896
International Nuclear Information System (INIS)
Conceicao, Cirilo C.S.
2009-01-01
The determination of rare earth elements as natural analogue in patterns geologic has grown as a tool for predicting the long-term safety of nuclear disposal in geological formation. Migration of natural radionuclides is one of the most serious problems in the waste deposit from nuclear fuel cycle. Rare earth elements show the same kinetic behavior in rocks as natural radionuclides. This similar property of the analogues allows perform studies and models on the subject of radionuclides migration. The aim of this study was to determine the distribution of rare earth elements in rocks located at Espinharas - Paraiba - Brazil, uranium deposit. In this work are presented the results from the study above the distribution of rare earth elements in function of the degree of mineralized rocks, composition and the conditions of radioactive equilibrium of the uranium and thorium in some fractures on the rocks from radioactive occurrence of Espinharas-Brazil. The results show that there is a correlation of heavy rare earth elements, uranium and Thorium concentrations to oxidation factor of the rocks. However this correlation was not observed for light rare earth elements. It means that heavy rare earth elements follow the natural radionuclides in oxidation process of rocks. The samples were analyzed by ICP-MS, alpha and gamma spectrometry, X-ray diffraction and fluorimetry. (author)
Responding to flow: How phytoplankton adapt migration strategies to tackle turbulence
Sengupta, Anupam; Carrara, Francesco; Stocker, Roman
2014-11-01
Phytoplankton are among the ocean's most important organisms and it has long been recognized that turbulence is a primary determinant of their fitness. Yet, mechanisms by which phytoplankton may adapt to turbulence have remained unknown. We present experiments that demonstrate how phytoplankton are capable of rapid adaptive behavior in response to fluid flow disturbances that mimic turbulence. Our study organism was the toxic marine alga Heterosigma akashiwo, known to exhibit ``negative gravitaxis,'' i . e . , to frequently migrate upwards against gravity. To mimic the effect of Kolmogorov-scale turbulent eddies, which expose cells to repeated reorientations, we observed H. akashiwo in a ``flip chamber,'' whose orientation was periodically flipped. Tracking of single cells revealed a striking, robust behavioral adaptation, whereby within tens of minutes half of the population reversed its direction of migration to swim downwards, demonstrating an active response to fluid flow. Using confocal microscopy, we provide a physiological rationalization of this behavior in terms of the redistribution of internal organelles, and speculate on the motives for this bet-hedging-type strategy. This work suggests that the effects of fluid flow - not just passive but also active - on plankton represents a rich area of investigation with considerable implications for some of earth's most important organisms.
International Nuclear Information System (INIS)
Egorov, V.N.
1999-01-01
This report considers peculiarities of the mathematical description of radionuclides migration between water environment and biotic and abiotic components of the Black Sea ecosystems at different periods of averaging, from the time scale of metabolic processes, taking place in hydrobionts, to the large-scale description of radionuclides migration in the Black Sea
A Finite Element Method for Simulation of Compressible Cavitating Flows
Shams, Ehsan; Yang, Fan; Zhang, Yu; Sahni, Onkar; Shephard, Mark; Oberai, Assad
2016-11-01
This work focuses on a novel approach for finite element simulations of multi-phase flows which involve evolving interface with phase change. Modeling problems, such as cavitation, requires addressing multiple challenges, including compressibility of the vapor phase, interface physics caused by mass, momentum and energy fluxes. We have developed a mathematically consistent and robust computational approach to address these problems. We use stabilized finite element methods on unstructured meshes to solve for the compressible Navier-Stokes equations. Arbitrary Lagrangian-Eulerian formulation is used to handle the interface motions. Our method uses a mesh adaptation strategy to preserve the quality of the volumetric mesh, while the interface mesh moves along with the interface. The interface jump conditions are accurately represented using a discontinuous Galerkin method on the conservation laws. Condensation and evaporation rates at the interface are thermodynamically modeled to determine the interface velocity. We will present initial results on bubble cavitation the behavior of an attached cavitation zone in a separated boundary layer. We acknowledge the support from Army Research Office (ARO) under ARO Grant W911NF-14-1-0301.
GPU-accelerated Modeling and Element-free Reverse-time Migration with Gauss Points Partition
Zhen, Z.; Jia, X.
2014-12-01
Element-free method (EFM) has been applied to seismic modeling and migration. Compared with finite element method (FEM) and finite difference method (FDM), it is much cheaper and more flexible because only the information of the nodes and the boundary of the study area are required in computation. In the EFM, the number of Gauss points should be consistent with the number of model nodes; otherwise the accuracy of the intermediate coefficient matrices would be harmed. Thus when we increase the nodes of velocity model in order to obtain higher resolution, we find that the size of the computer's memory will be a bottleneck. The original EFM can deal with at most 81×81 nodes in the case of 2G memory, as tested by Jia and Hu (2006). In order to solve the problem of storage and computation efficiency, we propose a concept of Gauss points partition (GPP), and utilize the GPUs to improve the computation efficiency. Considering the characteristics of the Gaussian points, the GPP method doesn't influence the propagation of seismic wave in the velocity model. To overcome the time-consuming computation of the stiffness matrix (K) and the mass matrix (M), we also use the GPUs in our computation program. We employ the compressed sparse row (CSR) format to compress the intermediate sparse matrices and try to simplify the operations by solving the linear equations with the CULA Sparse's Conjugate Gradient (CG) solver instead of the linear sparse solver 'PARDISO'. It is observed that our strategy can significantly reduce the computational time of K and Mcompared with the algorithm based on CPU. The model tested is Marmousi model. The length of the model is 7425m and the depth is 2990m. We discretize the model with 595x298 nodes, 300x300 Gauss cells and 3x3 Gauss points in each cell. In contrast to the computational time of the conventional EFM, the GPUs-GPP approach can substantially improve the efficiency. The speedup ratio of time consumption of computing K, M is 120 and the
Size-selective sorting in bubble streaming flows: Particle migration on fast time scales
Thameem, Raqeeb; Rallabandi, Bhargav; Hilgenfeldt, Sascha
2015-11-01
Steady streaming from ultrasonically driven microbubbles is an increasingly popular technique in microfluidics because such devices are easily manufactured and generate powerful and highly controllable flows. Combining streaming and Poiseuille transport flows allows for passive size-sensitive sorting at particle sizes and selectivities much smaller than the bubble radius. The crucial particle deflection and separation takes place over very small times (milliseconds) and length scales (20-30 microns) and can be rationalized using a simplified geometric mechanism. A quantitative theoretical description is achieved through the application of recent results on three-dimensional streaming flow field contributions. To develop a more fundamental understanding of the particle dynamics, we use high-speed photography of trajectories in polydisperse particle suspensions, recording the particle motion on the time scale of the bubble oscillation. Our data reveal the dependence of particle displacement on driving phase, particle size, oscillatory flow speed, and streaming speed. With this information, the effective repulsive force exerted by the bubble on the particle can be quantified, showing for the first time how fast, selective particle migration is effected in a streaming flow. We acknowledge support by the National Science Foundation under grant number CBET-1236141.
Directory of Open Access Journals (Sweden)
Asad Rehman
Full Text Available An upwind space-time conservation element and solution element (CE/SE scheme is extended to numerically approximate the dusty gas flow model. Unlike central CE/SE schemes, the current method uses the upwind procedure to derive the numerical fluxes through the inner boundary of conservation elements. These upwind fluxes are utilized to calculate the gradients of flow variables. For comparison and validation, the central upwind scheme is also applied to solve the same dusty gas flow model. The suggested upwind CE/SE scheme resolves the contact discontinuities more effectively and preserves the positivity of flow variables in low density flows. Several case studies are considered and the results of upwind CE/SE are compared with the solutions of central upwind scheme. The numerical results show better performance of the upwind CE/SE method as compared to the central upwind scheme. Keywords: Dusty gas flow, Solid particles, Upwind schemes, Rarefaction wave, Shock wave, Contact discontinuity
Sun, Y.; Luo, G.
2017-12-01
Seismicity in a region is usually characterized by earthquake clusters and earthquake migration along its major fault zones. However, we do not fully understand why and how earthquake clusters and spatio-temporal migration of earthquakes occur. The northeastern Tibetan Plateau is a good example for us to investigate these problems. In this study, we construct and use a three-dimensional viscoelastoplastic finite-element model to simulate earthquake cycles and spatio-temporal migration of earthquakes along major fault zones in northeastern Tibetan Plateau. We calculate stress evolution and fault interactions, and explore effects of topographic loading and viscosity of middle-lower crust and upper mantle on model results. Model results show that earthquakes and fault interactions increase Coulomb stress on the neighboring faults or segments, accelerating the future earthquakes in this region. Thus, earthquakes occur sequentially in a short time, leading to regional earthquake clusters. Through long-term evolution, stresses on some seismogenic faults, which are far apart, may almost simultaneously reach the critical state of fault failure, probably also leading to regional earthquake clusters and earthquake migration. Based on our model synthetic seismic catalog and paleoseismic data, we analyze probability of earthquake migration between major faults in northeastern Tibetan Plateau. We find that following the 1920 M 8.5 Haiyuan earthquake and the 1927 M 8.0 Gulang earthquake, the next big event (M≥7) in northeastern Tibetan Plateau would be most likely to occur on the Haiyuan fault.
Prediction of radionuclide migration in the geosphere: is the porous-flow model adequate
International Nuclear Information System (INIS)
Neretnieks, I.
1982-01-01
Practically all models used today to describe radionuclide migration in geologic media are based on the concept of flow in porous media. Recently it has been questioned if Fickian dispersion is the most important dispersion mechanism. Field observations of dispersion indicate that the dispersion coefficient increases with observation distance. This should not be the case in a homogeneous porous medium. For a medium with essentially independent channels, on the other hand, such an effect can be predicted. In some calculated examples it is shown that the use of the Fickian dispersion mechanism will very seriously underestimate the radionuclide concentration at a point downstream if the spreading mechanism in reality is channelling. The consequences of the often-used assumption that the interaction between the radionuclides and the rock is instantaneous is also discussed. It has been shown that in sparsely fissured crystalline rock the whole rock mass will not be able to participate in the sorption reactions, because the radionuclides will not have time to penetrate all through the large blocks. On the other hand, the assumption that only the surface of the fissures interacts with the radionuclides is likely to be an extremely conservative assumption in view of some recent diffusion experiments in crystalline rocks performed in our laboratories and at the Canadian Geologic Survey. Some experimental results on radionuclide migration in a single natural fissure under well-controlled conditions in the laboratory are also presented and interpreted using a model which includes channelling, surface sorption, diffusion in the rock matrix and sorption in the rock matrix. Some implications of these mechanisms in predicting radionuclide migration in the geosphere are discussed and compared with what a porous-flow model would predict
Data base for site specific migration analysis of radioactive elements in repositories
Energy Technology Data Exchange (ETDEWEB)
Hadermann, J
1982-01-01
Migration analysis is of considerable importance in long-term safety aspects of radioactive waste repositories. The present work gives the data base for a selected part of a comprehensive geosphere transport calculation. We restrict ourselves to a critical evaluation of parameters pertinent to the migration analysis of the /sup 245/Cm chain. This includes the important nuclide /sup 237/Np. With these we are able to perform a site specific calculation for repositories planned in deep geologic formations in Switzerland. It is shown that the granitic basement induces strong time delays in nuclide migration. In contrast to that, the overlaying sedimentary layers cause primarily a dilution of the radionuclide concentrations.
International Nuclear Information System (INIS)
Rosa, Faena Machado Leite
2008-01-01
For decades migration study of chemical compounds from packaging into food, such as metals, residual monomers and additives, is a very important issue, concerning public health and minimize chemical contamination. In this work, it was done irradiations of packagings taken in contact with food simulant, and it was studied this migration through a mathematical model of the diffusion process, compiled in a computational simulation method in order to study the microscopic behavior of migration of metallic elements cadmium, chromium, antimony and cobalt, present in metallic plastics from dairy product packagings, and also the migration of - caprolactam monomer, present in nylon polymeric plastics used for package meat stuffs, to the food simulant acetic acid 3%. The results from simulations of the migration of -caprolactam monomer were compared with experimental results obtained from high resolution gas chromatography (HRGC) measurements, and the simulation of metallic elements migration were compared with the neutron activation analysis measurements (NAA). These experimental results were performed and kindly informed by another research groups, partners in this project. The food packaging system was discretized in one-dimension space and in time and the partial differential equation that defines the diffusive process, the second 'Fick's law', together with an equation of Arrhenius type dealing with the thermal influence, were solved using finite differences. The final step of the resolution was a tridiagonal linear system, solved using the Thomas algorithm. It was studied, and in some cases even foreseen, experimental quantities, like the diffusion coefficient, activation energy and concentration profile of migrant compounds, allowing the understanding of the diffusion process and the quantitative estimate of the migration of such compounds under ionizing radiation influence. Variation on the initial concentration levels (C 0 ) of the monomer inside the packaging
Element flows associated with marine shore mine tailings deposits.
Dold, Bernhard
2006-02-01
From 1938 until 1975, flotation tailings from the Potrerillos--El Salvador mining district (porphyry copper deposits) were discharged into the El Salado valley and transported in suspension to the sea at Chaliaral Bay, Atacama Desert, northern Chile. Over 220 Mt of tailings, averaging 0.8 +/- 0.25 wt % of pyrite, were deposited into the bay, resulting in over a 1 kilometer seaward displacement of the shoreline and an estimated 10-15 m thick tailings accumulation covering a approximately 4 km2 surface area. The Chaniaral case was classified by the United Nations Environmental Programme (UNEP) in 1983 as one of the most serious cases of marine contamination in the Pacific area. Since 1975, the tailings have been exposed to oxidation, resulting in a 70-188 cm thick low-pH (2.6-4) oxidation zone at the top with liberation of divalent metal cations, such as Cu2+, Ni2+, and Zn2+ (up to 2265 mg/L, 18.1 mg/L, and 20.3 mg/ L, respectively). Evaporation-induced transport capillarity led to metal enrichment atthe tailings surface (e.g. up to 2.4% Cu) in the form of secondary chlorides and/or sulfates (dominated by eriochalcite [CuCl.H2O] and halite). These, mainly water-soluble, secondary minerals were exposed to eolian transport in the direction of the Village of Chañaral by the predominant W-SW winds. Two element-flow directions (toward the tailings surface, via capillarity, and toward the sea) and two element groups with different geochemical behaviors (cations such as Cu, Zn, Ni, and oxyanions such as As and Mo) could be distinguished. It can be postulated, that the sea is mainly affected by the following: As, Mo, Cu, and Zn contamination, which were liberated from the oxidation zone from the tailings and mobilized through the tidal cycle, and by Cu and Zn from the subsurface waters flowing in the El Salado valley (up to 19 mg/L and 12 mg/L Zn, respectively), transported as chloro complexes at neutral pH.
DEFF Research Database (Denmark)
Qvist, Niels; Rafaelsen, Søren Rafael; Troensegaard, P.
1994-01-01
Objective: To measure variation in portal blood flow during the interdigestive state in relation to the migrating motor complex (MMC) in healthy volunteers. Design: Portal blood flow was measured by a duplex and colour Doppler technique with 5-min intervals during an entire MMC cycle. Total....... Conclusion: Blood flow in the portal vein varies with the characteristics of the MMC, a relationship which must be considered in future studies in health and disease....
Rehman, Asad; Ali, Ishtiaq; Qamar, Shamsul
An upwind space-time conservation element and solution element (CE/SE) scheme is extended to numerically approximate the dusty gas flow model. Unlike central CE/SE schemes, the current method uses the upwind procedure to derive the numerical fluxes through the inner boundary of conservation elements. These upwind fluxes are utilized to calculate the gradients of flow variables. For comparison and validation, the central upwind scheme is also applied to solve the same dusty gas flow model. The suggested upwind CE/SE scheme resolves the contact discontinuities more effectively and preserves the positivity of flow variables in low density flows. Several case studies are considered and the results of upwind CE/SE are compared with the solutions of central upwind scheme. The numerical results show better performance of the upwind CE/SE method as compared to the central upwind scheme.
Xia, Xiaohong; Qin, Yong; Yang, Weifeng
2013-03-01
Coal liquefaction is an adoptable method to transfer the solid fossil energy into liquid oil in large scale, but the dirty material in which will migrate to different step of liquefaction. The migration rule of some trace elements is response to the react activity of macerals in coal and the geological occurrence of the element nature of itself. In this paper, from the SPSS data correlation analysis and hierarchical clustering dendrogram about the trace elements with macerals respond to coal liquefaction yield, it shows the trace elements in No.11 Antaibao coal seam originated from some of lithophile and sulphophle elements. Correlation coefficient between liquefaction yield of three organic macerals and migration of the elements in liquefaction residue indicated that the lithophile are easy to transfer to residue, while sulphophle are apt to in the liquid products. The activated macerals are response to sulphophle trace elements. The conclusion is useful to the coal blending and environmental effects on coal direct liquefaction.
Cash flows: The Gap Between Reported and Estimated Operating Cash Flow Elements
Directory of Open Access Journals (Sweden)
Mark Hughes
2010-03-01
Full Text Available The FASB and the IASB recently released a joint Discussion Paper “Preliminary Views on FinancialStatement Presentation” (International Accounting Standards Board 2008, which contains a major proposalrequiring companies to report operating cash flows using the direct method and it also requires that theindirect method of calculating operating cash flows be disclosed in the notes. This is a departure from currentrules and has generated considerable debate among respondents’ comment letters on the Discussion Paper.This paper adds to this debate by providing some evidence as to the size of the gap users confront when usingthe indirect method to estimate the major operating cash flow elements, such as cash collected fromcustomers and cash paid to suppliers. Using a sample of Australian companies which reported operating cashflows using the direct method, and presented the indirect method in the notes, we find significant differencesbetween reported and estimated figures for both cash collected from customers and cash paid to suppliers.These findings support the discussion paper’s proposal that companies be required to report cash flows usingboth the direct and indirect methods.
Finite element analysis of helical flows in human aortic arch: A novel index
Lee, Cheng-Hung; Liu, Kuo-Sheng; Jhong, Guan-Heng; Liu, Shih-Jung; Hsu, Ming-Yi; Wang, Chao-Jan; Hung, Kuo-Chun
2014-01-01
This study investigates the helical secondary flows in the aortic arch using finite element analysis. The relationship between helical flow and the configuration of the aorta in patients of whose three-dimensional images constructed from computed tomography scans was examined. A finite element model of the pressurized root, arch, and supra-aortic vessels was developed to simulate the pattern of helical secondary flows. Calculations indicate that most of the helical secondary flow was formed i...
Hughes Clarke, John E.
2016-01-01
Field observations of turbidity currents remain scarce, and thus there is continued debate about their internal structure and how they modify underlying bedforms. Here, I present the results of a new imaging method that examines multiple surge-like turbidity currents within a delta front channel, as they pass over crescent-shaped bedforms. Seven discrete flows over a 2-h period vary in speed from 0.5 to 3.0 ms−1. Only flows that exhibit a distinct acoustically attenuating layer at the base, appear to cause bedform migration. That layer thickens abruptly downstream of the bottom of the lee slope of the bedform, and the upper surface of the layer fluctuates rapidly at that point. The basal layer is inferred to reflect a strong near-bed gradient in density and the thickening is interpreted as a hydraulic jump. These results represent field-scale flow observations in support of a cyclic step origin of crescent-shaped bedforms. PMID:27283503
Selection or network effects? Migration flows into 27 OECD countries, 1990-2000
DEFF Research Database (Denmark)
Pedersen, Peder J.; Pytlikova, Mariola; Smith, Nina
Recent migration patterns show growing migration pressure and changing composition of immigrants in many Western countries. During the latest decade, an increasing proportion of the OECD immigrants have been from poor countries, where the educational level of the population is low. The migration ...... evidence that selection effects have had a major influence on the observed migration patterns until now. This may partly be explained by restrictive migration policies in many OECD countries which may have dampened the potential selection effects....
Selection or Network Effects? Migration Flows into 27 OECD Countries, 1990-2000
DEFF Research Database (Denmark)
Pedersen, P.J.; Pytlikova, Mariola; Smith, Nina
Recent migration patterns show growing migration pressure and changing composition of immigrants in many Western countries. During the latest decade, an increasing proportion of the OECD immigrants have been from poor countries, where the educational level of the population is low. The migration ...... evidence that selection effects have had a major influence on the observed migration patterns until now. This may partly be explained by restrictive migration policies in many OECD countries which may have dampened the potential selection effects....
Impact of kinetics and flow path heterogeneity on nanoparticle/radionuclide migration
International Nuclear Information System (INIS)
Huber, Florian M.
2011-01-01
The prevailing PhD thesis experimentally investigates the impact of both sorption/desorption (reversibility) and reduction kinetics on radionuclide migration in synthetic and natural systems from the nano-to the centimeter scale. Furthermore, the impact of fracture heterogeneity on flow and solute/nanoparticle transport as a potential additional retardation mechanism is examined both on an experimental and numerical basis. The process of sorptive reduction of U(VI) to sparingly soluble tetravalent uranium by structural bound Fe(II) in magnetite shows fast kinetics (hours to a few days contact time). A clear correlation between the Fe(II) content on the magnetite surface and the amount of U(VI) was observed, that is, increasing U(IV) with increasing Fe(II). Moreover, a congruency between the measured Eh(SHE) and the U valence state can partly been derived within the analytical uncertainties of the redox potential measurements. Thus, secondary phases as the stainless steel corrosion product magnetite can have beneficial effects on radionuclide migration as an effective retardation pathway for redox sensitive radionuclides. Beside, the studies on U(VI) maghemite sorption show that oxidized surfaces can possess long-term reduction capacities further enhancing radionuclide retention. Concerning the colloid-facilitated radionuclide transport, the batch sorption reversibility studies revealed the significance of kinetically controlled radionuclide desorption from the colloidal phase and subsequent sorption to the fracture filling materials (independent of the mineralogy and/or size fraction). By this process, initially colloidal associated radionuclides like the tri-and tetravalent radionuclides Th, Pu and Am are effectively retarded leading to an increase in the residence time. These reversibility results need to be included in codes for simulating colloid-facilitated radionuclide transport to reduce the conservatism and degree of uncertainties in input parameters
Impact of kinetics and flow path heterogeneity on nanoparticle/radionuclide migration
Energy Technology Data Exchange (ETDEWEB)
Huber, Florian M.
2011-11-29
The prevailing PhD thesis experimentally investigates the impact of both sorption/desorption (reversibility) and reduction kinetics on radionuclide migration in synthetic and natural systems from the nano-to the centimeter scale. Furthermore, the impact of fracture heterogeneity on flow and solute/nanoparticle transport as a potential additional retardation mechanism is examined both on an experimental and numerical basis. The process of sorptive reduction of U(VI) to sparingly soluble tetravalent uranium by structural bound Fe(II) in magnetite shows fast kinetics (hours to a few days contact time). A clear correlation between the Fe(II) content on the magnetite surface and the amount of U(VI) was observed, that is, increasing U(IV) with increasing Fe(II). Moreover, a congruency between the measured Eh(SHE) and the U valence state can partly been derived within the analytical uncertainties of the redox potential measurements. Thus, secondary phases as the stainless steel corrosion product magnetite can have beneficial effects on radionuclide migration as an effective retardation pathway for redox sensitive radionuclides. Beside, the studies on U(VI) maghemite sorption show that oxidized surfaces can possess long-term reduction capacities further enhancing radionuclide retention. Concerning the colloid-facilitated radionuclide transport, the batch sorption reversibility studies revealed the significance of kinetically controlled radionuclide desorption from the colloidal phase and subsequent sorption to the fracture filling materials (independent of the mineralogy and/or size fraction). By this process, initially colloidal associated radionuclides like the tri-and tetravalent radionuclides Th, Pu and Am are effectively retarded leading to an increase in the residence time. These reversibility results need to be included in codes for simulating colloid-facilitated radionuclide transport to reduce the conservatism and degree of uncertainties in input parameters
Hong, Tao; Xu, Xing-Wang; Gao, Jun; Peters, Stephen; Li, Jilei; Cao, Mingjian; Xiang, Peng; Wu, Chu; You, Jun
2017-01-01
fugacities from stage A to stage B, while temperature and oxygen fugacities decrease from stage B to stage C. The Co/Ni ratio of pyrite depends discriminates between the different mineralizing stages in the Yuleken porphyry copper deposit: Py II, associated with the deformation stage B and Cu-enrichment, shows higher Co/Ni ratios and enrichments of Pb, Zn, Mo, Te and Sb than the pyrites formed during the other two stages. The Co/Ni ratio of pyrite can not only apply to discriminate the submarine exhalative, magmatic or sedimentary origins for ore deposits but also can distinguish different ore-forming stages in a single porphyry Cu deposit. Thus, Co/Ni ratio of pyrites may act as an important exploration tool to distinguish pyrites from Cu-rich versus barren area. Furthermore, the distribution of Cu, Mo, Pb, Au, Bi, Sb and Zn in the variably deformed pyrite is proportional to the extent of deformation of the pyrites, indicating in accordance with variable physicochemical conditions different element migration behavior during the different stages of deformation and, thus, mineralisation.
Tittarelli, Francesca; Mobili, Alessandra; Bellezze, Tiziano
2017-08-01
The use of sodium monofluorophosphate (MFP) was experimented as migrator inhibiting treatment against corrosion of reinforced concrete elements induced by chlorides. The results show that sodium monofluorophosphate, applied by surface impregnation, is able to slow down reinforcement corrosion only for reinforcing steel bars with concrete cover not thicker than 1 cm. This limitation is most probably due to the difficulty, with the type of application adopted, in making MFP to reach concentrations high enough to inhibit the corrosive process at greater depths from the impregnation surface.
Davletshin, I. A.; Dushina, O. A.; Mikheev, N. I.; Kolchin, S. A.
2017-11-01
The pulsating flow in a circular channel with semicircular annular ribs as discrete roughness elements has been studied experimentally. Air flow under atmospheric conditions at the channel inlet has been considered. Steady and pulsating air flow has been studied under different frequencies and amplitudes of forced pulsations generated by periodic blockage of the channel cross section by a rotating flap. Flow resistance in pulsating regimes has been estimated from the average static pressure drop. The resistance values attained twice the steady flow ones.
Laboratory and field tests for radionuclide migration and high flow paths in clay
International Nuclear Information System (INIS)
Bourke, P.J.; Jefferies, N.L.; Lineham, T.R.; Nesirky, P.
1991-01-01
Two investigations have been undertaken in this programme. The principal investigation was at Culham Laboratory, England, where water flow within the Kimmeridge clay was measured. A subsidiary investigation at SCK/CEN was undertaken at the Underground Research Laboratory SCK/CEN Mol, Belgium, where an in situ measurement of solute transport by diffusion was attempted. The in situ migration experiment at the Underground Research Laboratory at SCK/CEN Mol, Belgium, was unsuccessful, due to problems with the engineering installation. These difficulties caused significant disturbance to the Boom clay which was to be tested. Nevertheless the laboratory test proved the feasibility of the experiment. The field measurements at Culham Laboratory, Oxfordshire, were completed with the flow testing of a very silty clay horizon in the Kimmeridge clay. This layer was proved to be laterally continuous after drilling three exploratory boreholes. The hydraulic conductivity of the layer was ≥ 10 -8 ms -1 and comparative tests in the clay showed the conductivity of the clay to be at least 50 times less. 12 figs
A porous flow approach to model thermal non-equilibrium applicable to melt migration
Schmeling, Harro; Marquart, Gabriele; Grebe, Michael
2018-01-01
We develop an approach for heat exchange between a fluid and a solid phase of a porous medium where the temperatures of the fluid and matrix are not in thermal equilibrium. The formulation considers moving of the fluid within a resting or deforming porous matrix in an Eulerian coordinate system. The approach can be applied, for example, to partially molten systems or to brine transport in porous rocks. We start from an existing theory for heat exchange where the energy conservation equations for the fluid and the solid phases are separated and coupled by a heat exchange term. This term is extended to account for the full history of heat exchange. It depends on the microscopic geometry of the fluid phase. For the case of solid containing hot, fluid-filled channels, we derive an expression based on a time-dependent Fourier approach for periodic half-waves. On the macroscopic scale, the temporal evolution of the heat exchange leads to a convolution integral along the flow path of the solid, which simplifies considerably in case of a resting matrix. The evolution of the temperature in both phases with time is derived by inserting the heat exchange term into the energy equations. We explore the effects of thermal non-equilibrium between fluid and solid by considering simple cases with sudden temperature differences between fluid and solid as initial or boundary conditions, and by varying the fluid velocity with respect to the resting porous solid. Our results agree well with an analytical solution for non-moving fluid and solid. The temperature difference between solid and fluid depends on the Peclet number based on the Darcy velocity. For Peclet numbers larger than 1, the temperature difference after one diffusion time reaches 5 per cent of \\tilde{T} or more (\\tilde{T} is a scaling temperature, e.g. the initial temperature difference). Thus, our results imply that thermal non-equilibrium can play an important role for melt migration through partially molten systems
Data base for a site-specific migration analysis radioactive elements out of a waste repository
Energy Technology Data Exchange (ETDEWEB)
Hadermann, J
1981-11-01
Migration analysis is of considerable importance in long-term safety analysis of radioactive waste repositories. In a first step our plans are to calculate transport of radionuclides using data - as far as possible - for an undisturbed hydrogeology. Thereby a reference case is defined. In a later step, possible events and processes can be considered leading to a deviation from the reference case. The present work gives the data base for a selected part of a comprehensive geosphere transport calculation. We restrict ourselves to a critical evaluation of parameters pertinent to the migration analysis of the /sup 245/Cm chain. This includes the important nuclide /sup 237/Np. For the first time we are able to perform a site specific calculation for repositories planned in deep geologic formations in Switzerland. The well-known fact that the data basis is extremely sparse is pointed out once more and concretized in detail.
Element Free Lattice Boltzmann Method for Fluid-Flow Problems
International Nuclear Information System (INIS)
Jo, Jong Chull; Roh, Kyung Wan; Yune, Young Gill; Kim, Hho Jhung; Kwon, Young Kwon
2007-01-01
The Lattice Boltzmann Method (LBM) has been developed for application to thermal-fluid problems. Most of the those studies considered a regular shape of lattice or mesh like square and cubic grids. In order to apply the LBM to more practical cases, it is necessary to be able to solve complex or irregular shapes of problem domains. Some techniques were based on the finite element method. Generally, the finite element method is very powerful for solving two or three-dimensional complex or irregular shapes of domains using the iso-parametric element formulation which is based on a mathematical mapping from a regular shape of element in an imaginary domain to a more general and irregular shape of element in the physical domain. In addition, the element free technique is also quite useful to analyze a complex shape of domain because there is no need to divide a domain by a compatible finite element mesh. This paper presents a new finite element and element free formulations for the lattice Boltzmann equation using the general weighted residual technique. Then, a series of validation examples are presented
Element Free Lattice Boltzmann Method for Fluid-Flow Problems
Energy Technology Data Exchange (ETDEWEB)
Jo, Jong Chull; Roh, Kyung Wan; Yune, Young Gill; Kim, Hho Jhung [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Kwon, Young Kwon [US Naval Postgraduate School, New York (United States)
2007-10-15
The Lattice Boltzmann Method (LBM) has been developed for application to thermal-fluid problems. Most of the those studies considered a regular shape of lattice or mesh like square and cubic grids. In order to apply the LBM to more practical cases, it is necessary to be able to solve complex or irregular shapes of problem domains. Some techniques were based on the finite element method. Generally, the finite element method is very powerful for solving two or three-dimensional complex or irregular shapes of domains using the iso-parametric element formulation which is based on a mathematical mapping from a regular shape of element in an imaginary domain to a more general and irregular shape of element in the physical domain. In addition, the element free technique is also quite useful to analyze a complex shape of domain because there is no need to divide a domain by a compatible finite element mesh. This paper presents a new finite element and element free formulations for the lattice Boltzmann equation using the general weighted residual technique. Then, a series of validation examples are presented.
WILLEKENS, F
1994-01-01
The paper reviews techniques developed in demography, geography and statistics that are useful for bridging the gap between available data on international migration flows and the information required for policy making and research. The basic idea of the paper is as follows: to establish a coherent
Replacement of fluid-filter elements without interruption of flow
Kotler, R. A.; Ward, J. B.
1969-01-01
Gatling-type filter assembly, preloaded with several filter elements enables filter replacement without breaking into the operative fluid system. When the filter element becomes contaminated, a unit inner subassembly is rotated 60 degrees to position a clean filter in the line.
Cellular Structures in the Flow Over the Flap of a Two-Element Wing
Yon, Steven A.; Katz, Joseph
1997-01-01
Flow visualization information and time dependent pressure coefficients were recorded for the flow over a two-element wing. The investigation focused on the stall onset; particularly at a condition where the flow is attached on the main element but separated on the flap. At this condition, spanwise separation cells were visible in the flow over the flap, and time dependent pressure data was measured along the centerline of the separation cell. The flow visualizations indicated that the spanwise occurrence of the separation cells depends on the flap (and not wing) aspect ratio.
Coupling nonlinear Stokes and Darcy flow using mortar finite elements
Ervin, Vincent J.; Jenkins, Eleanor W.; Sun, Shuyu
2011-01-01
We study a system composed of a nonlinear Stokes flow in one subdomain coupled with a nonlinear porous medium flow in another subdomain. Special attention is paid to the mathematical consequence of the shear-dependent fluid viscosity for the Stokes
Gailey, Robert M.
2017-11-01
Water supply wells can act as conduits for vertical flow and contaminant migration between water-bearing strata under common hydrogeologic and well construction conditions. While recognized by some for decades, there is little published data on the magnitude of flows and extent of resulting water quality impacts. Consequently, the issue may not be acknowledged widely enough and the need for better management persists. This is especially true for unconsolidated alluvial groundwater basins that are hydrologically stressed by agricultural activities. Theoretical and practical considerations indicate that significant water volumes can migrate vertically through wells. The flow is often downward, with shallow groundwater, usually poorer in quality, migrating through conduit wells to degrade deeper water quality. Field data from locations in California, USA, are presented in combination with modeling results to illustrate both the prevalence of conditions conducive to intraborehole flow and the resulting impacts to water quality. Suggestions for management of planned wells include better enforcement of current regulations and more detailed consideration of hydrogeologic conditions during design and installation. A potentially greater management challenge is presented by the large number of existing wells. Monitoring for evidence of conduit flow and solute transport in areas of high well density is recommended to identify wells that pose greater risks to water quality. Conduit wells that are discovered may be addressed through approaches that include structural modification and changes in operations.
A CFD numerical model for the flow distribution in a MTR fuel element
International Nuclear Information System (INIS)
Andrade, Delvonei Alves de; Santos, Pedro Henrique Di Giovanni; Oliveira, Fabio Branco Vaz de; Torres, Walmir Maximo; Umbehaun, Pedro Ernesto; Souza, Jose Antonio Batista de; Belchior Junior, Antonio; Sabundjian, Gaiane; Prado, Adelk de Carvalho; Angelo, Gabriel
2015-01-01
Previously, an instrumented dummy fuel element (DMPV-01), with the same geometric characteristics of a MTR fuel element, was designed and constructed for pressure drop and flow distribution measurement experiments at the IEA-R1 reactor core. This dummy element was also used to measure the flow distribution among the rectangular flow channels formed by element fuel plates. A CFD numerical model was developed to complement the studies. This work presents the proposed CFD model as well as a comparison between numerical and experimental results of flow rate distribution among the internal flow channels. Numerical results show that the model reproduces the experiments very well and can be used for the studies as a more convenient and complementary tool. (author)
A CFD numerical model for the flow distribution in a MTR fuel element
Energy Technology Data Exchange (ETDEWEB)
Andrade, Delvonei Alves de; Santos, Pedro Henrique Di Giovanni; Oliveira, Fabio Branco Vaz de; Torres, Walmir Maximo; Umbehaun, Pedro Ernesto; Souza, Jose Antonio Batista de; Belchior Junior, Antonio; Sabundjian, Gaiane; Prado, Adelk de Carvalho, E-mail: acprado@ipen.br, E-mail: delvonei@ipen.br, E-mail: dpedro_digiovanni_s@hotmail.com, E-mail: fabio@ipen.br, E-mail: wmtorres@ipen.br, E-mail: umbehaun@ipen.br, E-mail: jasouza@ipen.br, E-mail: abelchior@ipen.br, E-mail: gdjian@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Engenharia Nuclear; Angelo, Edvaldo, E-mail: eangelo@mackenzie.br [Universidade Presbiteriana Mackenzie, Sao Paulo, SP (Brazil); Angelo, Gabriel, E-mail: gangelo@fei.edu.br [Fundacao Educacional Inaciana (FEI), Sao Bernardo do Campo, SP (Brazil)
2015-07-01
Previously, an instrumented dummy fuel element (DMPV-01), with the same geometric characteristics of a MTR fuel element, was designed and constructed for pressure drop and flow distribution measurement experiments at the IEA-R1 reactor core. This dummy element was also used to measure the flow distribution among the rectangular flow channels formed by element fuel plates. A CFD numerical model was developed to complement the studies. This work presents the proposed CFD model as well as a comparison between numerical and experimental results of flow rate distribution among the internal flow channels. Numerical results show that the model reproduces the experiments very well and can be used for the studies as a more convenient and complementary tool. (author)
International Nuclear Information System (INIS)
Trotignon, L.; Bienvenu, P.; Provitina, O.; Rose, J.; Khoury, H.; Trocellier, P.; Mercier, F.; Raimbault, L.
2005-01-01
Full text of publication follows: The site of Maqarin (Jordan), in which natural cements occur as a result of the combustion metamorphism of a bio-micrite, is studied since 1989 as a natural analogue for the long term evolution of a cementitious repository environment [1]. Several trace elements of interest (Cr, Se, Mo, Re) are mobilized on this site by percolating groundwaters and migrate along high pH plumes. Laboratory scale column experiments were conducted in which crushed materials (cement, bio-micrite) collected on site were submitted to leaching by deionized water or Ca(OH) 2 equilibrated solutions. The evolution of Cr, Mo, Se and Re was monitored in leachates during the experiments. Characterizations of the solid phase using several techniques were also conducted in order to locate these elements in the mineral phases. Comparison of experimental data with records of trace element concentration in Maqarin groundwaters gives some insight on Re, Cr, Se and Mo sources and sinks in this environment. Both the imprint of the past combustion event and present day redox transformations explain several features of the datasets. However, due to the high complexity of the cements, in which trace elements are often distributed among several mineral phases, it is presently not possible to link in a straightforward way individual mineral dissolution processes and trace element signals in waters. [1] Khoury H. N., Salameh E., Clark I. D., Fritz P., Bajjali W., Milodowski A. E., Cave M. R. and Alexander W. R. 1992. A natural analogue of high pH cement pore waters from the Maqarin area of northern Jordan. I: Introduction to the site. J. Geochem. Explor. 46: 117-132. (authors)
Measurement and analysis of vibrational behaviour of an SNR-fuel element in sodium flow
International Nuclear Information System (INIS)
Hess, B.F.H.; Ruppert, E.; Schmidt, H.; Vinzens, K.
1975-01-01
Within the framework of SNR-300 fuel element development programme a complete full size fuel element dummy has been tested thoroughly for nearly 3000 hours at 650 0 C system temperature in the AKB sodium loop at Interatom, Bensberg. Investigations of the hydraulic characteristics by measurements of specific pressure losses, flow velocities, leakage flow through the piston rings and investigations of its vibrational behaviour were part of this endurance test at elevated temperatures. The pressure drop versus flow and the leakage measurement are mentioned briefly to confirm the correctness of the test hydraulics. The vibrational behaviour of the element and the approach to analysis is the main object of this report. (Auth.)
International Nuclear Information System (INIS)
Kakuta, Izuru; Iizuka, Keiki; Sugawara, Yoshio; Tsuchiya, Takeshi; Ishii, Keizo
2000-01-01
The elemental composition (Ca, Sr, Zn and Fe) of otoliths from migrating chum salmon, Oncorhynchus keta, captured at the Kitakami river and Ishinomaki Bay was analyzed to understand the migratory history using a particle induced X-ray emission (PIXE) technique. The Sr/Ca ratio of salmon otoliths was lower (less than 1 x 10 -3 ) in the portion formed in a freshwater environment and higher (approximately 4.8 x 10 -3 ) in a sea water environment. When the fish migrated from sea water into a freshwater environment, the otoliths' Sr/Ca ratios significantly increased. The highest values were found in the fish captured at the lower part of the Kitakami river (about 20 km upriver from the mouth). The values from the fish captured at the upper part of the Kitakami river (about 200 km upriver from the mouth) were also not less than those of the fish captured at Ishinomaki Bay. Abnormally high otolith Sr/Ca ratios for these upriver-migrating fish, when compared to the values from non-migrating salmon inhabiting stable environmental (salinity and temperature) conditions, provided evidence that they were stressed. No significant changes in the otoliths' Zn/Ca ratios were found, while these values were inversely proportional to the Sr/Ca ratios. However, a rapid drop in the Zn/Ca ratio and an increase in the Sr/Ca ratio was observed in some individuals in which higher values for the Fe/Ca were found. These results suggest that these otolith parameters don't exactly reflect the salinity and temperature history in upriver-migrating chum salmon because the physiological mechanism of incorporation of Sr, Zn and Ca within the otolith of those fish is abnormal, though for fish in non-stressful conditions the Sr/Ca and the Zn/Ca ratios in otoliths are effective indices for predicting the history of environmental conditions experienced by the fish in the past. Regarding the relationship between the Sr/Ca and the Zn/Ca ratios, and also the Fe/Ca ratio, there is a possibility that they
Flow Applications of the Least Squares Finite Element Method
Jiang, Bo-Nan
1998-01-01
The main thrust of the effort has been towards the development, analysis and implementation of the least-squares finite element method (LSFEM) for fluid dynamics and electromagnetics applications. In the past year, there were four major accomplishments: 1) special treatments in computational fluid dynamics and computational electromagnetics, such as upwinding, numerical dissipation, staggered grid, non-equal order elements, operator splitting and preconditioning, edge elements, and vector potential are unnecessary; 2) the analysis of the LSFEM for most partial differential equations can be based on the bounded inverse theorem; 3) the finite difference and finite volume algorithms solve only two Maxwell equations and ignore the divergence equations; and 4) the first numerical simulation of three-dimensional Marangoni-Benard convection was performed using the LSFEM.
Experimental investigation of the flow near the ram element in the brush turbine
Directory of Open Access Journals (Sweden)
Schmirler M.
2015-01-01
Full Text Available The paper focuses on the investigating of the parameters of the fluid flow around the brush turbine ram element. The flow field was evaluated qualitatively by observing changes in density using a Schlieren method. It was also evaluated the influence of the element geometry on the total aerodynamic force of the element. The aerodynamic force was measured directly using a special aerodynamic balance. The aim of the project was to find the simplest element geometry with a maximum force effect and achieve an increase in overall efficiency and reduce the manufacturing costs.
Mixed finite element simulations in two-dimensional groundwater flow problems
International Nuclear Information System (INIS)
Kimura, Hideo
1989-01-01
A computer code of groundwater flow in two-dimensional porous media based on the mixed finite element method was developed for accurate approximations of Darcy velocities in safety evaluation of radioactive waste disposal. The mixed finite element procedure solves for both the Darcy velocities and pressure heads simultaneously in the Darcy equation and continuity equation. Numerical results of a single well pumping at a constant rate in a uniform flow field showed that the mixed finite element method gives more accurate Darcy velocities nearly 50 % on average error than standard finite element method. (author)
DEFF Research Database (Denmark)
Pedersen, Peder J.; Pytlikova, Mariola
In this paper we look at migration flows from 10 Central and Eastern European Countries (CEEC) to 5 Nordic countries over the years 1985 - 2007. We exploit a natural experiment that arose from the fact that while Sweden opened its labour market from the day one of the 2004 EU enlargement......, and Finland and Iceland from year 2006, the other Nordic countries chose a transition period in relation to the "new" EU members. The results based on a differences-in-differences estimator show that the estimated effect of the opening of the Swedish, Finnish and Icelandic labour markets on migration from...... the CEECs that entered the EU in 2004 is not significantly different from zero. However, the effect of the opening of the Swedish and Finnish labour markets in 2007 on migration from the 2007 EU entrants, Bulgaria and Romania, is significantly positive. Further, we are interested in the overall effect...
Vadim V., Ermakov; Valentina, Danilova; Sabsbakhor, Khushvakhtova; Aklexander, Degtyarev; Sergey, Tyutikov; Victor, Berezkin; Elena, Karpova
2014-05-01
The comparative evaluation of the levels of biologically active chemical elements and their migration in the soil-plant complex of two Urov endemic locations in East Transbaikalia (Zolinsky and Uryumkansky) and background areas (Western Baikal region and the western area of the Trans-Baikal region) was conducted. The predominant soil-forming rocks in East Transbaikalia are weathering products of Proterozoic carbonated granitoids PR2. The surface rocks consist from granite, granodiorite, diorite quartz diorite, gabbro, norite, gabbro-norite and other. Soils - mountain and cryogenic meadow forests, mountain permafrost taiga podzolised, meadow alluvial, peaty meadow [2]. The paludification of narrow valleys and thermokarst phenomena are typical in Urov endemic localities. It reflects on the spotted of soil and differentiation of chemical composition of soils and plants. Most of the chemical elements in soils were determined by means of X-ray fluorescence, and trace elements in soils and plants - by atomic absorption spectrometry. The selenium content was measured by spectrofluorimetric method [3]. The research processed by methods of variation statistics. It was found that the soils of two locations of the Urov subregion of the biosphere were more enriched with iron, barium, calcium, uranium, thorium, phosphorus, and to a lesser extent strontium compared to background soils. The ratio of Ca: P was significantly higher in the soil of background areas, and Ca: Sr, on the contrary, in endemic soils. In assessing the migration of trace elements in soil-plant complex by means of the total content of trace elements and biological absorption coefficient found a marked accumulation by plants manganese, chromium, arsenic and weak plants accumulation of cobalt and nickel. Soil landscape is not much different in content of selenium, but its migration in plants was reduced in places of spread of Urov disease [1]. The concentrators of cadmium (leaves of different species of willow
International Nuclear Information System (INIS)
Ogawa, Hiromichi; Nagao, Seiya; Yamaguchi, Tetsuji
2001-01-01
The Japan Atomic Energy Research Institute (JAERI) conducted a collaboration program Phase II with the Atomic Energy of Canada Limited (AECL) from 1994 to 1998. The program was started to contribute the establishment of safety assessment methodology for the geological disposal of high-level radioactive wastes on the basis of the results from the Phase I program (1987-1993). The Phase II program consisted of following experimental items: (1) radionuclide migration experiments for quarried blocks (1m x 1m x 1m) of granite with natural fracture under in-situ geochemical conditions at 240 m level of Underground Research Laboratory of AECL; (2) study on the effects of dissolved organic materials extracted from natural groundwaters on radionuclide migration; (3) study on groundwater flow using environmental isotopes at two different geologic environments; (4) development of groundwater flow and radionuclide transport model for heterogeneous geological media. The mobility of radionuclides was retarded in the fracture by the deep geological conditions and the fracture paths. The groundwater humic substances with high molecular size were enhanced for the mobility of radionuclides in the sand and granitic media due to the complexation. The application of 36 Cl and 129 I for the analysis on the long-term groundwater flow can be validated on the basis of investigation at the URL site. Moreover, the geostatistical model for the analysis on groundwater flow and radionuclide migration was developed, and was able to describe the groundwater flow and the migration of environmental tracers at AECL sites. This report summaries the results of the Phase II program between JAERI and AECL. (author)
Energy Technology Data Exchange (ETDEWEB)
Ogawa, Hiromichi; Nagao, Seiya; Yamaguchi, Tetsuji [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment] [and others
2001-01-01
The Japan Atomic Energy Research Institute (JAERI) conducted a collaboration program Phase II with the Atomic Energy of Canada Limited (AECL) from 1994 to 1998. The program was started to contribute the establishment of safety assessment methodology for the geological disposal of high-level radioactive wastes on the basis of the results from the Phase I program (1987-1993). The Phase II program consisted of following experimental items: (1) radionuclide migration experiments for quarried blocks (1m x 1m x 1m) of granite with natural fracture under in-situ geochemical conditions at 240 m level of Underground Research Laboratory of AECL; (2) study on the effects of dissolved organic materials extracted from natural groundwaters on radionuclide migration; (3) study on groundwater flow using environmental isotopes at two different geologic environments; (4) development of groundwater flow and radionuclide transport model for heterogeneous geological media. The mobility of radionuclides was retarded in the fracture by the deep geological conditions and the fracture paths. The groundwater humic substances with high molecular size were enhanced for the mobility of radionuclides in the sand and granitic media due to the complexation. The application of {sup 36}Cl and {sup 129}I for the analysis on the long-term groundwater flow can be validated on the basis of investigation at the URL site. Moreover, the geostatistical model for the analysis on groundwater flow and radionuclide migration was developed, and was able to describe the groundwater flow and the migration of environmental tracers at AECL sites. This report summaries the results of the Phase II program between JAERI and AECL. (author)
International Nuclear Information System (INIS)
Tawara, Y.; Mori, K.; Tada, K.; Shimura, T.; Sato, S.; Yamamoto, S.; Asano, H.; Namiki, K.
2012-01-01
Document available in extended abstract form only. After the completion of field-scaled Gas Migration Test (GMT) at the Grimsel Test Site (GTS Phase V Project, 1996-2004), an advanced gas migration modelling study has been implemented to increase the accuracy and reliability as a part of the R and D programs by the Radioactive Waste Management funding and research Center (RWMC) in Japan. The multiple gas migration modes which consist of diffusive transport of dissolved gas, conventional two phase flow, pore failure induced microscopic fissuring and macroscopic fracturing flow, were identified in GMT bentonite. However the required parameters and constitutive models governing those modes are still uncertain. To tackle this issue, an extended validation and scoping study aiming to generalize such gas migration behavior has been performed in the advanced gas migration modelling study. One of the main objectives of the validation study is to identify gas migration modes using laboratory test data and to qualify the alternative models and parameters. In the scoping study, we have extracted the specific THMC (Thermal, Hydrological, Mechanical and Chemical) coupled processes which have impacts on the performance measures such as the pressure built-up in EBS (Engineered Barrier System) and expelled water to the geosphere by gas generation and transport. The measured data of hydration tests and gas injection tests using bentonite specimens with different water contents were reproduced. Two phase flow parameters were estimated using the observed data of both types of tests, independently. The simulated results of the conventional two phase flow model were well-matched with the hydration test data. In the gas injection test, the extended two phase flow model which simulates the pressure-induced pore failure (pathway dilation), was able to reproduce observed data reasonably. However, we found that the identified parameters obtained from the hydration test data were
Das, Sayan; Chakraborty, Suman
2018-02-01
The effect of surface viscosity on the motion of a surfactant-laden droplet in the presence of a non-isothermal Poiseuille flow is studied, both analytically and numerically. The presence of bulk-insoluble surfactants along the droplet surface results in interfacial shear and dilatational viscosities. This, in turn, is responsible for the generation of surface-excess viscous stresses that obey the Boussinesq-Scriven constitutive law for constant values of surface shear and dilatational viscosities. The present study is primarily focused on finding out how this confluence can be used to modulate droplet dynamics in the presence of Marangoni stress induced by nonuniform distribution of surfactants and temperature along the droplet surface, by exploiting an intricate interplay of the respective forcing parameters influencing the interfacial stresses. Under the assumption of negligible fluid inertia and thermal convection, the steady-state migration velocity of a non-deformable spherical droplet, placed at the centerline of an imposed unbounded Poiseuille flow, is obtained for the limiting case when the surfactant transport along the interface is dominated by surface diffusion. Our analysis proves that the droplet migration velocity is unaffected by the shear viscosity whereas the dilatational viscosity has a significant effect on the same. The surface viscous effects always retard the migration of a surfactant-laden droplet when the temperature in the far-field increases in the direction of the imposed flow although the droplet always migrates towards the hotter region. On the contrary, if a large temperature gradient is applied in a direction opposite to that of the imposed flow, the direction of droplet migration gets reversed. However, for a sufficiently high value of dilatational surface viscosity, the direction of droplet migration reverses. For the limiting case in which the surfactant transport along the droplet surface is dominated by surface convection, on
Adaptive Multiscale Finite Element Method for Subsurface Flow Simulation
Van Esch, J.M.
2010-01-01
Natural geological formations generally show multiscale structural and functional heterogeneity evolving over many orders of magnitude in space and time. In subsurface hydrological simulations the geological model focuses on the structural hierarchy of physical sub units and the flow model addresses
Chun, Byoungjin; Kwon, Ilyoung; Jung, Hyun Wook; Hyun, Jae Chun
2017-12-01
The shear-induced migration of concentrated non-Brownian monodisperse suspensions in combined plane Couette-Poiseuille (C-P) flows is studied using a lattice Boltzmann simulation. The simulations are mainly performed for a particle volume fraction of ϕbulk = 0.4 and H/a = 44.3, 23.3, where H and a denote the channel height and radius of suspended particles, respectively. The simulation method is validated in two simple flows, plane Poiseuille and plane Couette flows. In the Poiseuille flow, particles migrate to the mid-plane of the channel where the local concentration is close to the limit of random-close-packing, and a random structure is also observed at the plane. In the Couette flow, the particle distribution remains in the initial uniform distribution. In the combined C-P flows, the behaviors of migration are categorized into three groups, namely, Poiseuille-dominant, Couette-dominant, and intermediate regimes, based on the value of a characteristic force, G, where G denotes the relative magnitude of the body force (P) against the wall-driving force (C). With respect to the Poiseuille-dominant regime, the location of the maximum concentration is shifted from the mid-plane to the lower wall moving in the same direction as the external body force, when G decreases. With respect to the Couette-dominant regime, the behavior is similar to that of a simple shear flow with the exception that a slightly higher concentration of particles is observed near the lower wall. However, with respect to the intermediate value of G, several layers of highly ordered particles are unexpectedly observed near the lower wall where the plane of maximum concentration is located. The locally ordered structure is mainly due to the lateral migration of particles and wall confinement. The suspended particles migrate toward a vanishingly small shear rate at the wall, and they are consequently layered into highly ordered two-dimensional structures at the high local volume fraction.
A strongly conservative finite element method for the coupling of Stokes and Darcy flow
Kanschat, G.; Riviè re, B.
2010-01-01
We consider a model of coupled free and porous media flow governed by Stokes and Darcy equations with the Beavers-Joseph-Saffman interface condition. This model is discretized using divergence-conforming finite elements for the velocities
International Nuclear Information System (INIS)
Aoki, Hiroomi; Shimomura, Masanori; Kawakami, Hiroto; Suzuki, Shunichi
2011-01-01
In safety assessments of radioactive waste disposal facilities, ground water flow analysis are used for calculating the radionuclide transport pathway and the infiltration flow rate of groundwater into the disposal facilities. For this type of calculations, the mixed hybrid finite element method has been used and discussed about the accuracy of ones in Europe. This paper puts great emphasis on the infiltration flow rate of groundwater into the disposal facilities, and describes the accuracy of results obtained from mixed hybrid finite element method by comparing of local water mass conservation and the reliability of the element breakdown numbers among the mixed hybrid finite element method, finite volume method and nondegenerated finite element method. (author)
Directory of Open Access Journals (Sweden)
Maslovskiy Andrey N.
2013-12-01
Full Text Available The data on the emergence of new Oriental material culture elements in the city of Azaq, such as new housing and pottery types, characteristic of the mid-14th-century Golden Horde cities of the Lower Volga region, are provided in the article. Particular attention is paid to the appearance of new types of dwellings with the kang-based system of heating. They make up about 10 per cent of all residential complexes studied in Azaq: mostly ground dwellings, as semi-subterranean dwellings with kangs are rarely met. It has been suggested that in the mid-14th century a considerable group of residents of the Golden Horde Lower Volga towns had migrated to Azaq. The reasons for this relocation can be discussed only hypothetically.
Computation of 2D compressible flows with a finite element method
International Nuclear Information System (INIS)
Montagne, J.L.
1981-04-01
When the homogeneous modelisation of the two phase flow is used the set of equations describing the flow is similar to an Euler system. Mixed finite elements are appropriate to discretize the equations. First, main properties of this kind of elements are reminded. Then, some properties of semi-implicite schemes on stability and entropy are given. Numerical tests have been performed, and the scheme gave satisfactory results
Numerical solution of recirculating flow by a simple finite element recursion relation
Energy Technology Data Exchange (ETDEWEB)
Pepper, D W; Cooper, R E
1980-01-01
A time-split finite element recursion relation, based on linear basis functions, is used to solve the two-dimensional equations of motion. Recirculating flow in a rectangular cavity and free convective flow in an enclosed container are analyzed. The relation has the advantage of finite element accuracy and finite difference speed and simplicity. Incorporating dissipation parameters in the functionals decreases numerical dispersion and improves phase lag.
Energy Technology Data Exchange (ETDEWEB)
Im, Sang Hyuk; Lee, Su Jin [Kyung Hee University, Yongin (Korea, Republic of); Suh, Duck Jong; Park, O Ok [Korea Advanced Institute of Science and Technology (KAIST), Daejeon (Korea, Republic of); Kwon, Moo Hyun [Woosuk University, Wanju (Korea, Republic of)
2015-07-15
We investigated whether a graded-index profile, specified by the polymer compositional gradient, could be formed using shear-induced polymer migration phenomenon in a polymer solution. For the presented model system, we generated a shear flow by rotating a glass rod at the center of a polystyrene/methylmethacrylate (PS/MMA) solution and measured the degree of polymer migration by the shear flow field by examining the concentration of polymer solution along the radial direction from the rotating axis to the periphery. Through model experiments, we formed a compositional gradient and controlled its profile in the solution by varying the concentration of polymer solution, molecular weight of polymer, and shear rate. Finally, we solidified the gradient profiles by the polymerization of the PS/MMA solution and confirmed that the gradient profiles were maintained with a compositional gradient twice larger than the mother PS/MMA solution.
Hill, J K; Mendez, J A
1984-08-01
"Microeconomic simulations are performed to determine the impact of liberalized commodity trade on Mexican immigrant supply to the United States. The results suggest that a removal of trade barriers will reduce migration flows, but that the reduction will be fairly modest. Specifically, if both countries move from the levels of protection characteristic of the mid-1960s to completely free trade, the ratio of real U.S.-Mexican wages falls by roughly 18 percent. Using an upper bound for the range of empirical estimates of the wage elasticity of immigrant supply, this implies a maximum reduction in migration flows of 35 percent. A unilateral elimination of trade barriers by the United States reduces Mexican immigrant supply by a maximum of 14 percent." excerpt
Mece, Merita H.
2016-01-01
Irregular migration on the Western Balkan route has marked an unprecedented number during the last five years. Evidence indicates that both, non-European nationals and Western Balkan citizens have been involved in this complex migratory flow being exposed to various risks of human trafficking. But Western Balkan countries are source, transit and destination countries of human trafficking while their states are not well organized to implement a comprehensive and well-coordinated regional respo...
Movements of Croatian Labour Supply and Their Implications on Migration Flows
Directory of Open Access Journals (Sweden)
Alka Obadić
2008-06-01
Full Text Available The Croatian labour market is characterised by a low degree of activity on the part of the population, a high unemployment rate, a pronounced problem with long-term unemployment and a high structural disproportion between supply and demand. Because of the relatively high share of the unofficial economy, there is a large difference between the administrative unemployment rate and that shown by surveys. Analysis of the situation on the Croatian labour market shows that significant structural issues still remained unsolved (such as inflexibility, mismatch between supply and demand with respect to profession and education, and similar. There is still very limited creation of new jobs. The employment rates of men and women and the employment of young people are among the lowest in comparison with the EU-27 and are far from attainment of the Lisbon objectives. The high rate of economic inactivity indicates the lack of utilisation of the existing work force potential. The conducted research shows that the continued advised needs for workers is 25 time higher than the annual number of approved work permits to foreigners from 1992 to 2006, while that number was negligible in 1991. Due to this situation, Croatia still has a very strict protectionist orientation towards employing foreigners, although the fact is that this situation will have to change very quickly with accession to the EU. It can be concluded that no major changes in migration flows or any significant shifts in em¬ployment and unemployment rates can be expected until the year 2010. Although opening the borders could mean, on the one hand, the possibility of increased emigration of the Croatian work force, the expectations are that such movements, nonetheless, will not occur. It is more likely that opening borders would be connected with greater mobility of workers, both from Croatia into other countries and from other countries towards Croatia.
Elemental transport coefficients in viscous plasma flows near local thermodynamic equilibrium
International Nuclear Information System (INIS)
Orsini, Alessio; Kustova, Elena V.
2009-01-01
We propose a convenient formulation of elemental transport coefficients in chemically reacting and plasma flows locally approaching thermodynamic equilibrium. A set of transport coefficients for elemental diffusion velocities, heat flux, and electric current is introduced. These coefficients relate the transport fluxes with the electric field and with the spatial gradients of elemental fractions, pressure, and temperature. The proposed formalism based on chemical elements and fully symmetric with the classical transport theory based on chemical species, is particularly suitable to model mixing and demixing phenomena due to diffusion of chemical elements. The aim of this work is threefold: to define a simple and rigorous framework suitable for numerical implementation, to allow order of magnitude estimations and qualitative predictions of elemental transport phenomena, and to gain a deeper insight into the physics of chemically reacting flows near local equilibrium.
Finite element simulation of internal flows with heat transfer using a ...
Indian Academy of Sciences (India)
Unknown
Velocity correction method; finite element simulation; turbulent .... CFD, developments in turbulence modeling have been only evolutionary and ...... variables are made dimensionless using appropriate combinations of Uav, H, ...... Srinivas M 1994 Finite element analysis of internal flows with heat transfer Ph D thesis, Indian.
Analysis of Migration Flows of the Population of the Vologda Oblast Districts
Directory of Open Access Journals (Sweden)
Mikhail Mikhailovich Panov
2015-09-01
Full Text Available The article presents the research on the main directions and scale of migration in municipal districts of the Vologda Oblast and considers the main types of migration and the specifics of their statistical accounting. The data by Rosstat served as a basis upon which a general analysis of migration dynamics in the Vologda Oblast districts was carried out; and the article presents its periodization. Three main periods are defined: the “migration shock” of 1991–1999 after the collapse of the Soviet Union, the migration stability of 2000–2008 and the post-crisis rural out-migration that began in 2009 and is increasing year by year. At the same time, gross migration indicators have shown high sensitivity to significant socioeconomic change, in particular, to the economic crises of 1999 and 2008. The article describes the main age and gender characteristics of migrants, it has been determined that the most active migrants are girls aged 15–29, who move from rural to urban settlements. In general, it is the young people aged 15–34 who are most likely to migrate. The author has found out that most of the Vologda Oblast districts are characterized by a higher outflow of the population, which is in some places restrained by a relative migration attractiveness of a number of areas. The author has found out that most districts of the Oblast are characterized by a higher outflow of the population, which is sometimes restrained by relative migration attractiveness of some areas. The author highlights the region’s territories with the highest migration attraction; in the long run they can play the role of “growth points” in the region; these territories comprise Velikoustyugsky and Chagodoshchensky districts, as well as several districts of the central part of the Vologda Oblast – Ust-Kubinsky and Vologodsky. The author also points out the territories that suffered the most from out-migration: Kichmengsko-Gorodetsky, Vashkinsky
Figueredo-Cardero, Alvio; Chico, Ernesto; Castilho, Leda R; Medronho, Ricardo A
2009-11-01
In the present work Computational Fluid Dynamics (CFD) was used to study the flow field and particle dynamics in an internal spin-filter (SF) bioreactor system. Evidence of a radial exchange flow through the filter mesh was detected, with a magnitude up to 130-fold higher than the perfusion flow, thus significantly contributing to radial drag. The exchange flow magnitude was significantly influenced by the filter rotation rate, but not by the perfusion flow, within the ranges evaluated. Previous reports had only given indirect evidences of this exchange flow phenomenon in spin-filters, but the current simulations were able to quantify and explain it. Flow pattern inside the spin-filter bioreactor resembled a typical Taylor-Couette flow, with vortices being formed in the annular gap and eventually penetrating the internal volume of the filter, thus being the probable reason for the significant exchange flow observed. The simulations also showed that cells become depleted in the vicinity of the mesh due to lateral particle migration. Cell concentration near the filter was approximately 50% of the bulk concentration, explaining why cell separation achieved in SFs is not solely due to size exclusion. The results presented indicate the power of CFD techniques to study and better understand spin-filter systems, aiming at the establishment of effective design, operation and scale-up criteria.
Several advances in the analytic element method have been made to enhance its performance and facilitate three-dimensional ground-water flow modeling in a regional aquifer setting. First, a new public domain modular code (ModAEM) has been developed for modeling ground-water flow ...
A Flow of Entrepreneurial Learning Elements in Experiential Learning Settings
DEFF Research Database (Denmark)
Ramsgaard, Michael Breum; Christensen, Marie Ernst
This paper explored the concept of learning in an experiential learning setting and whether the learning process can be understood as a flow of learning factors influencing the outcome. If many constituting factors lead to the development of learning outcomes, there might need to be developed...... that are a part of experiential learning settings and curriculum development....... a differentiated approach to facilitate experiential learning. Subsequently the paper investigated how facilitators of learning processes can design a learning space where the boundary of what is expected from the learner is challenged. In other words the aim was to explore the transformative learning processes...
International Nuclear Information System (INIS)
Onishi, Y.; Arnold, E.M.; Mayer, D.W.
1979-08-01
The finite element model, FETRA, simulates transport of sediment and radionuclides (and other contaminants, such as heavy metals, pesticides, and other toxic substances) in surface water bodies. The model is an unsteady, two-dimensional (longitudinal and lateral) model which consists of the following three submodels coupled to include sediment-contaminant interactions: (1) sediment transport submodel, (2) dissolved contaminant transport submodel, and (3) particulate contaminant (contaminant adsorbed by sediment) transport submodel. Under the current phase of the study, FETRA was modified to include sediment-wave interaction in order to extend the applicability of the model to coastal zones and large lakes (e.g., the Great Lakes) where wave actions can be one of the dominant mechanisms to transport sediment and toxic contaminant. FETRA was further modified to handle both linear and quadratic approximations to velocity and depth distributions in order to be compatible with various finite element hydrodynamic models (e.g., RMA II and CAFE) which supply hydrodynamic input data to FETRA. The next step is to apply FETRA to coastal zones to simulate transport of sediment and radionuclides with their interactions in order to test and verify the model under marine and large lacustrine environments
Spectral Element Method for the Simulation of Unsteady Compressible Flows
Diosady, Laslo Tibor; Murman, Scott M.
2013-01-01
This work uses a discontinuous-Galerkin spectral-element method (DGSEM) to solve the compressible Navier-Stokes equations [1{3]. The inviscid ux is computed using the approximate Riemann solver of Roe [4]. The viscous fluxes are computed using the second form of Bassi and Rebay (BR2) [5] in a manner consistent with the spectral-element approximation. The method of lines with the classical 4th-order explicit Runge-Kutta scheme is used for time integration. Results for polynomial orders up to p = 15 (16th order) are presented. The code is parallelized using the Message Passing Interface (MPI). The computations presented in this work are performed using the Sandy Bridge nodes of the NASA Pleiades supercomputer at NASA Ames Research Center. Each Sandy Bridge node consists of 2 eight-core Intel Xeon E5-2670 processors with a clock speed of 2.6Ghz and 2GB per core memory. On a Sandy Bridge node the Tau Benchmark [6] runs in a time of 7.6s.
Multiscale Finite Element Methods for Flows on Rough Surfaces
Efendiev, Yalchin
2013-01-01
In this paper, we present the Multiscale Finite Element Method (MsFEM) for problems on rough heterogeneous surfaces. We consider the diffusion equation on oscillatory surfaces. Our objective is to represent small-scale features of the solution via multiscale basis functions described on a coarse grid. This problem arises in many applications where processes occur on surfaces or thin layers. We present a unified multiscale finite element framework that entails the use of transformations that map the reference surface to the deformed surface. The main ingredients of MsFEM are (1) the construction of multiscale basis functions and (2) a global coupling of these basis functions. For the construction of multiscale basis functions, our approach uses the transformation of the reference surface to a deformed surface. On the deformed surface, multiscale basis functions are defined where reduced (1D) problems are solved along the edges of coarse-grid blocks to calculate nodalmultiscale basis functions. Furthermore, these basis functions are transformed back to the reference configuration. We discuss the use of appropriate transformation operators that improve the accuracy of the method. The method has an optimal convergence if the transformed surface is smooth and the image of the coarse partition in the reference configuration forms a quasiuniform partition. In this paper, we consider such transformations based on harmonic coordinates (following H. Owhadi and L. Zhang [Comm. Pure and Applied Math., LX(2007), pp. 675-723]) and discuss gridding issues in the reference configuration. Numerical results are presented where we compare the MsFEM when two types of deformations are used formultiscale basis construction. The first deformation employs local information and the second deformation employs a global information. Our numerical results showthat one can improve the accuracy of the simulations when a global information is used. © 2013 Global-Science Press.
An application of actinide elements for a redox flow battery
International Nuclear Information System (INIS)
Shiokawa, Yoshinobu; Yamana, Hajimu; Moriyama, Hirotake
2000-01-01
The electrochemical properties of U, Np, Pu and Am were discussed from the viewpoint of cell active materials. From the thermodynamic properties and the kinetics of electrode reactions, it is found that neptunium in the aqueous system can be utilized as an active material of the redox flow battery for the electric power storage. A new neptunium redox battery is proposed in the present article: the galvanic cell is expressed by (-)|Np 3+ , Np 4+ |NpO 2 + , NpO 2 2+ |(+). The neptunium battery is expected to have more excellent charge and discharge performance than the current vanadium battery, whereas the thermodynamic one of the former is comparable to the latter. For the development of a uranium redox battery, the application of the redox reactions in the non-aqueous solvents is essential. (author)
Adaptive mixed finite element methods for Darcy flow in fractured porous media
Chen, Huangxin; Salama, Amgad; Sun, Shuyu
2016-01-01
In this paper, we propose adaptive mixed finite element methods for simulating the single-phase Darcy flow in two-dimensional fractured porous media. The reduced model that we use for the simulation is a discrete fracture model coupling Darcy flows in the matrix and the fractures, and the fractures are modeled by one-dimensional entities. The Raviart-Thomas mixed finite element methods are utilized for the solution of the coupled Darcy flows in the matrix and the fractures. In order to improve the efficiency of the simulation, we use adaptive mixed finite element methods based on novel residual-based a posteriori error estimators. In addition, we develop an efficient upscaling algorithm to compute the effective permeability of the fractured porous media. Several interesting examples of Darcy flow in the fractured porous media are presented to demonstrate the robustness of the algorithm.
Adaptive mixed finite element methods for Darcy flow in fractured porous media
Chen, Huangxin
2016-09-21
In this paper, we propose adaptive mixed finite element methods for simulating the single-phase Darcy flow in two-dimensional fractured porous media. The reduced model that we use for the simulation is a discrete fracture model coupling Darcy flows in the matrix and the fractures, and the fractures are modeled by one-dimensional entities. The Raviart-Thomas mixed finite element methods are utilized for the solution of the coupled Darcy flows in the matrix and the fractures. In order to improve the efficiency of the simulation, we use adaptive mixed finite element methods based on novel residual-based a posteriori error estimators. In addition, we develop an efficient upscaling algorithm to compute the effective permeability of the fractured porous media. Several interesting examples of Darcy flow in the fractured porous media are presented to demonstrate the robustness of the algorithm.
De-entrainment on vertical elements in air droplet cross flow
International Nuclear Information System (INIS)
Dallman, J.C.; Kirchner, W.L.
1980-01-01
De-entrainment phenomena on vertical elements in air-water droplet cross flow are generated using a horizontal array of water spray nozzles and a draft-induced wind tunnel. These conditions are used to obtain experimental values of the de-entrainment efficiency of isolated elements (25.4-, 63.5-, and 101.6-mm-diam cylinders and a 76.2-mm-square tube), and of an array of 101.6-mm-diam cylinders. A flow model is developed that extrapolates the de-entrainment efficiency of isolated elements through the use of a correlation for the interference effect to predict the efficiency of large arrays of similar elements. This simple model is shown to provide a good prediction of the de-entrainment efficiency of arrays in terms of the efficiency of an isolated element
Finite elements for the calculation of turbulent flows in three-dimensional complex geometries
Ruprecht, A.
A finite element program for the calculation of incompressible turbulent flows is presented. In order to reduce the required storage an iterative algorithm is used which solves the necessary equations sequentially. The state of turbulence is defined by the k-epsilon model. In addition to the standard k-epsilon model, the modification of Bardina et al., taking into account the rotation of the mean flow, is investigated. With this program, the flow in the draft tube of a Kaplan turbine is examined. Calculations are carried out for swirling and nonswirling entrance flow. The results are compared with measurements.
Lagrangian analysis of multiscale particulate flows with the particle finite element method
Oñate, Eugenio; Celigueta, Miguel Angel; Latorre, Salvador; Casas, Guillermo; Rossi, Riccardo; Rojek, Jerzy
2014-05-01
We present a Lagrangian numerical technique for the analysis of flows incorporating physical particles of different sizes. The numerical approach is based on the particle finite element method (PFEM) which blends concepts from particle-based techniques and the FEM. The basis of the Lagrangian formulation for particulate flows and the procedure for modelling the motion of small and large particles that are submerged in the fluid are described in detail. The numerical technique for analysis of this type of multiscale particulate flows using a stabilized mixed velocity-pressure formulation and the PFEM is also presented. Examples of application of the PFEM to several particulate flows problems are given.
A Moving Discontinuous Galerkin Finite Element Method for Flows with Interfaces
2017-12-07
compressible (Euler) flow , both in steady and spacetime form. The Euler flow state variable is given by y = (r,rv1, . . . ,rvn,rE) 2 Rm, (18) where m = n+2...analogous flow was computed using a larger spatial velocity vx = 32 using MDG-ICE(p = 0), as shown in Figure 3. In this case, the upstream state ...spacetime domainW= (0,1)⇥ 0, 12 with six quadrilateral cells is shown in Figure 4. The flow state variable y was discretized using Q2 elements, while the
Energy Technology Data Exchange (ETDEWEB)
Abbas, M., E-mail: micheline.abbas@ensiacet.fr [Laboratoire de Génie Chimique, Université de Toulouse INPT-UPS, 31030, Toulouse (France); CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Magaud, P. [CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Institut Clément Ader, Université de Toulouse UPS-INSA-ISAE-Mines Albi, 31400, Toulouse (France); Gao, Y. [Institut Clément Ader, Université de Toulouse UPS-INSA-ISAE-Mines Albi, 31400, Toulouse (France); Geoffroy, S. [CNRS, Fédération de recherche FERMaT, CNRS, 31400, Toulouse (France); Laboratoire Matériaux et Durabilité des Constructions, Université de Toulouse (France); UPS, INSA, 31077, Toulouse (France)
2014-12-15
The migration of neutrally buoyant finite sized particles in a Newtonian square channel flow is investigated in the limit of very low solid volumetric concentration, within a wide range of channel Reynolds numbers Re = [0.07-120]. In situ microscope measurements of particle distributions, taken far from the channel inlet (at a distance several thousand times the channel height), revealed that particles are preferentially located near the channel walls at Re > 10 and near the channel center at Re < 1. Whereas the cross-streamline particle motion is governed by inertia-induced lift forces at high inertia, it seems to be controlled by shear-induced particle interactions at low (but finite) Reynolds numbers, despite the low solid volume fraction (<1%). The transition between both regimes is observed in the range Re = [1-10]. In order to exclude the effect of multi-body interactions, the trajectories of single freely moving particles are calculated thanks to numerical simulations based on the force coupling method. With the deployed numerical tool, the complete particle trajectories are accessible within a reasonable computational time only in the inertial regime (Re > 10). In this regime, we show that (i) the particle undergoes cross-streamline migration followed by a cross-lateral migration (parallel to the wall) in agreement with previous observations, and (ii) the stable equilibrium positions are located at the midline of the channel faces while the diagonal equilibrium positions are unstable. At low flow inertia, the first instants of the numerical simulations (carried at Re = O(1)) reveal that the cross-streamline migration of a single particle is oriented towards the channel wall, suggesting that the particle preferential positions around the channel center, observed in the experiments, are rather due to multi-body interactions.
International Nuclear Information System (INIS)
Abbas, M.; Magaud, P.; Gao, Y.; Geoffroy, S.
2014-01-01
The migration of neutrally buoyant finite sized particles in a Newtonian square channel flow is investigated in the limit of very low solid volumetric concentration, within a wide range of channel Reynolds numbers Re = [0.07-120]. In situ microscope measurements of particle distributions, taken far from the channel inlet (at a distance several thousand times the channel height), revealed that particles are preferentially located near the channel walls at Re > 10 and near the channel center at Re < 1. Whereas the cross-streamline particle motion is governed by inertia-induced lift forces at high inertia, it seems to be controlled by shear-induced particle interactions at low (but finite) Reynolds numbers, despite the low solid volume fraction (<1%). The transition between both regimes is observed in the range Re = [1-10]. In order to exclude the effect of multi-body interactions, the trajectories of single freely moving particles are calculated thanks to numerical simulations based on the force coupling method. With the deployed numerical tool, the complete particle trajectories are accessible within a reasonable computational time only in the inertial regime (Re > 10). In this regime, we show that (i) the particle undergoes cross-streamline migration followed by a cross-lateral migration (parallel to the wall) in agreement with previous observations, and (ii) the stable equilibrium positions are located at the midline of the channel faces while the diagonal equilibrium positions are unstable. At low flow inertia, the first instants of the numerical simulations (carried at Re = O(1)) reveal that the cross-streamline migration of a single particle is oriented towards the channel wall, suggesting that the particle preferential positions around the channel center, observed in the experiments, are rather due to multi-body interactions
Transformation of Migration Flows Between the Russian Far East and CIS and non-CIS States
Directory of Open Access Journals (Sweden)
Motrich E. L.
2010-06-01
Full Text Available Basic trends in the migration processes in the Russian Far East are shown. Special emphasis is placed on the transformation of migration interactions with CIS and non-CIS countries both at the level of the region as a whole, and at the level of the Far Eastern territories of the Russian Federation. An extent of using foreign labor in different periods of the Russian Far East socio-economic development and the regulatory support of this process are shown. Prospects for attracting and utilizing foreign labor are stated
Post war migration flows and disparities in mortality from age 50 onwards
DEFF Research Database (Denmark)
Zarulli, Virginia
are an important social and geopolitical feature of an area, there is still little empirical evidence on this effect. This paper contributes to deepen the knowledge about this phenomenon by investigating whether post-war internal migration in Italy affected the pattern of mortality inequality by socioeconomic...... status, from age 50 onwards, in Turin, one of the main industrial areas of the country, where many low educated individuals from the southern regions migrated to Turin with seeking jobs in the car factories. Migrants might be selected in terms of robustness because of the healthy migrant effect. However...
The Globalisation of migration
Milan Mesić
2002-01-01
The paper demonstrates that contemporary international migration is a constitutive part of the globalisation process. After defining the concepts of globalisation and the globalisation of migration, the author discusses six key themes, linking globalisation and international migration (“global cities”, the scale of migration; diversification of migration flows; globalisation of science and education; international migration and citizenship; emigrant communities and new identities). First, in ...
Energy flow in plate assembles by hierarchical version of finite element method
DEFF Research Database (Denmark)
Wachulec, Marcin; Kirkegaard, Poul Henning
method has been proposed. In this paper a modified hierarchical version of finite element method is used for modelling of energy flow in plate assembles. The formulation includes description of in-plane forces so that planes lying in different planes can be modelled. Two examples considered are: L......The dynamic analysis of structures in medium and high frequencies are usually focused on frequency and spatial averages of energy of components, and not the displacement/velocity fields. This is especially true for structure-borne noise modelling. For the analysis of complicated structures...... the finite element method has been used to study the energy flow. The finite element method proved its usefulness despite the computational expense. Therefore studies have been conducted in order to simplify and reduce the computations required. Among others, the use of hierarchical version of finite element...
Finite Element Analysis of Biot’s Consolidation with a Coupled Nonlinear Flow Model
Directory of Open Access Journals (Sweden)
Yue-bao Deng
2016-01-01
Full Text Available A nonlinear flow relationship, which assumes that the fluid flow in the soil skeleton obeys the Hansbo non-Darcian flow and that the coefficient of permeability changes with void ratio, was incorporated into Biot’s general consolidation theory for a consolidation simulation of normally consolidated soft ground with or without vertical drains. The governing equations with the coupled nonlinear flow model were presented first for the force equilibrium condition and then for the continuity condition. Based on the weighted residual method, the finite element (FE formulations were then derived, and an existing FE program was modified accordingly to take the nonlinear flow model into consideration. Comparative analyses using established theoretical solutions and numerical solutions were completed, and the results were satisfactory. On this basis, we investigated the effect of the coupled nonlinear flow on consolidation development.
A system for cooling electronic elements with an EHD coolant flow
International Nuclear Information System (INIS)
Tanski, M; Kocik, M; Barbucha, R; Garasz, K; Mizeraczyk, J; Kraśniewski, J; Oleksy, M; Hapka, A; Janke, W
2014-01-01
A system for cooling electronic components where the liquid coolant flow is forced with ion-drag type EHD micropumps was tested. For tests we used isopropyl alcohol as the coolant and CSD02060 diodes in TO-220 packages as cooled electronic elements. We have studied thermal characteristics of diodes cooled with EHD flow in the function of a coolant flow rate. The transient thermal impedance of the CSD02060 diode cooled with 1.5 ml/min EHD flow was 7.8°C/W. Similar transient thermal impedance can be achieved by applying to the diode a large RAD-A6405A/150 heat sink. We found out that EHD pumps can be successfully applied for cooling electronic elements.
Kawahara, Mutsuto
2016-01-01
This book focuses on the finite element method in fluid flows. It is targeted at researchers, from those just starting out up to practitioners with some experience. Part I is devoted to the beginners who are already familiar with elementary calculus. Precise concepts of the finite element method remitted in the field of analysis of fluid flow are stated, starting with spring structures, which are most suitable to show the concepts of superposition/assembling. Pipeline system and potential flow sections show the linear problem. The advection–diffusion section presents the time-dependent problem; mixed interpolation is explained using creeping flows, and elementary computer programs by FORTRAN are included. Part II provides information on recent computational methods and their applications to practical problems. Theories of Streamline-Upwind/Petrov–Galerkin (SUPG) formulation, characteristic formulation, and Arbitrary Lagrangian–Eulerian (ALE) formulation and others are presented with practical results so...
Large Eddy Simulation of turbulent flows in compound channels with a finite element code
International Nuclear Information System (INIS)
Xavier, C.M.; Petry, A.P.; Moeller, S.V.
2011-01-01
This paper presents the numerical investigation of the developing flow in a compound channel formed by a rectangular main channel and a gap in one of the sidewalls. A three dimensional Large Eddy Simulation computational code with the classic Smagorinsky model is introduced, where the transient flow is modeled through the conservation equations of mass and momentum of a quasi-incompressible, isothermal continuous medium. Finite Element Method, Taylor-Galerkin scheme and linear hexahedrical elements are applied. Numerical results of velocity profile show the development of a shear layer in agreement with experimental results obtained with Pitot tube and hot wires. (author)
Directory of Open Access Journals (Sweden)
Jilian Wu
2013-01-01
Full Text Available We discuss several stabilized finite element methods, which are penalty, regular, multiscale enrichment, and local Gauss integration method, for the steady incompressible flow problem with damping based on the lowest equal-order finite element space pair. Then we give the numerical comparisons between them in three numerical examples which show that the local Gauss integration method has good stability, efficiency, and accuracy properties and it is better than the others for the steady incompressible flow problem with damping on the whole. However, to our surprise, the regular method spends less CPU-time and has better accuracy properties by using Crout solver.
Simulation of incompressible flows with heat and mass transfer using parallel finite element method
Directory of Open Access Journals (Sweden)
Jalal Abedi
2003-02-01
Full Text Available The stabilized finite element formulations based on the SUPG (Stream-line-Upwind/Petrov-Galerkin and PSPG (Pressure-Stabilization/Petrov-Galerkin methods are developed and applied to solve buoyancy-driven incompressible flows with heat and mass transfer. The SUPG stabilization term allows us to solve flow problems at high speeds (advection dominant flows and the PSPG term eliminates instabilities associated with the use of equal order interpolation functions for both pressure and velocity. The finite element formulations are implemented in parallel using MPI. In parallel computations, the finite element mesh is partitioned into contiguous subdomains using METIS, which are then assigned to individual processors. To ensure a balanced load, the number of elements assigned to each processor is approximately equal. To solve nonlinear systems in large-scale applications, we developed a matrix-free GMRES iterative solver. Here we totally eliminate a need to form any matrices, even at the element levels. To measure the accuracy of the method, we solve 2D and 3D example of natural convection flows at moderate to high Rayleigh numbers.
Experimental investigation of flow-induced control-element movements by noise analysis
International Nuclear Information System (INIS)
Grunwald, G.; Liewers, P.; Schumann, P.; Weiss, F.P.
1978-01-01
The possibility has been reported of separating a single noise component due to flow-induced vibrations of a certain control element from a complex neutron signal which also contained contributions of many other control elements vibrating similarly. One of the basic assumptions for the different methods applied was that the body sound signal originating from touch events with the channel wall is closely correlated with the control-element movement. Some discrepancies between the results of the different methods showed that this assumption may not be entirely fulfilled. This paper investigates this correlation more accurately by measurements of an air flow model of the control-element channel. The pendulum movement of the element, and the body-sound signal due to the touch events with the channel wall, were measured at different flow-rates. The result is that the correlation is not an ideal one. For a constant flow-rate the touch events happen mainly within a small angle region, which means that the touch event marks a certain phase of the movement period and is therefore correlated with the movement. The dispersion of the touch events' angle distribution explains the small discrepancy between the so-called modified averaging method, which uses the sound signal to trigger the averaging procedure, and the partial spectral density method. But not all discrepancies can be explained by these results; they await further investigation. (author)
International Nuclear Information System (INIS)
Gartling, D.K.
1978-04-01
The theoretical background for the finite element computer program, NACHOS, is presented in detail. The NACHOS code is designed for the two-dimensional analysis of viscous incompressible fluid flows, including the effects of heat transfer. A general description of the fluid/thermal boundary value problems treated by the program is described. The finite element method and the associated numerical methods used in the NACHOS code are also presented. Instructions for use of the program are documented in SAND77-1334
Migration, financial flows and development in the Euro-Mediterranean area
DEFF Research Database (Denmark)
Gallina, Andrea
2006-01-01
as to the conclusions: that by the turn of the twenty-first century migration would become an explosive issue for the Mediterranean region, and that today we are facing the consequences. The risk described as a ‘demographic bomb’ is no longer a risk; it has exploded and can be seen in the daily dramas along the Italian...
Energy Technology Data Exchange (ETDEWEB)
Bizjak, D; Alujevic, A [Institut ' Jozef Stefan' , Ljubljana (Yugoslavia)
1988-07-01
The Complex Variable Boundary Element Method is a numerical method for solving two-dimensional problems of Laplace or Poisson type. It is based on the theory of analytic functions. This paper resumes the basic facts about the method. Application of the method to the stationary incompressible irrotational flow is carried out after that. At the end, a sample problem of flow through an abrupt area change channel is shown. (author)
Application of a finite element method to the calculation of compressible subsonic flows
International Nuclear Information System (INIS)
Montagne, J.L.
1980-01-01
The accidental transients in nuclear reactors requires two-phase flow calculation in complicated geometries. In the present case, the flow has been limited to the study of an homogeneous bidimensional flow model. One obtains equations analogous to those for compressible gas. The two-phase nature leads to sudden variations of specific mass as a function of pressure and enthalpy. In practice, the flows are in a transport regime, this is why one has sought a stable discretization scheme for the hyperbolic system of Euler equations. In order to take into account the thermal phenomena, the natural variables were kept, flow rate, pressure enthalpy and the equations were used in their conservative form. A Galerkin method was used to solve the momentum conservation equation. The space to which the flow rates belong is submitted to a matching condition, the normal component of these vectors is continuous at the boundary between elements. The pressures, enthalpy specific mass, in contrast, are discontinuous between two elements. Correspondences must be established between these two type of discretization. The program set into operation uses a discretization of lowest order, and has been conceived for processing time steps conditioned only by the flow speed. It has been tested in two cases where the thermal phenomena are important: cool liquid introduced in vapor, and heating along a plate [fr
A Lagrangian finite element method for the simulation of flow of non-newtonian liquids
DEFF Research Database (Denmark)
Hassager, Ole; Bisgaard, C
1983-01-01
A Lagrangian method for the simulation of flow of non-Newtonian liquids is implemented. The fluid mechanical equations are formulated in the form of a variational principle, and a discretization is performed by finite elements. The method is applied to the slow of a contravariant convected Maxwell...
2017-11-13
finite element flow solver JENRE developed at the Naval Research Laboratory. The Crocco- Busemann relation is used to account for the compressibility. In...3 1. Comparison with the measurement data...Naval Research Laboratory. The Crocco-Busemann relation is used to account for the compressibility. In this wall-model implementation, the first
Stable Galerkin versus equal-order Galerkin least-squares elements for the stokes flow problem
International Nuclear Information System (INIS)
Franca, L.P.; Frey, S.L.; Sampaio, R.
1989-11-01
Numerical experiments are performed for the stokes flow problem employing a stable Galerkin method and a Galerkin/Least-squares method with equal-order elements. Error estimates for the methods tested herein are reviewed. The numerical results presented attest the good stability properties of all methods examined herein. (A.C.A.S.) [pt
Mixed hybrid finite elements and streamline computation for the potential flow problem
Kaasschieter, E.F.; Huijben, A.J.M.
1992-01-01
An important class of problems in mathematical physics involves equations of the form -¿ · (A¿¿) = f. In a variety of problems it is desirable to obtain an accurate approximation of the flow quantity u = -A¿¿. Such an accurate approximation can be determined by the mixed finite element method. In
A 2D finite element implementation of the Fleck–Willis strain-gradient flow theory
DEFF Research Database (Denmark)
Nielsen, Kim Lau; Niordson, Christian Frithiof
2013-01-01
The lay-out of a numerical solution procedure for the strain gradient flow (rate-independent) theory by Fleck and Willis [A mathematical basis for strain-gradient theory – Part II: Tensorial plastic multiplier, 57:1045–1057; 2009, JMPS] has been an open issue, and its finite element implementation...
Kirk, Benjamin S.; Bova, Stephen W.; Bond, Ryan B.
2011-01-01
Presentation topics include background and motivation; physical modeling including governing equations and thermochemistry; finite element formulation; results of inviscid thermal nonequilibrium chemically reacting flow and viscous thermal equilibrium chemical reacting flow; and near-term effort.
Discrete-Roughness-Element-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers
Malik, Mujeeb; Liao, Wei; Li, Fei; Choudhari, Meelan
2015-01-01
Nonlinear parabolized stability equations and secondary-instability analyses are used to provide a computational assessment of the potential use of the discrete-roughness-element technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural-laminar-flow airfoil with a leading-edge sweep angle of 34.6 deg, freestream Mach number of 0.75, and chord Reynolds numbers of 17 × 10(exp 6), 24 × 10(exp 6), and 30 × 10(exp 6) suggest that discrete roughness elements could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small-wavelength stationary crossflow disturbances (i.e., discrete roughness element) also suppresses the growth of most amplified traveling crossflow disturbances.
Subsonic flow past three-dimensional localised heating elements in boundary layers
Energy Technology Data Exchange (ETDEWEB)
Aljohani, A F [Department of Mathematics, Faculty of Science, University of Tabuk (Saudi Arabia); Gajjar, J S B, E-mail: j.gajjar@manchester.ac.uk [School of Mathematics, University of Manchester, Manchester M13 9PL (United Kingdom)
2017-12-15
The problem of subsonic flow past three-dimensional micro-electro-mechanical-type (MEMS-type) heating elements placed on a flat surface, where the MEMS devices have hump-shaped surfaces, is investigated using the triple-deck theory. The compressible Navier–Stokes equations supplemented by the energy equation are considered in the limit when the Reynolds number is large. The dimensions of the MEMS devices considered are such that the flow perturbations are governed by the three-dimensional subsonic triple-deck equations formulated with the aid of method of matched expansions. The linear analysis of these equations is presented and our results provide an insight into how the MEMS heating elements may be used to positively control the local flow properties. (paper)
Analysis and Calculation of the Fluid Flow and the Temperature Field by Finite Element Modeling
Dhamodaran, M.; Jegadeesan, S.; Kumar, R. Praveen
2018-04-01
This paper presents a fundamental and accurate approach to study numerical analysis of fluid flow and heat transfer inside a channel. In this study, the Finite Element Method is used to analyze the channel, which is divided into small subsections. The small subsections are discretized using higher number of domain elements and the corresponding number of nodes. MATLAB codes are developed to be used in the analysis. Simulation results showed that the analyses of fluid flow and temperature are influenced significantly by the changing entrance velocity. Also, there is an apparent effect on the temperature fields due to the presence of an energy source in the middle of the domain. In this paper, the characteristics of flow analysis and heat analysis in a channel have been investigated.
International Nuclear Information System (INIS)
Melroy, L.A.; Huff, D.D.
1985-05-01
The discharge from Solid Waste Storage Area 4 (SWSA 4) at Oak Ridge National Laboratory was studied to determine the effect of a new flow diversion system on the annual flux of 90 Sr into White Oak Creek. The diversion structure was built in late 1983 to route runoff from the SWSA 4 catchment headwaters area (56% of the basin) around the burial ground, because an earlier study showed that this would be an effective remedial measure for reducing 90 Sr migration. A preliminary evaluation of the diversion was conducted during the winter of 1984, and an average flow reduction of 56% and a 90 Sr flux reduction of 44% were observed during the initial study period. The results presented here indicate that an overall annual flow reduction of 66% and an annual 90 Sr flux reduction of 47% were achieved during the 1984 calendar year. An additional goal of the study was to rank SWSA 4 and the surrounding areas as sources of 90 Sr input into White Oak Creek. Runoff from SWSA 4 was found to contribute 58% of the 90 Sr flux to the adjacent reach of White Oak Creek and therefore is the major source of contamination in that area. Statistical analysis suggests that the remaining 42% of the influx is attributable to groundwater inflows from adjacent contaminated areas rather than to the considerable uncertainty associated with flow and 90 Sr measurements
Small flow rate can supply inwardly migrating shortest-period planets
Directory of Open Access Journals (Sweden)
Taylor S.F.
2013-04-01
Full Text Available The number of exoplanets found with periods as short as one day and less was surprising given how fast these planets had been expected to migrate into the star due to the tides raised on the star by planets at such close distances. It has been seen as improbable that we would find planets in such a small final fraction of their lives [1]. The favored solution has been that the tidal dissipation is much weaker than expected, which would mean that the final infall would be a larger fraction of the planets’ life. We find no reason, however, to exclude the explanation that a small number of planets are continuously sent migrating inwards such that these planets indeed are in the last fraction of their lives. Following the observation that the distribution of medium planets disfavors tidal dissipation being significantly weaker than has been found from observations of binary stars [2], we now show that the numbers of planets in such a “flow” of excess planets migrating inwards is low enough that even depletion of the three-day pileup is a plausible source. Then the shortest period occurrence distribution would be shaped by planets continuously being sent into the star, which may explain the depletion of the pileup in the Kepler field relative to the solar neighborhood [3]. Because Kepler observes above the galactic plan, [3] suggested the Kepler field may include an older population of stars. The tidal dissipation strength in stars due to giant planets may be not greatly weaker than it is in binary stars.
DEFF Research Database (Denmark)
Jabbaribehnam, Mirmasoud; Spangenberg, Jon; Hattel, Jesper Henri
2016-01-01
In this paper, the migration of secondary particles in a non-Newtonian ceramic slurry inthe tape casting process is investigated with the purpose of understanding the particle distribution patterns along the casting direction. The Ostwald-de Waele power law model for the non-Newtonian flow...... the substratevelocity (casting speed) leads to a more uniform distribution of the particles inside the ceramic slurry, in which case the shear induced particle migration is dominating over the gravity induced one....
Energy Technology Data Exchange (ETDEWEB)
Shestopalov, Vyacheslav; Bohuslavskyy, Alexander; Shybetskyi, Iurii [National Academy of Science of Ukaraine, Kyiv (Ukraine). Radioenvironmental Centre
2015-07-01
Results are presented of a case groundwater flow-transport modeling to predict the radionuclide migration from a deep geological repository (DGR) of radioactive waste. The influence of hydrogeological conditions in the upper aquifers of a storey water exchange system on the rate of contaminant migration from the DGR to its natural far-field groundwater discharges (a shallow well and a river) as a general DGR safety condition is considered.
Lima, Ana T.
2012-03-01
An electro-osmosis experiment was set up on a former asphalt factory site, which is currently contaminated by tar, in Olst, the Netherlands. The main goal of this experiment was to remove polycyclic aromatic hydrocarbons (PAHs) from a contaminated clay layer by applying an electric gradient. But before calculating PAH removal, the direction and intensity of electro-osmosis have to be estimated. In field situations, tracers are used to get information about the water flow. In the present study, the inorganic elements concentration oscillations during electro-osmosis application are used as tracers. The experiment was set up in a clay layer, with the configuration 1m×1m×0.3m, at a depth of 4m below soil surface. Al, Ca, Cl, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, S, Si, Ti and Zn concentrations were determined in 28 measurements and were performed during the experimental period of 159days. Then they were used in a first evaluation where auto and cross-correlations were analyzed to aid in the geochemical interpretation and select the most conservative elements. The second part of this study is devoted to estimate the migration of water based on the concentrations development of Cl - at the anode and Na + at the cathode. Electro-osmotic flow was estimated to be intense (2.9 -10 -9-2.18 -10 -8m -s -1) during the first 10 to 50days of experiment and to cease after this period. © 2012.
Lima, Ana T.; Rodrigues, Paulo C.; Loch, J.P. Gustav
2012-01-01
An electro-osmosis experiment was set up on a former asphalt factory site, which is currently contaminated by tar, in Olst, the Netherlands. The main goal of this experiment was to remove polycyclic aromatic hydrocarbons (PAHs) from a contaminated clay layer by applying an electric gradient. But before calculating PAH removal, the direction and intensity of electro-osmosis have to be estimated. In field situations, tracers are used to get information about the water flow. In the present study, the inorganic elements concentration oscillations during electro-osmosis application are used as tracers. The experiment was set up in a clay layer, with the configuration 1m×1m×0.3m, at a depth of 4m below soil surface. Al, Ca, Cl, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, S, Si, Ti and Zn concentrations were determined in 28 measurements and were performed during the experimental period of 159days. Then they were used in a first evaluation where auto and cross-correlations were analyzed to aid in the geochemical interpretation and select the most conservative elements. The second part of this study is devoted to estimate the migration of water based on the concentrations development of Cl - at the anode and Na + at the cathode. Electro-osmotic flow was estimated to be intense (2.9 -10 -9-2.18 -10 -8m -s -1) during the first 10 to 50days of experiment and to cease after this period. © 2012.
Liquid metal flows in insulating elements of self-cooled blankets
International Nuclear Information System (INIS)
Molokov, S.
1995-01-01
Liquid metal flows in insulating rectangular ducts in strong magnetic fields are considered with reference to poloidal concepts of self-cooled blankets. Although the major part of the flow in poloidal blanket concepts is close to being fully developed, manifolds, expansions, contractions, elbows, etc., which are necessary elements in blanket designs, cause three-dimensional effects. The present investigation demonstrates the flow pattern in basic insulating geometries for actual and more advanced liquid metal blanket concepts and discusses the ways to avoid pressure losses caused by flow redistribution. Flows in several geometries, such as symmetric and non-symmetric 180 turns with and without manifolds, sharp and linear expansions with and without manifolds, etc., have been considered. They demonstrate the attractiveness of poloidal concepts of liquid metal blankets, since they guarantee uniform conditions for heat transfer. If changes in the duct cross-section occur in the plane perpendicular to the magnetic field (ideally a coolant should always flow in the radial-poloidal plane), the disturbances are local and the slug velocity profile is reached roughly at a distance equivalent to one duct width from the manifolds, expansions, etc. The effects of inertia in these flows are unimportant for the determination of the pressure drop and velocity profiles in the core of the flow but may favour heat transfer characteristics via instabilities and strongly anisotropic turbulence. (orig.)
The far field migration of radionuclides in two dimensional groundwater flows though geologic media
International Nuclear Information System (INIS)
Ting, D.K.S.; Chambre, P.
1985-01-01
An analytical method to model the radionuclides migration in a two dimensional groundwater flor through geologic media has been developed and implemented into the computer code UCBNE21. Using this method, the potential hazard to the biosphere posed by the accidental release of radionuclides from a candidate repository site (WIPP) is determined. I-129 and Ra-226 are potentially the most hazardous nuclides in these sites but their discharge into the biosphere will not result in concentrations larger than their maximum permissible concentrations. (Author) [pt
Post-War Migration Flows and Disparities in Mortality from Age 50 Years Onwards
DEFF Research Database (Denmark)
Zarulli, Virginia
2016-01-01
these inequalities being an important social and geopolitical feature of an area, there is still little empirical evidence on this effect. This paper contributes to deepening the knowledge about this phenomenon by investigating whether post-war internal migration in Italy affected the pattern of mortality inequality...... effect. However, low-educated individuals are employed in heavier and riskier jobs. They thus undergo a faster health selection due to exposure to a higher mortality risk that selects the most robust individuals. This paper hypothesised that the interplay of these mechanisms might have produced...
Small flow rate can supply inwardly migrating shortest-period planets
Taylor, Stuart F.
2013-01-01
The number of exoplanets found with periods as short as one day and less was surprising given how fast these planets had been expected to migrate into the star due to the tides raised on the star by planets at such close distances. It has been seen as improbable that we would find planets in such a small final fraction of their lives. The favored solution has been that the tidal dissipation is much weaker than expected, which would mean that the final infall would be a larger fraction of the ...
FEMWATER: a finite-element model of water flow through saturated-unsaturated porous media
International Nuclear Information System (INIS)
Yeh, G.T.; Ward, D.S.
1980-10-01
Upon examining the Water Movement Through Saturated-Unsaturated Porous Media: A Finite-Element Galerkin Model, it was felt that the model should be modified and expanded. The modification is made in calculating the flow field in a manner consistent with the finite element approach, in evaluating the moisture-content increasing rate within the region of interest, and in numerically computing the nonlinear terms. With these modifications, the flow field is continuous everywhere in the flow regime, including element boundaries and nodal points, and the mass loss through boundaries is much reduced. Expansion is made to include four additional numerical schemes which would be more appropriate for many situations. Also, to save computer storage, all arrays pertaining to the boundary condition information are compressed to smaller dimension, and to ease the treatment of different problems, all arrays are variably dimensioned in all subroutines. This report is intended to document these efforts. In addition, in the derivation of finite-element equations, matrix component representation is used, which is believed more readable than the matrix representation in its entirety. Two identical sample problems are simulated to show the difference between the original and revised models
On approximation of non-Newtonian fluid flow by the finite element method
Svácek, Petr
2008-08-01
In this paper the problem of numerical approximation of non-Newtonian fluid flow with free surface is considered. Namely, the flow of fresh concrete is addressed. Industrial mixtures often behaves like non-Newtonian fluids exhibiting a yield stress that needs to be overcome for the flow to take place, cf. [R.B. Bird, R.C. Armstrong, O. Hassager, Dynamics of Polymeric Liquids, vol. 1, Fluid Mechanics, Wiley, New York, 1987; R.P. Chhabra, J.F. Richardson, Non-Newtonian Flow in the Process Industries, Butterworth-Heinemann, London, 1999]. The main interest is paid to the mathematical formulation of the problem and to discretization with the aid of finite element method. The described numerical procedure is applied onto the solution of several problems.
International Nuclear Information System (INIS)
Yeh, G.T.; Wong, K.V.; Craig, P.M.; Davis, E.C.
1985-01-01
This paper presents the construction, verification, and application of two groundwater flow and contaminant transport models: A Finite Element Model of Water Flow through Aquifers (FEWA) and A Finite Element Model of Material Transport through Aquifers (FEMA). The construction is based on the finite element approximation of partial differential equations of groundwater flow (FEWA) and of solute movement (FEMA). The particular features of FEWA and FEMA are their versatility and flexibility for dealing with nearly all vertically integrated two-dimensional problems. The models were verified against both analytical solutions and widely used US Geological Survey finite difference approximations. They were then applied for calibration and validation, using data obtained in experiments at the Engineering Test Facility at Oak Ridge National Laboratory. Results indicated that the models are valid for this specific site. To demonstrate the versatility anf flexibility of the models, they were applied to two hypothetical, but realistic, complex problems and three field sites across the United States. In these applications the models yielded good agreement with the field data for all three sites. Finally, the predictive capabilities of the models were demonstrated using data obtained at the Hialeah Preston site in Florida. This case illustrates the capability of FEWA and FEMA as predictive tools and their usefulness in the management of groundwater flow and contaminant transport. 25 refs
Finite Element Method Analysis of An Out Flow With Free Surface In Transition Zones
Saoula, R. Iddir S.; Mokhtar, K. Ait
The object of this work is to present this part of the fluid mechanics that relates to out-flows of the fluid to big speeds in transitions. Results usually gotten by the classic processes can only have a qualitative aspect. The method fluently used for the count of these out-flows to big speeds is the one of characteristics, this approach remains interesting so much that doesn't appear within the out-flow of intersections of shock waves, as well as of reflections of these. In the simple geometry case, the method of finite differences satisfying result, But when the complexity of this geometry imposes itself, it is the method of finite elements that is proposed to solve this type of prob- lem, in particular for problems Trans critic. The goal of our work is to analyse free surface flows in channels no prismatic has oblong transverse section in zone of tran- sition. (Convergent, divergent). The basic mathematical model of this study is Saint Venant derivatives partial equations. To solve these equations we use the finite ele- ment method, the element of reference is the triangular element with 6 nodes which are quadratic in speed and linear in height (pressure). Our results and their obtains by others are very close to experimental results.
International Nuclear Information System (INIS)
Lund, Natalie; Henrion, Daniel; Tiede, Petra; Ziche, Marina; Schunkert, Heribert; Ito, Wulf D.
2010-01-01
The cytoskeleton plays a central role for the integration of biochemical and biomechanical signals across the cell required for complex cellular functions. Recent studies indicate that the intermediate filament vimentin is necessary for endothelial cell morphogenesis e.g. in the context of leukocyte transmigration. Here, we present evidence, that the scaffold provided by vimentin is essential for VASP localization and PKG mediated VASP phosphorylation and thus controls endothelial cell migration and proliferation. Vimentin suppression using siRNA technique significantly decreased migration velocity by 50% (videomicroscopy), diminished transmigration activity by 42.5% (Boyden chamber) and reduced proliferation by 43% (BrdU-incorporation). In confocal microscopy Vimentin colocalized with VASP and PKG in endothelial cells. Vimentin suppression was accompanied with a translocation of VASP from focal contacts to the perinuclear region. VASP/Vimentin and PKG/Vimentin colocalization appeared to be essential for proper PKG mediated VASP phosphorylation because we detected a diminished expression of PKG and p Ser239 -VASP in vimentin-suppressed cells, Furthermore, the induction of VASP phosphorylation in perfused arteries was markedly decreased in vimentin knockout mice compared to wildtypes. A link is proposed between vimentin, VASP phosphorylation and actin dynamics that delivers an explanation for the important role of vimentin in controlling endothelial cell morphogenesis.
Sweijen, Thomas; Hartog, Niels; Marsman, Annemieke; Keijzer, Thomas J S
2014-06-01
Mercury is a contaminant of global concern. The use of elemental mercury in various (former) industrial processes, such as chlorine production at chlor-alkali plants, is known to have resulted in soil and groundwater contaminations worldwide. However, the subsurface transport behaviour of elemental mercury as an immiscible dense non-aqueous phase liquid (DNAPL) in porous media has received minimal attention to date. Even though, such insight would aid in the remediation effort of mercury contaminated sites. Therefore, in this study a detailed field characterization of elemental mercury DNAPL distribution with depth was performed together with two-phase flow modelling, using STOMP. This is to evaluate the dynamics of mercury DNAPL migration and the controls on its distribution in saturated porous media. Using a CPT-probe mounted with a digital camera, in-situ mercury DNAPL depth distribution was obtained at a former chlor-alkali-plant, down to 9 m below ground surface. Images revealing the presence of silvery mercury DNAPL droplets were used to quantify its distribution, characteristics and saturation, using an image analysis method. These field-observations with depth were compared with results from a one-dimensional two-phase flow model simulation for the same transect. Considering the limitations of this approach, simulations reasonably reflected the variability and range of the mercury DNAPL distribution. To further explore the impact of mercury's physical properties in comparison with more common DNAPLs, the migration of mercury and PCE DNAPL in several typical hydrological scenarios was simulated. Comparison of the simulations suggest that mercury's higher density is the overall controlling factor in controlling its penetration in saturated porous media, despite its higher resistance to flow due to its higher viscosity. Based on these results the hazard of spilled mercury DNAPL to cause deep contamination of groundwater systems seems larger than for any other
A Two Element Laminar Flow Airfoil Optimized for Cruise. M.S. Thesis
Steen, Gregory Glen
1994-01-01
Numerical and experimental results are presented for a new two-element, fixed-geometry natural laminar flow airfoil optimized for cruise Reynolds numbers on the order of three million. The airfoil design consists of a primary element and an independent secondary element with a primary to secondary chord ratio of three to one. The airfoil was designed to improve the cruise lift-to-drag ratio while maintaining an appropriate landing capability when compared to conventional airfoils. The airfoil was numerically developed utilizing the NASA Langley Multi-Component Airfoil Analysis computer code running on a personal computer. Numerical results show a nearly 11.75 percent decrease in overall wing drag with no increase in stall speed at sailplane cruise conditions when compared to a wing based on an efficient single element airfoil. Section surface pressure, wake survey, transition location, and flow visualization results were obtained in the Texas A&M University Low Speed Wind Tunnel. Comparisons between the numerical and experimental data, the effects of the relative position and angle of the two elements, and Reynolds number variations from 8 x 10(exp 5) to 3 x 10(exp 6) for the optimum geometry case are presented.
International Nuclear Information System (INIS)
Ribeiro, Felipe Lopes; Pinto, Joao Pedro C.T.A.
2013-01-01
The 4 th generation Very High Temperature Reactor (VHTR) most popular concept uses a graphite-moderated and helium cooled core with an outlet gas temperature of approximately 1000 deg C. The high output temperature allows the use of the process heat and the production of hydrogen through the thermochemical iodine-sulfur process as well as highly efficient electricity generation. There are two concepts of VHTR core: the prismatic block and the pebble bed core. The prismatic block core has two popular concepts for the fuel element: multihole and annular. In the multi-hole fuel element, prismatic graphite blocks contain cylindrical flow channels where the helium coolant flows removing heat from cylindrical fuel rods positioned in the graphite. In the other hand, the annular type fuel element has annular channels around the fuel. This paper shows the numerical evaluations of prismatic multi-hole and annular VHTR fuel elements and does a comparison between the results of these assembly reactors. In this study the analysis were performed using the CFD code ANSYS CFX 14.0. The simulations were made in 1/12 fuel element models. A numerical validation was performed through the energy balance, where the theoretical and the numerical generated heat were compared for each model. (author)
International Nuclear Information System (INIS)
Juncosa, R.; Delgado, J.; Font, I.
2010-01-01
Radioactive decay is an important subject to take into account when studying the thermo-hydro-dynamic behavior of the buffer clay material used in the containment of radioactive waste. The modern concepts for the multibarrier design of a repository of high level waste in deep geologic formations consider that once canisters have failed, the buffer clay material must ensure the retention and/or delay of radionuclides within the time framework given in the assessment studies. Within the clay buffer, different chemical species are retarded/fixed according to several physicochemical processes (ion exchange, surface complexation, precipitation, matrix diffusion,..) but typical approaches do not consider the eventuality that radioactive species change their chemical nature (i.e. phase) thereby affecting their reactive behavior. The radioactive decay of an element takes place independently of the phase (aqueous, solid or gaseous) to which it belongs. This means that, in terms of radionuclide fixation, some geochemical processes will be effective scavengers (for instance mineral precipitation of crystal growth) while others will not (for instance ion exchange and/or sorption). In this contribution we present a reactive radioactive decay model of any number of chemical components including those that belong to decay series. The model, which is named FLOW-DECAY, also takes into account flow and isotopic migration and it has been applied considering a hypothetical model scenario provided by the project ENRESA 2000 and direct comparison with the results generated by the probabilistic code GoldSim. Results indicate that FLOW-DECAY may simulate the decay processes in a similar way that GoldSim, being the differences related to factors associated to code architecture. (orig.)
Discrete Element Method simulations of standing jumps in granular flows down inclines
Directory of Open Access Journals (Sweden)
Méjean Ségolène
2017-01-01
Full Text Available This paper describes a numerical set-up which uses Discrete Element Method to produce standing jumps in flows of dry granular materials down a slope in two dimensions. The grain-scale force interactions are modeled by a visco-elastic normal force and an elastic tangential force with a Coulomb threshold. We will show how it is possible to reproduce all the shapes of the jumps observed in a previous laboratory study: diffuse versus steep jumps and compressible versus incompressible jumps. Moreover, we will discuss the additional measurements that can be done thanks to discrete element modelling.
Simulation of three-dimensional, time-dependent, incompressible flows by a finite element method
International Nuclear Information System (INIS)
Chan, S.T.; Gresho, P.M.; Lee, R.L.; Upson, C.D.
1981-01-01
A finite element model has been developed for simulating the dynamics of problems encountered in atmospheric pollution and safety assessment studies. The model is based on solving the set of three-dimensional, time-dependent, conservation equations governing incompressible flows. Spatial discretization is performed via a modified Galerkin finite element method, and time integration is carried out via the forward Euler method (pressure is computed implicitly, however). Several cost-effective techniques (including subcycling, mass lumping, and reduced Gauss-Legendre quadrature) which have been implemented are discussed. Numerical results are presented to demonstrate the applicability of the model
Søe-Knudsen, Alf; Sorokin, Sergey
2011-06-01
This rapid communication is concerned with justification of the 'rule of thumb', which is well known to the community of users of the finite element (FE) method in dynamics, for the accuracy assessment of the wave finite element (WFE) method. An explicit formula linking the size of a window in the dispersion diagram, where the WFE method is trustworthy, with the coarseness of a FE mesh employed is derived. It is obtained by the comparison of the exact Pochhammer-Chree solution for an elastic rod having the circular cross-section with its WFE approximations. It is shown that the WFE power flow predictions are also valid within this window.
Simulation of granular and gas-solid flows using discrete element method
Boyalakuntla, Dhanunjay S.
2003-10-01
In recent years there has been increased research activity in the experimental and numerical study of gas-solid flows. Flows of this type have numerous applications in the energy, pharmaceuticals, and chemicals process industries. Typical applications include pulverized coal combustion, flow and heat transfer in bubbling and circulating fluidized beds, hopper and chute flows, pneumatic transport of pharmaceutical powders and pellets, and many more. The present work addresses the study of gas-solid flows using computational fluid dynamics (CFD) techniques and discrete element simulation methods (DES) combined. Many previous studies of coupled gas-solid flows have been performed assuming the solid phase as a continuum with averaged properties and treating the gas-solid flow as constituting of interpenetrating continua. Instead, in the present work, the gas phase flow is simulated using continuum theory and the solid phase flow is simulated using DES. DES treats each solid particle individually, thus accounting for its dynamics due to particle-particle interactions, particle-wall interactions as well as fluid drag and buoyancy. The present work involves developing efficient DES methods for dense granular flow and coupling this simulation to continuum simulations of the gas phase flow. Simulations have been performed to observe pure granular behavior in vibrating beds. Benchmark cases have been simulated and the results obtained match the published literature. The dimensionless acceleration amplitude and the bed height are the parameters governing bed behavior. Various interesting behaviors such as heaping, round and cusp surface standing waves, as well as kinks, have been observed for different values of the acceleration amplitude for a given bed height. Furthermore, binary granular mixtures (granular mixtures with two particle sizes) in a vibrated bed have also been studied. Gas-solid flow simulations have been performed to study fluidized beds. Benchmark 2D
Energy Technology Data Exchange (ETDEWEB)
Kim, Jihoon; Um, Evan; Moridis, George
2014-12-01
We investigate fracture propagation induced by hydraulic fracturing with water injection, using numerical simulation. For rigorous, full 3D modeling, we employ a numerical method that can model failure resulting from tensile and shear stresses, dynamic nonlinear permeability, leak-off in all directions, and thermo-poro-mechanical effects with the double porosity approach. Our numerical results indicate that fracture propagation is not the same as propagation of the water front, because fracturing is governed by geomechanics, whereas water saturation is determined by fluid flow. At early times, the water saturation front is almost identical to the fracture tip, suggesting that the fracture is mostly filled with injected water. However, at late times, advance of the water front is retarded compared to fracture propagation, yielding a significant gap between the water front and the fracture top, which is filled with reservoir gas. We also find considerable leak-off of water to the reservoir. The inconsistency between the fracture volume and the volume of injected water cannot properly calculate the fracture length, when it is estimated based on the simple assumption that the fracture is fully saturated with injected water. As an example of flow-geomechanical responses, we identify pressure fluctuation under constant water injection, because hydraulic fracturing is itself a set of many failure processes, in which pressure consistently drops when failure occurs, but fluctuation decreases as the fracture length grows. We also study application of electromagnetic (EM) geophysical methods, because these methods are highly sensitive to changes in porosity and pore-fluid properties due to water injection into gas reservoirs. Employing a 3D finite-element EM geophysical simulator, we evaluate the sensitivity of the crosswell EM method for monitoring fluid movements in shaly reservoirs. For this sensitivity evaluation, reservoir models are generated through the coupled flow
Moreno Chaparro, Nicolas; Vignal, Philippe; Li, Jun; Calo, Victor M.
2013-01-01
A variational multi scale approach to model blood flow through arteries is proposed. A finite element discretization to represent the coarse scales (macro size), is coupled to smoothed dissipative particle dynamics that captures the fine scale features (micro scale). Blood is assumed to be incompressible, and flow is described through the Navier Stokes equation. The proposed cou- pling is tested with two benchmark problems, in fully coupled systems. Further refinements of the model can be incorporated in order to explicitly include blood constituents and non-Newtonian behavior. The suggested algorithm can be used with any particle-based method able to solve the Navier-Stokes equation.
Moreno Chaparro, Nicolas
2013-06-01
A variational multi scale approach to model blood flow through arteries is proposed. A finite element discretization to represent the coarse scales (macro size), is coupled to smoothed dissipative particle dynamics that captures the fine scale features (micro scale). Blood is assumed to be incompressible, and flow is described through the Navier Stokes equation. The proposed cou- pling is tested with two benchmark problems, in fully coupled systems. Further refinements of the model can be incorporated in order to explicitly include blood constituents and non-Newtonian behavior. The suggested algorithm can be used with any particle-based method able to solve the Navier-Stokes equation.
Microchip Flow Cytometer with Integrated Polymer Optical Elements for Measurement of Scattered Light
DEFF Research Database (Denmark)
Wang, Zhenyu; El-Ali, Jamil; Perch-Nielsen, Ivan Ryberg
2004-01-01
channels to form a complete microchip flow cytometer. All the optical elements, the microfluidic system, and the fiber-to-waveguide couplers were defined in one layer of polymer (SU-8, negative photoresist) by standard photolithography. With only one single mask procedure, all the fabrication and packaging...... processes can be finished in one day. Polystyrene beads were measured in the microchip flow cytometer, and three signals (forward scattering, large angle scattering and extinction) were measured simultaneously for each bead. The average intensities of the forward Scattered light and the incident light...
International Nuclear Information System (INIS)
Semino, Carlos E.; Kamm, Roger D.; Lauffenburger, Douglas A.
2006-01-01
We show here that autocrine ligand activation of epidermal growth factor (EGF) receptor in combination with interstitial flow is critically involved in the morphogenetic response of endothelial cells to VEGF stimulation. Human umbilical vein endothelial cell (HUVEC) monolayers cultured on a collagen gel and exposed to low interstitial flow in the absence of EGF and VEGF remained viable and mitotic but exhibited little evidence of vascular morphogenesis. Addition of VEGF produced a flow-dependent morphogenetic response within 48 to 72 h, characterized by branched capillary-like structures. The response was substantially abolished by inhibitors related to the autocrine EGF receptor pathway including Galardin, AG1478, PD98059, and an EGF receptor-blocking antibody, indicating that regulation of the morphogenetic process operates via autocrine EGF receptor activation. Moreover, we observed that in our system the EGF receptor was always activated independently of the interstitial flow, and, in addition, the EGF receptor inhibitors used above reduced the phosphorylation state of the receptor, correlating with inhibition of capillary morphogenesis. Finally, 5'bromo-2'-deoxyuridine (BrdU) labeling identified dividing cells at the monolayer but not in the extending capillary-like structures. EGF pathway inhibitors Galardin and AG1478 did not reduce BrdU incorporation in the monolayer, indicating that the EGF-receptor-mediated morphogenetic behavior is mainly due to cell migration rather than proliferation. Based on these results, we propose a two-step model for in vitro capillary morphogenesis in response to VEGF stimulation with interstitial fluid flow: monolayer maintenance by mitotic activity independent of EGF receptors and a migratory response mediated by autocrine EGF receptor activation wherein cells establish capillary-like structures
Directory of Open Access Journals (Sweden)
Jamal Benamar
2016-10-01
Full Text Available Irregular migration, fueled in recent years by a massive influx of sub-Saharans who leave North Africa, where Morocco is included as destination in Europe (Spain and Italy as privileged points of entry is taking alarming dimensions and repeatedly dramatic, taking into account the price paid in lives to cross the Mediterranean. Faced with this new reality, Morocco raises revise its immigration policy and take legislative, institutional and even operational to respond to this new situation for the country measures. We analyze this situation based on a survey (ETF et AMERM, 2012, covering the entire national territory, although we will focus especially in the north of Morocco, who was interested returnees immigrants, candidates for illegal immigration and our experience in a European project POCTEFEX 2011-2013 program to which you have participated as a partner (Czech, 2014, were studied: the evolution of process control and management of migration flows; the main challenges of sub-Saharan immigration to Morocco, and the challenges and opportunities for Morocco as new host country of immigrants.
Directory of Open Access Journals (Sweden)
Merita H. Mece
2016-05-01
Full Text Available Irregular migration on the Western Balkan route has marked an unprecedented number during the last five years. Evidence indicates that both, non-European nationals and Western Balkan citizens have been involved in this complex migratory flow being exposed to various risks of human trafficking. But Western Balkan countries are source, transit and destination countries of human trafficking while their states are not well organized to implement a comprehensive and well-coordinated regional response to combat it. This paper aims at examining challenges faced by the Western Balkan countries to converge anti-trafficking response while facing increased irregular migratory waves. Using secondary data it illustrates various disparities and differences among them concluding that a well-coordinated, multi-faceted and integrated regional response is needed to combat this humanitarian problem.
Finite element methods for viscous incompressible flows a guide to theory, practice, and algorithms
Gunzburger, Max D
2012-01-01
In this book, the author examines mathematical aspects of finite element methods for the approximate solution of incompressible flow problems. The principal goal is to present some of the important mathematical results that are relevant to practical computations. In so doing, useful algorithms are also discussed. Although rigorous results are stated, no detailed proofs are supplied; rather, the intention is to present these results so that they can serve as a guide for the selection and, in certain respects, the implementation of algorithms.
The application of finite element method for mhd viscous flow over a porous stretching sheet
International Nuclear Information System (INIS)
Mahmood, R.; Sajid, M.
2007-01-01
This work is concerned with the magnetohydrodynamic (MHD) viscous flow due to a porous stretching sheet. The similarity solution of the problem is obtained using finite element method. The physical quantities of interest like the fluid velocity and skin friction coefficient is obtained and discussed under the influence of suction parameter and Hartman number. It is evident from the results that MHD can be used to control the boundary layer thickness. (author)
Five-point Element Scheme of Finite Analytic Method for Unsteady Groundwater Flow
Institute of Scientific and Technical Information of China (English)
Xiang Bo; Mi Xiao; Ji Changming; Luo Qingsong
2007-01-01
In order to improve the finite analytic method's adaptability for irregular unit, by using coordinates rotation technique this paper establishes a five-point element scheme of finite analytic method. It not only solves unsteady groundwater flow equation but also gives the boundary condition. This method can be used to calculate the three typical questions of groundwater. By compared with predecessor's computed result, the result of this method is more satisfactory.
On the Mutual Dynamics of Interregional Gross Migration Flows in Space and Time
DEFF Research Database (Denmark)
Mitze, Timo
2016-01-01
This paper applies spatial dynamic panel data models to analyse the labor market dimension of interregional population flows among German federal states in the period 1993–2009. Making use of recent improvements in the estimation of space-time dynamic panel data models and the computation of mean...
Mountain scale modeling of transient, coupled gas flow, heat transfer and carbon-14 migration
International Nuclear Information System (INIS)
Lu, Ning; Ross, B.
1993-01-01
We simulate mountain-scale coupled heat transfer and gas flow at Yucca Mountain. A coupled rock-gas flow and heat transfer model, TGIF2, is used to simulate mountain-scale two-dimensional transient heat transfer and gas flow. The model is first verified against an analytical solution for the problem of an infinite horizontal layer of fluid heated from below. Our numerical results match very well with the analytical solution. Then, we obtain transient temperature and gas flow distributions inside the mountain. These distributions are used by a transient semianalytical particle tracker to obtain carbon-14 travel times for particles starting at different locations within the repository. Assuming that the repository is filled with 30-year-old waste at an initial areal power density of 57 kw/acre, we find that repository temperatures remain above 60 degrees C for more than 10,000 years. Carbon-14 travel times to the surface are mostly less than 1000 years, for particles starting at any time within the first 10,000 years
International Nuclear Information System (INIS)
Kaiser, H.G.
1985-01-01
The author is concerned with the flow conditions in case of narrow fuel element grids of pressurised-water reactors. Starting from the mathematical formulation of the flow processes for incompressible, isothermal flows, models of the turbulence characteristics are being developed. Besides turbulence models, and network structure the finite element method is treated as numeric solution process. Finally the results are summarized and discussed. (HAG) [de
Energy Technology Data Exchange (ETDEWEB)
Shadid, J.N.; Moffat, H.K.; Hutchinson, S.A.; Hennigan, G.L.; Devine, K.D.; Salinger, A.G.
1996-05-01
The theoretical background for the finite element computer program, MPSalsa, is presented in detail. MPSalsa is designed to solve laminar, low Mach number, two- or three-dimensional incompressible and variable density reacting fluid flows on massively parallel computers, using a Petrov-Galerkin finite element formulation. The code has the capability to solve coupled fluid flow, heat transport, multicomponent species transport, and finite-rate chemical reactions, and to solver coupled multiple Poisson or advection-diffusion- reaction equations. The program employs the CHEMKIN library to provide a rigorous treatment of multicomponent ideal gas kinetics and transport. Chemical reactions occurring in the gas phase and on surfaces are treated by calls to CHEMKIN and SURFACE CHEMKIN, respectively. The code employs unstructured meshes, using the EXODUS II finite element data base suite of programs for its input and output files. MPSalsa solves both transient and steady flows by using fully implicit time integration, an inexact Newton method and iterative solvers based on preconditioned Krylov methods as implemented in the Aztec solver library.
Tomasi, Lydio E., Ed.
1995-01-01
Presents data on international migration and its effects in and between various countries in North America, Europe, and Africa. Discussions include refugee, immigrant, and migrant worker flows; the legal, political, and social problems surrounding immigrants; alien terrorism and law enforcement problems; and migrant effects on education, social…
Studies to single subassembly flow monitoring with a complete 7 element array under sodium
International Nuclear Information System (INIS)
Hess, B.; Ruppert, E.; Stehle, H.; Vinzens, K.
1975-01-01
As part of the SNR-300 R and D programme a complete clamped array, consisting of 4 full size fuel elements and 3 blanket elements was tested for more than 4000 hours at 600 deg C in the AKB sodium loop at Interatom, Bensberg. The test was split into two phases and the total cluster was prestrained in the second phase to simulate 15 mm subassembly displacement at the level of the upper bearing pads. Although this test was mainly considered as an endurance test to demonstrate the integrity of prestrained core elements, efforts were made to study the feasibility of single subassembly flow monitoring with this full size model of a core section. The results of these investigations are presented and discussed in this paper
Studies to single subassembly flow monitoring with a complete 7 element array under sodium
International Nuclear Information System (INIS)
Hess, B.; Ruppert, E.; Stehle, H.; Vinzens, K.
1975-01-01
A core restraint system in a fast reactor serves to limit fuel element movement leading to reactivity changes and misalignment of control rod drives and instrumentation. To guarantee proper control rod function the upper ring of the passive restraint system for the SNR-300 should keep subassembly displacement below 20 mm, whereas a free bowing up to 25 mm does not impair subassembly handling. With respect to single subassembly instrumentation the influences of subassembly displacement on temperature and flow monitoring were not exactly known. As part of the SNR-300 R and D programme a complete clamped array, consisting of 4 full size fuel elements and 3 blanket elements was tested for more than 4000 hours at 600 0 C in the AKB sodium loop at Interatom, Bensberg. The test was split into two phases and the total cluster was prestrained in the second phase to simulate 15 mm subassembly displacement at the level of the upper pads. Although this test was mainly considered as an endurance test to demonstrate the integrity of prestrained core elements, effort were made to study the feasibility of single subassembly flow monitoring with this full size model of a core section. (Auth.)
A study of flow patterns for staggered cylinders at low Reynolds number by spectral element method
Energy Technology Data Exchange (ETDEWEB)
Hsu, Li-Chieh; Chen, Chien-Lin; Ye, Jian-Zhi [National Yunlin University of Science and Technology, Taiwan (China)
2017-06-15
This study investigates the pattern of flow past two staggered array cylinders using the spectral element method by varying the distance between the cylinders and the angle of incidence (α) at low Reynolds numbers (Re = 100-800). Six flow patterns are identified as Shear layer reattachment (SLR), Induced separation (IS), Vortex impingement (VI), Synchronized vortex shedding (SVS), Vortex pairing and enveloping (VPE), and Vortex pairing splitting and enveloping (VPSE). These flow patterns can be transformed from one to another by changing the distance between the cylinders, the angle of incidence, or Re. SLR, IS and VI flow patterns appear in regimes with small angles of incidence (i.e., α ≤ 30° ) and hold only a single von Karman vortex shedding in a wake with one shedding frequency. SVS, VPE and VPSE flow patterns appear in regimes with large angles of incidence (i.e., 30° ≤ α ≤ 50° ) and present two synchronized von Karman vortices. Quantitative analyses and physical interpretation are also conducted to determine the generation mechanisms of the said flow patterns.
Compositional modeling of three-phase flow with gravity using higher-order finite element methods
Moortgat, Joachim
2011-05-11
A wide range of applications in subsurface flow involve water, a nonaqueous phase liquid (NAPL) or oil, and a gas phase, such as air or CO2. The numerical simulation of such processes is computationally challenging and requires accurate compositional modeling of three-phase flow in porous media. In this work, we simulate for the first time three-phase compositional flow using higher-order finite element methods. Gravity poses complications in modeling multiphase processes because it drives countercurrent flow among phases. To resolve this issue, we propose a new method for the upwinding of three-phase mobilities. Numerical examples, related to enhanced oil recovery and carbon sequestration, are presented to illustrate the capabilities of the proposed algorithm. We pay special attention to challenges associated with gravitational instabilities and take into account compressibility and various phase behavior effects, including swelling, viscosity changes, and vaporization. We find that the proposed higher-order method can capture sharp solution discontinuities, yielding accurate predictions of phase boundaries arising in computational three-phase flow. This work sets the stage for a broad extension of the higher-order methods for numerical simulation of three-phase flow for complex geometries and processes.
Hydrodynamics of free surface flows modelling with the finite element method
Hervouet, Jean-Michel
2007-01-01
A definitive guide for accurate state-of-the-art modelling of free surface flows Understanding the dynamics of free surface flows is the starting point of many environmental studies, impact studies, and waterworks design. Typical applications, once the flows are known, are water quality, dam impact and safety, pollutant control, and sediment transport. These studies used to be done in the past with scale models, but these are now being replaced by numerical simulation performed by software suites called "hydro-informatic systems". The Telemac system is the leading software package worldwide, and has been developed by Electricité de France and Jean-Michel Hervouet, who is the head and main developer of the Telemac project. Written by a leading authority on Computational Fluid Dynamics, the book aims to provide environmentalists, hydrologists, and engineers using hydro-informatic systems such as Telemac and the finite element method, with the knowledge of the basic principles, capabilities, different hypothese...
An investigation of noise produced by unsteady gas flow through silencer elements
Mawhinney, Graeme Hugh
This thesis presents an investigation of the noise produced by unsteady gas flow through silencer elements. The central aim of the research project was to produce a tool for assistance in the design of the exhaust systems of diesel powered electrical generator sets, with the modelling techniques developed having a much wider application in reciprocating internal combustion engine exhaust systems. An automotive cylinder head was incorporated in a purpose built test rig to supply exhaust pulses, typical of those found in the exhaust system of four stroke diesel engines, to various experimental exhaust systems. Exhaust silencer elements evaluated included expansion, re- entrant, concentric tube resonator and absorptive elements. Measurements taken on the test rig included, unsteady superposition pressure in the exhaust ducting, cyclically averaged mass flow rate through the system and exhaust noise levels radiated into a semi-anechoic measurement chamber. The entire test rig was modelled using the 1D finite volume method developed previously developed at Queen's University Belfast. Various boundary conditions, developed over the years, were used to model the various silencer elements being evaluated. The 1D gas dynamic simulation thus estimated the mass flux history at the open end of the exhaust system. The mass flux history was then broken into its harmonic components and an acoustic radiation model was developed to model the sound pressure level produced by an acoustic monopole over a reflecting plane. The accuracy of the simulation technique was evaluated by correlation of measured and simulated superposition pressure and noise data. In general correlation of superposition pressure was excellent for all of the silencer elements tested. Predicted sound pressure level radiated from the open end of the exhaust tailpipe was seen to be accurate in the 100 Hz to 1 kHz frequency range for all of the silencer elements tested.
Ceresa, Francesco; Belda, E.J.; Kvist, Laura; Rguibi-Idrissi, Hamid; Monrós González, Juan Salvador
2015-01-01
Wetlands are naturally patchy habitats, but patchiness has been accentuated by the extensive wetlands loss due to human activities. In such a fragmented habitat, dispersal ability is especially important to maintain gene flow between populations. Here we studied population structure, genetic diversity and demographic history of Iberian and North African populations of two wetland passerines, the Eurasian reed warbler Acrocephalus scirpaceus and the moustached warbler Acrocephalus melanopogon....
Energy Technology Data Exchange (ETDEWEB)
Hadermann, J
1981-11-01
Migration analysis is of considerable importance in long-term safety analysis of radioactive waste repositories. In a first step our plans are to calculate transport of radionuclides using data - as far as possible - for an undisturbed hydrogeology. Thereby a reference case is defined. In a later step, possible events and processes can be considered leading to a deviation from the reference case. The present work gives the data base for a selected part of a comprehensive geosphere transport calculation. We restrict ourselves to a critical evaluation of parameters pertinent to the migration analysis of the /sup 245/Cm chain. This includes the important nuclide /sup 237/Np. For the first time we are able to perform a site specific calculation for repositories planned in deep geologic formations in Switzerland. The well known fact that the data basis is extremely sparse is pointed out once more and concretized in detail.
In-core fuel element temperature and flow measurment of HFETR
International Nuclear Information System (INIS)
Chen Daolong; Jiang Pei
1988-02-01
The HFETR in-core fuel element temperature-flow measurement facility and its measurement system are expounded. The applications of the instrumented fuel element to stationary and transient states measurements during the lift of power, the operation test of all lifetime at first load, and the deepening burn-up test at second load are described. The method of determination of the hot point temperature under the fin is discussed. The error analysis is made. The fuel element out-of-pile water deprivation test is described. The development of this measurement facility and succesful application have made important contribution to high power and deep burn-up safe operation at two load, in-core fuel element irradiation, and varied investigation of HFETR. After operation at two loads, the integrated power of this instrumented fuel element arrives at 90.88 MWd, its maximum point burn-up is about 64.9%, so that the economy of fuel use of HFETR is raised very much
International Nuclear Information System (INIS)
1986-02-01
All published proposals for the deep level burial of radioactive waste recognise that the access shafts, tunnels and boreholes must be sealed, and that the sealing of these openings plays an integral role in the overall isolation of the waste. Previous studies have identified the interface between the host ground formation and the various sealing materials as potential defects in the overall quality of the waste isolation. The significance of groundwater flow at and near the interface has been assessed for representative conditions in generic repository materials. A range of design options to minimise the significance of flow in the interface zone have been proposed, and the most practical of these options have been selected for quantitative analysis. It has been found that isolated high impermeability collars are of limited value unless a highly effective method of minimising ground disturbance during excavation can be developed. It has also been found that control of radionuclide migration by sorptive processes provides an attractive option. The effect of various geometrical arrangements of sorptive materials has been investigated. Consideration has also been given to the particular conditions in the near field, to the behaviour of weak plastic clay host formations and to the mechanical interaction between the backfill material and the host formation. (author)
Directory of Open Access Journals (Sweden)
Thair Sharif Khayyun
2018-02-01
Full Text Available This study provides a simulation of groundwater flow and advective-dispersive migration of radioactive Co-60 through an aquifer with three layers, which release or leak to groundwater from the Active Metallurgy Testing Laboratory (LAMA Nuclear Facility-Iraq due to the nuclear accident scenario. Processing Modflow for windows (PMWIN and Modular Three-Dimensional Multispecies Transport (MT3DMS Models were used for this purpose. The study area and the contaminated area were 12.7 km2 and 0.005625 km2, respectively. Water levels of the groundwater have been measured in six monitoring wells. The simulation time was assumed to have started in 2016. The PMWIN model simulated the flow for two scenarios of water level in Tigris River (average and minimum water levels. The MT3DMS model simulated 10 years of plume travel, beginning in 2016. The simulated Co-60 concentrations after five years of travel were 32.34 and 34.44 μg/m3 for the two scenarios. The maximum predicted Co-60 concentrations at the end of Year 10 were 34.86 and 37.31 μg/m3, respectively. The sensitivity analysis showed that the simulated hydraulic heads in the observation wells and the simulated plume of Co-60 were highly sensitive to changes in the effective porosity but less sensitive to changes in other parameters of the dispersion and chemical reaction processes. The time necessary to reach steady state condition was predicted to be approximately 16 years. The contaminated area was isolated by using remedial process which is represented by three fully penetrating pumping wells with a suitable flow rate (0.045 m3/s for controlling the movement of Co-60 pollutant.
Energy Technology Data Exchange (ETDEWEB)
Andrew Wolfsberg; Lee Glascoe; Guoping Lu; Alyssa Olson; Peter Lichtner; Maureen McGraw; Terry Cherry; Guy Roemer
2002-09-01
Recent field studies have led to the discovery of trace quantities of plutonium originating from the BENHAM underground nuclear test in two groundwater observation wells on Pahute Mesa at the Nevada Test Site. These observation wells are located 1.3 km from the BENHAM underground nuclear test and approximately 300 m from the TYBO underground nuclear test. In addition to plutonium, several other conservative (e.g. tritium) and reactive (e.g. cesium) radionuclides were found in both observation wells. The highest radionuclide concentrations were found in a well sampling a welded tuff aquifer more than 500m above the BENHAM emplacement depth. These measurements have prompted additional investigations to ascertain the mechanisms, processes, and conditions affecting subsurface radionuclide transport in Pahute Mesa groundwater. This report describes an integrated modeling approach used to simulate groundwater flow, radionuclide source release, and radionuclide transport near the BENHAM and TYBO underground nuclear tests on Pahute Mesa. The components of the model include a flow model at a scale large enough to encompass many wells for calibration, a source-term model capable of predicting radionuclide releases to aquifers following complex processes associated with nonisothermal flow and glass dissolution, and site-scale transport models that consider migration of solutes and colloids in fractured volcanic rock. Although multiple modeling components contribute to the methodology presented in this report, they are coupled and yield results consistent with laboratory and field observations. Additionally, sensitivity analyses are conducted to provide insight into the relative importance of uncertainty ranges in the transport parameters.
Measurement and analysis of vibrational behavior of an SNR-fuel element in sodium flow
International Nuclear Information System (INIS)
Hess, B.F.H.; Ruppert, E.; Schmidt, H.; Vinzens, K.
1975-01-01
Within the framework of SNR-300 fuel element development programme a complete full size fuel element dummy has been tested thoroughly for nearly 3000 hours at 650 deg C system temperature in the AKB sodium loop at Interatom, Bensberg. It is known that the coolant flow through a subassembly can induce flutter or vibrations of structural parts such as single pins, the wrapper and the total pin bundle all of which have been of interest during this test. To detect these vibrations of different structural parts simultaneously with a minimum of instrumentation only 3 weldable high temperature strain gauges were employed. These strain gauges were especially prepared and bent in such a way as to form a bridge between the inner wrapper and a fuel pin top and spot-welded to both the wrapper and the fuel pin. Although this arrangement seems to be a rather unusual one, the simultaneous-measurement of bundle, wrapper and pin vibrations was possible and periodic flow fluctuations were also detected. The presented results are only relative due to calibration difficulties with these deformed strain gauges which were first used during this test. It is, however, believed that this arrangement, in connection with the proposed anlytical approach, leads to a simple and technical representation of the vibrational behavior of core elements during sodium tests. Detailed information needed for check and calibration of computer codes are however displayed by the respective power spectral density functions
Power flow as a complement to statistical energy analysis and finite element analysis
Cuschieri, J. M.
1987-01-01
Present methods of analysis of the structural response and the structure-borne transmission of vibrational energy use either finite element (FE) techniques or statistical energy analysis (SEA) methods. The FE methods are a very useful tool at low frequencies where the number of resonances involved in the analysis is rather small. On the other hand SEA methods can predict with acceptable accuracy the response and energy transmission between coupled structures at relatively high frequencies where the structural modal density is high and a statistical approach is the appropriate solution. In the mid-frequency range, a relatively large number of resonances exist which make finite element method too costly. On the other hand SEA methods can only predict an average level form. In this mid-frequency range a possible alternative is to use power flow techniques, where the input and flow of vibrational energy to excited and coupled structural components can be expressed in terms of input and transfer mobilities. This power flow technique can be extended from low to high frequencies and this can be integrated with established FE models at low frequencies and SEA models at high frequencies to form a verification of the method. This method of structural analysis using power flo and mobility methods, and its integration with SEA and FE analysis is applied to the case of two thin beams joined together at right angles.
International Nuclear Information System (INIS)
Zhongchun, Li; Xiaoming, Song; Shengyao, Jiang; Jiyang, Yu
2014-01-01
Highlights: • A VOF simulation of bubble in low viscosity fluid was conducted. • Lift force in different viscosity fluid had different lateral migration characteristics. • Bubble with different size migrated to different direction. • Shear stress triggered the bubble deformation process and the bubble deformation came along with the oscillation behaviors. - Abstract: Two phase flow systems have been widely used in industrial engineering. Phase distribution characteristics are vital to the safety operation and optimization design of two phase flow systems. Lift force has been known as perpendicular to the bubbles’ moving direction, which is one of the mechanisms of interfacial momentum transfer. While most widely used lift force correlations, such as the correlation of Tomiyama et al. (2002), were obtained by experimentally tracking single bubble trajectories in high viscosity glycerol–water mixture, the applicability of these models into low viscosity fluid, such as water in nuclear engineering system, needs to be further evaluated. In the present paper, bubble in low viscosity fluid in shear flow was investigated in a full 3D numerical simulation and the volume of fluid (VOF) method was applied to capture the interface. The fluid parameter: fluid viscosity, bubble parameter: diameter and external flow parameters: shear stress magnitude and liquid velocity were examined. Comparing with bubble in high viscosity shear flow and bubble in low viscosity still flow, relative large bubble in low viscosity shear flow keep an oscillation way towards the moving wall and experienced a shape deformation process. The oscillation amplitude increased as the viscosity of fluid decreased. Small bubble migrated to the static wall in a line with larger migration velocity than that in high viscosity fluid and no deformation occurred. The shear stress triggered the oscillation behaviors while it had no direct influence with the behavior. The liquid velocity had no effect on
Variational Multiscale Finite Element Method for Flows in Highly Porous Media
Iliev, O.; Lazarov, R.; Willems, J.
2011-01-01
We present a two-scale finite element method (FEM) for solving Brinkman's and Darcy's equations. These systems of equations model fluid flows in highly porous and porous media, respectively. The method uses a recently proposed discontinuous Galerkin FEM for Stokes' equations by Wang and Ye and the concept of subgrid approximation developed by Arbogast for Darcy's equations. In order to reduce the "resonance error" and to ensure convergence to the global fine solution, the algorithm is put in the framework of alternating Schwarz iterations using subdomains around the coarse-grid boundaries. The discussed algorithms are implemented using the Deal.II finite element library and are tested on a number of model problems. © 2011 Society for Industrial and Applied Mathematics.
Finite element analysis-based design of a fluid-flow control nano-valve
International Nuclear Information System (INIS)
Grujicic, M.; Cao, G.; Pandurangan, B.; Roy, W.N.
2005-01-01
A finite element method-based procedure is developed for the design of molecularly functionalized nano-size devices. The procedure is aimed at the single-walled carbon nano-tubes (SWCNTs) used in the construction of such nano-devices and utilizes spatially varying nodal forces to represent electrostatic interactions between the charged groups of the functionalizing molecules. The procedure is next applied to the design of a fluid-flow control nano-valve. The results obtained suggest that the finite element-based procedure yields the results, which are very similar to their molecular modeling counterparts for small-size nano-valves, for which both types of analyses are feasible. The procedure is finally applied to optimize the design of a larger-size nano-valve, for which the molecular modeling approach is not practical
Variational Multiscale Finite Element Method for Flows in Highly Porous Media
Iliev, O.
2011-10-01
We present a two-scale finite element method (FEM) for solving Brinkman\\'s and Darcy\\'s equations. These systems of equations model fluid flows in highly porous and porous media, respectively. The method uses a recently proposed discontinuous Galerkin FEM for Stokes\\' equations by Wang and Ye and the concept of subgrid approximation developed by Arbogast for Darcy\\'s equations. In order to reduce the "resonance error" and to ensure convergence to the global fine solution, the algorithm is put in the framework of alternating Schwarz iterations using subdomains around the coarse-grid boundaries. The discussed algorithms are implemented using the Deal.II finite element library and are tested on a number of model problems. © 2011 Society for Industrial and Applied Mathematics.
PARALLEL ALGORITHM FOR THREE-DIMENSIONAL STOKES FLOW SIMULATION USING BOUNDARY ELEMENT METHOD
Directory of Open Access Journals (Sweden)
D. G. Pribytok
2016-01-01
Full Text Available Parallel computing technique for modeling three-dimensional viscous flow (Stokes flow using direct boundary element method is presented. The problem is solved in three phases: sampling and construction of system of linear algebraic equations (SLAE, its decision and finding the velocity of liquid at predetermined points. For construction of the system and finding the velocity, the parallel algorithms using graphics CUDA cards programming technology have been developed and implemented. To solve the system of linear algebraic equations the implemented software libraries are used. A comparison of time consumption for three main algorithms on the example of calculation of viscous fluid motion in three-dimensional cavity is performed.
Study of Dynamic Flow and Mixing Performances of Tri-Screw Extruders with Finite Element Method
X. Z. Zhu; G. Wang; Y. D. He; Z. F. Cheng
2013-01-01
There is a special circumfluence in the center region of cross-section for a tri-screw extruder. To study the effect of the dynamic center region on the flow and mixing mechanism of the tri-screw extruder, 2D finite element modeling was used to reduce the axial effects. Based on the particle tracking technology, the nonlinear dynamics of a typical particle motions in the center region was carried out and the mixing process in the tri-screw extruder was analyzed with Poincaré maps. Moreover, m...
Device for determining element contents of lignite mass flows by activation analysis
International Nuclear Information System (INIS)
Goeldner, R.; Maul, E.; Rose, W.; Wagner, D.
1987-01-01
A simple device is presented, apt for continuous operation, to determine the element contents of bulk goods of flowable materials with a suitable granularity, in particular of lignite mass flows to assess the coal quality. Several kilograms of samples can be reproducibly dosed and homogeneously activated by a device consisting of a shielding container with activation chamber and radiation source, a measuring unit with detectors, and a source container, and characterized by a blade wheel in the activation chamber which causes the dosing and homogeneous activation of the sample
NAMMU: finite element program for coupled heat and groundwater flow problems
International Nuclear Information System (INIS)
Rae, J.; Robinson, P.C.
1979-11-01
NAMMU is a computer program which will calculate the evolution in time of coupled water and heat flow in a porous medium. It is intended to be used primarily for modelling studies of underground nuclear waste repositories. NAMMU is based on the Galerkin-Finite-element method and has self-adjusting time stepping. The present version is written for 2-dimensional cartesian or cylindrical coordinate systems. It has been checked against two calculations from the KBS study and an exact solution by Hodgkinson for a very idealised repository design. (author)
Sohn, J. L.; Heinrich, J. C.
1990-01-01
The calculation of pressures when the penalty-function approximation is used in finite-element solutions of laminar incompressible flows is addressed. A Poisson equation for the pressure is formulated that involves third derivatives of the velocity field. The second derivatives appearing in the weak formulation of the Poisson equation are calculated from the C0 velocity approximation using a least-squares method. The present scheme is shown to be efficient, free of spurious oscillations, and accurate. Examples of applications are given and compared with results obtained using mixed formulations.
A strongly conservative finite element method for the coupling of Stokes and Darcy flow
Kanschat, G.
2010-08-01
We consider a model of coupled free and porous media flow governed by Stokes and Darcy equations with the Beavers-Joseph-Saffman interface condition. This model is discretized using divergence-conforming finite elements for the velocities in the whole domain. Discontinuous Galerkin techniques and mixed methods are used in the Stokes and Darcy subdomains, respectively. This discretization is strongly conservative in Hdiv(Ω) and we show convergence. Numerical results validate our findings and indicate optimal convergence orders. © 2010 Elsevier Inc.
Flow instability tests for a particle bed reactor nuclear thermal rocket fuel element
Lawrence, Timothy J.
1993-05-01
Recent analyses have focused on the flow stability characteristics of a particle bed reactor (PBR). These laminar flow instabilities may exist in reactors with parallel paths and are caused by the heating of the gas at low Reynolds numbers. This phenomena can be described as follows: several parallel channels are connected at the plenum regions and are stabilized by some inlet temperature and pressure; a perturbation in one channel causes the temperature to rise and increases the gas viscosity and reduces the gas density; the pressure drop is fixed by the plenum regions, therefore, the mass flow rate in the channel would decrease; the decrease in flow reduces the ability to remove the energy added and the temperature increases; and finally, this process could continue until the fuel element fails. Several analyses based on different methods have derived similar curves to show that these instabilities may exist at low Reynolds numbers and high phi's ((Tfinal Tinitial)/Tinitial). These analyses need to be experimentally verified.
Numerical Modeling of Cavitating Venturi: A Flow Control Element of Propulsion System
Majumdar, Alok; Saxon, Jeff (Technical Monitor)
2002-01-01
In a propulsion system, the propellant flow and mixture ratio could be controlled either by variable area flow control valves or by passive flow control elements such as cavitating venturies. Cavitating venturies maintain constant propellant flowrate for fixed inlet conditions (pressure and temperature) and wide range of outlet pressures, thereby maintain constant, engine thrust and mixture ratio. The flowrate through the venturi reaches a constant value and becomes independent of outlet pressure when the pressure at throat becomes equal to vapor pressure. In order to develop a numerical model of propulsion system, it is necessary to model cavitating venturies in propellant feed systems. This paper presents a finite volume model of flow network of a cavitating venturi. The venturi was discretized into a number of control volumes and mass, momentum and energy conservation equations in each control volume are simultaneously solved to calculate one-dimensional pressure, density, and flowrate and temperature distribution. The numerical model predicts cavitations at the throat when outlet pressure was gradually reduced. Once cavitation starts, with further reduction of downstream pressure, no change in flowrate is found. The numerical predictions have been compared with test data and empirical equation based on Bernoulli's equation.
DEFF Research Database (Denmark)
Albu, Oana Brindusa
The study investigates the practices of different forms of anticipatory knowledge of actors involved in the global management of forced migration flows in ‘migration hotspots’ (European Parliament, 2016). The study draws on an ongoing multi-sited study of professionals working in IGOs, NGOs......—all for estimating the movements and framing the choices, freedoms and rights of asylum seekers. The study shows how anticipatory practices constitute asylum seekers as ‘global problems’ which reinforce dominance relations of ‘vulnerability’ and remove individuals’ agency while providing them with life...
Vescovi, Dalila; Berzi, Diego; Richard, Patrick; Brodu, Nicolas
2014-01-01
International audience; We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed av...
Brijs, Jeroen; Axelsson, Michael; Gräns, Albin; Pichaud, Nicolas; Olsson, Catharina; Sandblom, Erik
2015-01-01
The large-scale migrations of anadromous fish species from freshwater to seawater have long been considered particularly enigmatic, as this life history necessitates potentially energetically costly changes in behaviour and physiology. A significant knowledge gap concerns the integral role of cardiovascular responses, which directly link many of the well-documented adaptations (i.e. through oxygen delivery, water and ion transport) allowing fish to maintain osmotic homeostasis in the sea. Using long-term recordings of cardiorespiratory variables and a novel method for examining drinking dynamics, we show that euryhaline rainbow trout (Oncorhynchus mykiss) initiate drinking long before the surrounding environment reaches full seawater salinity (30–33 ppt), suggesting the presence of an external osmo-sensing mechanism. Onset of drinking was followed by a delayed, yet substantial increase in gastrointestinal blood flow through increased pulse volume exclusively, as heart rate remained unchanged. While seawater entry did not affect whole animal energy expenditure, enhanced gastrointestinal perfusion represents a mechanism crucial for ion and water absorption, as well as possibly increasing local gastrointestinal oxygen supply. Collectively, these modifications are essential for anadromous fish to maintain homeostasis at sea, whilst conserving cardiac and metabolic scope for activities directly contributing to fitness and reproductive success. PMID:26000616
International Nuclear Information System (INIS)
Fokin, B.S.; Gol'dberg, E.N.
1979-01-01
Analytical results of statistical nature of forces exciting vibrations of tubular elements, which are flown around with two-phase flows, are given. Relationships for the calculation of a mean-square amplitude and vibration frequency of a tubular element flown around with a two-phase mixture have been obtained. The relationships are confirmed experimentally
Discrete element simulation studies of angles of repose and shear flow of wet, flexible fibers.
Guo, Y; Wassgren, C; Ketterhagen, W; Hancock, B; Curtis, J
2018-04-18
A discrete element method (DEM) model is developed to simulate the dynamics of wet, flexible fibers. The angles of repose of dry and wet fibers are simulated, and the simulation results are in good agreement with experimental results, validating the wet, flexible fiber model. To study wet fiber flow behavior, the model is used to simulate shear flows of wet fibers in a periodic domain under Lees-Edwards boundary conditions. Significant agglomeration is observed in dilute shear flows of wet fibers. The size of the largest agglomerate in the flow is found to depend on a Bond number, which is proportional to liquid surface tension and inversely proportional to the square of the shear strain rate. This Bond number reflects the relative importance of the liquid-bridge force to the particle's inertial force, with a larger Bond number leading to a larger agglomerate. As the fiber aspect ratio (AR) increases, the size of the largest agglomerate increases, while the coordination number in the largest agglomerate initially decreases and then increases when the AR is greater than four. A larger agglomerate with a larger coordination number is more likely to form for more flexible fibers with a smaller bond elastic modulus due to better connectivity between the more flexible fibers. Liquid viscous force resists pulling of liquid bridges and separation of contacting fibers, and therefore it facilitates larger agglomerate formation. The effect of liquid viscous force is more significant at larger shear strain rates. The solid-phase shear stress is increased due to the presence of liquid bridges in moderately dense flows. As the solid volume fraction increases, the effect of fiber-fiber friction coefficient increases sharply. When the solid volume fraction approaches the maximum packing density, the fiber-fiber friction coefficient can be a more dominant factor than the liquid bridge force in determining the solid-phase shear stress.
Rienstra, S.W.; Eversman, W.
2001-01-01
An explicit, analytical, multiple-scales solution for modal sound transmission through slowly varying ducts with mean flow and acoustic lining is tested against a numerical finite-element solution solving the same potential flow equations. The test geometry taken is representative of a high-bypass
Assessment of the ecological impacts of macroroughness elements in stream flows
Niayifar, Amin; Oldroyd, Holly J.; Perona, Paolo
2017-04-01
The environmental suitability of flow release rules is often assessed for different fish species by modeling (e.g., CASiMir and PHABSIM) Weighted Usable Area (WUA) curves. However, these models are not able to resolve the hydrodynamic at small scales, e.g. that induced by the presence of macroroughness (e.g., single stones), which yet determine relatively large wakes that may contribute significantly in terms of habitat suitability. The presence of stones generates sheltered zones (i.e., the wake), which are typically temporary stationary points for many fish species. By resting in these low velocity regions, fishes minimize energy expenditure, and can quickly move to nearby fast water to feed (Hayes and Jowett, 1994). Following the analytical model proposed by Negretti et al., (2006), we developed an analytical solution for the wake area behind the macroroughness elements. The total wake area in the river reach being monitored is a function of the streamflow, Q, and it is an actual Usable Area for fishes that can be used to correct the one computed by classic software such as PHABSIM or CASIMIR at each flow rate. By quantifying these wake areas we can therefore assess how the physical properties and number of such zones change in response to the changing hydrologic regime. In order to validate the concept, we selected a 400 meter reach from the Aare river in the center of Switzerland. The statistical distribution of macroroughness elements is obtained by taking orthorectified aerial photographs by drone surveys during low flow conditions. Then, the distribution of the wakes is obtained analytically as a derived distribution. This methodology allows to save computational costs and the time for detailed field surveys.
Efendiev, Yalchin R.
2015-06-05
In this paper, we develop a multiscale finite element method for solving flows in fractured media. Our approach is based on generalized multiscale finite element method (GMsFEM), where we represent the fracture effects on a coarse grid via multiscale basis functions. These multiscale basis functions are constructed in the offline stage via local spectral problems following GMsFEM. To represent the fractures on the fine grid, we consider two approaches (1) discrete fracture model (DFM) (2) embedded fracture model (EFM) and their combination. In DFM, the fractures are resolved via the fine grid, while in EFM the fracture and the fine grid block interaction is represented as a source term. In the proposed multiscale method, additional multiscale basis functions are used to represent the long fractures, while short-size fractures are collectively represented by a single basis functions. The procedure is automatically done via local spectral problems. In this regard, our approach shares common concepts with several approaches proposed in the literature as we discuss. We would like to emphasize that our goal is not to compare DFM with EFM, but rather to develop GMsFEM framework which uses these (DFM or EFM) fine-grid discretization techniques. Numerical results are presented, where we demonstrate how one can adaptively add basis functions in the regions of interest based on error indicators. We also discuss the use of randomized snapshots (Calo et al. Randomized oversampling for generalized multiscale finite element methods, 2014), which reduces the offline computational cost.
Shih, D.; Yeh, G.
2009-12-01
This paper applies two numerical approximations, the particle tracking technique and Galerkin finite element method, to solve the diffusive wave equation in both one-dimensional and two-dimensional flow simulations. The finite element method is one of most commonly approaches in numerical problems. It can obtain accurate solutions, but calculation times may be rather extensive. The particle tracking technique, using either single-velocity or average-velocity tracks to efficiently perform advective transport, could use larger time-step sizes than the finite element method to significantly save computational time. Comparisons of the alternative approximations are examined in this poster. We adapt the model WASH123D to examine the work. WASH123D is an integrated multimedia, multi-processes, physics-based computational model suitable for various spatial-temporal scales, was first developed by Yeh et al., at 1998. The model has evolved in design capability and flexibility, and has been used for model calibrations and validations over the course of many years. In order to deliver a locally hydrological model in Taiwan, the Taiwan Typhoon and Flood Research Institute (TTFRI) is working with Prof. Yeh to develop next version of WASH123D. So, the work of our preliminary cooperationx is also sketched in this poster.
Eliasson, David
2017-01-01
This thesis presents a comparative study between Overwatch (2016) and Doom (2016) to determine how these fast-paced games facilitate flow in their gameplay. The second chapter looks at formal definitions of flow and level design to establish a vocabulary for following chapters. Through formal analysis the level designs of both games are then examined to establish what elements in them guide players and keep the flow in gameplay. The thesis also examines how the initial gameplay design princip...
Flow Dynamics of green sand in the DISAMATIC moulding process using Discrete element method (DEM)
International Nuclear Information System (INIS)
Hovad, E; Walther, J H; Thorborg, J; Hattel, J H; Larsen, P
2015-01-01
The DISAMATIC casting process production of sand moulds is simulated with DEM (discrete element method). The main purpose is to simulate the dynamics of the flow of green sand, during the production of the sand mould with DEM. The sand shot is simulated, which is the first stage of the DISAMATIC casting process. Depending on the actual casting geometry the mould can be geometrically quite complex involving e.g. shadowing effects and this is directly reflected in the sand flow during the moulding process. In the present work a mould chamber with “ribs” at the walls is chosen as a baseline geometry to emulate some of these important conditions found in the real moulding process. The sand flow is simulated with the DEM and compared with corresponding video footages from the interior of the chamber during the moulding process. The effect of the rolling resistance and the static friction coefficient is analysed and discussed in relation to the experimental findings. (paper)
MPSalsa a finite element computer program for reacting flow problems. Part 2 - user`s guide
Energy Technology Data Exchange (ETDEWEB)
Salinger, A.; Devine, K.; Hennigan, G.; Moffat, H. [and others
1996-09-01
This manual describes the use of MPSalsa, an unstructured finite element (FE) code for solving chemically reacting flow problems on massively parallel computers. MPSalsa has been written to enable the rigorous modeling of the complex geometry and physics found in engineering systems that exhibit coupled fluid flow, heat transfer, mass transfer, and detailed reactions. In addition, considerable effort has been made to ensure that the code makes efficient use of the computational resources of massively parallel (MP), distributed memory architectures in a way that is nearly transparent to the user. The result is the ability to simultaneously model both three-dimensional geometries and flow as well as detailed reaction chemistry in a timely manner on MT computers, an ability we believe to be unique. MPSalsa has been designed to allow the experienced researcher considerable flexibility in modeling a system. Any combination of the momentum equations, energy balance, and an arbitrary number of species mass balances can be solved. The physical and transport properties can be specified as constants, as functions, or taken from the Chemkin library and associated database. Any of the standard set of boundary conditions and source terms can be adapted by writing user functions, for which templates and examples exist.
Chung, Eric
2015-12-11
In this paper, we develop a mass conservative multiscale method for coupled flow and transport in heterogeneous porous media. We consider a coupled system consisting of a convection-dominated transport equation and a flow equation. We construct a coarse grid solver based on the Generalized Multiscale Finite Element Method (GMsFEM) for a coupled system. In particular, multiscale basis functions are constructed based on some snapshot spaces for the pressure and the concentration equations and some local spectral decompositions in the snapshot spaces. The resulting approach uses a few multiscale basis functions in each coarse block (for both the pressure and the concentration) to solve the coupled system. We use the mixed framework, which allows mass conservation. Our main contributions are: (1) the development of a mass conservative GMsFEM for the coupled flow and transport; (2) the development of a robust multiscale method for convection-dominated transport problems by choosing appropriate test and trial spaces within Petrov-Galerkin mixed formulation. We present numerical results and consider several heterogeneous permeability fields. Our numerical results show that with only a few basis functions per coarse block, we can achieve a good approximation.
Features and validation of discrete element method for simulating pebble flow in reactor core
International Nuclear Information System (INIS)
Xu Yong; Li Yanjie
2005-01-01
The core of a High-Temperature Gas-cooled Reactor (HTGR) is composed of big number of fuel pebbles, their kinetic behaviors are of great importance in estimating the path and residence time of individual pebble, the evolution of the mixing zone for the assessment of the efficiency of a reactor. Numerical method is highlighted in modern reactor design. In view of granular flow, the Discrete Element Model based on contact mechanics of spheres was briefly described. Two typical examples were presented to show the capability of the DEM method. The former is piling with glass/steel spheres, which provides validated evidences that the simulated angles of repose are in good coincidence with the experimental results. The later is particle discharge in a flat- bottomed silo, which shows the effects of material modulus and demonstrates several features. The two examples show the DEM method enables to predict the behaviors, such as the evolution of pebble profiles, streamlines etc., and provides sufficient information for pebble flow analysis and core design. In order to predict the cyclic pebble flow in a HTGR core precisely and efficiently, both model and code improvement are needed, together with rational specification of physical properties with proper measuring techniques. Strategic and methodological considerations were also discussed. (authors)
Gimenez, Juan M.; González, Leo M.
2015-03-01
In this paper, a new generation of the particle method known as Particle Finite Element Method (PFEM), which combines convective particle movement and a fixed mesh resolution, is applied to free surface flows. This interesting variant, previously described in the literature as PFEM-2, is able to use larger time steps when compared to other similar numerical tools which implies shorter computational times while maintaining the accuracy of the computation. PFEM-2 has already been extended to free surface problems, being the main topic of this paper a deep validation of this methodology for a wider range of flows. To accomplish this task, different improved versions of discontinuous and continuous enriched basis functions for the pressure field have been developed to capture the free surface dynamics without artificial diffusion or undesired numerical effects when different density ratios are involved. A collection of problems has been carefully selected such that a wide variety of Froude numbers, density ratios and dominant dissipative cases are reported with the intention of presenting a general methodology, not restricted to a particular range of parameters, and capable of using large time-steps. The results of the different free-surface problems solved, which include: Rayleigh-Taylor instability, sloshing problems, viscous standing waves and the dam break problem, are compared to well validated numerical alternatives or experimental measurements obtaining accurate approximations for such complex flows.
Chung, Eric; Efendiev, Yalchin R.; Leung, Wing; Ren, Jun
2015-01-01
In this paper, we develop a mass conservative multiscale method for coupled flow and transport in heterogeneous porous media. We consider a coupled system consisting of a convection-dominated transport equation and a flow equation. We construct a coarse grid solver based on the Generalized Multiscale Finite Element Method (GMsFEM) for a coupled system. In particular, multiscale basis functions are constructed based on some snapshot spaces for the pressure and the concentration equations and some local spectral decompositions in the snapshot spaces. The resulting approach uses a few multiscale basis functions in each coarse block (for both the pressure and the concentration) to solve the coupled system. We use the mixed framework, which allows mass conservation. Our main contributions are: (1) the development of a mass conservative GMsFEM for the coupled flow and transport; (2) the development of a robust multiscale method for convection-dominated transport problems by choosing appropriate test and trial spaces within Petrov-Galerkin mixed formulation. We present numerical results and consider several heterogeneous permeability fields. Our numerical results show that with only a few basis functions per coarse block, we can achieve a good approximation.
Finite element simulation of dynamic wetting flows as an interface formation process
Sprittles, J.E.
2013-01-01
A mathematically challenging model of dynamic wetting as a process of interface formation has been, for the first time, fully incorporated into a numerical code based on the finite element method and applied, as a test case, to the problem of capillary rise. The motivation for this work comes from the fact that, as discovered experimentally more than a decade ago, the key variable in dynamic wetting flows - the dynamic contact angle - depends not just on the velocity of the three-phase contact line but on the entire flow field/geometry. Hence, to describe this effect, it becomes necessary to use the mathematical model that has this dependence as its integral part. A new physical effect, termed the \\'hydrodynamic resist to dynamic wetting\\', is discovered where the influence of the capillary\\'s radius on the dynamic contact angle, and hence on the global flow, is computed. The capabilities of the numerical framework are then demonstrated by comparing the results to experiments on the unsteady capillary rise, where excellent agreement is obtained. Practical recommendations on the spatial resolution required by the numerical scheme for a given set of non-dimensional similarity parameters are provided, and a comparison to asymptotic results available in limiting cases confirms that the code is converging to the correct solution. The appendix gives a user-friendly step-by-step guide specifying the entire implementation and allowing the reader to easily reproduce all presented results, including the benchmark calculations. © 2012 Elsevier Inc.
Development of a Cl-impregnated activated carbon for entrained-flow capture of elemental mercury.
Ghorishi, S Behrooz; Keeney, Robert M; Serre, Shannon D; Gullett, Brian K; Jozewicz, Wojciech S
2002-10-15
Efforts to discern the role of an activated carbon's surface functional groups on the adsorption of elemental mercury (Hg0) and mercuric chloride demonstrated that chlorine (Cl) impregnation of a virgin activated carbon using dilute solutions of hydrogen chloride leads to increases (by a factor of 2-3) in fixed-bed capture of these mercury species. A commercially available activated carbon (DARCO FGD, NORITAmericas Inc. [FGD])was Cl-impregnated (Cl-FGD) [5 lb (2.3 kg) per batch] and tested for entrained-flow, short-time-scale capture of Hg0. In an entrained flow reactor, the Cl-FGD was introduced in Hg0-laden flue gases (86 ppb of Hg0) of varied compositions with gas/solid contact times of about 3-4 s, resulting in significant Hg0 removal (80-90%), compared to virgin FGD (10-15%). These levels of Hg0 removal were observed across a wide range of very low carbon-to-mercury weight ratios (1000-5000). Variation of the natural gas combustion flue gas composition, by doping with nitrogen oxides and sulfur dioxide, and the flow reactor temperature (100-200 degrees C) had minimal effects on Hg0 removal bythe Cl-FGD in these carbon-to-mercury weight ratios. These results demonstrate significant enhancement of activated carbon reactivity with minimal treatment and are applicable to combustion facilities equipped with downstream particulate matter removal such as an electrostatic precipitator.
International Nuclear Information System (INIS)
Tanaka, Yukihisa
2011-01-01
In the current concept of repository for radioactive waste disposal, compacted bentonite will be used as an engineered barrier mainly for inhibiting migration of radioactive nuclides. Hydrogen gas can be generated inside of the engineered barrier by anaerobic corrosion of metals used for containers, etc. It is expected to be not easy for gas to entering into the bentonite as a discrete gaseous phase because the pore of compacted bentonite is so minute. Therefore it is necessary to investigate the effect of gas pressure generation and gas migration on the engineered barrier, peripheral facilities and ground. In this study, a method for simulating gas migration through the compacted bentonite is proposed. The proposed method can analyze coupled hydrological-mechanical processes using the model of two-phase flow through deformable porous media. Validity of the proposed analytical method is examined by comparing gas migration test results with the calculated results, which revealed that the proposed method can simulate gas migration behavior through compacted bentonite with accuracy. (author)
Kwon, Chang-Il; Kim, Gwangil; Jeong, Seok; Lee, Don Haeng; Kim, Kyoung Ah; Ko, Kwang Hyun; Cho, Joo Young; Hong, Sung Pyo
2017-05-01
In research and development of biliary plastic stents (PS), continuous efforts have been made to overcome short patency time and high rate of migration. The aim of this study was to evaluate the patency and migration rate of different PS shapes for a given period of time. Using an in vitro bile phantom model, we compared the patency among different shapes of PS (three straight PS, four double-pigtail PS, and a new screw-shaped PS). We performed an analysis of the degree of luminal narrowing by light microscopic examination. Using an in vivo swine model, we compared the patency and migration rate among the three different types of PS. Eight weeks after the bile exposure in the bile flow phantom model, 80 PS were retrieved and analyzed. The straight PS showed less biofilm formation and luminal narrowing than other types of PS (p stent migration occurred less frequently in the double-pigtail PS and the screw-shaped PS than it did in the straight PS (11.1, 10, and 27.3%, respectively). However, there was no statistical difference in stent patency among the different shapes. Stent patency may not be significantly different depending on the shape of PS for 8 weeks. The screw-shaped PS showed similar patency and migration rate to the double-pigtail PS. These results may help guiding future PS development and clinical decisions.
Wouterse, F.S.; Berg, van den M.M.
2011-01-01
This paper uses a system of labour supply equations and data from Burkina Faso collected in 2003 to test the conditions underlying two different migratory movements: continental and intercontinental migration. We provide theoretical reasoning and empirical evidence that heterogeneity in migration is
Network Dependency in Migration Flows – A Space-time Analysis for Germany since Re-unification
DEFF Research Database (Denmark)
Mitze, Timo
The contribution of this paper is to analyse the role of network interdependencies in a dynamic panel data model for German internal migration fl ows since re-unification. So far, a capacious account of spatial patterns in German migration data is still missing in the empirical literature. In the...
Hancock, W.; Weatherley, D.; Wruck, B.; Chitombo, G. P.
2012-04-01
The flow dynamics of granular materials is of broad interest in both the geosciences (e.g. landslides, fault zone evolution, and brecchia pipe formation) and many engineering disciplines (e.g chemical engineering, food sciences, pharmaceuticals and materials science). At the interface between natural and human-induced granular media flow, current underground mass-mining methods are trending towards the induced failure and subsequent gravitational flow of large volumes of broken rock, a method known as cave mining. Cave mining relies upon the undercutting of a large ore body, inducement of fragmentation of the rock and subsequent extraction of ore from below, via hopper-like outlets. Design of such mines currently relies upon a simplified kinematic theory of granular flow in hoppers, known as the ellipsoid theory of mass movement. This theory assumes that the zone of moving material grows as an ellipsoid above the outlet of the silo. The boundary of the movement zone is a shear band and internal to the movement zone, the granular material is assumed to have a uniformly high bulk porosity compared with surrounding stagnant regions. There is however, increasing anecdotal evidence and field measurements suggesting this theory fails to capture the full complexity of granular material flow within cave mines. Given the practical challenges obstructing direct measurement of movement both in laboratory experiments and in-situ, the Discrete Element Method (DEM [1]) is a popular alternative to investigate granular media flow. Small-scale DEM studies (c.f. [3] and references therein) have confirmed that movement within DEM silo flow models matches that predicted by ellipsoid theory, at least for mono-disperse granular material freely outflowing at a constant rate. A major draw-back of these small-scale DEM studies is that the initial bulk porosity of the simulated granular material is significantly higher than that of broken, prismatic rock. In this investigation, more
International Nuclear Information System (INIS)
Green, W.J.
1977-01-01
Using two twice full-size models of a HIFAR research reactor fuel element, experiments have been performed to determine how the flow distribution of coolant gas through the element in a transfer flask is affected by removal of the central instrumentation thimble. With the thimble present, experimental flow results agree with theoretical predictions. Over the range of total flowrates considered, mass flow apportioning among the five annular channels was independent of annular channel Reynolds number (in the range 3500 to 10,500) and ranged between 13% and 27% of the total flowrate. For the case with the thimble removed, interesting experimental flow characteristics were obtained which could not have been predicted. Flow apportioning among the annular channels was found to be uniquely dependent upon total flowrate and ranged between 3% and 8% for the experimental conditions investigated (annular channel Reynolds numbers in the range 800 to 4000). (Author)
Youth Labor Migration in Nepal
Bossavie, Laurent; Denisova, Anastasiya
2018-01-01
This descriptive study investigates internal and external labor migration by Nepalese youth. External labor migration is separated into the flow to India, which is unregulated, and the flow to other countries, which typically takes the form of temporary contract migration to countries with bilateral labor agreements with Nepal (referred to in Nepal as foreign employment). The study finds t...
Lavery, N.; Taylor, C.
1999-07-01
Multigrid and iterative methods are used to reduce the solution time of the matrix equations which arise from the finite element (FE) discretisation of the time-independent equations of motion of the incompressible fluid in turbulent motion. Incompressible flow is solved by using the method of reduce interpolation for the pressure to satisfy the Brezzi-Babuska condition. The k-l model is used to complete the turbulence closure problem. The non-symmetric iterative matrix methods examined are the methods of least squares conjugate gradient (LSCG), biconjugate gradient (BCG), conjugate gradient squared (CGS), and the biconjugate gradient squared stabilised (BCGSTAB). The multigrid algorithm applied is based on the FAS algorithm of Brandt, and uses two and three levels of grids with a V-cycling schedule. These methods are all compared to the non-symmetric frontal solver. Copyright
Comparing DNS and Experiments of Subcritical Flow Past an Isolated Surface Roughness Element
Doolittle, Charles; Goldstein, David
2009-11-01
Results are presented from computational and experimental studies of subcritical roughness within a Blasius boundary layer. This work stems from discrepancies presented by Stephani and Goldstein (AIAA Paper 2009-585) where DNS results did not agree with hot-wire measurements. The near wake regions of cylindrical surface roughness elements corresponding to roughness-based Reynolds numbers Rek of about 202 are of specific concern. Laser-Doppler anemometry and flow visualization in water, as well as the same spectral DNS code used by Stephani and Goldstein are used to obtain both quantitative and qualitative comparisons with previous results. Conclusions regarding previous studies will be presented alongside discussion of current work including grid resolution studies and an examination of vorticity dynamics.
International Nuclear Information System (INIS)
Cliffe, K.A.; Garratt, T.J.; Spence, A.
1992-03-01
This paper is concerned with the problem of computing a small number of eigenvalues of large sparse generalised eigenvalue problems arising from mixed finite element discretisations of time dependent equations modelling viscous incompressible flow. The eigenvalues of importance are those with smallest real part and can be used in a scheme to determine the stability of steady state solutions and to detect Hopf bifurcations. We introduce a modified Cayley transform of the generalised eigenvalue problem which overcomes a drawback of the usual Cayley transform applied to such problems. Standard iterative methods are then applied to the transformed eigenvalue problem to compute approximations to the eigenvalue of smallest real part. Numerical experiments are performed using a model of double diffusive convection. (author)
Some applications of the moving finite element method to fluid flow and related problems
International Nuclear Information System (INIS)
Berry, R.A.; Williamson, R.L.
1983-01-01
The Moving Finite Element (MFE) method is applied to one-dimensional, nonlinear wave type partial differential equations which are characteristics of fluid dynamic and related flow phenomena problems. These equation systems tend to be difficult to solve because their transient solutions exhibit a spacial stiffness property, i.e., they represent physical phenomena of widely disparate length scales which must be resolved simultaneously. With the MFE method the node points automatically move (in theory) to optimal locations giving a much better approximation than can be obtained with fixed mesh methods (with a reasonable number of nodes) and with significantly reduced artificial viscosity or diffusion content. Three applications are considered. In order of increasing complexity they are: (1) a thermal quench problem, (2) an underwater explosion problem, and (3) a gas dynamics shock tube problem. The results are briefly shown
Progress on a Taylor weak statement finite element algorithm for high-speed aerodynamic flows
Baker, A. J.; Freels, J. D.
1989-01-01
A new finite element numerical Computational Fluid Dynamics (CFD) algorithm has matured to the point of efficiently solving two-dimensional high speed real-gas compressible flow problems in generalized coordinates on modern vector computer systems. The algorithm employs a Taylor Weak Statement classical Galerkin formulation, a variably implicit Newton iteration, and a tensor matrix product factorization of the linear algebra Jacobian under a generalized coordinate transformation. Allowing for a general two-dimensional conservation law system, the algorithm has been exercised on the Euler and laminar forms of the Navier-Stokes equations. Real-gas fluid properties are admitted, and numerical results verify solution accuracy, efficiency, and stability over a range of test problem parameters.
MANAGING MIGRATION: TURKISH PERSPECTIVE
Directory of Open Access Journals (Sweden)
İhsan GÜLAY
2018-04-01
Full Text Available Conducting migration studies is of vital importance to Turkey, a country which has been experiencing migration throughout history due to its “open doors policy”. The objective of this study is to evaluate the strategic management of migration in Turkey in order to deal with the issue of migration. The main focus of the study is Syrian migrants who sought refuge in Turkey due to the civil war that broke out in their country in April 2011. This study demonstrates the policies and processes followed by Turkey for Syrian migration flow in terms of the social acceptance and harmonisation of the migrants within a democratic environment. The study addresses some statistical facts and issues related to Syrian migration as it has become an integral part of daily life in Turkey. The study also reviews how human rights are protected in the migration process. The study will provide insights for developing sound strategic management policies for the migration issue.
A discontinuous finite element approach to cracking in coupled poro-elastic fluid flow models
Wilson, C. R.; Spiegelman, M. W.; Evans, O.; Ulven, O. I.; Sun, W.
2016-12-01
Reaction-driven cracking is a coupled process whereby fluid-induced reactions drive large volume changes in the host rock which produce stresses leading to crack propagation and failure. This in turn generates new surface area and fluid-flow pathways for subsequent reaction in a potentially self-sustaining system. This mechanism has has been proposed for the pervasive serpentinization and carbonation of peridotite, as well as applications to mineral carbon sequestration and hydrocarbon extraction. The key computational issue in this problem is implementing algorithms that adequately model the formation of discrete fractures. Here we present models using a discontinuous finite element method for modeling fracture formation (Radovitsky et al., 2011). Cracks are introduced along facets of the mesh by the relaxation of penalty parameters once a failure criterion is met. It is fully described in the weak form of the equations, requiring no modification of the underlying mesh structure and allowing fluid properties to be easily adjusted along cracked facets. To develop and test the method, we start by implementing the algorithm for the simplified Biot equations for poro-elasticity using the finite element model assembler TerraFERMA. We consider hydro-fracking around a borehole (Grassl et al., 2015), where elevated fluid pressure in the poro-elastic solid causes it to fail radially in tension. We investigate the effects of varying the Biot coefficient and adjusting the fluid transport properties in the vicinity of the crack and compare our results to related dual-graph models (Ulven & Sun, submitted). We discuss issues arising from this method, including the formation of null spaces and appropriate preconditioning and solution strategies. Initial results suggest that this method provides a promising way to incorporate cracking into our reactive fluid flow models and future work aims to integrate the mechanical and chemical aspects of this process.
Towards an integrated model of international migration
Directory of Open Access Journals (Sweden)
Douglas S. MASSEY
2012-12-01
Full Text Available Demographers have yet to develop a suitable integrated model of international migration and consequently have been very poor at forecasting immigration. This paper outlines the basic elements of an integrated model and surveys recent history to suggest the key challenges to model construction. A comprehensive theory must explain the structural forces that create a supply of people prone to migrate internationally, the structural origins of labour demand in receiving countries, the motivations of those who respond to these forces by choosing to migrate internationally, the growth and structure of transnational networks that arise to support international movement, the behaviour states in response to immigrant flows, and the influence of state actions on the behaviour of migrants. Recent history suggests that a good model needs to respect the salience of markets, recognize the circularity of migrant flows, appreciate the power of feedback effects, and be alert unanticipated consequences of policy actions.
Bakker, Mark; Kuhlman, Kristopher L.
2011-09-01
Two new approaches are presented for the accurate computation of the potential due to line elements that satisfy the modified Helmholtz equation with complex parameters. The first approach is based on fundamental solutions in elliptical coordinates and results in products of Mathieu functions. The second approach is based on the integration of modified Bessel functions. Both approaches allow evaluation of the potential at any distance from the element. The computational approaches are applied to model transient flow with the Laplace transform analytic element method. The Laplace domain solution is computed using a combination of point elements and the presented line elements. The time domain solution is obtained through a numerical inversion. Two applications are presented to transient flow fields, which could not be modeled with the Laplace transform analytic element method prior to this work. The first application concerns transient single-aquifer flow to wells near impermeable walls modeled with line-doublets. The second application concerns transient two-aquifer flow to a well near a stream modeled with line-sinks.
International Nuclear Information System (INIS)
Thornton, E.A.; Ramakrishnan, R.
1986-06-01
Prediction of compressible flow phenomena using the finite element method is of recent origin and considerable interest. Two shock capturing finite element formulations for high speed compressible flows are described. A Taylor-Galerkin formulation uses a Taylor series expansion in time coupled with a Galerkin weighted residual statement. The Taylor-Galerkin algorithms use explicit artificial dissipation, and the performance of three dissipation models are compared. A Petrov-Galerkin algorithm has as its basis the concepts of streamline upwinding. Vectorization strategies are developed to implement the finite element formulations on the NASA Langley VPS-32. The vectorization scheme results in finite element programs that use vectors of length of the order of the number of nodes or elements. The use of the vectorization procedure speeds up processing rates by over two orders of magnitude. The Taylor-Galerkin and Petrov-Galerkin algorithms are evaluated for 2D inviscid flows on criteria such as solution accuracy, shock resolution, computational speed and storage requirements. The convergence rates for both algorithms are enhanced by local time-stepping schemes. Extension of the vectorization procedure for predicting 2D viscous and 3D inviscid flows are demonstrated. Conclusions are drawn regarding the applicability of the finite element procedures for realistic problems that require hundreds of thousands of nodes
Analysis of a discrete element method and coupling with a compressible fluid flow method
International Nuclear Information System (INIS)
Monasse, L.
2011-01-01
This work aims at the numerical simulation of compressible fluid/deformable structure interactions. In particular, we have developed a partitioned coupling algorithm between a Finite Volume method for the compressible fluid and a Discrete Element method capable of taking into account fractures in the solid. A survey of existing fictitious domain methods and partitioned algorithms has led to choose an Embedded Boundary method and an explicit coupling scheme. We first showed that the Discrete Element method used for the solid yielded the correct macroscopic behaviour and that the symplectic time-integration scheme ensured the preservation of energy. We then developed an explicit coupling algorithm between a compressible inviscid fluid and an un-deformable solid. Mass, momentum and energy conservation and consistency properties were proved for the coupling scheme. The algorithm was then extended to the coupling with a deformable solid, in the form of a semi implicit scheme. Finally, we applied this method to unsteady inviscid flows around moving structures: comparisons with existing numerical and experimental results demonstrate the excellent accuracy of our method. (author) [fr
Expanded Mixed Multiscale Finite Element Methods and Their Applications for Flows in Porous Media
Jiang, L.
2012-01-01
We develop a family of expanded mixed multiscale finite element methods (MsFEMs) and their hybridizations for second-order elliptic equations. This formulation expands the standard mixed multiscale finite element formulation in the sense that four unknowns (hybrid formulation) are solved simultaneously: pressure, gradient of pressure, velocity, and Lagrange multipliers. We use multiscale basis functions for both the velocity and the gradient of pressure. In the expanded mixed MsFEM framework, we consider both separable and nonseparable spatial scales. Specifically, we analyze the methods in three categories: periodic separable scales, G-convergent separable scales, and a continuum of scales. When there is no scale separation, using some global information can significantly improve the accuracy of the expanded mixed MsFEMs. We present a rigorous convergence analysis of these methods that includes both conforming and nonconforming formulations. Numerical results are presented for various multiscale models of flow in porous media with shale barriers that illustrate the efficacy of the proposed family of expanded mixed MsFEMs. © 2012 Society for Industrial and Applied Mathematics.
Stability and migration of vacancy in V–4Cr–4Ti alloy: Effects of Al, Si, Y trace elements
International Nuclear Information System (INIS)
Zhang, Chong; Zhang, Pengbo; Li, Ruihuan; Zhao, Jijun; Dong, Chuang
2013-01-01
Addition of trace amounts of Al, Si and Y into V–4Cr–4Ti alloy is beneficial for the mechanical properties under irradiation. It is thus important to investigate the influence of solute/trace elements on stabilities, energetics and diffusion behaviors of vacancy defects. We performed first-principles calculations to evaluate vacancy–solute/trace interaction inside dilute V–X (X = Ti, Cr, Al, Si, Y) and V–4Cr–4Ti–(Al, Si, Y) alloys. With addition of Si and Y, vacancy-based complexes tend to form near Ti–Si and Ti–Y pairs, while the effect of Al is negligible. Moreover, diffusion coefficients of solute/trace element in vanadium were derived using nine-frequency model. With high binding energy and low diffusion coefficient, Si atom is strongly attractive to vacancy in vanadium matrix. Our theoretical results suggest that the interactions between vacancy and solute/trace elements play some role in the evolution of microstructures inside vanadium alloys
Noise and DC balanced outlet temperature signals for monitoring coolant flow in LMFBR fuel elements
International Nuclear Information System (INIS)
Edelmann, M.
1977-01-01
Local cooling disturbances in LMFBR fuel elements may have serious safety implications for the whole reactor core. They have to be detected reliably in an early stage of their formation therefore. This can be accomplished in principle by individual monitoring of the coolant flow rate or the coolant outlet temperature of the sub-assemblies with high precision. In this paper a method is proposed to increase the sensitivity of outlet temperature signals to cooling disturbances. Using balanced temperature signals provides a means for eliminating the normal variations from the original signals which limit the sensitivity and speed of response to cooling disturbances. It is shown that a balanced signal can be derived easily from the original temperature signal by subtracting an inlet temperature and a neutron detector signal with appropriate time shift. The method was tested with tape-recorded noise signals of the KNK I reactor at Karlsruhe. The experimental results confirm the theoretical predictions. A significant reduction of the uncertainty of measured outlet temperatures was achieved. This enables very sensitive and fast response monitoring of coolant flow. Furthermore, it was found that minimizing the variance of the balanced signal offers the possibility for a rough determination of the heat transfer coefficient of the fuel rods during normal reactor operation at power. (author)
An experimental and analytical study of fluid flow and critical heat flux in PWR fuel elements
International Nuclear Information System (INIS)
Bowditch, F.H.; Mogford, D.J.
1987-02-01
This report describes experiments that have been carried out at the Winfrith Establishment of the United Kingdom Atomic Energy Authority to determine the critical heat flux characteristics of pressurized water reactor fuel elements over an unusually wide range of coolant flow conditions that are relevant to both normal and fault conditions of reactor operation. The experiments were carried out in the TITAN loop using an electrically heated bundle of 25 rods of 9.5 mm diameter on a 12.7 mm pitch fitted with plain grids in order to provide a generic base for code validation. The fully tabulated experimental data for critical heat flux, pressure drop and sub-channel mixing are encompassed by ranges of pressure between 20 and 160 Bar, coolant flow between 150 and 3600 Kg/m 2 s, and coolant inlet temperature between 150 and 320 0 C. The results of the experiments are compared with predicted data based upon several established critical heat flux correlations. It is concluded that the extrapolation of some correlations to conditions beyond their intended range of application can lead to dangerous over estimates of critical heat flux, but the Winfrith WSC-2 and the EPRI NP-2609 correlations perform well over the whole data range and correlate all data with RMS errors of 9% and 6% respectively. (author)
International Nuclear Information System (INIS)
Bastos, K.F.
1981-01-01
A method of U and Th isotope ratio determination by α-spectroscopy to analyse the migration process of these elements at an uranium bearing region in Goias, Brazil, is described. The method consists of simultaneous extraction of U and Th with TOPO/cyclohexane, reextraction of Th with H 2 SO 4 (0.3M) and further purification of both phases. The interferent coextracted ions are eliminated by scrubbing with EDTA/NaNO 3 , and pure U is extracted with (NH 4 ) 2 CO 3 . The counting sources are prepared via extraction with TTA or MIBK, and evaporation of suitable aliquots on stainless steel disks. The recovery of U about 98% is obtained. The energy resolutions of U 238 peak (E α =4.195 MeV) are 52 and 83 KeV. The counting efficiencies are between 11 and 21+. Th is separated from the stripping solution by direct coprecipitation with macro amounts of LaF 3 and subsequent extraction with TTA/benzene for source preparation. Alternatively coprecipitation is proposed with micro quantities of LaF 3 and posterior filtration with membrane filters, where LaF 3 layer was previously deposited. This method allows direct counting of the filters and is superior in relation to energy resolution and counting efficiency. The U 238 /U 234 and U 234 /Th 230 isotope ratios in geological standards and prospecting samples were determined. The U 234 /Th 230 isotope ratio was used for analysing the migration of these elements because the most of analysed samples presented values, for this ratio, greater than unity, indicating that the anomalous concentrations of U are due to secondary enrichment processes. Aditional results of non equilibrium of the radioactivity of samples by γ-spectroscopy, are presented. (author) [pt
Takizawa, Kenji; Tezduyar, Tayfun E.; Otoguro, Yuto
2018-04-01
Stabilized methods, which have been very common in flow computations for many years, typically involve stabilization parameters, and discontinuity-capturing (DC) parameters if the method is supplemented with a DC term. Various well-performing stabilization and DC parameters have been introduced for stabilized space-time (ST) computational methods in the context of the advection-diffusion equation and the Navier-Stokes equations of incompressible and compressible flows. These parameters were all originally intended for finite element discretization but quite often used also for isogeometric discretization. The stabilization and DC parameters we present here for ST computations are in the context of the advection-diffusion equation and the Navier-Stokes equations of incompressible flows, target isogeometric discretization, and are also applicable to finite element discretization. The parameters are based on a direction-dependent element length expression. The expression is outcome of an easy to understand derivation. The key components of the derivation are mapping the direction vector from the physical ST element to the parent ST element, accounting for the discretization spacing along each of the parametric coordinates, and mapping what we have in the parent element back to the physical element. The test computations we present for pure-advection cases show that the parameters proposed result in good solution profiles.
Energy Technology Data Exchange (ETDEWEB)
Qi, M.; Wegner, J.; Ganzer, L. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE
2013-08-01
Polymer flooding, as an EOR method, has become one of the most important driving forces after water flooding. The conventional believe is that polymer flooding can only improve sweep efficiency, but it has no contribution to residual oil saturation reduction. However, experimental studies indicated that polymer solution can also improve displacement efficiency and decrease residual oil saturation. To get a better understanding of the mechanism to increase the microscopic sweep efficiency and the displacement efficiency, theoretical studies are required. In this paper, we studied the viscoelasticity effect of polymer by using a numerical simulator, which is based on Finite Element Analysis. Since it is showed experimentally that the first normal stress difference of viscoelastic polymer solution is higher than the second stress difference, the Oldroyd-B model was selected as the constitutive equation in the simulation. Numerical modelling of Oldroyd-B viscoelastic fluids is notoriously difficult. Standard Galerkin finite element methods are prone to numerical oscillations, and there is no convergence as the elasticity of fluid increases. Therefore, we use a stabilised finite element model. In order to verify our model, we first built up a model with the same geometry and fluid properties as presented in literature and compared the results. Then, with the tested model we simulated the effect of viscoelastic polymer fluid on dead pores in three simplified pore structures, which are contraction structure, expansion structure and expansion-contraction structure. Correspondingly, the streamlines and velocity contours of polymer solution, with different Reynolds numbers (Re) and Weissenberg numbers (We), flowing in these three structures are showed. The simulation results indicate that the viscoelasticity of polymer solution is the main contribution to increase the micro-scale sweep efficiency. With higher elasticity, the velocity of polymer solution is getting bigger at
International Nuclear Information System (INIS)
Eguchi, Yuzuru
2005-07-01
The report is concerned with the evaluation of applicability of numerical modelling methods for the prediction of gas entrainment in an upper plenum of a sodium-cooled fast breeder reactor (FBR). Special attention was paid to applicability of variational multiscale (VMS) modelling in the context of the Finite Element Method. Two flow problems, which were experimentally shown to induce gas entrainment, are solved by a VMS code (MISTRAL). First, computing a benchmark problem of a gas entrainment swirl flow in a cylindrical vessel has led to the following results; (1) the VMS solution is able to resolve the precise vortex core structure more accurately than the non-VMS solution computed by Smart-fem. The circumferential velocity obtained from VMS computation rises almost double in comparison with the non-VMS solution, though it still underestimates the experimental values. (2) the half-value radius of the negative region of the second invariant of velocity gradient matches well between the VMS solution and non-VMS solution. (3) the negative/positive boundary of the second invariant of velocity gradient obtained from the VMS solution is closer to the vortex core radius observed in the experiment than that of the non-VMS solution, though the vortex dip length computed from the VMS result is shorter than the experimental value. Second, computing a benchmark problem of open channel flow with a square pillar and downstream suction pipe has led to the following results; (4) 2Δx-type spatial oscillation was observed due to lack of mesh subdivisions. (5) the distributional profile of the second invariant of velocity gradient is similar to that of the first problem (swirl flow in a cylindrical vessel), characterized by a strong negative region surrounded by a weak positive region. As a possible future plan, it may be necessary to analyze more precisely the features of unsteady vortices obtained in the second benchmark problem and to identify the difference (if any) from the
analysis of flow in a concentric annulus using finite element method
African Journals Online (AJOL)
user
ABSTRACT. This work presents the computational modelling of the velocity distribution of an incompressible fluid flowing in a ... The flow of fluids is important for many engineering applications. ... on an annulus shaped channel. Annular flow ...
DEFF Research Database (Denmark)
Chougule, Prasad; Nielsen, Søren R.K.
2014-01-01
been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade...... for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel...... that there is an increase in the lift coefficient by 26% for single-element airfoil at analysed conditions. The CFD simulation results were validated with wind tunnel tests. It is also observe that by selecting proper airfoil configuration and blade sizes an increase in lift coefficient can further be achieved....
International Nuclear Information System (INIS)
Arutunjan, R.V.; Bolshov, L.A.; Vitukov, V.V.; Goloviznin, V.M.; Dykhne, A.M.; Kiselev, V.P.; Klementova, S.V.; Krayushkin, I.E.; Moskovchenko, A.V.; Pismennii, V.D.; Popkov, A.G.; Chernov, S.Y.; Chudanov, V.V.; Khoruzhii, O.V.; Yudin, A.I.
1990-01-01
Migration of fuel fragments and core fission products during severe accidents on nuclear plants is studied analytically and numerically. The problems of heat transfer and migration of volume heat sources in construction materials and underlying soils are considered
International Nuclear Information System (INIS)
Fruchter, J.S.; Rancitelli, L.A.
1976-01-01
Samples of basalt from three deep core holes drilled in the Pasco Basin, Washington (DDH-3, DH-4, DH-5) were analyzed by instrumental neutron activation (INAA) for up to fifteen trace and major elements. These analyses were used to assign each basalt flow to one of a series of previously defined chemical types of the Columbia River Basalt Group. All of the flows except the two flows at the bottom of well DDH-3 were clearly assignable to one of the defined chemical types. These two flows apparently represent new, as yet undefined chemical types. Average values and standard deviations for compositions of each of the chemical types found in the three wells are presented along with two-element variation diagrams for the geochemically important pair La-Cr, La-Fe, La-Th and La-Sc. The assignment of the flows to known chemical types accomplished in this study was very helpful in relating the basalts in the core holes to stratigraphically defined basalt flows in surface sections. A correlation diagram relating the flows in the core holes to one another on the basis of chemical type is presented
Population, migration and urbanization.
1982-06-01
Despite recent estimates that natural increase is becoming a more important component of urban growth than rural urban transfer (excess of inmigrants over outmigrants), the share of migration in the total population growth has been consistently increasing in both developed and developing countries. From a demographic perspective, the migration process involves 3 elements: an area of origin which the mover leaves and where he or she is considered an outmigrant; the destination or place of inmigration; and the period over which migration is measured. The 2 basic types of migration are internal and international. Internal migration consists of rural to urban migration, urban to urban migration, rural to rural migration, and urban to rural migration. Among these 4 types of migration various patterns or processes are followed. Migration may be direct when the migrant moves directly from the village to the city and stays there permanently. It can be circular migration, meaning that the migrant moves to the city when it is not planting season and returns to the village when he is needed on the farm. In stage migration the migrant makes a series of moves, each to a city closer to the largest or fastest growing city. Temporary migration may be 1 time or cyclical. The most dominant pattern of internal migration is rural urban. The contribution of migration to urbanization is evident. For example, the rapid urbanization and increase in urban growth from 1960-70 in the Republic of Korea can be attributed to net migration. In Asia the largest component of the population movement consists of individuals and groups moving from 1 rural location to another. Recently, because urban centers could no longer absorb the growing number of migrants from other places, there has been increased interest in the urban to rural population redistribution. This reverse migration also has come about due to slower rates of employment growth in the urban centers and improved economic opportunities
A finite-element model for moving contact line problems in immiscible two-phase flow
Kucala, Alec
2017-11-01
Accurate modeling of moving contact line (MCL) problems is imperative in predicting capillary pressure vs. saturation curves, permeability, and preferential flow paths for a variety of applications, including geological carbon storage (GCS) and enhanced oil recovery (EOR). The macroscale movement of the contact line is dependent on the molecular interactions occurring at the three-phase interface, however most MCL problems require resolution at the meso- and macro-scale. A phenomenological model must be developed to account for the microscale interactions, as resolving both the macro- and micro-scale would render most problems computationally intractable. Here, a model for the moving contact line is presented as a weak forcing term in the Navier-Stokes equation and applied directly at the location of the three-phase interface point. The moving interface is tracked with the level set method and discretized using the conformal decomposition finite element method (CDFEM), allowing for the surface tension and the wetting model to be computed at the exact interface location. A variety of verification test cases for simple two- and three-dimensional geometries are presented to validate the current MCL model, which can exhibit grid independence when a proper scaling for the slip length is chosen. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.
Energy Technology Data Exchange (ETDEWEB)
Weitzman, Morley
1992-07-15
A three-dimensional finite-element code was developed and used to simulate the flow of groundwater towards an excavation in a saturated porous medium, allowing for seepage faces. An iterative procedure was used to predict the movement of the water table and the seepage flux. The numerical solution agreed well with experimental results from a sandbox experiment. (auth)
THE EFFECT OF WATER (VAPOR-PHASE) AND CARBON ON ELEMENTAL MERCURY REMOVAL IN A FLOW REACTOR
The paper gives results of studying the effect of vapor-phase moisture on elemental mercury (Hgo) removal by activated carbon (AC) in a flow reactor. tests involved injecting AC into both a dry and a 4% moisture nitrogen (N2) /Hgo gas stream. A bituminous-coal-based AC (Calgon WP...
Energy Technology Data Exchange (ETDEWEB)
Rodrigues, Lorena Escriche, E-mail: ler@cdtn.br [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET), Belo Horizonte, MG (Brazil); Rezende, Hugo Cesar; Mattos, Joao Roberto Loureiro de; Barros Filho, Jose Afonso; Santos, Andre Augusto Campagnole dos, E-mail: hcr@cdtn.br, E-mail: jrmattos@cdtn.br, E-mail: jabf@cdtn.br, E-mail: aacs@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)
2013-07-01
This work aims to develop an experimental methodology for investigating the water flow through rod bundles after spacer grids of nuclear fuel elements of PWR type reactors. Speed profiles, with the device LDV (Laser Doppler Velocimetry), and the pressure drop between two sockets located before and after the spacer grid, using pressure transducers were measured.
Huyghe, J.M.R.J.; Oomens, C.W.J.; Campen, van D.H.; Heethaar, R.M.
1989-01-01
This research aims at formulating and verifying a finite element mixture formulation for blood perfusion. The equations derived in a companion paper [3] are discretized according to the Galerkin method. A flow experiment in a rigid model of a vascular tree of about 500 vessels is performed in order
Deng, Q.; Ginting, V.; McCaskill, B.; Torsu, P.
2017-10-01
We study the application of a stabilized continuous Galerkin finite element method (CGFEM) in the simulation of multiphase flow in poroelastic subsurfaces. The system involves a nonlinear coupling between the fluid pressure, subsurface's deformation, and the fluid phase saturation, and as such, we represent this coupling through an iterative procedure. Spatial discretization of the poroelastic system employs the standard linear finite element in combination with a numerical diffusion term to maintain stability of the algebraic system. Furthermore, direct calculation of the normal velocities from pressure and deformation does not entail a locally conservative field. To alleviate this drawback, we propose an element based post-processing technique through which local conservation can be established. The performance of the method is validated through several examples illustrating the convergence of the method, the effectivity of the stabilization term, and the ability to achieve locally conservative normal velocities. Finally, the efficacy of the method is demonstrated through simulations of realistic multiphase flow in poroelastic subsurfaces.
George, Gavin; Atujuna, Millicent; Gow, Jeff
2013-08-06
The loss of human resource capacity has had a severe impact on the health system in South Africa. This study investigates the causes of migration focussing on the role of salaries and benefits. Health professionals from public, private and non-governmental (NGO) health facilities located in selected peri-urban and urban areas in KwaZulu-Natal, South Africa were surveyed about their current positions and attitudes toward migration. The study uses cross-sectional data collected in 2009. A total of 694 health professionals (430 in the public sector, 133 in the NGO sector and 131 in the private sector) were surveyed. An additional 11 health professionals were purposively selected for in-depth interviews. Odds ratios with 95% confidence intervals were calculated to determine whether salaries influenced HWs decisions to migrate. HWs decision to move was not positively associated with lower salaries. It was found, instead, that the consideration to move was determined by other factors including age, levels of stress experienced and the extent to which they were satisfied at their current place of work. The OSD appears to have lowered the risk of HWs migrating due to low salaries. However, the results also indicate that the South African Department of Health needs to improve working conditions for HWs within the public health sector to assist in retention.
Directory of Open Access Journals (Sweden)
Junhong Bai
Full Text Available Soil profiles were collected in three salt marshes with different plant species (i.e. Phragmites australis, Tamarix chinensis and Suaeda salsa in the Yellow River Delta (YRD of China during three seasons (summer and fall of 2007 and the following spring of 2008 after the flow-sediment regulation regime. Total elemental contents of As, Cd, Cu, Pb and Zn were determined using inductively coupled plasma atomic absorption spectrometry to investigate temporal variations in trace elements in soil profiles of the three salt marshes, assess the enrichment levels and ecological risks of these trace elements in three sampling seasons and identify their influencing factors. Trace elements did not change significantly along soil profiles at each site in each sampling season. The highest value for each sampling site was observed in summer and the lowest one in fall. Soils in both P. australis and S. salsa wetlands tended to have higher trace element levels than those in T. chinensis wetland. Compared to other elements, both Cd and As had higher enrichment factors exceeding moderate enrichment levels. However, the toxic unit (TU values of these trace elements did not exceed probable effect levels. Correlation analysis showed that these trace elements were closely linked to soil properties such as moisture, sulfur, salinity, soil organic matter, soil texture and pH values. Principal component analysis showed that the sampling season affected by the flow-sediment regulation regime was the dominant factor influencing the distribution patterns of these trace elements in soils, and plant community type was another important factor. The findings of this study could contribute to wetland conservation and management in coastal regions affected by the hydrological engineering.
International Nuclear Information System (INIS)
Fried, S.; Friedman, A.M.; Hines, J.J.; Atcher, R.W.; Quarterman, L.A.; Volesky, A.
1976-12-01
Studies have been carried out on the migration of plutonium and americium in solutions flowing through porous and crushed rock and through fissures. The migration process can be described in terms of the surface absorption of these elements. In addition, chemical effects on the absorption have been observed. One of these effects is possibly due to the presence of a plutonium polymer that migrates at a more rapid rate than normal plutonium
Directory of Open Access Journals (Sweden)
Галина Викторовна Ерёменко
2014-03-01
Full Text Available The article considers the dynamics of the population of the Republic of Sakha (Yakutia, as well as migration processes, which negatively influence on formation of labor resources of the Republic. Socio-political, socio-economic transformations in recent years, could not affect the demographic situation of the Republic of Sakha (Yakutia. In the Republic, as in other regions of Russia the demographic situation deteriorated over the past decades. Deformed main functions of the family, its structure, the increased number of divorces, the growing number of single-parent families, decreased fertility. Fertility decline led to reduction of the share of children and adolescents under the age of 16 years and intensified the process of population aging. The ageing of the population, gives rise to a number of demographic, economic and social problems. An important role is also being played outflow from the Republic of working-age people. Issues of internal and external migration represent a very large layer of problems, both economic and social interaction of people from different cultures and walks of life in the majority is not without conflict. Organization of civilized (adjustable migration, i.e. the creation of conditions for improvement of the migration attractiveness of the Republic of Sakha (Yakutia, on the one hand, and combating illegal migration, on the other, should be directed on realization of the strategic course of the Government of the Russian Federation of the stabilization of the total population and promote sustainable socio-economic development of the country in General and of the Republic in particular.DOI: http://dx.doi.org/10.12731/2218-7405-2014-2-9
Vescovi, D.; Berzi, D.; Richard, P.; Brodu, N.
2014-05-01
We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed average volume fraction and distance between the walls. The results of the numerical simulations are used to derive boundary conditions appropriated in the cases of large and small bumpiness. Those boundary conditions are, then, employed to numerically integrate the differential equations of Extended Kinetic Theory, where the breaking of the molecular chaos assumption at volume fraction larger than 0.49 is taken into account in the expression of the dissipation rate. We show that the Extended Kinetic Theory is in very good agreement with the numerical simulations, even for coefficients of restitution as low as 0.50. When the bumpiness is increased, we observe that some of the flowing particles are stuck in the gaps between the wall spheres. As a consequence, the walls are more dissipative than expected, and the flows resemble simple shear flows, i.e., flows of rather constant volume fraction and granular temperature.
International Nuclear Information System (INIS)
Vescovi, D.; Berzi, D.; Richard, P.; Brodu, N.
2014-01-01
We use existing 3D Discrete Element simulations of simple shear flows of spheres to evaluate the radial distribution function at contact that enables kinetic theory to correctly predict the pressure and the shear stress, for different values of the collisional coefficient of restitution. Then, we perform 3D Discrete Element simulations of plane flows of frictionless, inelastic spheres, sheared between walls made bumpy by gluing particles in a regular array, at fixed average volume fraction and distance between the walls. The results of the numerical simulations are used to derive boundary conditions appropriated in the cases of large and small bumpiness. Those boundary conditions are, then, employed to numerically integrate the differential equations of Extended Kinetic Theory, where the breaking of the molecular chaos assumption at volume fraction larger than 0.49 is taken into account in the expression of the dissipation rate. We show that the Extended Kinetic Theory is in very good agreement with the numerical simulations, even for coefficients of restitution as low as 0.50. When the bumpiness is increased, we observe that some of the flowing particles are stuck in the gaps between the wall spheres. As a consequence, the walls are more dissipative than expected, and the flows resemble simple shear flows, i.e., flows of rather constant volume fraction and granular temperature
Expanded Mixed Multiscale Finite Element Methods and Their Applications for Flows in Porous Media
Jiang, L.; Copeland, D.; Moulton, J. D.
2012-01-01
We develop a family of expanded mixed multiscale finite element methods (MsFEMs) and their hybridizations for second-order elliptic equations. This formulation expands the standard mixed multiscale finite element formulation in the sense that four
Migration and Remittances : Recent Developments and Outlook - Transit Migration
World Bank Group
2018-01-01
This Migration and Development Brief reports global trends in migration and remittance flows, as well as developments related to the Global Compact on Migration (GCM), and the Sustainable Development Goal (SDG) indicators for volume of remittances as percentage of gross domestic product (GDP) (SDG indicator 17.3.2), reducing remittance costs (SDG indicator 10.c.1) and recruitment costs (SD...
The Finite Element Analysis for a Mini-Conductance Probe in Horizontal Oil-Water Two-Phase Flow
Directory of Open Access Journals (Sweden)
Weihang Kong
2016-08-01
Full Text Available Oil-water two-phase flow is widespread in petroleum industry processes. The study of oil-water two-phase flow in horizontal pipes and the liquid holdup measurement of oil-water two-phase flow are of great importance for the optimization of the oil production process. This paper presents a novel sensor, i.e., a mini-conductance probe (MCP for measuring pure-water phase conductivity of oil-water segregated flow in horizontal pipes. The MCP solves the difficult problem of obtaining the pure-water correction for water holdup measurements by using a ring-shaped conductivity water-cut meter (RSCWCM. Firstly, using the finite element method (FEM, the spatial sensitivity field of the MCP is investigated and the optimized MCP geometry structure is determined in terms of the characteristic parameters. Then, the responses of the MCP for the oil-water segregated flow are calculated, and it is found that the MCP has better stability and sensitivity to the variation of water-layer thickness in the condition of high water holdup and low flow velocity. Finally, the static experiments for the oil-water segregated flow were carried out and a novel calibration method for pure-water phase conductivity measurements was presented. The validity of the pure-water phase conductivity measurement with segregated flow in horizontal pipes was verified by experimental results.
The Finite Element Analysis for a Mini-Conductance Probe in Horizontal Oil-Water Two-Phase Flow.
Kong, Weihang; Kong, Lingfu; Li, Lei; Liu, Xingbin; Xie, Ronghua; Li, Jun; Tang, Haitao
2016-08-24
Oil-water two-phase flow is widespread in petroleum industry processes. The study of oil-water two-phase flow in horizontal pipes and the liquid holdup measurement of oil-water two-phase flow are of great importance for the optimization of the oil production process. This paper presents a novel sensor, i.e., a mini-conductance probe (MCP) for measuring pure-water phase conductivity of oil-water segregated flow in horizontal pipes. The MCP solves the difficult problem of obtaining the pure-water correction for water holdup measurements by using a ring-shaped conductivity water-cut meter (RSCWCM). Firstly, using the finite element method (FEM), the spatial sensitivity field of the MCP is investigated and the optimized MCP geometry structure is determined in terms of the characteristic parameters. Then, the responses of the MCP for the oil-water segregated flow are calculated, and it is found that the MCP has better stability and sensitivity to the variation of water-layer thickness in the condition of high water holdup and low flow velocity. Finally, the static experiments for the oil-water segregated flow were carried out and a novel calibration method for pure-water phase conductivity measurements was presented. The validity of the pure-water phase conductivity measurement with segregated flow in horizontal pipes was verified by experimental results.
Energy Technology Data Exchange (ETDEWEB)
Li, Mao; Qiu, Zihua; Liang, Chunlei; Sprague, Michael; Xu, Min
2017-01-13
In the present study, a new spectral difference (SD) method is developed for viscous flows on meshes with a mixture of triangular and quadrilateral elements. The standard SD method for triangular elements, which employs Lagrangian interpolating functions for fluxes, is not stable when the designed accuracy of spatial discretization is third-order or higher. Unlike the standard SD method, the method examined here uses vector interpolating functions in the Raviart-Thomas (RT) spaces to construct continuous flux functions on reference elements. Studies have been performed for 2D wave equation and Euler equa- tions. Our present results demonstrated that the SDRT method is stable and high-order accurate for a number of test problems by using triangular-, quadrilateral-, and mixed- element meshes.
Directory of Open Access Journals (Sweden)
Hamed Safikhani
2017-07-01
Full Text Available In this paper, the Al2O3-water nanofluid flow in laminar and turbulent flows inside tubes fitted with diamond-shaped turbulators is numerically modeled. The nanofluid flow is modeled by employing a two-phase mixture method and applying the constant heat flux boundary condition at tube walls. In the results, the effects of different parameters such as the geometry of turbulators, volume fraction and diameter of nanoparticles, etc. on the flow field in the tubes have been investigated. The obtained results indicate that, with the reduction of tail length ratio (TR and increase of vertex angle of turbulators (θ, the heat transfer coefficient as well as the wall shear stress increase. Similarly, with the reduction of TR and increase of θ, the amount of secondary flows, vortices and the turbulent kinetic energy increase. Moreover, the increase in the volume fraction of nanoparticles and the reduction of nanoparticles diameter lead to the increase of the heat transfer coefficient and wall shear stress.
Bianchi; Ferrigno; Girault
2000-05-01
A finite element formulation is developed for the simulation of an electroosmotic flow in rectangular microscale channel networks. The distribution of the flow at a decoupling T-junction is investigated from a hydrodynamic standpoint in the case of a pressure-driven and an electroosmotically driven flow. The calculations are carried out in two steps: first solving the potential distribution arising from the external electric field and from the inherent zeta potential. These distributions are then injected in the Navier Stokes equation for the calculation of the velocity profile. The influence of the various parameters such as the zeta potential distribution, the Reynolds number, and the relative channel widths on the flow distribution is investigated.
2014-05-01
we however focus on the continuum regime, where we can use the governing equations like Euler equations or Navier Stokes equations. The flow chemistry can...assumption. Instead the flow is considered to be a mixture of ideal gases, and the flow chemistry accounts for production and destruction of all the species. A
International Nuclear Information System (INIS)
Klotz, D.; Lang, H.; Moser, H.
1985-07-01
The studies were intended to provide information on the sorptive properties of 15 samples of fine-grain and medium-grain sands with regard to the radionuclides of I, Sr, Cs, Co, and Pd, and on their hydraulic properties. The samples were taken from the geologic formations in the area surrounding the projected waste repository in the Gorleben salt mine, at depth of up to 250 m down from terrain surface, and were analysed by means of column and batch experiments. Further goals were to determine the radionuclide migration as a function of flow velocity of the groundwater, and of sand compactness, as well as the effects of carrier ions and main groundwater contituents. The margins of retardation factors for the various radionuclides are given. One important result of the studies is that it could be expeimentally verified that there is the process of quasi irreversible sorption, i.e. it could be shown that desorption of radionuclides from natural, unconsolidated rock proceeds very much slowlier than sorption, so that this finding is of great significance to the safety assessment of a radioactive waste repository in geologic formations. (orig./HP) [de
Raju, R. Srinivasa; Ramesh, K.
2018-05-01
The purpose of this work is to study the grid independence of finite element method on MHD Casson fluid flow past a vertically inclined plate filled in a porous medium in presence of chemical reaction, heat absorption, an external magnetic field and slip effect has been investigated. For this study of grid independence, a mathematical model is developed and analyzed by using appropriate mathematical technique, called finite element method. Grid study discussed with the help of numerical values of velocity, temperature and concentration profiles in tabular form. avourable comparisons with previously published work on various special cases of the problem are obtained.
Behavior of EBR-II Mk-V-type fuel elements in simulated loss-of-flow tests
International Nuclear Information System (INIS)
Liu, Y.Y.; Tsai, H.; Billone, M.C.; Holland, J.W.; Kramer, J.M.
1993-01-01
Three furnace heating tests were conducted with irradiated, HT9-clad and U-19wt%Pu-10wt%Zr-alloy, EBR-II Mk-V-type fuel elements to evaluate the behavior that could be expected during a loss-of-flow event in the reactor. In general, very significant safety margins for cladding breaching have been demonstrated in these tests, under conditions that would envelop a bounding unlikely loss-of-flow event in EBR-II. Highlights of the test results are presented, as are discussions of the cladding breaching mechanisms, axial fuel motion, and fuel surface liquefaction that were found in these tests. (orig.)
Kou, Jisheng; Sun, Shuyu
2013-01-01
We analyze a combined method consisting of the mixed finite element method for pressure equation and the discontinuous Galerkin method for saturation equation for the coupled system of incompressible two-phase flow in porous media. The existence and uniqueness of numerical solutions are established under proper conditions by using a constructive approach. Optimal error estimates in L2(H1) for saturation and in L∞(H(div)) for velocity are derived. Copyright © 2013 John Wiley & Sons, Ltd.
Kou, Jisheng
2013-06-20
We analyze a combined method consisting of the mixed finite element method for pressure equation and the discontinuous Galerkin method for saturation equation for the coupled system of incompressible two-phase flow in porous media. The existence and uniqueness of numerical solutions are established under proper conditions by using a constructive approach. Optimal error estimates in L2(H1) for saturation and in L∞(H(div)) for velocity are derived. Copyright © 2013 John Wiley & Sons, Ltd.
International Nuclear Information System (INIS)
Chougule, Prasad; Nielsen, Søren R K
2014-01-01
Nowadays, small vertical axis wind turbines are receiving more attention due to their suitability in micro-electricity generation. There are few vertical axis wind turbine designs with good power curve. However, the efficiency of power extraction has not been improved. Therefore, an attempt has been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel test an orientation parameter for the slat airfoil is initially obtained. Further a computational fluid dynamics (CFD) has been used to obtain the aerodynamic characteristics of double-element airfoil. The CFD simulations were carried out using ANSYS CFX software. It is observed that there is an increase in the lift coefficient by 26% for single-element airfoil at analysed conditions. The CFD simulation results were validated with wind tunnel tests. It is also observe that by selecting proper airfoil configuration and blade sizes an increase in lift coefficient can further be achieved
Discrete conservation properties for shallow water flows using mixed mimetic spectral elements
Lee, D.; Palha, A.; Gerritsma, M.
2018-01-01
A mixed mimetic spectral element method is applied to solve the rotating shallow water equations. The mixed method uses the recently developed spectral element histopolation functions, which exactly satisfy the fundamental theorem of calculus with respect to the standard Lagrange basis functions in
Taneja, Ankur; Higdon, Jonathan
2018-01-01
A high-order spectral element discontinuous Galerkin method is presented for simulating immiscible two-phase flow in petroleum reservoirs. The governing equations involve a coupled system of strongly nonlinear partial differential equations for the pressure and fluid saturation in the reservoir. A fully implicit method is used with a high-order accurate time integration using an implicit Rosenbrock method. Numerical tests give the first demonstration of high order hp spatial convergence results for multiphase flow in petroleum reservoirs with industry standard relative permeability models. High order convergence is shown formally for spectral elements with up to 8th order polynomials for both homogeneous and heterogeneous permeability fields. Numerical results are presented for multiphase fluid flow in heterogeneous reservoirs with complex geometric or geologic features using up to 11th order polynomials. Robust, stable simulations are presented for heterogeneous geologic features, including globally heterogeneous permeability fields, anisotropic permeability tensors, broad regions of low-permeability, high-permeability channels, thin shale barriers and thin high-permeability fractures. A major result of this paper is the demonstration that the resolution of the high order spectral element method may be exploited to achieve accurate results utilizing a simple cartesian mesh for non-conforming geological features. Eliminating the need to mesh to the boundaries of geological features greatly simplifies the workflow for petroleum engineers testing multiple scenarios in the face of uncertainty in the subsurface geology.
Income Inequality and Migration in Vietnam
NGUYEN, Tien Dung
2012-01-01
In this paper, we have analyzed the recent trends in income inequality, internal and international migrations and investigated the impact of migration on income distribution in Vietnam. Our analysis shows that the effects of migration on income inequality vary with different types of migration, depending on who migrate and where they migrate. Foreign remittances tend to flow toward more affluent households, and they increase income inequality. By contrast, domestic remittances accrue more to ...
International Nuclear Information System (INIS)
Yeh, G.T.
1980-01-01
Darcian velocity has been conventionally calculated in the finite-element modeling of groundwater flow by taking the derivatives of the computed pressure field. This results in discontinuities in the velocity field at nodal points and element boundaries. Discontinuities become enormous when the computed pressure field is far from a linear distribution. It is proposed in this paper that the finite element procedure that is used to simulate the pressure field or the moisture content field also be applied to Darcy's law with the derivatives of the computed pressure field as the load function. The problem of discontinuity is then eliminated, and the error of mass balance over the region of interest is much reduced. The reduction is from 23.8 to 2.2% by one numerical scheme and from 29.7 to -3.6% by another for a transient problem
Behavior of EBR-II Mk-V-type fuel elements in simulated loss-of-flow tests
International Nuclear Information System (INIS)
Liu, Y.Y.; Tsai, H.; Billone, M.C.; Holland, J.W.; Kramer, J.M.
1992-11-01
This report discusses three furnace heating tests which were conducted with irradiated, HT9-clad and U-19wt.%Pu-l0wt.%Zr-alloy fuel, Mk-V-type fuel elements in the Alpha-Gamma Hot Cell Facility at Argonne National Laboratory, Illinois. In general, very significant safety margins for fuel-element cladding breaching have been demonstrated in these tests, under conditions that would envelop a bounding unlikely loss-of-flow event in EBR-II. Highlights of the test results will be given, as well as discussions of the cladding breaching mechanisms, axial fuel motion, and fuel surface liquefaction found in high-temperature testing of irradiated metallic fuel elements
International Nuclear Information System (INIS)
Johnson, K.; Bittorf, K.J.
2002-01-01
A novel approach for computer aided modeling and optimizing mixing process has been developed using Galerkin least-squares finite element technology. Computer aided mixing modeling and analysis involves Lagrangian and Eulerian analysis for relative fluid stretching, and energy dissipation concepts for laminar and turbulent flows. High quality, conservative, accurate, fluid velocity, and continuity solutions are required for determining mixing quality. The ORCA Computational Fluid Dynamics (CFD) package, based on a finite element formulation, solves the incompressible Reynolds Averaged Navier Stokes (RANS) equations. Although finite element technology has been well used in areas of heat transfer, solid mechanics, and aerodynamics for years, it has only recently been applied to the area of fluid mixing. ORCA, developed using the Galerkin Least-Squares (GLS) finite element technology, provides another formulation for numerically solving the RANS based and LES based fluid mechanics equations. The ORCA CFD package is validated against two case studies. The first, a free round jet, demonstrates that the CFD code predicts the theoretical velocity decay rate, linear expansion rate, and similarity profile. From proper prediction of fundamental free jet characteristics, confidence can be derived when predicting flows in a stirred tank, as a stirred tank reactor can be considered a series of free jets and wall jets. (author)
Sun, Qiang; Wu, Guo Xiong
2013-03-01
A mathematical model and a numerical solution procedure are developed to simulate flow field through a 3D permeable vessel with multibranches embedded in a solid tumour. The model is based on Poisseuille's law for the description of the flow through the vessels, Darcy's law for the fluid field inside the tumour interstitium, and Starling's law for the flux transmitted across the vascular walls. The solution procedure is based on a coupled method, in which the finite difference method is used for the flow in the vessels and the boundary element method is used for the flow in the tumour. When vessels meet each other at a junction, the pressure continuity and mass conservation are imposed at the junction. Three typical representative structures within the tumour vasculature, symmetrical dichotomous branching, asymmetrical bifurcation with uneven radius of daughter vessels and trifurcation, are investigated in detail as case studies. These results have demonstrated the features of tumour flow environment by the pressure distributions and flow velocity field. Copyright © 2012 John Wiley & Sons, Ltd.
Sanfilippo, Alessio; Tribuzio, Riccardo; Ottolini, Luisa; Hamada, Morihisa
2017-10-01
Replacive mantle dunites are considered to be shallow pathways for extraction of mantle melts from their source region. Dunites offer a unique possibility to unravel the compositional variability of the melts produced in the upper mantle, before mixing and crystal fractionation modify their original signature. This study includes a quantification of H2O, Li and trace elements (Ni, Mn, Co, Sc, V, Ti, Zr, Y and HREE) in olivine from large replacive dunite bodies (>20 m) within a mantle section exposed in the Western Italian Alps (Lanzo South ophiolite). On the basis of olivine, clinopyroxene and spinel compositions, these dunites were previously interpreted to be formed by melts with a MORB signature. Variations in Ni, Mn, Co and Ca contents in olivine from different dunite bodies suggested formation by different melt batches. The variable H2O and Li contents of these olivines agree with this idea. Compared to olivine from residual peridotites and olivine phenocrysts in MORB (both having H2O 1 ppm), the Lanzo South dunite olivine has high H2O (18-40 ppm) and low Li (0.35-0.83 ppm) contents. Geochemical modelling suggests that the dunite-forming melts were produced by low melting degrees of a mixed garnet-pyroxenite-peridotite mantle source, with a contribution of a garnet pyroxenite component variable from 20 to 80%. The Lanzo dunites experienced migration of melts geochemically enriched and mainly produced in the lowermost part of the melting region. Extraction of enriched melts through dunite channels are probably characteristic of cold thermal regimes, where low temperatures and a thick mantle lithosphere inhibit mixing with melts produced at shallower depths.
International Nuclear Information System (INIS)
Costa, Gustavo Koury
2004-11-01
Although incompressible fluid flows can be regarded as a particular case of a general problem, numerical methods and the mathematical formulation aimed to solve compressible and incompressible flows have their own peculiarities, in such a way, that it is generally not possible to attain both regimes with a single approach. In this work, we start from a typically compressible formulation, slightly modified to make use of pressure variables and, through augmenting the stabilising parameters, we end up with a simplified model which is able to deal with a wide range of flow regimes, from supersonic to low speed gas flows. The resulting methodology is flexible enough to allow for the simulation of liquid flows as well. Examples using conservative and pressure variables are shown and the results are compared to those published in the literature, in order to validate the method. (author)
International Nuclear Information System (INIS)
Mallants, D.; Volckaert, G.; Marivoet, J.; Neerdael, B.
2000-01-01
Low-level radioactive waste often contains large quantities of inorganic chemical substances. Due attention should therefore be given to the safety implications of both the radiological and chemical substances in the waste. Our study develops the safety assessment methodology for surface disposal with emphasis on the potential effects of inorganic nonradiological elements on human health. Contamination of groundwater was considered as the major exposure pathway. The applied methodology first screens all elements on the basis of five criteria. Conservative screening calculations were used to screen out the elements that do not pose danger to humans, and to select those that could have a negative impact and thus require further analysis. The latter was done by first calculating the elemental mass fluxes out of the repository and into the aquifer followed by the calculation of groundwater concentrations. The results showed that on the basis of the screening calculations, 75% of all elements could be classified as non-hazardous. The detailed calculations showed that the majority of the remaining elements had groundwater concentrations below the drinking water or groundwater standards. The results further showed that for a few elements the maximum groundwater concentration was above the standard, but below the background concentrations. (author)
Finite element simulation of dynamic wetting flows as an interface formation process
Sprittles, J.E.; Shikhmurzaev, Y.D.
2013-01-01
A mathematically challenging model of dynamic wetting as a process of interface formation has been, for the first time, fully incorporated into a numerical code based on the finite element method and applied, as a test case, to the problem
Zhang, Shaotong; Jia, Yonggang; Wen, Mingzheng; Wang, Zhenhao; Zhang, Yaqi; Zhu, Chaoqi; Li, Bowen; Liu, Xiaolei
2017-02-01
A scientific hypothesis is proposed and preliminarily verified in this paper: under the driving of seepage flows, there might be a vertical migration of fine-grained soil particles from interior to surface of seabed, which is defined as `sub-bottom sediment pump action' in this paper. Field experiments were performed twice on the intertidal flat of the Yellow River delta to study this process via both trapping the pumped materials and recording the pore pressures in the substrate. Experimental results are quite interesting as we did observe yellow slurry which is mainly composed of fine-grained soil particles appearing on the seabed surface; seepage gradients were also detected in the intertidal flat, under the action of tides and small wind waves. Preliminary conclusions are that `sediment pump' occurs when seepage force exceeds a certain threshold: firstly, it is big enough to disconnect the soil particles from the soil skeleton; secondly, the degree of seabed fluidization or bioturbation is big enough to provide preferred paths for the detached materials to migrate upwards. Then they would be firstly pumped from interior to the surface of seabed and then easily re-suspended into overlying water column. Influential factors of `sediment pump' are determined as hydrodynamics (wave energy), degree of consolidation, index of bioturbation (permeability) and content of fine-grained materials (sedimentary age). This new perspective of `sediment pump' may provide some implications for the mechanism interpretation of several unclear geological phenomena in the Yellow River delta area.
FEFLOW finite element modeling of flow, mass and heat transport in porous and fractured media
Diersch, Hans-Jörg G
2013-01-01
Placing advanced theoretical and numerical methods in the hands of modeling practitioners and scientists, this book explores the FEFLOW system for solving flow, mass and heat transport processes in porous and fractured media. Offers applications and exercises.
Cortese, B.; Croon, de M.H.J.M.; Hessel, V.
2012-01-01
The soybean oil epoxidation reaction is investigated theoretically through kinetic modeling of temperature effects enabled through flow processing under superheated conditions. Different from previous studies on such processing, here a complex reaction network superimposed by multiphase transport is
International Nuclear Information System (INIS)
Masoud Ziaei-Rad
2010-01-01
In this paper, a two-dimensional numerical scheme is presented for the simulation of turbulent, viscous, transient compressible flows in the simultaneously developing hydraulic and thermal boundary layer region. The numerical procedure is a finite-volume-based finite-element method applied to unstructured grids. This combination together with a new method applied for the boundary conditions allows for accurate computation of the variables in the entrance region and for a wide range of flow fields from subsonic to transonic. The Roe-Riemann solver is used for the convective terms, whereas the standard Galerkin technique is applied for the viscous terms. A modified κ-ε model with a two-layer equation for the near-wall region combined with a compressibility correction is used to predict the turbulent viscosity. Parallel processing is also employed to divide the computational domain among the different processors to reduce the computational time. The method is applied to some test cases in order to verify the numerical accuracy. The results show significant differences between incompressible and compressible flows in the friction coefficient, Nusselt number, shear stress and the ratio of the compressible turbulent viscosity to the molecular viscosity along the developing region. A transient flow generated after an accidental rupture in a pipeline was also studied as a test case. The results show that the present numerical scheme is stable, accurate and efficient enough to solve the problem of transient wall-bounded flow.
Deville, E. P.; Prinzhofer, A.; Vacquand, C.; Chavagnac, V.; Monnin, C.; Ceuleneer, G.; Arcilla, C. A.
2009-12-01
We compare the geological environments of sites of emission of natural hydrogen in the Oman ophiolite and the Zambales ophiolite (Luzon, Philippines). The genesis of natural H2 results from the interaction between ultrabasic rocks and aqueous solutions circulating in deep fracture networks, by oxidation of metals (Fe2+, Mn2+) and reduction of water, probably under high temperature conditions. This process generates very reducing conditions capable of destabilizing other molecules (notably reduction of deep CO2 being transformed into CH4 by Fisher-Tropsch type reactions). Nitrogen is also commonly associated to the H2-rich fluids. H2 flows are associated with the expulsion of hyperalkaline waters rich in ions OH- and Ca2+ and characterized by high pH (between 11 and 12). Most alkaline springs are found in the vicinity of major faults and/or lithological discontinuities like the basal thrust plane of the ophiolites and the peridotite-gabbro contact (Moho). Within the fracture networks, gas and water separate probably at shallow depth, i.e. close to the top of the upper aquifer level. Locally high flows of gas migrate vertically through fracture pathways and they are able to inflame spontaneously on the surface. Aqueous fluids tends to migrate laterally in the fracture network toward the creeks where most of the hyperalkaline springs are found. This water circulation induces a chain of diagenetic reactions starting in the fracture systems and continuing at the surface where it leads to the precipitation of calcite, aragonite, brucite and more rarely portlandite. This chain of diagenetic reactions is associated with the capture of the atmospheric CO2 during the precipitation of carbonates.
Guérin, Frédéric; Arnaiz, Olivier; Boggetto, Nicole; Denby Wilkes, Cyril; Meyer, Eric; Sperling, Linda; Duharcourt, Sandra
2017-04-26
DNA elimination is developmentally programmed in a wide variety of eukaryotes, including unicellular ciliates, and leads to the generation of distinct germline and somatic genomes. The ciliate Paramecium tetraurelia harbors two types of nuclei with different functions and genome structures. The transcriptionally inactive micronucleus contains the complete germline genome, while the somatic macronucleus contains a reduced genome streamlined for gene expression. During development of the somatic macronucleus, the germline genome undergoes massive and reproducible DNA elimination events. Availability of both the somatic and germline genomes is essential to examine the genome changes that occur during programmed DNA elimination and ultimately decipher the mechanisms underlying the specific removal of germline-limited sequences. We developed a novel experimental approach that uses flow cell imaging and flow cytometry to sort subpopulations of nuclei to high purity. We sorted vegetative micronuclei and macronuclei during development of P. tetraurelia. We validated the method by flow cell imaging and by high throughput DNA sequencing. Our work establishes the proof of principle that developing somatic macronuclei can be sorted from a complex biological sample to high purity based on their size, shape and DNA content. This method enabled us to sequence, for the first time, the germline DNA from pure micronuclei and to identify novel transposable elements. Sequencing the germline DNA confirms that the Pgm domesticated transposase is required for the excision of all ~45,000 Internal Eliminated Sequences. Comparison of the germline DNA and unrearranged DNA obtained from PGM-silenced cells reveals that the latter does not provide a faithful representation of the germline genome. We developed a flow cytometry-based method to purify P. tetraurelia nuclei to high purity and provided quality control with flow cell imaging and high throughput DNA sequencing. We identified 61
International Nuclear Information System (INIS)
Pauna, E.; Olteanu, G.; Catana, A.
2013-01-01
In this paper, a Computation Fluid Dynamics (CFD) simulation was performed in order to find the flow conditions in the CANDU Channel for the standard (37 elements) and the new designed bundle (43 elements) using the CFD Code S aturne software. Due to the fact that the code is a single-phase one it was considered an inlet temperature of 250 O C, a flow rate of 24.17 kg/s, an outlet pressure of 10.3 MPa and a linear power of 800 kW/m. The flow conditions were achieved by using a CFD typical chain of steps which was performed starting from preprocessing (geometry, mesh and boundary conditions), through solver and post-processing. Open Source platform (Salome-Meca geometry and mesh modules, the Code S aturne solver, Paraview and Visit for post-processing) were used as computational tool kit and an unsteady state was considered. Some simplifications were considered: the tube creep was not taken into account and all the bundles were considered aligned. The three dimensional thermal-hydraulic distributions of the temperature, pressure and velocity parameters offered information for the geometry comparison and the results were in agreement with some experimental data. CFD analysis results provided valuable data regarding the thermal-hydraulic operating conditions inside the CANDU reactor channel. (authors)
Finite element approximations of the stokes flow problem based upon various variational principles
International Nuclear Information System (INIS)
Franca, L.P.; Hughers, T.J.R.; Stenberg, R.
1989-05-01
Finite element methods are constructed by adding to the usual Galerkin method terms that are mesh-dependent least-squares forms of the Euler-Lagrange equations. The methods are consistent and possess additional stability compared to the Galerkin method. Finite element interpolations, which are unstable in the Galerkin approach, are now convergent. The methodology is applied to the velocity-pressure formulation, a.k.a., Herrmann's formulation, to the stress-velocity formulation, a.k.a., Hellinger-Reissner's formulation and to a new formulation based on augmented stress, pressure and velocity [pt
NUMERICAL INVESTIGATION OF TWO ELEMENT CAMBER MORPHING AIRFOIL IN LOW REYNOLDS NUMBER FLOWS
RAJESH SENTHIL KUMAR T.; V. SIVAKUMAR; BALAJEE RAMAKRISHNANANDA; ARJHUN A.K, SURIYAPANDIYAN
2017-01-01
Aerodynamic performance of a two-element camber morphing airfoil was investigated at low Reynolds number using the transient SST model in ANSYS FLUENT 14.0 and eN method in XFLR5. The two-element camber morphing concept was employed to morph the baseline airfoil into another airfoil by altering the orientation of mean-line at 35% of the chord to achieve better aerodynamic efficiency. NACA 0012 was selected as baseline airfoil. NACA 23012 was chosen as the test case as it has the camber-line s...
International Nuclear Information System (INIS)
Ngo, Manh Thang; Beck, H.P; Geckeis, H.; Kim, J.I.
1999-01-01
Groundwater samples containing aquatic humic substances are analyzed by flow field- flow fractionation (FFFF) and gel permeation chromatography (GPC). Natural concentrations of U, Th and rare earth elements (REE) in a size-fractionated groundwater sample are analyzed by on-line coupling of inductively coupled plasma-mass spectrometry (ICP-MS) to either FFFF or GPC. The uranium, thorium, and REE are found to be quantitatively attached to colloidal species in the investigated groundwater sample. Their distribution in different colloid size fractions, however, is quite heterogeneous. Both, FFFF and GPC reveal that Th and REE are preferentially located in the size fraction > 50 kDalton. U is also attached to low molecular weight humic acid, similar to Fe and Al. This finding could be qualitatively reproduced by sequential ultrafiltration. The results are interpreted in terms of different binding mechanisms for the individual elements in the heterogeneous humic macromolecules. The inclusion of actinides into larger aggregates of aquatic humic acid might explain the considerable kinetic hindrance of actinide-humic acid dissociation reactions described in the literature. (authors)
Schäfer, L.; Dierksheide, U.; Klaas, M.; Schröder, W.
2011-03-01
A new method to describe statistical information from passive scalar fields has been proposed by Wang and Peters ["The length-scale distribution function of the distance between extremal points in passive scalar turbulence," J. Fluid Mech. 554, 457 (2006)]. They used direct numerical simulations (DNS) of homogeneous shear flow to introduce the innovative concept. This novel method determines the local minimum and maximum points of the fluctuating scalar field via gradient trajectories, starting from every grid point in the direction of the steepest ascending and descending scalar gradients. Relying on gradient trajectories, a dissipation element is defined as the region of all the grid points, the trajectories of which share the same pair of maximum and minimum points. The procedure has also been successfully applied to various DNS fields of homogeneous shear turbulence using the three velocity components and the kinetic energy as scalar fields [L. Wang and N. Peters, "Length-scale distribution functions and conditional means for various fields in turbulence," J. Fluid Mech. 608, 113 (2008)]. In this spirit, dissipation elements are, for the first time, determined from experimental data of a fully developed turbulent channel flow. The dissipation elements are deduced from the gradients of the instantaneous fluctuation of the three velocity components u', v', and w' and the instantaneous kinetic energy k', respectively. The measurements are conducted at a Reynolds number of 1.7×104 based on the channel half-height δ and the bulk velocity U. The required three-dimensional velocity data are obtained investigating a 17.75×17.75×6 mm3 (0.355δ×0.355δ×0.12δ) test volume using tomographic particle-image velocimetry. Detection and analysis of dissipation elements from the experimental velocity data are discussed in detail. The statistical results are compared to the DNS data from Wang and Peters ["The length-scale distribution function of the distance between
Siirila-Woodburn, Erica R.; Steefel, Carl I.; Williams, Kenneth H.; Birkholzer, Jens T.
2018-03-01
The effects of land use and land cover (LULC) change on environmental systems across the land surface's "critical zone" are highly uncertain, often making prediction and risk management decision difficult. In a series of numerical experiments with an integrated hydrologic model, overland flow generation is quantified for both present day and forest thinning scenarios. A typhoon storm event in a watershed near the Fukushima Dai-ichi Nuclear Power Plant is used as an example application in which the interplay between LULC change and overland flow generation is important given that sediment-bound radionuclides may cause secondary contamination via surface water transport. Results illustrate the nonlinearity of the integrated system spanning from the deep groundwater to the atmosphere, and provide quantitative tools when determining the tradeoffs of different risk-mitigation strategies.
van der Vegt, Jacobus J.W.; van der Ven, H.
1998-01-01
A new discretization method for the three-dimensional Euler equations of gas dynamics is presented, which is based on the discontinuous Galerkin finite element method. Special attention is paid to an efficient implementation of the discontinuous Galerkin method that minimizes the number of flux
Larese De Tetto, Antonia; Rossi, Riccardo; Idelsohn Barg, Sergio Rodolfo; Oñate Ibáñez de Navarra, Eugenio
2006-01-01
Several comparisons between experiments and computational models are presented in the following pages. The objective is to verify the ability of Particle Finite Elements Methods (PFEM) [1] [2] to reproduce hydraulic phenomena involving large deformation of the fluid domain [4]. Peer Reviewed
Simulations of singularity dynamics in liquid crystal flows: A C finite element approach
International Nuclear Information System (INIS)
Lin Ping; Liu Chun
2006-01-01
In this paper, we present a C finite element method for a 2a hydrodynamic liquid crystal model which is simpler than existing C 1 element methods and mixed element formulation. The energy law is formally justified and the energy decay is used as a validation tool for our numerical computation. A splitting method combined with only a few fixed point iteration for the penalty term of the director field is applied to reduce the size of the stiffness matrix and to keep the stiffness matrix time-independent. The latter avoids solving a linear system at every time step and largely reduces the computational time, especially when direct linear system solvers are used. Our approach is verified by comparing its computational results with those obtained by C 1 elements and by mixed formulation. Through numerical experiments of a few other splittings and explicit-implicit strategies, we recommend a fast and reliable algorithm for this model. A number of examples are computed to demonstrate the algorithm
Rosenauer, M.; Buchegger, W.; Finoulst, I.; Verhaert, P.D.E.M.; Vellekoop, M.
2010-01-01
In this study, the design, realization and measurement results of a novel optofluidic system capable of performing absorbance-based flow cytometric analysis is presented. This miniaturized laboratory platform, fabricated using SU-8 on a silicon substrate, comprises integrated polymer-based
Air Distribution in a Room and Design Considerations of Mixing Ventilation by Flow Elements
DEFF Research Database (Denmark)
Nielsen, Peter V.; Jensen, Rasmus Lund; Pedersen, D. N.
2001-01-01
The paper shows detailed measurements of the air distribution in a room ventilated by mixing ventilation according to the specifications given by the International Energy Agency work. (Energy Conservation in Buildings and Community Systems Programme, Annex 20). It describes a number of flow...
Flow Dynamics of green sand in the DISAMATIC moulding process using Discrete element method (DEM)
DEFF Research Database (Denmark)
Hovad, Emil; Larsen, P.; Walther, Jens Honore
2015-01-01
casting process. Depending on the actual casting geometry the mould can be geometrically quite complex involving e.g. shadowing effects and this is directly reflected in the sand flow during the moulding process. In the present work a mould chamber with “ribs” at the walls is chosen as a baseline geometry...
International Nuclear Information System (INIS)
Pereira, P H R; Langdon, T G; Figueiredo, R B; Cetlin, P R
2014-01-01
High-pressure torsion (HPT) is a metal-working technique used to impose severe plastic deformation into disc-shaped samples under high hydrostatic pressures. Different HPT facilities have been developed and they may be divided into three distinct categories depending upon the configuration of the anvils and the restriction imposed on the lateral flow of the samples. In the present paper, finite element simulations were performed to compare the flow process, temperature, strain and hydrostatic stress distributions under unconstrained, quasi-constrained and constrained conditions. It is shown there are distinct strain distributions in the samples depending on the facility configurations and a similar trend in the temperature rise of the HPT workpieces
Liu, Nan-Suey; Shih, Tsan-Hsing; Wey, C. Thomas
2011-01-01
A series of numerical simulations of Jet-A spray reacting flow in a single-element lean direct injection (LDI) combustor have been conducted by using the National Combustion Code (NCC). The simulations have been carried out using the time filtered Navier-Stokes (TFNS) approach ranging from the steady Reynolds-averaged Navier-Stokes (RANS), unsteady RANS (URANS), to the dynamic flow structure simulation (DFS). The sub-grid model employed for turbulent mixing and combustion includes the well-mixed model, the linear eddy mixing (LEM) model, and the filtered mass density function (FDF/PDF) model. The starting condition of the injected liquid spray is specified via empirical droplet size correlation, and a five-species single-step global reduced mechanism is employed for fuel chemistry. All the calculations use the same grid whose resolution is of the RANS type. Comparisons of results from various models are presented.
International Nuclear Information System (INIS)
Hermanns, H.J.
1977-04-01
By the example of light-water cooled nuclear reactors, the state of the calculation methods at disposal for calculating mass flow and steam quality distribution (sub-channel analysis) is indicated. Particular regard was paid to the transport phenomena occurring in reactor fuel elements in the range of two phase flow. Experimentally determined values were compared with recalculations of these experiments with the sub-channel code COBRA; from the results of these comparing calculations, conclusions could be drawn on the suitability of this code for defined applications. Limits of reliability could be determined to some extent. Based on the experience gained and the study of individual physical model concepts, recognized as being important, a sub-channel model was drawn up and the corresponding numerical computer code (SIEWAS) worked out. Experiments made at GE could be reproduced with the code SIEWAS with sufficient accuracy. (orig.) [de
Energy Technology Data Exchange (ETDEWEB)
Mellor, A.; Domenech-Garret, J.L.; Chemisana, D.; Rosell, J.I. [Departament de Medi Ambient i C.S., University of Lleida, Av. Alcalde Rovira Roure 191, E25198 (Spain)
2009-09-15
A two-dimensional finite element model of current flow in the front surface of a PV cell is presented. In order to validate this model we perform an experimental test. Later, particular attention is paid to the effects of non-uniform illumination in the finger direction which is typical in a linear concentrator system. Fill factor, open circuit voltage and efficiency are shown to decrease with increasing degree of non-uniform illumination. It is shown that these detrimental effects can be mitigated significantly by reoptimization of the number of front surface metallization fingers to suit the degree of non-uniformity. The behavior of current flow in the front surface of a cell operating at open circuit voltage under non-uniform illumination is discussed in detail. (author)
International Nuclear Information System (INIS)
Yashiki, Taturou; Yagawa, Genki; Okuda, Hiroshi
1995-01-01
The adaptive finite element method based on an 'a posteriori error estimation' is known to be a powerful technique for analyzing the engineering practical problems, since it excludes the instinctive aspect of the mesh subdivision and gives high accuracy with relatively low computational cost. In the adaptive procedure, both the error estimation and the mesh generation according to the error estimator are essential. In this paper, the adaptive procedure is realized by the automatic mesh generation based on the control of node density distribution, which is decided according to the error estimator. The global percentage error, CPU time, the degrees of freedom and the accuracy of the solution of the adaptive procedure are compared with those of the conventional method using regular meshes. Such numerical examples as the driven cavity flows of various Reynolds numbers and the flows around a cylinder have shown the very high performance of the proposed adaptive procedure. (author)
Barrett, John W.; Garcke, Harald; Nürnberg, Robert
2017-01-01
A finite element method for the evolution of a two-phase membrane in a sharp interface formulation is introduced. The evolution equations are given as an $L^2$--gradient flow of an energy involving an elastic bending energy and a line energy. In the two phases Helfrich-type evolution equations are prescribed, and on the interface, an evolving curve on an evolving surface, highly nonlinear boundary conditions have to hold. Here we consider both $C^0$-- and $C^1$--matching conditions for the su...
Ashwal, L. D.; Morgan, P.; Kelley, S. A.; Percival, J. A.
1987-01-01
Concentrations of heat producing elements (Th, U, and K) in 58 samples representative of the main lithologies in a 100-km transect of the Superior Province of the Canadian Shield have been obtained. The relatively large variation in heat production found among the silicic plutonic rocks is shown to correlate with modal abundances of accessory minerals, and these variations are interpreted as premetamorphic. The present data suggest fundamental differences in crustal radioactivity distributions between granitic and more mafic terrains, and indicate that a previously determined apparently linear heat flow-heat production relationship for the Kapuskasing area does not relate to the distribution of heat production with depth.
International Nuclear Information System (INIS)
Hua Jinsong; Lin Ping; Liu Chun; Wang Qi
2011-01-01
Highlights: → We study phase-field models for multi-phase flow computation. → We develop an energy-law preserving C0 FEM. → We show that the energy-law preserving method work better. → We overcome unphysical oscillation associated with the Cahn-Hilliard model. - Abstract: We use the idea in to develop the energy law preserving method and compute the diffusive interface (phase-field) models of Allen-Cahn and Cahn-Hilliard type, respectively, governing the motion of two-phase incompressible flows. We discretize these two models using a C 0 finite element in space and a modified midpoint scheme in time. To increase the stability in the pressure variable we treat the divergence free condition by a penalty formulation, under which the discrete energy law can still be derived for these diffusive interface models. Through an example we demonstrate that the energy law preserving method is beneficial for computing these multi-phase flow models. We also demonstrate that when applying the energy law preserving method to the model of Cahn-Hilliard type, un-physical interfacial oscillations may occur. We examine the source of such oscillations and a remedy is presented to eliminate the oscillations. A few two-phase incompressible flow examples are computed to show the good performance of our method.
A free surface algorithm in the N3S finite element code for turbulent flows
International Nuclear Information System (INIS)
Nitrosso, B.; Pot, G.; Abbes, B.; Bidot, T.
1995-08-01
In this paper, we present a free surface algorithm which was implemented in the N3S code. Free surfaces are represented by marker particles which move through a mesh. It is assumed that the free surface is located inside each element that contains markers and surrounded by at least one element with no marker inside. The mesh is then locally adjusted in order to coincide with the free surface which is well defined by the forefront marker particles. After describing the governing equations and the N3S solving methods, we present the free surface algorithm. Results obtained for two-dimensional and three-dimensional industrial problems of mould filling are presented. (authors). 5 refs., 2 figs
International Nuclear Information System (INIS)
Noy, D.J.
1984-11-01
A group of finite element programs are described which may be used for the analysis of complex single borehole hydraulic and tracer experiments in porous media. An outline is given of the theoretical development of the model and the computational procedures used. The equations are solved with the aid of routines specifically designed for efficient operation on vector processing machines. Finally, two simple examples of output generated by the programs are given. (author)
Comparative Political Economy and International Migration
Afonso, A.; Devitt, C.
2016-01-01
This article provides an overview of the literature connecting comparative political economy and international migration in advanced industrialized countries with a focus on the relationship between labour migration, labour markets and welfare institutions. Immigration flows and policies are
Directory of Open Access Journals (Sweden)
ADEGUN, I. K.
2014-08-01
Full Text Available The paper investigated the flow of incompressible fluid and contaminant transport through a Porous Landfill using a numerical technique. A threedimensional finite element analysis technique was adopted for the solution. The problem was based on the Darcy’s Law and the Advection-Dispersion equation. The solutions of the Darcy’s and Advection-Dispersion equations were generated using Finite Element Analysis Software known as COMSOL Multiphysics. This simulation tool tracked the contaminant transport in the Landfill for 360 days at 10 days interval. It first modeled steady-state fluid flow by employing the Darcy’s Law Application Mode and then followed up with a transient solute-transport simulation by employing the Solute-Transport Application Mode from the Earth Science Module of COMSOL. The solution results obtained from this model were found to be in close agreement with reallife data obtained at the 130- million ton Bukit Tagar Mega Sanitary Landfill site, Selangor near Kuala Lumpur, Malaysia. This showed that the model can effectively predict the trends in the distributions of pollutants from a Municipal Solid Waste Landfill into nearby land and water sources. The model is thus applicable to the issues of environmental protection and safety of groundwater.
International Nuclear Information System (INIS)
Laval, H.
1981-01-01
This report describes the theoretical and numerical aspects of the finite element computer code CONVEC designed for the transient analysis of two-dimensional plane or three-dimensional axisymmetric incompressible flows including the effects of heat transfer. The governing equations for the above class of problems are the time-dependent incompressible Navier-Stokes equations and the thermal energy equation. The general class of flow problems analysed by CONVEC is discussed and the equations for the initial-boundary value problem are represented. A brief description of the finite element method and the weighted residual formulation is presented. The numerical solution of the incompressible equations is achieved by using a fractional step method. The mass lumping process associated with an explicit time integration scheme is described. The time integration is analysed and the stability conditions are derived. Numerical applications are presented. Standard problems of natural and forced convection are solved and the solutions obtained are compared with other numerical solutions published in the literature
International Nuclear Information System (INIS)
Holford, D.J.
1994-01-01
This document is a user's manual for the Rn3D finite element code. Rn3D was developed to simulate gas flow and radon transport in variably saturated, nonisothermal porous media. The Rn3D model is applicable to a wide range of problems involving radon transport in soil because it can simulate either steady-state or transient flow and transport in one-, two- or three-dimensions (including radially symmetric two-dimensional problems). The porous materials may be heterogeneous and anisotropic. This manual describes all pertinent mathematics related to the governing, boundary, and constitutive equations of the model, as well as the development of the finite element equations used in the code. Instructions are given for constructing Rn3D input files and executing the code, as well as a description of all output files generated by the code. Five verification problems are given that test various aspects of code operation, complete with example input files, FORTRAN programs for the respective analytical solutions, and plots of model results. An example simulation is presented to illustrate the type of problem Rn3D is designed to solve. Finally, instructions are given on how to convert Rn3D to simulate systems other than radon, air, and water
Webb, J Angus; Koster, Wayne M; Stuart, Ivor G; Reich, Paul; Stewardson, Michael J
2018-03-01
Environmental water managers must make best use of allocations, and adaptive management is one means of improving effectiveness of environmental water delivery. Adaptive management relies on generation of new knowledge from monitoring and evaluation, but it is often difficult to make clear inferences from available monitoring data. Alternative approaches to assessment of flow benefits may offer an improved pathway to adaptive management. We developed Bayesian statistical models to inform adaptive management of the threatened Australian grayling (Prototroctes maraena) in the coastal Thomson River, South-East Victoria Australia. The models assessed the importance of flows in spring and early summer (migration flows) for upstream dispersal and colonization of juveniles of this diadromous species. However, Australian grayling young-of-year were recorded in low numbers, and models provided no indication of the benefit of migration flows. To overcome this limitation, we applied the same models to young-of-year of a surrogate species (tupong-Pseudaphritis urvilli)-a more common diadromous species expected to respond to flow similarly to Australian grayling-and found strong positive responses to migration flows. Our results suggest two complementary approaches to supporting adaptive management of Australian grayling. First, refine monitoring approaches to allow direct measurement of effects of migration flows, a process currently under way. Second, while waiting for improved data, further investigate the use of tupong as a surrogate species. More generally, alternative approaches to assessment can improve knowledge to inform adaptive management, and this can occur while monitoring is being revised to directly target environmental responses of interest.
Finite element approximation of flow of fluids with shear-rate- and pressure-dependent viscosity
Czech Academy of Sciences Publication Activity Database
Hirn, A.; Lanzendörfer, Martin; Stebel, Jan
2012-01-01
Roč. 32, č. 4 (2012), s. 1604-1634 ISSN 0272-4979 R&D Projects: GA ČR GA201/09/0917; GA AV ČR IAA100300802; GA MŠk LC06052 Institutional research plan: CEZ:AV0Z10300504; CEZ:AV0Z10190503 Keywords : non-Newtonian fluid * shear-rate- and pressure-dependent viscosity * finite element method * error analysis Subject RIV: BK - Fluid Dynamics Impact factor: 1.326, year: 2012
Structural elements of collapses in shallow water flows with horizontally nonuniform density
Energy Technology Data Exchange (ETDEWEB)
Goncharov, V. P., E-mail: v.goncharov@rambler.ru [Russian Academy of Sciences, Obukhov Institute of Atmospheric Physics (Russian Federation); Pavlov, V. I., E-mail: Vadim.Pavlov@univ-lille1.fr [Universite de Lille 1, UFR de Mathematiques Pures et Appliquees-LML UMR 8107 (France)
2013-10-15
The mechanisms and structural elements of instability whose evolution results in the occurrence of the collapse are studied in the scope of the rotating shallow water model with a horizontally nonuniform density. The diagram stability based on the integral collapse criterion is suggested to explain system behavior in the space of constants of motion. Analysis of the instability shows that two collapse scenarios are possible. One scenario implies anisotropic collapse during which the contact area of a collapsing drop-like fragment with the bottom contracts into a rotating segment. The other implies isotropic contraction of the area into a point.
International Nuclear Information System (INIS)
Volevatyj, A.A.; Tolkach, A.V.; Bykovskij, Yu.M.
2002-01-01
Certain problems of objective visualization of two-phases flows in the energy-technique elements at the investigations by means of photo-, cinema- and video-registration are considered. It is shown an advisability of using of the more long-wave illumination of the medium at the high steam-content values in the flow
The Globalisation of migration
Directory of Open Access Journals (Sweden)
Milan Mesić
2002-04-01
Full Text Available The paper demonstrates that contemporary international migration is a constitutive part of the globalisation process. After defining the concepts of globalisation and the globalisation of migration, the author discusses six key themes, linking globalisation and international migration (“global cities”, the scale of migration; diversification of migration flows; globalisation of science and education; international migration and citizenship; emigrant communities and new identities. First, in accordance with Saskia Sassen’s analysis, the author rejects the wide-spread notion that unqualified migrants have lost an (important role in »global cities«, i.e. in the centres of the new (global economy. Namely, the post-modern service sector cannot function without the support of a wide range of auxiliary unqualified workers. Second, a critical comparison with traditional overseas mass migration to the USA at the turn of the 19th and 20th centuries indicates that present international migration is, perhaps, less extensive – however it is important to take into consideration various limitations that previously did not exist, and thus the present migration potential is in really greater. Third, globalisation is more evident in a diversification of the forms of migration: the source area of migrants to the New World and Europe has expanded to include new regions in the world; new immigration areas have arisen (the Middle East, new industrial countries of the Far East, South Europe; intra-regional migration has intensified. Forth, globalisation is linked to an increased migration of experts and the pessimistic notion of a brain drain has been replaced by the optimistic idea of a brain gain. Fifth, contemporary international migration has been associated with a crisis of the national model of citizenship. Sixth, the interlinking of (migrant cultural communities regardless of distance and the physical proximity of cultural centres (the
Directory of Open Access Journals (Sweden)
Mojtaba Darabi
2016-06-01
Full Text Available Considering the fact that a large volume of iron reserve in the Sechahoon Iron Mine in Yazd Province has located under the water table, it is necessary to conduct a comprehensive study on water flow within the pit and its surroundings. The conceptual model of the aquifer was created using surface and underground geological information compared with water table data of the area of interest. In the data preparation stages, in order to create the numerical model, Logan and Lufran tests were studied to determine the hydrodynamic coefficients of the layers, precipitation and evaporation were investigated, and fractures and faults of the region, as a medium for flow channels in the hard formation, were also studied. The model was created in a transient state between 2000 and 2014. To validate its results, the water table was measured 4 times in the last 4 months of 2014. Considering the complexities in the heterogeneous fractured aquifer of the study area, numerical modeling results for the basin in a transient state present 90 percent correlation with field studies. Having investigated the water balance in the region, the boundary condition of the model was determined as the input water from the eastern south and the runoff water in the western north of the region. Since the general trend of faults in the area is north-south, variation in the water table is slight on north-south and intense on the east-west direction. On the other hand, due to the fact that the maximum flow is along the faults and fractures, the water table contour lines in different locations over the region are closed.
Labonte, Alison Louise
Detecting seafloor deformation events in the offshore convergent margin environment is of particular importance considering the significant seismic hazard at subduction zones. Efforts to gain insight into the earthquake cycle have been made at the Cascadia and Costa Rica subduction margins through recent expansions of onshore GPS and seismic networks. While these studies have given scientists the ability to quantify and locate slip events in the seismogenic zone, there is little technology available for adequately measuring offshore aseismic slip. This dissertation introduces an improved flow meter for detecting seismic and aseismic deformation in submarine environments. The value of such hydrologic measurements for quantifying the geodetics at offshore margins is verified through a finite element modeling (FEM) study in which the character of deformation in the shallow subduction zone is determined from previously recorded hydrologic events at the Costa Rica Pacific margin. Accurately sensing aseismic events is one key to determining the stress state in subduction zones as these slow-slip events act to load or unload the seismogenic zone during the interseismic period. One method for detecting seismic and aseismic strain events is to monitor the hydrogeologic response to strain events using fluid flow meters. Previous instrumentation, the Chemical Aqueous Transport (CAT) meter which measures flow rates through the sediment-water interface, can detect transient events at very low flowrates, down to 0.0001 m/yr. The CAT meter performs well in low flow rate environments and can capture gradual changes in flow rate, as might be expected during ultra slow slip events. However, it cannot accurately quantify high flow rates through fractures and conduits, nor does it have the temporal resolution and accuracy required for detecting transient flow events associated with rapid deformation. The Optical Tracer Injection System (OTIS) developed for this purpose is an
Discrete conservation properties for shallow water flows using mixed mimetic spectral elements
Lee, D.; Palha, A.; Gerritsma, M.
2018-03-01
A mixed mimetic spectral element method is applied to solve the rotating shallow water equations. The mixed method uses the recently developed spectral element histopolation functions, which exactly satisfy the fundamental theorem of calculus with respect to the standard Lagrange basis functions in one dimension. These are used to construct tensor product solution spaces which satisfy the generalized Stokes theorem, as well as the annihilation of the gradient operator by the curl and the curl by the divergence. This allows for the exact conservation of first order moments (mass, vorticity), as well as higher moments (energy, potential enstrophy), subject to the truncation error of the time stepping scheme. The continuity equation is solved in the strong form, such that mass conservation holds point wise, while the momentum equation is solved in the weak form such that vorticity is globally conserved. While mass, vorticity and energy conservation hold for any quadrature rule, potential enstrophy conservation is dependent on exact spatial integration. The method possesses a weak form statement of geostrophic balance due to the compatible nature of the solution spaces and arbitrarily high order spatial error convergence.
Numerical simulation of a flow-like landslide using the particle finite element method
Zhang, Xue; Krabbenhoft, Kristian; Sheng, Daichao; Li, Weichao
2015-01-01
In this paper, an actual landslide process that occurred in Southern China is simulated by a continuum approach, the particle finite element method (PFEM). The PFEM attempts to solve the boundary-value problems in the framework of solid mechanics, satisfying the governing equations including momentum conservation, displacement-strain relation, constitutive relation as well as the frictional contact between the sliding mass and the slip surface. To warrant the convergence behaviour of solutions, the problem is formulated as a mathematical programming problem, while the particle finite element procedure is employed to tackle the issues of mesh distortion and free-surface evolution. The whole procedure of the landslide, from initiation, sliding to deposition, is successfully reproduced by the continuum approach. It is shown that the density of the mass has little influence on the sliding process in the current landslide, whereas both the geometry and the roughness of the slip surface play important roles. Comparative studies are also conducted where a satisfactory agreement is obtained.
NUMERICAL INVESTIGATION OF TWO ELEMENT CAMBER MORPHING AIRFOIL IN LOW REYNOLDS NUMBER FLOWS
Directory of Open Access Journals (Sweden)
RAJESH SENTHIL KUMAR T.
2017-07-01
Full Text Available Aerodynamic performance of a two-element camber morphing airfoil was investigated at low Reynolds number using the transient SST model in ANSYS FLUENT 14.0 and eN method in XFLR5. The two-element camber morphing concept was employed to morph the baseline airfoil into another airfoil by altering the orientation of mean-line at 35% of the chord to achieve better aerodynamic efficiency. NACA 0012 was selected as baseline airfoil. NACA 23012 was chosen as the test case as it has the camber-line similar to that of the morphed airfoil and as it has the same thickness as that of the baseline airfoil. The simulations were carried out at chord based Reynolds numbers of 2.5×105 and 3.9×105. The aerodynamic force coefficients, aerodynamic efficiency and the location of the transition point of laminar separation bubble over these airfoils were studied for various angles of attack. It was found that the aerodynamic efficiency of the morphed airfoil was 12% higher than that of the target airfoil at 4° angle of attack for Reynolds number of 3.9×105 and 54% rise in aerodynamic performance was noted as Reynolds number was varied from 2.5×105 to 3.9×105. The morphed airfoil exhibited the nature of low Reynolds number airfoil.
Directory of Open Access Journals (Sweden)
Cristina Dinu
2009-06-01
Full Text Available The European Drinking Water Directive (98/83/EC, transposed in Romanian Legislation as Low 458/2002, amended by Low 311/2004, imposes the limit of concentration for metallic elements in water intended for human consumption. The toxic metals arsenic and selenium are among these elements and the limit value is 10 μg/L. In the paper there are presented the working conditions for determination of As and Se from drinking water using modern techniques based on the fl ow injection-hydride generation with the inductively coupled plasma atomic emission spectrometry (FIAS-ICP-EOS. The analyses were performed on Optima 5300 DV Perkin Elmer equipment with FIAS 400 Flow Injection System, Perkin Elmer type. For the hydride generation two types of solution were used: 10% (v/v HCl as a carrier solution and 0.2 % NaBH4 in 0.05%NaOH solution as a reducing agent [1]. The treatment step of the samples and standard solutions consisted in reducing with mixed solutions of KI and ascorbic acid in acidic condition (HCl for As and only with HCl and high temperature for Se [2,3]. The paper contains the characteristic parameters of the methods, such as: low detection limit, quantifi cation limit, repeatability, precision, recovery, which were evaluated using Certifi ed Reference Materials for each element.
International Nuclear Information System (INIS)
Curi, Marcos Filardy
2011-01-01
In view of the problem of global warming and the search for clean energy sources, a worldwide expansion on the use of nuclear energy is foreseen. Thus, the development of science and technology regarding nuclear power plants is essential, in particular in the field of reactor engineering. Fluid mechanics and heat transfer play an important role in the development of nuclear reactors. Computational Fluid Mechanics (CFD) is becoming ever more important in the optimization of cost and safety of the designs. This work presents a stabilized second-order time accurate finite element formulation for incompressible flows with heat transfer. A second order time discretization precedes a spatial discretization using finite elements. The terms that stabilize the finite element method arise naturally from the discretization process, rather than being introduced a priori in the variational formulation. The method was implemented in the program 'ns n ew s olvec2d av 2 M PI' written in FORTRAN90, developed in the Parallel Computing Laboratory at the Institute of Nuclear Engineering (LCP/IEN). Numerical solutions of some representative examples, including free, mixed and forced convection, demonstrate that the proposed stabilized formulation attains very good agreement with experimental and computational results available in the literature. (author)
International Nuclear Information System (INIS)
Lee, Kyue-Hyung; Ohshima, Mitsuko; Motomizu, Shoji
2002-01-01
Multielement determination of major to trace metals in a deep seawater malt was accomplished by inductively coupled plasma-mass spectrometry (ICP-MS) together with inductively coupled plasma-atomic emission spectrometry (ICP-AES). Major elements, such as Na, K, Mg, and Ca, were measured by ICP-AES and normal continuos nebulization ICP-MS after sample dilution by 10 3 -10 6 fold. Fifteen trace elements in the concentrated metal solutions pretreated with cation-exchange resin or chelating resin could be simultaneously determined by air-flow injection/ICP-mass spectrometry (AFI/ICP-MS). Since the injection volume for AFI/ICP-MS was 25 μl, final samples volumes less than 500 μl were enough for several replicate measurements. Three different preconcentration methods assisted with AFI/ICP-MS were examined and could be successfully applied to a deep seawater malt. The analytical results of rate earth elements (REEs) and Co, Ni, Cu, Zn, Cd, and Pb obtained by AFI/ICP-MS coupled with disk filtration method using iminodiacetate (IDA)-type chelating resin were favorably agreed with the data obtained by AFI/ICP-MS coupled with column preconcentration method using chitosan-based chelating resin. (author)
Mori, Masanobu; Nakano, Koji; Sasaki, Masaya; Shinozaki, Haruka; Suzuki, Shiho; Okawara, Chitose; Miró, Manuel; Itabashi, Hideyuki
2016-02-01
A dynamic flow-through microcolumn extraction system based on extractant re-circulation is herein proposed as a novel analytical approach for simplification of bioaccessibility tests of trace elements in sediments. On-line metal leaching is undertaken in the format of all injection (AI) analysis, which is a sequel of flow injection analysis, but involving extraction under steady-state conditions. The minimum circulation times and flow rates required to determine the maximum bioaccessible pools of target metals (viz., Cu, Zn, Cd, and Pb) from lake and river sediment samples were estimated using Tessier's sequential extraction scheme and an acid single extraction test. The on-line AIA method was successfully validated by mass balance studies of CRM and real sediment samples. Tessier's test in on-line AI format demonstrated to be carried out by one third of extraction time (6h against more than 17 h by the conventional method), with better analytical precision (15% by the conventional method) and significant decrease in blank readouts as compared with the manual batch counterpart. Copyright © 2015 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Armand, Patrick
1995-01-01
The aim of this work consists in the Fluid Mechanics and aerosol Physics coupling. In the first part, the order of magnitude analysis of the particle dynamics is done. This particle is embedded in a non-uniform unsteady flow. Flow approximations around the inclusion are described. Corresponding aerodynamic drag formulae are expressed. Possible situations related to the problem data are extensively listed. In the second part, one studies the turbulent particles transport. Eulerian approach which is particularly well adapted to industrial codes is preferred in comparison with the Lagrangian methods. One chooses the two-fluid formalism in which career gas-particles slip is taken into account. Turbulence modelling gets through a k-epsilon modulated by the inclusions action on the flow. The model is implemented In a finite elements code. Finally, In the third part, one validates the modelling in laminar and turbulent cases. We compare simulations to various experiments (settling battery, inertial impaction in a bend, jets loaded with glass beads particles) which are taken in the literature or done by ourselves at the laboratory. The results are very close. It is a good point when it is thought of the particles transport model and associated software future use. (author) [fr
Directory of Open Access Journals (Sweden)
Lehner F. K.
2006-11-01
Full Text Available A mathematical model of secondary migration is described which permits the prediction of hydrocarbon migration and accumulation patterns in a sedimentary basin, if source rock expulsion rates and geometrical and hydraulic properties of major carrier systems are known through geological time. In this model, secondary migration is treated as buoyancy-driven, segregated flow of hydrocarbons in hydrostatic aquifers. Lateral, updip migration is conceived as a Boussinesq-type, free-surface flow, with source and sink terms representing supply from source rocks and leakage through cap rocks and faults. This permits a two-dimensional, map-view mathematical description of a three-dimensional, time-dependent secondary migration system. A nine-point finite difference approximation has been developed to minimize numerical dispersion, and upstream-weighting is used to obtain stable solutions. Example computations for simple, single carrier bed structures are presented. L'article décrit un modèle mathématique de migration secondaire prédisant la migration des hydrocarbures et leur accumulation dans un bassin sédimentaire, lorsque les taux d'expulsion des roches mères et les propriétés géométriques et hydrauliques des principaux systèmes de drainage sont connus à l'échelle du temps géologique. Dans ce modèle, la migration secondaire est traitée comme un écoulement des hydrocarbures en phase séparée, contrôlé par la poussée d'Archimède, dans des aquifères hydrostatiques. La migration latérale est considérée comme un écoulement de type Boussinesq, à surface libre, avec des termes sources et puits représentant les apports venant des roches mères et les fuites à travers les couvertures et les failles. Ceci permet une description mathématique bidimensionnelle cartographiable d'un système de migration secondaire tridimensionnel et dépendant du temps. On utilise une approximation type différences finies à neuf points pour minimiser
International Elderly Migration in Hungary
Directory of Open Access Journals (Sweden)
Sándor Illés
2006-06-01
Full Text Available The paper examines international elderly migration (IEM related to Hungary. Little effort has been made to investigate this increasingly important element of human migration in Central and Eastern Europe. The general objective of this study is to contribute to filling this gap. IEM is investigated using register-based data on migration flows, stocks and citizenship statistics. The analysis focuses on the time series but the paper also considers the historical context and the recent patterns of IEM. The aim of the research was fourfold. Firstly, we tried to establish when IEM related to Hungary began. Secondly, we detected the accelerating character of this phenomenon. Thirdly, we were able to identify the main macrofactors influencing the level of IEM. Fourthly, the main result of the study was that it allowed exploration of a Hungarian peculiarity. “Pension seeking” is one very distinctive feature of IEM and is in many ways a legacy of the state socialism period. Therefore, its emergence on such a large scale is the result of the transformation period. We suppose that pension-hunting type migration will be temporary in nature. Conclusions about the motivational structure of IEM are discussed with reference to policy implications in the light of the ageing population structure in Hungary.
Simulation of Turbulent, Obstructed and Thermaly Coupled flow by the Finite Element Method
International Nuclear Information System (INIS)
Cantero, M.I.
2000-01-01
In the present work we develop a numerical methodology to deal with natural and free convection, in laminar or turbulent regimes, and in the presence of flow obstructions. The mathematical formulations allows the use of moderate-size meshes (104 106 grid points) to model big thermal hydraulic components with affordable computing costs. The main idea is the introduction of two hierarchy levels in the geometric modeling, a macroscopic one that is incorporated in the mesh design, and a microscopic one that is replaced by an equivalent ''porous'' medium. This is done in such a way that the main quantities (head loss, net fluid mass, net solid mass, heat and mass exchanges) are conserved, by means of three free parameters to be defined pointwise:The distributed friction coefficient, the fluid volume fraction,and the distributed heat exchange coefficient between fluid and solid. Many numerical tests were carried out to tune the numerical algorithm so as to obtain stable and physically realistic results.The final code implementing this methodology, PARFEMCO, also incorporates buoyancy forces, Smagorinsky's algebraic turbulence model, and fluid-structure thermal interaction.We also report on two applications of the code, one in computational hemodynamics and, the most important one that motivated most of the development, in the simulation of the pre-heating (non-nuclear) transient of a compact nuclear reactor, CAREM, under development by the Comision Nacional de Energia Atomica
Ryzhenkov, V.; Ivashchenko, V.; Vinuesa, R.; Mullyadzhanov, R.
2016-10-01
We use the open-source code nek5000 to assess the accuracy of high-order spectral element large-eddy simulations (LES) of a turbulent channel flow depending on the spatial resolution compared to the direct numerical simulation (DNS). The Reynolds number Re = 6800 is considered based on the bulk velocity and half-width of the channel. The filtered governing equations are closed with the dynamic Smagorinsky model for subgrid stresses and heat flux. The results show very good agreement between LES and DNS for time-averaged velocity and temperature profiles and their fluctuations. Even the coarse LES grid which contains around 30 times less points than the DNS one provided predictions of the friction velocity within 2.0% accuracy interval.
Gas migration in argillaceous rock
International Nuclear Information System (INIS)
Alonso, E. E.; Olivella, S.
2007-01-01
The intrinsic gas permeability of fractured argillaceous rocks depends on the current structure of micro-cracks and fissures of the rock. They are a consequence of the initial state and the subsequent deformations induced by stress and gas pressure changes. Stresses are also coupled with fluid pressures and, therefore, gas flow and mechanical behaviour are intensely coupled. Laboratory experiments, aimed at determining intrinsic permeability, show the relevant effect of volumetric deformations induced by isotropic, as well as deviatoric stress changes. The relevance, in practice, of the flow-mechanical coupling is illustrated by means of some results obtained during the performance of the drift scale test (DST) in fractured tuff in the Yucca Mountain facility. The technique of embedding discontinuities in continuum thermo-hydro-mechanical elements is capable of reproducing observed features of gas flow migration in clayey rocks. An example is described. It is believed that the developed approach provides a powerful computational procedure to handle complex gas phenomena in clayey rocks. (author)
Behavior of EBR-II Mk-V-type fuel elements in simulated loss-of-flow tests
International Nuclear Information System (INIS)
Liu, Y.Y.; Tsai, H.; Billone, M.C.; Kramer, J.M.
1992-01-01
The next step in the development of metal fuels for the integral fast reactor (IFR) is the conversion of the Experimental Breeder Reactor II (EBR-II) core to one containing the ternary U-20 Pu-10 Zr alloy clad with HT-9 cladding, i.e., the Mk-V core. This paper presents results of three hot-cell furnace simulation tests on irradiated Mk-V-type fuel elements (U-19 Pu-10 Zr/HT-9), which were performed to support the safety case for the Mk-V core. These tests were designed to envelop an umbrella (bounding) unlikely loss-of-flow (LOF) event in EBR-II during which the calculated peak cladding temperature would reach 776 degree C for < 2 min. The principal objectives of these tests were (a) demonstration of the safety margin of the fuel element, (b) investigation of cladding breaching behavior, and (c) provision of data for validation of the FPIN2 and LIFE-METAL codes
Lin, Kunning; Ma, Jian; Yuan, Dongxing; Feng, Sichao; Su, Haitao; Huang, Yongming; Shangguan, Qipei
2017-05-15
An integrated system was developed for automatic and sequential determination of NO 2 - , NO 3 - , PO 4 3- , Fe 2+ , Fe 3+ and Mn 2+ in natural waters based on reverse flow injection analysis combined with spectrophotometric detection. The system operation was controlled by a single chip microcomputer and laboratory-programmed software written in LabVIEW. The experimental parameters for each nutrient element analysis were optimized based on a univariate experimental design, and interferences from common ions were evaluated. The upper limits of the linear range (along with detection limit, µmolL -1 ) of the proposed method was 20 (0.03), 200 (0.7), 12 (0.3), 5 (0.03), 5 (0.03), 9 (0.2) µmolL -1 , for NO 2 - , NO 3 - , PO 4 3- , Fe 2+ , Fe 3+ and Mn 2+ , respectively. The relative standard deviations were below 5% (n=9-13) and the recoveries varied from 88.0±1.0% to 104.5±1.0% for spiked water samples. The sample throughput was about 20h -1 . This system has been successfully applied for the determination of multi-nutrient elements in different kinds of water samples and showed good agreement with reference methods (slope 1.0260±0.0043, R 2 =0.9991, n=50). Copyright © 2017 Elsevier B.V. All rights reserved.
Saad, Bilal Mohammed; Saad, Mazen Naufal B M
2014-01-01
We propose and analyze a combined finite volume-nonconforming finite element scheme on general meshes to simulate the two compressible phase flow in porous media. The diffusion term, which can be anisotropic and heterogeneous, is discretized by piecewise linear nonconforming triangular finite elements. The other terms are discretized by means of a cell-centered finite volume scheme on a dual mesh, where the dual volumes are constructed around the sides of the original mesh. The relative permeability of each phase is decentred according the sign of the velocity at the dual interface. This technique also ensures the validity of the discrete maximum principle for the saturation under a non restrictive shape regularity of the space mesh and the positiveness of all transmissibilities. Next, a priori estimates on the pressures and a function of the saturation that denote capillary terms are established. These stabilities results lead to some compactness arguments based on the use of the Kolmogorov compactness theorem, and allow us to derive the convergence of a subsequence of the sequence of approximate solutions to a weak solution of the continuous equations, provided the mesh size tends to zero. The proof is given for the complete system when the density of the each phase depends on its own pressure. © 2014 Springer-Verlag Berlin Heidelberg.
International Nuclear Information System (INIS)
Gupta, S.K.; Cole, C.R.; Bond, F.W.
1979-12-01
The Assessment of Effectiveness of Geologic Isolation Systems (AEGIS) Program is developing and applying the methodology for assessing the far-field, long-term post-closure safety of deep geologic nuclear waste repositories. AEGIS is being performed by Pacific Northwest Laboratory (PNL) under contract with the Office of Nuclear Waste Isolation (OWNI) for the Department of Energy (DOE). One task within AEGIS is the development of methodology for analysis of the consequences (water pathway) from loss of repository containment as defined by various release scenarios. Analysis of the long-term, far-field consequences of release scenarios requires the application of numerical codes which simulate the hydrologic systems, model the transport of released radionuclides through the hydrologic systems to the biosphere, and, where applicable, assess the radiological dose to humans. Hydrologic and transport models are available at several levels of complexity or sophistication. Model selection and use are determined by the quantity and quality of input data. Model development under AEGIS and related programs provides three levels of hydrologic models, two levels of transport models, and one level of dose models (with several separate models). This document consists of the description of the FE3DGW (Finite Element, Three-Dimensional Groundwater) Hydrologic model third level (high complexity) three-dimensional, finite element approach (Galerkin formulation) for saturated groundwater flow
Saad, Bilal Mohammed
2014-06-28
We propose and analyze a combined finite volume-nonconforming finite element scheme on general meshes to simulate the two compressible phase flow in porous media. The diffusion term, which can be anisotropic and heterogeneous, is discretized by piecewise linear nonconforming triangular finite elements. The other terms are discretized by means of a cell-centered finite volume scheme on a dual mesh, where the dual volumes are constructed around the sides of the original mesh. The relative permeability of each phase is decentred according the sign of the velocity at the dual interface. This technique also ensures the validity of the discrete maximum principle for the saturation under a non restrictive shape regularity of the space mesh and the positiveness of all transmissibilities. Next, a priori estimates on the pressures and a function of the saturation that denote capillary terms are established. These stabilities results lead to some compactness arguments based on the use of the Kolmogorov compactness theorem, and allow us to derive the convergence of a subsequence of the sequence of approximate solutions to a weak solution of the continuous equations, provided the mesh size tends to zero. The proof is given for the complete system when the density of the each phase depends on its own pressure. © 2014 Springer-Verlag Berlin Heidelberg.
International Nuclear Information System (INIS)
Tuerker, A.
1989-10-01
The quantity of spent fuel elements is increasing due to the extended peaceful uses of nuclear energy. Of the numerous fission products, strontium has an interesting application potential as a radiation or energy source for utilization in various industrial fields. A necessary condition for its use is its isolation in high radiochemical purity from the highly radioactive waste flow of the Purex process. In the present study, precipitation and coprecipitation reactions, and in particular ion exchange reactions, were chosen from among the various possible chemical and physical separation methods and examined with respect to their suitability for a selective separation of strontium from the other fission products. In selecting separation materials, particularly with respect to radiation resistance, thermal stability and selectivity, polyantimonic acid proved to be the best absorbent (even in a very acid medium) for strontium. Furthermore, the behaviour of the most important radionuclides was studied with respect to the denitration reaction from a 5 molar nitric acid solution. On the basis of the high demands made on the purity of the product, a method was developed by combining lead sulphate carrier precipitation with an ion exchange reaction on polyantimonic acid and is shown in a flow chart. (orig.) [de
Carlos Varas, Álvaro E; Peters, E A J F; Kuipers, J A M
2017-05-17
We report a computational fluid dynamics-discrete element method (CFD-DEM) simulation study on the interplay between mass transfer and a heterogeneous catalyzed chemical reaction in cocurrent gas-particle flows as encountered in risers. Slip velocity, axial gas dispersion, gas bypassing, and particle mixing phenomena have been evaluated under riser flow conditions to study the complex system behavior in detail. The most important factors are found to be directly related to particle cluster formation. Low air-to-solids flux ratios lead to more heterogeneous systems, where the cluster formation is more pronounced and mass transfer more influenced. Falling clusters can be partially circumvented by the gas phase, which therefore does not fully interact with the cluster particles, leading to poor gas-solid contact efficiencies. Cluster gas-solid contact efficiencies are quantified at several gas superficial velocities, reaction rates, and dilution factors in order to gain more insight regarding the influence of clustering phenomena on the performance of riser reactors.
Shih, Tsan-Hsing; Liu, Nan-Suey
2012-01-01
This paper presents the numerical simulations of the Jet-A spray reacting flow in a single element lean direct injection (LDI) injector by using the National Combustion Code (NCC) with and without invoking the Eulerian scalar probability density function (PDF) method. The flow field is calculated by using the Reynolds averaged Navier-Stokes equations (RANS and URANS) with nonlinear turbulence models, and when the scalar PDF method is invoked, the energy and compositions or species mass fractions are calculated by solving the equation of an ensemble averaged density-weighted fine-grained probability density function that is referred to here as the averaged probability density function (APDF). A nonlinear model for closing the convection term of the scalar APDF equation is used in the presented simulations and will be briefly described. Detailed comparisons between the results and available experimental data are carried out. Some positive findings of invoking the Eulerian scalar PDF method in both improving the simulation quality and reducing the computing cost are observed.
Finite element modeling of melting and fluid flow in the laser-heated diamond-anvil cell
Gomez-Perez, N.; Rodriguez, J. F.; McWilliams, R. S.
2017-04-01
The laser-heated diamond anvil cell is widely used in the laboratory study of materials behavior at high-pressure and high-temperature, including melting curves and liquid properties at extreme conditions. Laser heating in the diamond cell has long been associated with fluid-like motion in samples, which is routinely used to determine melting points and is often described as convective in appearance. However, the flow behavior of this system is poorly understood. A quantitative treatment of melting and flow in the laser-heated diamond anvil cell is developed here to physically relate experimental motion to properties of interest, including melting points and viscosity. Numerical finite-element models are used to characterize the temperature distribution, melting, buoyancy, and resulting natural convection in samples. We find that continuous fluid motion in experiments can be explained most readily by natural convection. Fluid velocities, peaking near values of microns per second for plausible viscosities, are sufficiently fast to be detected experimentally, lending support to the use of convective motion as a criterion for melting. Convection depends on the physical properties of the melt and the sample geometry and is too sluggish to detect for viscosities significantly above that of water at ambient conditions, implying an upper bound on the melt viscosity of about 1 mPa s when convective motion is detected. A simple analytical relationship between melt viscosity and velocity suggests that direct viscosity measurements can be made from flow speeds, given the basic thermodynamic and geometric parameters of samples are known.
Comparative test on nuclide migration in aerated zone
International Nuclear Information System (INIS)
Li Shushen; Zhao Yingjie; Wu Qinghua; Wang Zhiming; Hao Janzhong; Ji Shaowei; Guo Liangtian; Guo Zhiming
2002-01-01
In order to study the influence of different tracer source layer material on nuclide migration behavior, the comparative test on stable elements Sr, Nd and Ce migration in aerated loess zone was carried out using loess and arenaceous quartz as the tracer source layer materials respectively. The test lasted 470 days. During the test, four times of sampling were done. The testing results indicate that under artificial sprinkling of 5 mm/h and 3 h/d, Nd and Ce not only in loess tracer source layer but also in arenaceous quartz tracer source layer did not obviously downwards migrated. Concentration peak of Sr for loess layer migrated down about 15 cm in 470 d (mass center moved down about 10 cm) but for arenaceous quartz layer the concentration peak of Sr did not obviously migrated down (mass center moved down about 2.7 cm). The test results show that very thin arenaceous quartz layer with thickness of 7 mm is also able to shield unsaturated water flow obviously. This is the main reason why the nuclides in arenaceous quartz layer migrate down slowly
[The foundation of international migration policies in Latin America].
Marmora, L
1988-12-01
A government's international migration policies are intended to influence the size, composition, direction, destination, or integration of international migratory flows. The justification for migratory policies has been based on a series of themes that have had varied weights in different stages of Latin American history. Migrations as population settlement, the desired or undesired characteristics of migrants, the economic impact of migration, the role of migration in relations between countries, and the ethical dimensions of migratory movement have been the major policy issues. The 1st migration policies in Latin America saw international migration as a means of settling the colonies. After independence, migratory policies oriented toward massive settlement became common. Although the stated goals were to settle entire territories with immigrants, the usual result was to absorb immigrants in certain economic sectors with high demand for labor. In the colonial period both Spain and Portugal attempted to restrict immigration to the Catholic segment of their own populations. After independence, the criteria were liberalized somewhat but still reflected prejudices about the racial superiority of certain types of European immigration. The selection principals which appeared most clearly during the 19th century were overwhelmed to the extent that immigration was tranformed into provision of labor to meet unsatisfied needs for workers. Indiscriminate admissions and recourse to nontraditional elements such as Chinese and Japanese was strongest in countries needing labor for tropical agriculture or extractive industries. The economic argument that migration contributed to development was widespread economic argument that migration contributed to development was widespread in the 19th and early 20th centuries, but new rules were made to restrict immigration to protect local labor markets during the worldwide depression of the 1930s. In recent decades, migration policies
Energy Technology Data Exchange (ETDEWEB)
Sarler, B [Institut Jozef Stefan, Ljubljana (Yugoslavia)
1987-07-01
The basic principles of the boundary element method numerical treatment of the radial flow heat diffusion equation are presented. The algorithm copes the time dependent Dirichlet and Neumann boundary conditions, temperature dependent material properties and regions from different materials in thermal contact. It is verified on the several analytically obtained test cases. The developed method is used for the modelling of unsteady radial heat flow in pressurized water reactor fuel rod. (author)
International Nuclear Information System (INIS)
Carlsen, L.
1992-05-01
Migration chemistry, the influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour of pollutants in the environment, is an interplay between the actual natur of the pollutant and the characteristics of the environment, such as pH, redox conditions and organic matter content. The wide selection of possible pollutants in combination with varying geological media, as well as the operation of different chemical -, biochemical - and physico-chemical reactions compleactes the prediction of the influence of these processes on the mobility of pollutants. The report summarizes a wide range of potential pollutants in the terrestrial environment as well as a variety of chemical -, biochemical - and physico-chemical reactions, which can be expected to influence the migration behaviour, comprising diffusion, dispersion, convection, sorption/desorption, precipitation/dissolution, transformations/degradations, biochemical reactions and complex formation. The latter comprises the complexation of metal ions as well as non-polar organics to naturally occurring organic macromolecules. The influence of the single types of processes on the migration process is elucidated based on theoretical studies. The influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour is unambiguous, as the processes apparently control the transport of pollutants in the terrestrial environment. As the simple, conventional K D concept breaks down, it is suggested that the migration process should be described in terms of the alternative concepts chemical dispersion, average-elution-time and effective retention. (AB) (134 refs.)
Energy Technology Data Exchange (ETDEWEB)
Baer, T.A.; Cairncross, R.A.; Rao, R.R.; Sackinger, P.A.; Schunk, P.R.
1999-01-29
To date, few researchers have solved three-dimensional free-surface problems with dynamic wetting lines. This paper extends the free-surface finite element method described in a companion paper [Cairncross, R.A., P.R. Schunk, T.A. Baer, P.A. Sackinger, R.R. Rao, "A finite element method for free surface flows of incompressible fluid in three dimensions, Part I: Boundary-Fitted mesh motion.", to be published (1998)] to handle dynamic wetting. A generalization of the technique used in two dimensional modeling to circumvent double-valued velocities at the wetting line, the so-called kinematic paradox, is presented for a wetting line in three dimensions. This approach requires the fluid velocity normal to the contact line to be zero, the fluid velocity tangent to the contact line to be equal to the tangential component of web velocity, and the fluid velocity into the web to be zero. In addition, slip is allowed in a narrow strip along the substrate surface near the dynamic contact line. For realistic wetting-line motion, a contact angle which varies with wetting speed is required because contact lines in three dimensions typically advance or recede a different rates depending upon location and/or have both advancing and receding portions. The theory is applied to capillary rise of static fluid in a corner, the initial motion of a Newtonian droplet down an inclined plane, and extrusion of a Newtonian fluid from a nozzle onto a moving substrate. The extrusion results are compared to experimental visualization. Subject Categories
Migration and Remittances Factbook 2016, Third Edition
World Bank Group
2016-01-01
The Migration and Remittances Factbook 2016 attempts to present numbers and facts behind the stories of international migration and remittances, drawing on authoritative, publicly available data. It provides a snapshot of statistics on immigration, emigration, skilled emigration, and remittance flows for 210 countries and 15 regional and income groups. The Migration and Remittances Factbook 2016 updates the 2011 edition of the Factbook with additional data on bilateral migration and remittanc...
Globalization and formal sector migration in Brazil
Aguayo-Tellez, Ernesto; Muendler, Marc-Andreas; Poole, Jennifer Pamela
2008-01-01
We use novel linked employer–employee data to study the relationship between globalization and formal sector interstate migration for Brazil. We estimate the worker’s multichoice migration problem and document that previously unobserved employer covariates are significant predictors associated with migration flows. Our results provide support for the idea that globalization acts on internal migration through the growth of employment opportunities at locations with a high concentration of fore...
Wu, Jie; Yu, Sheng-Tao; Jiang, Bo-nan
1996-01-01
In this paper a numerical procedure for simulating two-fluid flows is presented. This procedure is based on the Volume of Fluid (VOF) method proposed by Hirt and Nichols and the continuum surface force (CSF) model developed by Brackbill, et al. In the VOF method fluids of different properties are identified through the use of a continuous field variable (color function). The color function assigns a unique constant (color) to each fluid. The interfaces between different fluids are distinct due to sharp gradients of the color function. The evolution of the interfaces is captured by solving the convective equation of the color function. The CSF model is used as a means to treat surface tension effect at the interfaces. Here a modified version of the CSF model, proposed by Jacqmin, is used to calculate the tension force. In the modified version, the force term is obtained by calculating the divergence of a stress tensor defined by the gradient of the color function. In its analytical form, this stress formulation is equivalent to the original CSF model. Numerically, however, the use of the stress formulation has some advantages over the original CSF model, as it bypasses the difficulty in approximating the curvatures of the interfaces. The least-squares finite element method (LSFEM) is used to discretize the governing equation systems. The LSFEM has proven to be effective in solving incompressible Navier-Stokes equations and pure convection equations, making it an ideal candidate for the present applications. The LSFEM handles all the equations in a unified manner without any additional special treatment such as upwinding or artificial dissipation. Various bench mark tests have been carried out for both two dimensional planar and axisymmetric flows, including a dam breaking, oscillating and stationary bubbles and a conical liquid sheet in a pressure swirl atomizer.
Directory of Open Access Journals (Sweden)
Valentina VASILE
2011-06-01
Full Text Available The youths’ labour market, and especially insertion employment has a series of particularities defined by aspects such as: flexibility, efficient employment, interest for career but also informal employment, external mobility, including brain drain, segmentation, employment precariousness, income disadvantages, etc. Therefore, also the labour market policy and particularly managing labour mobility especially through the economic and social effects that might be triggered on the local labour market in the origin country, presents a special importance under the conditions of the economic turnaround stage, by promoting new and sustainable jobs, based on knowledge and competences. In the present paper an analysis is made about the youths’ labour market features, and the outcomes of an empirical analysis about graduates’ migration propensity are presented. Suggestions are made for developing a balanced policy for youths’ labour mobility to the benefit of the country of origin.
Creasey, C. L.; Flegal, A. R.
The combined use of both (1) low-flow purging and sampling and (2) trace-metal clean techniques provides more representative measurements of trace-element concentrations in groundwater than results derived with standard techniques. The use of low-flow purging and sampling provides relatively undisturbed groundwater samples that are more representative of in situ conditions, and the use of trace-element clean techniques limits the inadvertent introduction of contaminants during sampling, storage, and analysis. When these techniques are applied, resultant trace-element concentrations are likely to be markedly lower than results based on standard sampling techniques. In a comparison of data derived from contaminated and control groundwater wells at a site in California, USA, trace-element concentrations from this study were 2-1000 times lower than those determined by the conventional techniques used in sampling of the same wells prior to (5months) and subsequent to (1month) the collections for this study. Specifically, the cadmium and chromium concentrations derived using standard sampling techniques exceed the California Maximum Contaminant Levels (MCL), whereas in this investigation concentrations of both of those elements are substantially below their MCLs. Consequently, the combined use of low-flow and trace-metal clean techniques may preclude erroneous reports of trace-element contamination in groundwater. Résumé L'utilisation simultanée de la purge et de l'échantillonnage à faible débit et des techniques sans traces de métaux permet d'obtenir des mesures de concentrations en éléments en traces dans les eaux souterraines plus représentatives que les résultats fournis par les techniques classiques. L'utilisation de la purge et de l'échantillonnage à faible débit donne des échantillons d'eau souterraine relativement peu perturbés qui sont plus représentatifs des conditions in situ, et le recours aux techniques sans éléments en traces limite l
OECD migration, welfare and skill selectivity
DEFF Research Database (Denmark)
Pedersen, Peder; Pytlikova, Mariola; Smith, Nina
into 27 OECD countries over the period of 12 years, 1989-2000. Using a fixed effects panel data model, we analyze the determinants of the migration flows during the latest decade. We study whether there are significant selectivity effects in international migration flows, i.e. whether the countries...
1DFEMWATER: A one-dimensional finite element model of WATER flow through saturated-unsaturated media
International Nuclear Information System (INIS)
Yeh, G.T.
1988-08-01
This report presents the development and verification of a one- dimensional finite element model of water flow through saturated- unsaturated media. 1DFEMWATER is very flexible and capable of modeling a wide range of real-world problems. The model is designed to (1) treat heterogeneous media consisting of many geologic formations; (2) consider distributed and point sources/sinks that are spatially and temporally variable; (3) accept prescribed initial conditions or obtain them from steady state simulations; (4) deal with transient heads distributed over the Dirichlet boundary; (5) handle time-dependent fluxes caused by pressure gradient on the Neumann boundary; (6) treat time-dependent total fluxes (i.e., the sum of gravitational fluxes and pressure-gradient fluxes) on the Cauchy boundary; (7) automatically determine variable boundary conditions of evaporation, infiltration, or seepage on the soil-air interface; (8) provide two options for treating the mass matrix (consistent and lumping); (9) provide three alternatives for approximating the time derivative term (Crank-Nicolson central difference, backward difference, and mid-difference); (10) give three options (exact relaxation, underrelaxation, and overrelaxation) for estimating the nonlinear matrix; (11) automatically reset the time step size when boundary conditions or source/sinks change abruptly; and (12) check mass balance over the entire region for every time step. The model is verified with analytical solutions and other numerical models for three examples
Pasquariello, Vito; Hammerl, Georg; Örley, Felix; Hickel, Stefan; Danowski, Caroline; Popp, Alexander; Wall, Wolfgang A.; Adams, Nikolaus A.
2016-02-01
We present a loosely coupled approach for the solution of fluid-structure interaction problems between a compressible flow and a deformable structure. The method is based on staggered Dirichlet-Neumann partitioning. The interface motion in the Eulerian frame is accounted for by a conservative cut-cell Immersed Boundary method. The present approach enables sub-cell resolution by considering individual cut-elements within a single fluid cell, which guarantees an accurate representation of the time-varying solid interface. The cut-cell procedure inevitably leads to non-matching interfaces, demanding for a special treatment. A Mortar method is chosen in order to obtain a conservative and consistent load transfer. We validate our method by investigating two-dimensional test cases comprising a shock-loaded rigid cylinder and a deformable panel. Moreover, the aeroelastic instability of a thin plate structure is studied with a focus on the prediction of flutter onset. Finally, we propose a three-dimensional fluid-structure interaction test case of a flexible inflated thin shell interacting with a shock wave involving large and complex structural deformations.
International Nuclear Information System (INIS)
Pasquariello, Vito; Hammerl, Georg; Örley, Felix; Hickel, Stefan; Danowski, Caroline; Popp, Alexander; Wall, Wolfgang A.; Adams, Nikolaus A.
2016-01-01
We present a loosely coupled approach for the solution of fluid–structure interaction problems between a compressible flow and a deformable structure. The method is based on staggered Dirichlet–Neumann partitioning. The interface motion in the Eulerian frame is accounted for by a conservative cut-cell Immersed Boundary method. The present approach enables sub-cell resolution by considering individual cut-elements within a single fluid cell, which guarantees an accurate representation of the time-varying solid interface. The cut-cell procedure inevitably leads to non-matching interfaces, demanding for a special treatment. A Mortar method is chosen in order to obtain a conservative and consistent load transfer. We validate our method by investigating two-dimensional test cases comprising a shock-loaded rigid cylinder and a deformable panel. Moreover, the aeroelastic instability of a thin plate structure is studied with a focus on the prediction of flutter onset. Finally, we propose a three-dimensional fluid–structure interaction test case of a flexible inflated thin shell interacting with a shock wave involving large and complex structural deformations.
Directory of Open Access Journals (Sweden)
Guodong Liu
2013-01-01
Full Text Available Modular pebble-bed nuclear reactor (MPBNR technology is promising due to its attractive features such as high fuel performance and inherent safety. Particle motion of fuel and graphite pebbles is highly associated with the performance of pebbled-bed modular nuclear reactor. To understand the mechanism of pebble’s motion in the reactor, we numerically studied the influence of number ratio of fuel and graphite pebbles, funnel angle of the reactor, height of guide ring on the distribution of pebble position, and velocity by means of discrete element method (DEM in a two-dimensional MPBNR. Velocity distributions at different areas of the reactor as well as mixing characteristics of fuel and graphite pebbles were investigated. Both fuel and graphite pebbles moved downward, and a uniform motion was formed in the column zone, while pebbles motion in the cone zone was accelerated due to the decrease of the cross sectional flow area. The number ratio of fuel and graphite pebbles and the height of guide ring had a minor influence on the velocity distribution of pebbles, while the variation of funnel angle had an obvious impact on the velocity distribution. Simulated results agreed well with the work in the literature.
International Nuclear Information System (INIS)
Amor, H.; Bourgeois, M.
2012-01-01
Document available in extended abstract form only. The disposal of high level, long lived waste in deep underground clay formations is investigated by several countries including France. In the safety assessment of such geological repositories, a thoughtful consideration must be given to the mechanisms and possible pathways of migration of radionuclides released from waste packages. However, when modelling the transfer of radionuclides throughout the disposal facilities and geological formations, the numerical simulations must take into consideration, in addition to long durations of concern, the variety in the properties as well as in geometrical scales of the different components of the overall disposal, including the host formation. This task presents significant computational challenges. Numerical methods used in the MELODIE software The MELODIE software is developed by IRSN, and constantly upgraded, with the aim to assess the long-term containment capabilities of underground and surface radioactive waste repositories. The MELODIE software models water flow and the phenomena involved in the transport of radionuclides in saturated and unsaturated porous media in 2 and 3 dimensions; chemical processes are represented by a retardation factor and a solubility limit, for sorption and solubility respectively, integrated in the computational equations. These equations are discretized using a so-called Finite Volume Finite Element method (FVFE), which is based on a Galerkin method to discretize time and variables, together with a Finite Volume method using the Godunov scheme for the convection term. The FVFE method is used to convert partial differential equations into a finite number of algebraic equations that match the number of nodes in the mesh used to model the considered domain. It is also used to stabilise the numerical scheme. In order to manage the variety in properties and geometrical scales of underground disposal components, an a posteriori error estimator
TRIANDAFYLLIDOU, Anna
2015-01-01
Proceedings from the conference "Governing Irregular Migration : States, Actors and Intermediaries", Athens 8-9 July 2015 The loss of over a thousand human lives in the effort to cross the Mediterranean during April 2015 has once again drawn media and political attention to the challenges that the EU is facing in its efforts to govern migration and asylum. However, what seems to be still far from complete is our (the experts and the politicians) understanding of what drives people to put t...
International Nuclear Information System (INIS)
Vitorge, P.; Oliver, J.; Mangin, J.P.; Billon, A.
1991-01-01
In the first part, the properties of the transuranium elements (TRU) mainly Pu Np Am have been investigated in terms of complexation by OH and CO3 ligands in aqueous solution. The species which are formed in given physicochemical conditions (ionic strength, concentrations...) are studied with no direct reference to well defined ground waters. Equilibrium constants of complexes and redox potential values are useful in the drawing up of Pourbaix's diagrams. Areas of stability of species in function of Eh pH pCO2 are given for the different elements in a few cases. The second part of this report deals with the study of the transfer of tritiated water cesium and strontium through highly compacted clay (diffusion coefficient). In a third part a code for the computation of ion migration and diffusion in areas close to radwaste storage facilities has been developed. This type of application was found to require a mesh pattern and boundary conditions different from the usual, which justifies the writing of a new code called CONDIMENT. (Convection and Diffusion of elements) 49 figs.; 18 tabs.; 21 refs
Quinquis, M. E. T.; Buiter, S. J. H.
2013-10-01
Subduction of oceanic lithosphere brings water into Earth's upper mantle. Previous numerical studies have shown how slab dehydration and mantle hydration can impact the dynamics of a subduction system by allowing a more vigorous mantle flow and promoting localisation of deformation in lithosphere and mantle. The depths at which dehydration reactions occur in the hydrated portions of the slab are well constrained in these models by thermodynamic calculations. However, the mechanism by which free water migrates in the mantle is incompletely known. Therefore, models use different numerical schemes to model the migration of free water. We aim to show the influence of the numerical scheme of free water migration on the dynamics of the upper mantle and more specifically the mantle wedge. We investigate the following three migration schemes with a finite-element model: (1) element-wise vertical migration of free water, occurring independent of the material flow; (2) an imposed vertical free water velocity; and (3) a Darcy velocity, where the free water velocity is calculated as a function of the pressure gradient between water and the surrounding rocks. In addition, the material flow field also moves the free water in the imposed vertical velocity and Darcy schemes. We first test the influence of the water migration scheme using a simple Stokes flow model that simulates the sinking of a cold hydrated cylinder into a hot dry mantle. We find that the free water migration scheme has only a limited impact on the water distribution after 1 Myr in these models. We next investigate slab dehydration and mantle hydration with a thermomechanical subduction model that includes brittle behaviour and viscous water-dependent creep flow laws. Our models show how the bound water distribution is not greatly influenced by the water migration scheme whereas the free water distribution is. We find that a water-dependent creep flow law results in a broader area of hydration in the mantle
Directory of Open Access Journals (Sweden)
Torsten J. Gerpott
2015-04-01
Full Text Available Due to more than three million people in Germany with a Turkish migration background country-of-origin (COO-sensitive, designs of offers directed at this customer segment have been implemented by various corporations and discussed in the management literature for quite a while. Unfortunately, to date most publications have a weak empirical foundation and refrain from simultaneously investigating preference effects of several country-of-origin-sensitive and -neutral offer characteristics among Turkish migrants living in Germany. Therefore, the present paper explores the relative impacts of three COO-sensitive offer characteristics and one COO-neutral attribute of bundled mobile communication offers on preference statements derived from a conjoint-analysis of questionnaire responses of 249 consumers in Germany with Turkish roots. The results suggest that for the offering category in question a COO-neutral feature (cell phone type/brand shapes the preferences of Turkish migrants almost to the same extent as the three remaining price- and communication-related characteristics investigated. Furthermore, we found that Turkish consumers in Germany encompass four subsegments with distinct preferences with respect to the design of mobile communication offerings. The members of these subsegments in turn differ primarily in terms of their age and gender structures as well as their level of accommodation to the German culture.
International Migration with Heterogeneous Agents: Theory and Evidence
DEFF Research Database (Denmark)
Schröder, Philipp J.H.; Brücker, Herbert
Temporary migration, though empirically relevant, is often ignored in formal models. This paper proposes a migration model with heterogeneous agents and persistent cross country income differentials that features temporary migration. In equilibrium there exists a positive relation between the stock...... of migrants and the income differential, while the net migration flow becomes zero. Consequently, existing empirical migration models, estimating net migration flows, instead of stocks, may be misspecified. This suspicion appears to be confirmed by our investigation of the cointegration relationships...... of German migration stocks and flows since 1967. We find that (i) panel-unit root tests reject the hypothesis that migration flows and the explanatory variables are integrated of the same order, while migration stocks and the explanatory variables are all I(1) variables, and (ii) the hypothesis...
International Nuclear Information System (INIS)
Menendez-Miranda, Mario; Fernandez-Arguelles, Maria T.; Costa-Fernandez, Jose M.; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo
2014-01-01
Highlights: • The hyphenated system allows unequivocal identification of nanoparticle populations. • AF4 separation permitted detection of unexpected nanosized species in a sample. • ICP-QQQ provides elemental ratios with adequate accuracy in every nanoparticle. • Purity and chemical composition of different quantum dot samples were assessed. - Abstract: Separation and identification of nanoparticles of different composition, with similar particle diameter, coexisting in heterogeneous suspensions of polymer-coated CdSe/ZnS quantum dots (QDs) have been thoroughly assessed by asymmetric flow field-flow fractionation (AF4) coupled on-line to fluorescence and inductively coupled plasma mass spectrometry (ICPMS) detectors. Chemical characterization of any previously on-line separated nanosized species was achieved by the measurement of the elemental molar ratios of every element involved in the synthesis of the QDs, using inorganic standards and external calibration by flow injection analysis (FIA). Such elemental molar ratios, strongly limited so far to pure single nanoparticles suspensions, have been achieved with adequate accuracy by coupling for the first time an ICP-QQQ instrument to an AF4 system. This hyphenation turned out to be instrumental to assess the chemical composition of the different populations of nanoparticles coexisting in the relatively complex mixtures, due to its capabilities to detect the hardly detectable elements involved in the synthesis. Interestingly such information, complementary to that obtained by fluorescence, was very valuable to detect and identify unexpected nanosized species, present at significant level, produced during QDs synthesis and hardly detectable by standard approaches
Placidi, M.; Ganapathisubramani, B.
2018-04-01
Wind-tunnel experiments were carried out on fully-rough boundary layers with large roughness (δ /h ≈ 10, where h is the height of the roughness elements and δ is the boundary-layer thickness). Twelve different surface conditions were created by using LEGO™ bricks of uniform height. Six cases are tested for a fixed plan solidity (λ _P) with variations in frontal density (λ _F), while the other six cases have varying λ _P for fixed λ _F. Particle image velocimetry and floating-element drag-balance measurements were performed. The current results complement those contained in Placidi and Ganapathisubramani (J Fluid Mech 782:541-566, 2015), extending the previous analysis to the turbulence statistics and spatial structure. Results indicate that mean velocity profiles in defect form agree with Townsend's similarity hypothesis with varying λ _F, however, the agreement is worse for cases with varying λ _P. The streamwise and wall-normal turbulent stresses, as well as the Reynolds shear stresses, show a lack of similarity across most examined cases. This suggests that the critical height of the roughness for which outer-layer similarity holds depends not only on the height of the roughness, but also on the local wall morphology. A new criterion based on shelter solidity, defined as the sheltered plan area per unit wall-parallel area, which is similar to the `effective shelter area' in Raupach and Shaw (Boundary-Layer Meteorol 22:79-90, 1982), is found to capture the departure of the turbulence statistics from outer-layer similarity. Despite this lack of similarity reported in the turbulence statistics, proper orthogonal decomposition analysis, as well as two-point spatial correlations, show that some form of universal flow structure is present, as all cases exhibit virtually identical proper orthogonal decomposition mode shapes and correlation fields. Finally, reduced models based on proper orthogonal decomposition reveal that the small scales of the turbulence
Kurt, Melike; Moored, Keith
2018-04-19
-dimensions. These results can aid in the design of networked bio-inspired control elements that through integrated sensing can synchronize to three-dimensional flow interactions. © 2018 IOP Publishing Ltd.
Energy Technology Data Exchange (ETDEWEB)
Damsohn, M., E-mail: damsohn@lke.mavt.ethz.c [ETH Zurich, Department of Mechanical and Process Engineering, Sonneggstrasse 3, 8092 Zuerich (Switzerland); Prasser, H.-M. [ETH Zurich, Department of Mechanical and Process Engineering, Sonneggstrasse 3, 8092 Zuerich (Switzerland)
2010-10-15
For the prediction of dryout in fuel elements of boiling water reactors, the dynamic behavior of the water film covering the fuel rod has to be understood. This paper provides high resolved experimental data of the liquid film and gives insight into the dynamic film behavior. The experiments of this work were conducted in a vertical channel representing a pair of neighboring subchannels of a BWR fuel rod bundle. Air and water at ambient pressure and temperature are used as model fluids, creating an annular flow in the test section. The influence of different functional spacer shapes on the liquid film has been studied. The heart of the instrumentation is a liquid film sensor (LFS), which measures the film thickness distribution around a half cylinder with a matrix of 64 x 16 measuring points with a time resolution of 10,000 frames per second and a spatial resolution of 2 mm x 2 mm. The high resolution allows for a visualization of the dynamic liquid film as a movie animation. Principals of the dynamic behavior of the liquid film are observed. The time-averaged film thickness distributions show that the spacers structure the liquid film significantly. The gaseous phase is accelerated due to the cross-section blockage caused by the spacer. This leads to a local thinning of the liquid film downstream of the spacer. Two statistical evaluation methods are presented to determine different dynamic wave properties: The wave velocity as function of the wave height, the traveling path of the waves and the location of wave separation and merge events. The first evaluation method shows that big waves move generally faster than small waves. The analysis further shows wave acceleration in close proximity of the spacer with subsequent deceleration further downstream. Analyzing the wave as a two-dimensional entity it can be seen that the wave paths are clearly structured by the spacer and hence do not travel circumferentially around the fuel rod. Wave separation and merge has a
International Nuclear Information System (INIS)
Damsohn, M.; Prasser, H.-M.
2010-01-01
For the prediction of dryout in fuel elements of boiling water reactors, the dynamic behavior of the water film covering the fuel rod has to be understood. This paper provides high resolved experimental data of the liquid film and gives insight into the dynamic film behavior. The experiments of this work were conducted in a vertical channel representing a pair of neighboring subchannels of a BWR fuel rod bundle. Air and water at ambient pressure and temperature are used as model fluids, creating an annular flow in the test section. The influence of different functional spacer shapes on the liquid film has been studied. The heart of the instrumentation is a liquid film sensor (LFS), which measures the film thickness distribution around a half cylinder with a matrix of 64 x 16 measuring points with a time resolution of 10,000 frames per second and a spatial resolution of 2 mm x 2 mm. The high resolution allows for a visualization of the dynamic liquid film as a movie animation. Principals of the dynamic behavior of the liquid film are observed. The time-averaged film thickness distributions show that the spacers structure the liquid film significantly. The gaseous phase is accelerated due to the cross-section blockage caused by the spacer. This leads to a local thinning of the liquid film downstream of the spacer. Two statistical evaluation methods are presented to determine different dynamic wave properties: The wave velocity as function of the wave height, the traveling path of the waves and the location of wave separation and merge events. The first evaluation method shows that big waves move generally faster than small waves. The analysis further shows wave acceleration in close proximity of the spacer with subsequent deceleration further downstream. Analyzing the wave as a two-dimensional entity it can be seen that the wave paths are clearly structured by the spacer and hence do not travel circumferentially around the fuel rod. Wave separation and merge has a
DEFF Research Database (Denmark)
Hansen, Hans
This is the preliminary report on the results obtained in the Migrating Worker-project. This project was initiated by the Danish Ministry of Finance with the aim of illustrating the effects of the 1408/71 agreement and the bilateral double taxation agreements Denmark has with the countries included...
Directory of Open Access Journals (Sweden)
M. Nawaz
Full Text Available In this article, we developed a computer code of Galerikan Finite Element method (GFEM for three dimensional flow equations of nano-plasma fluid (blood in the presence of uniform applied magnetic field when Hall and ion slip current are significant. Lorentz force is calculated through generalized Ohm’s law with Maxwell equations. A series of numerical simulations are carried out to search ηmax and algebraic equations are solved by Gauss-Seidel method with simulation tolerance 10-8. Simulated results for special case have an excellent agreement with the already published results. Velocity components and temperature of the nano-plasma (blood are influenced significantly by the inclusion of nano-particles of Copper (Cu and Silver (Ag. Heat enhancement is observed when copper and silver nonmagnetic nanoparticles are used instead of simple base fluid (conventional fluid. Radiative nature of nano-plasma in the presence of magnetic field causes a decrease in the temperature due to the transfer of heat by the electromagnetic waves. In contrast to this, due to heat dissipated by Joule heating and viscous dissipation phenomena, temperature of nano-plasmaincreases as thermal radiation parameter is increased. Thermal boundary layer thickness can be controlled by using radiative fluid instead of non-radiative fluid. Momentum boundary layer thickness can be reduced by increasing the intensity of the applied magnetic field. Temperature of plasma in the presence magnetic field is higher than the plasma in the absence of magnetic field. Keywords: Nanofluid, Grid independent study, Convergence, Error analysis, Skin friction, Joule heating, Viscous dissipation, Hall and ion currents
International Nuclear Information System (INIS)
Fiumara, Alessandro; Gourdain, Nicolas; Chapin, Vincent; Senter, Julien; Bury, Yannick
2016-01-01
Highlights: • An experimental campaign including pressure measurements, oil visualizations and PIV was performed on a scale wingsail. • Unsteady RANS simulations were carried out on the wingsail scale model reproducing also the wind tunnel domain. • The geometrical slot parameters affect the circulation around the main element influencing the pressure distribution on it. - Abstract: The rigid wingsail is a propulsion system, utilized in sailing competitions in order to enhance the yacht performance in both upwind and downwind conditions. Nevertheless, this new rig is sensitive to upstream flow variations, making its steering difficult. This issue suggests the need to perform a study on wingsail aerodynamics. Thus this paper reports some investigations done to better understand the flow physics around a scaled model of an America’s Cup wingsail, based on a two-element AC72 profile. First a wind tunnel test campaign was carried out to generate a database for aerodynamic phenomena analyses and CFD validation. Unsteady RANS simulations were performed to predict and validate the flow characteristics on the wingsail, in the wind tunnel test conditions. The wind tunnel domain was fully modeled, in order to take into account the facility confinement effects. Numerical simulations in freestream and wind tunnel conditions were then compared with experimental data. This analysis shows the necessity to consider the wind tunnel walls when experimental and numerical data are compared. Numerical simulations correctly reproduce the flow field for low-to-moderate flow angles. However, discrepancies on the pressure distribution increase when the boundary layer starts to separate from the wingsail. In this regard, the flow generated by the slot between both elements of the wingsail is of paramount importance. This slot flow is analyzed in details through PIV measurements and numerical simulations. While the numerical simulation correctly predicts the jet flow itself, it only
MIGRATION – EFFECTS AND SOLUTIONS
Directory of Open Access Journals (Sweden)
Raluca Cruceru
2012-12-01
Full Text Available There are three main flows that influence workforce performance—worker migration, the dissemination of knowledge, and overseas development assistance. For the present paper we decided to deal with the analyses of these three, yet mainly migration. We considered it to be one of the most important phenomenon existent on the market at this hour and with the highest negative impact on the economic and social situation. We presented a case study regarding the situation of migration in Romania and the main candidates to Romanian intelligence imports, the main issues and possible solutions to the problems encountered.
International Nuclear Information System (INIS)
Barber, R.W.; Fonty, A.
2003-01-01
This paper describes a novel vortex element method for simulating incompressible laminar flow over a two-dimensional backward-facing step. The model employs an operator-splitting technique to compute the evolution of the vorticity field downstream of abrupt changes in flow geometry. During the advective stage of the computation, a semi-Lagrangian scheme is used to update the positions of the vortex elements, whilst an analytical diffusion algorithm employing Oseen vortices is implemented during the diffusive time step. Redistributing the vorticity analytically instead of using the more traditional random-walk method enables the numerical model to simulate steady flows directly and avoids the need to filter the results to remove the oscillations created by the random-walk procedure. Model validation has been achieved by comparing the length of the recirculating eddy behind a confined backward-facing step against data from experimental and alternative numerical investigations. In addition, results from the vortex element method are compared against predictions obtained using the commercial finite-volume computational fluid dynamics code, CFD-ACE+. The results show that the vortex element scheme marginally overpredicts the length of the downstream recirculating eddy, implying that the method may be associated with an artificial reduction in the vorticity diffusion rate. Nevertheless the results demonstrate that the proposed vortex redistribution scheme provides a practical alternative to traditional random-walk discrete vortex algorithms. (author)
Energy Technology Data Exchange (ETDEWEB)
Prothro, Lance; Drellack Jr., Sigmund; Mercadante, Jennifer
2009-01-31
Underground Test Area (UGTA) corrective action unit (CAU) groundwater flow and contaminant transport models of the Nevada Test Site (NTS) and vicinity are built upon hydrostratigraphic framework models (HFMs) that utilize the hydrostratigraphic unit (HSU) as the fundamental modeling component. The delineation and three-dimensional (3-D) modeling of HSUs within the highly complex geologic terrain that is the NTS requires a hydrostratigraphic system that is internally consistent, yet flexible enough to account for overlapping model areas, varied geologic terrain, and the development of multiple alternative HFMs. The UGTA CAU-scale hydrostratigraphic system builds on more than 50 years of geologic and hydrologic work in the NTS region. It includes 76 HSUs developed from nearly 300 stratigraphic units that span more than 570 million years of geologic time, and includes rock units as diverse as marine carbonate and siliciclastic rocks, granitic intrusives, rhyolitic lavas and ash-flow tuffs, and alluvial valley-fill deposits. The UGTA CAU-scale hydrostratigraphic system uses a geology-based approach and two-level classification scheme. The first, or lowest, level of the hydrostratigraphic system is the hydrogeologic unit (HGU). Rocks in a model area are first classified as one of ten HGUs based on the rock’s ability to transmit groundwater (i.e., nature of their porosity and permeability), which at the NTS is mainly a function of the rock’s primary lithology, type and degree of postdepositional alteration, and propensity to fracture. The second, or highest, level within the UGTA CAU-scale hydrostratigraphic system is the HSU, which is the fundamental mapping/modeling unit within UGTA CAU-scale HFMs. HSUs are 3-D bodies that are represented in the finite element mesh for the UGTA groundwater modeling process. HSUs are defined systematically by stratigraphically organizing HGUs of similar character into larger HSUs designations. The careful integration of
International Nuclear Information System (INIS)
Prothro, Lance; Drellack Jr, Sigmund; Mercadante, Jennifer
2009-01-01
Underground Test Area (UGTA) corrective action unit (CAU) groundwater flow and contaminant transport models of the Nevada Test Site (NTS) and vicinity are built upon hydrostratigraphic framework models (HFMs) that utilize the hydrostratigraphic unit (HSU) as the fundamental modeling component. The delineation and three-dimensional (3-D) modeling of HSUs within the highly complex geologic terrain that is the NTS requires a hydrostratigraphic system that is internally consistent, yet flexible enough to account for overlapping model areas, varied geologic terrain, and the development of multiple alternative HFMs. The UGTA CAU-scale hydrostratigraphic system builds on more than 50 years of geologic and hydrologic work in the NTS region. It includes 76 HSUs developed from nearly 300 stratigraphic units that span more than 570 million years of geologic time, and includes rock units as diverse as marine carbonate and siliciclastic rocks, granitic intrusives, rhyolitic lavas and ash-flow tuffs, and alluvial valley-fill deposits. The UGTA CAU-scale hydrostratigraphic system uses a geology-based approach and two-level classification scheme. The first, or lowest, level of the hydrostratigraphic system is the hydrogeologic unit (HGU). Rocks in a model area are first classified as one of ten HGUs based on the rock's ability to transmit groundwater (i.e., nature of their porosity and permeability), which at the NTS is mainly a function of the rock's primary lithology, type and degree of postdepositional alteration, and propensity to fracture. The second, or highest, level within the UGTA CAU-scale hydrostratigraphic system is the HSU, which is the fundamental mapping/modeling unit within UGTA CAU-scale HFMs. HSUs are 3-D bodies that are represented in the finite element mesh for the UGTA groundwater modeling process. HSUs are defined systematically by stratigraphically organizing HGUs of similar character into larger HSUs designations. The careful integration of stratigraphic
International Nuclear Information System (INIS)
Waheed, S.; Siddique, N.; Daud, M.
2011-01-01
Long term urban air quality of Islamabad, the capital city of Pakistan, has been investigated as a part of the joint UNDP/IAEA/RCA/RAS/7/015 project, entitled C haracterization and source identification of particulate air pollution in the Asian region (RCA) . Around 380 pairs of fine (PM2.5) and coarse (PM10-2.5) polycarbonate filters from the Nilore area were collected using GENT sampler. The average PM2.5 and PM2.5-10 masses at this site were found to be 15.02 and 37.01 g/m/sup 3/ respectively that are far below to the Pakistani limit for PM10 of 100 g/m/sup 3/. The average Black Carbon (BC) was found to be 2.58 and 1.22 g/m/sup 3/ corresponding to 20.7% and 4.54% of the fine and coarse mass respectively. The non destructive Ion Beam Analysis method, Proton induced X-ray emission (PIXE) and Proton induced gamma ray emission (PIGE) were employed to quantify more than 40 elements in both fine and coarse fractions. The acquired elemental data has been statistically treated and subjected to mass closure studies, principal component and factor analysis to calculate correlation matrices. The reconstructed mass (RCM) was calculated for both particle modes using soil, sulphate, smoke, sea salt and BC as pseudo sources. Data analysis performed using EPA-PMF3 shows that the fine and coarse data for the suburban site identifies 4 sources; biomass/ combustion, road dust, soil and automobile. Long range transport of pollutants was studied using HYSPLIT4 model. It was observed that high fine soil contributions in this area were mainly from dust storms arriving from west and North West of the country. (author)
Custer, Christine M.; Custer, T.W.
2000-01-01
Because of the potential for increased trophic transfer of contaminants by zebra mussels (Dreissena sp.) to higher trophic levels, we collected four species of waterfowl (n = 65 ducks) from four locations in Lake Erie, Lake St. Clair, and Lake Michigan, USA, between 1991 and 1993 for organochlorine contaminant and trace element analyses. Geometric mean concentrations of total polychlorinated biphenyls (PCBs) and p,pa??-dichlorodiphenyldichloroethylene (DDE) were 1.35 and 0.15 I?g/g wet weight in lesser scaup (Aythya affinis) carcasses and were below known effect levels. Total PCBs in 80% of carcasses, however, were above the U.S. Food and Drug Administration's threshold of 3.0 I?g/g lipid weight for consumption of poultry. With the exception of selenium, trace elements were also at background or no-effect levels. Selenium concentrations in livers of 95% of lesser scaup, 90% of bufflehead (Bucephala albeola), and 72% of common goldeneye (Bucephala clangula) were in the elevated (>10 I?g/g dry wt) or potentially harmful range (>33 I?g/g dry wt). The effects of these high selenium concentrations are unknown but should be investigated further based on reproductive effects observed in field and laboratory studies of dabbling ducks and because lesser scaup populations are declining. Concentrations of total PCBs in dreissenid mussels in western Lake Erie were 10 times higher than in the upper Mississippi River but were similar to concentrations in other industrialized rivers in Europe and the United States. Metal concentrations were similar to other industrialized sites where zebra mussels have been sampled.
International Nuclear Information System (INIS)
Kim, Geon Young; Hahn, Pil Soo; Kang, Moon Ja; Baik, Min Hoon; Kim, Seung
2003-12-01
The objectives of this report are overview of the chemistry and migration behavior of actinide for the HLW disposal safety assessment and to summarise the present status of actinide science and future developments. Actinides in HLW are very toxic and long-life time radionuclides. Therefore, the understanding of their characteristics and reaction behaviors in the deep subsurface environment is necessary for improving the reliability of HLW disposal safety assessment. This report presents an overview of the recent developments in the fundamental chemistry of actinides and fission products in natural aquifer systems, their interactions and migration in the geosphere, and the processes involved in modeling their geochemical behavior for the high level radioactive waste management. In addition, the thesis presented in MIGRATION '03 conference were described briefly. Actinide science in relation to the HLW disposal management can be classified into three main subjects; aquatic chemistry of actinides and fission products, migration behavior of radionuclides and geochemical and transport modeling. The radionuclides leached from waste forms are intruded into human environment along the groundwater flowing in the fracture around the waster disposal facility. To analyze and predict such radionuclide migration phenomena, the data that were obtained from well defined condition are required. Data obtained from studies on the chemical behaviors of actinide elements and fission products in the groundwater are essential in the safety assessment of HLW management. This report is intended to suggest the direction of R and D in actinide chemistry for the national program of HLW management in future
Energy Technology Data Exchange (ETDEWEB)
Kim, Geon Young; Hahn, Pil Soo; Kang, Moon Ja; Baik, Min Hoon; Kim, Seung
2003-12-15
The objectives of this report are overview of the chemistry and migration behavior of actinide for the HLW disposal safety assessment and to summarise the present status of actinide science and future developments. Actinides in HLW are very toxic and long-life time radionuclides. Therefore, the understanding of their characteristics and reaction behaviors in the deep subsurface environment is necessary for improving the reliability of HLW disposal safety assessment. This report presents an overview of the recent developments in the fundamental chemistry of actinides and fission products in natural aquifer systems, their interactions and migration in the geosphere, and the processes involved in modeling their geochemical behavior for the high level radioactive waste management. In addition, the thesis presented in MIGRATION '03 conference were described briefly. Actinide science in relation to the HLW disposal management can be classified into three main subjects; aquatic chemistry of actinides and fission products, migration behavior of radionuclides and geochemical and transport modeling. The radionuclides leached from waste forms are intruded into human environment along the groundwater flowing in the fracture around the waster disposal facility. To analyze and predict such radionuclide migration phenomena, the data that were obtained from well defined condition are required. Data obtained from studies on the chemical behaviors of actinide elements and fission products in the groundwater are essential in the safety assessment of HLW management. This report is intended to suggest the direction of R and D in actinide chemistry for the national program of HLW management in future.
Energy Technology Data Exchange (ETDEWEB)
Robert S. Dahlin; E. Carl Landham; Xiaofeng Guan [Southern Research Institute, Wilsonville, AL (United States). Power Systems Development Facility
2008-07-01
At the Power Systems Development Facility (PSDF), a variety of filter elements and failsafes are being tested for the cleanup of coal-generated syngas from the Kellogg Brown and Root (KBR) Transport Gasifier. Thus far, no evidence of corrosion or plugging has been found in the HR-160 failsafes or sinterned metal fiber elements. However, a progressive corrosion and increase in pressure drop has been noted in the iron aluminide elements. The corrosion was first detected as reddish-brown spots of iron oxide after about 2,000 to 3,000 hours of syngas exposure. As the corrosion progressed, the spots of iron oxide merged to form a continuous scale after about 5,000 to 5,500 hours of exposure. With additional exposure, a black scale containing iron sulfide also appeared, and localized areas of sulfidation and plugging were noted in element cross sections. These effects have not resulted in any significant reduction in tensile strength, but a gradual increase in the clean element pressure drop has been noted. Flow test results suggest that there is an interaction between the corroded filter surface and the dustcake that effectively increases the residual cake flow resistance and baseline pressure drop. 10 refs., 14 figs., 1 tab.
International Nuclear Information System (INIS)
Hoefer, I.
1980-12-01
For the calculation of flows in high-temperature reactors and of their temperature behavior the equations of the method of turbulent flow in the primitive form are derived for inhomogeneous regions. This system of equations is appropriate for the investigation of transient and quasi-stationary phenomena in pebble beds. By modification of the flow function in parallel arranged reflector channels a parallel flow can be simulated. For simplification the flow in region with a smaller pressure loss is assumed to be a potential flow. For the numerical solution of the time-dependent convective parts of the system of equations a number of explicit and implicit difference methods are compared. If the method using UP-WIND differences is taken to be an interpolation method the introduction of an extension becomes possible, which together with preliminary integration of the fictional terms allows to apply larger time steps. The algebraic system of equations for numerical calculation of a steady flow field also is established by formation of UP-WIND differences for the convective terms. By mathematical verification of some examples the applicability of the mathematical model for flow problems in pebble beds with forced or natural convection is shown. (orig.) [de
Menendez-Miranda, Mario; Fernandez-Arguelles, Maria T; Costa-Fernandez, Jose M; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo
2014-08-11
Separation and identification of nanoparticles of different composition, with similar particle diameter, coexisting in heterogeneous suspensions of polymer-coated CdSe/ZnS quantum dots (QDs) have been thoroughly assessed by asymmetric flow field-flow fractionation (AF4) coupled on-line to fluorescence and inductively coupled plasma mass spectrometry (ICPMS) detectors. Chemical characterization of any previously on-line separated nanosized species was achieved by the measurement of the elemental molar ratios of every element involved in the synthesis of the QDs, using inorganic standards and external calibration by flow injection analysis (FIA). Such elemental molar ratios, strongly limited so far to pure single nanoparticles suspensions, have been achieved with adequate accuracy by coupling for the first time an ICP-QQQ instrument to an AF4 system. This hyphenation turned out to be instrumental to assess the chemical composition of the different populations of nanoparticles coexisting in the relatively complex mixtures, due to its capabilities to detect the hardly detectable elements involved in the synthesis. Interestingly such information, complementary to that obtained by fluorescence, was very valuable to detect and identify unexpected nanosized species, present at significant level, produced during QDs synthesis and hardly detectable by standard approaches. Copyright © 2014. Published by Elsevier B.V.
Rill and gully erosion in upland and agricultural areas can result in significant soil degradation worldwide, and headcuts are the primary mechanism by which this landscape dissection occurs. Experiments were conducted to further examine the morphodynamic behavior of actively migrating headcuts in u...
International Nuclear Information System (INIS)
Geldermalsen, L.A. van
1985-02-01
This report presents the results of a study on the effects of temperatures up to 90 0 C on the migration of the radionuclides plutonium, neptunium and americium through marine sediments in the near field of a canister with radioactive waste. Topics entered were; (i) the influence of temperature on the distribution coefficients of the transuranics plutonium, americium and neptunium, (ii) the effect of temperature on the composition and characteristics of interstitial water and (iii) the effects of a point heat source on the temperature distributions and flow velocities in interstitial water of sediments. (Auth.)
Fussell, Elizabeth; DeWaard, Jack
2015-01-01
Changes in the human migration systems of Hurricane Katrina- and Rita-affected Gulf of Mexico coastline counties provide an example of how climate change may affect coastal populations. Crude climate change models predict a mass migration of “climate refugees,” but an emerging literature on environmental migration suggests most migration will be short-distance and short-duration within existing migration systems, with implications for the population recovery of disaster-struck places. In this research, we derive a series of hypotheses on recovery migration predicting how the migration system of hurricane-affected coastline counties in the Gulf of Mexico was likely to have changed between the pre-disaster and the recovery periods. We test these hypotheses using data from the Internal Revenue Service on annual county-level migration flows, comparing the recovery period migration system (2007–2009) to the pre-disaster period (1999–2004). By observing county-to-county ties and flows we find that recovery migration was strong, as the migration system of the disaster-affected coastline counties became more spatially concentrated while flows within it intensified and became more urbanized. Our analysis demonstrates how migration systems are likely to be affected by the more intense and frequent storms anticipated by climate change scenarios with implications for the population recovery of disaster-affected places. PMID:26084982
Curtis, Katherine J; Fussell, Elizabeth; DeWaard, Jack
2015-08-01
Changes in the human migration systems of the Gulf of Mexico coastline counties affected by Hurricanes Katrina and Rita provide an example of how climate change may affect coastal populations. Crude climate change models predict a mass migration of "climate refugees," but an emerging literature on environmental migration suggests that most migration will be short-distance and short-duration within existing migration systems, with implications for the population recovery of disaster-stricken places. In this research, we derive a series of hypotheses on recovery migration predicting how the migration system of hurricane-affected coastline counties in the Gulf of Mexico was likely to have changed between the pre-disaster and the recovery periods. We test these hypotheses using data from the Internal Revenue Service on annual county-level migration flows, comparing the recovery period migration system (2007-2009) with the pre-disaster period (1999-2004). By observing county-to-county ties and flows, we find that recovery migration was strong: the migration system of the disaster-affected coastline counties became more spatially concentrated, while flows within it intensified and became more urbanized. Our analysis demonstrates how migration systems are likely to be affected by the more intense and frequent storms anticipated by climate change scenarios, with implications for the population recovery of disaster-affected places.
International Nuclear Information System (INIS)
Klotz, D.; Lang, H.; Moser, H.
1988-01-01
The studies were mainly concerned with investigations of the sorption of radioactive Cs and C using three sandy and three cohesive samples with the help of batch and continuous-flow column tests. The results show that the sorption behaviour of Cs-134 can be described with the help of an exponential isotherm. Differences in sorption and desorption behaviour as well as the dependence of the results on the volume/mass ratios applied in the batch tests are explained in this way. Accordingly, the transportation of the Cs in continuous-column tests reveals a delay increase proportional to an increase of path length. The tests using C-14 are strongly inhibited by a rapid exchange of the applied C-14 labelled carbonate ions with the CO 2 of the supernatant gaseous phase. This notwithstanding, it could be shown that the carbonate ions are only slightly delayed, and that substantial quantities of the radioactive carbon applied are held back with the examined sediments. (orig./HP) [de
International Nuclear Information System (INIS)
Ansanay-Alex, G.
2009-01-01
The development of simulation codes aimed at a precise simulation of fires requires a precise approach of flame front phenomena by using very fine grids. The need to take different spatial scale into consideration leads to a local grid refinement and to a discretization with homogeneous grid for computing time and memory purposes. The author reports the approximation of the non-linear convection term, the scalar advection-diffusion in finite volumes, numerical simulations of a flow in a bent tube, of a three-dimensional laminar flame and of a low Mach number an-isotherm flow. Non conformal finite elements are also presented (Rannacher-Turek and Crouzeix-Raviart elements)
DEFF Research Database (Denmark)
Nielsen, Erland Hejn
2002-01-01
From time to time most real life job/flow shops will experience more or less severe buffer problems in relation to the operation at its various stations in the shop. Due to temporary non-predictable variations in the job flow intensity the assigned buffer space in front of a given critical station...... to temporary buffer overflow situations. This paper will investigate the impact of buffer overflow on several key performance measures of relevance to the overall operation of a job/flow shop facility. Several simple job/flow shop structures will be considered in this paper including re-entrant system set......-ups (a re-entrant system is a system where some of the job-routes revisit a given station more than once)....
DEFF Research Database (Denmark)
Nielsen, Erland Hejn
2002-01-01
From time to time most real life job/flow shops will experience more or less severe buffer problems in relation to the operation at its various stations in the shop. Due to temporary non-predictable variations in the job flow intensity the assigned buffer space in front of a given critical station...... to temporary buffer overflow situations. This paper will investigate the impact of buffer overflow on several key performance measures of relevance to the overall operation of a job/flow shop facility. Several simple job/flow shop structures will be considered in this paper including re-entrant system set......-ups (a re-entrant system is a system where some of the job-routes revisit a given station more than once)....
Effect of crystal orientation on grain boundary migration and radiation-induced segregation
International Nuclear Information System (INIS)
Hashimoto, N.; Eda, Y.; Takahashi, H.
1996-01-01
Fe-Cr-Ni, Ni-Al and Ni-Si alloys were electron-irradiated using a high voltage electron microscope (1 MeV), and in situ observations of the structural evolution and micro-chemical analysis were carried out. During the irradiation, the grain boundaries in the irradiated region migrated, while no grain boundary migration occurred in the unirradiated area. The occurrence of boundary migration depended on the orientation relationship of the boundary interfaces. Grain boundary migration took place in Fe-Cr-Ni and Ni-Si alloys with large crystal orientation difference between the two grains across a grain boundary. In Ni-Al, however, the grain boundary migration did not occur. The solute segregation was caused at grain boundary under irradiation and this segregation behavior was closely related to solute size, namely the concentrations of undersized Ni and oversized Cr elements in Fe-Cr-Ni alloy increased and reduced at grain boundary, respectively. The same dependence of segregation on the solute size was derived in Ni-Si and Ni-Al alloys, in which Si and Al solutes are undersized and oversized elements, respectively. Therefore, Si solute enriched and Al solute depleted at grain boundary. From the present segregation behavior, it is suggested that the flow of point defects into the boundary is the cause of grain boundary migration. (orig.)
International Nuclear Information System (INIS)
Zhang, Z.; Li, M.; Xie, Z.; Barron, R.M.
2002-01-01
In recent years, the two-fluids model in an Eulerian-Eulerian coordinate system has been the main tool for solving two-phase flow problems because of its convenient mathematical representation and its feasibility for large-scale computations. However, the assumptions of local equilibrium and continuity for the solid phase in the two-fluids model essentially mask the nonuniform and discontinuous features of the solid phase flow. This paper discusses a further study of the particle flow dynamics in two kinds of fluidized beds and a horizontal plug-flow pneumatic conveying pipe
Stark, Oded
2007-01-01
At least to some extent migration behavior is the outcome of a preference for migration. The pattern of migration as an outcome of a preference for migration depends on two key factors: imitation technology and migration feasibility. We show that these factors jointly determine the outcome of a preference for migration and we provide examples that illustrate how the prevalence and transmission of a migration-forming preference yield distinct migration patterns. In particular, the imitation of...
International Nuclear Information System (INIS)
Mathieu, Regis
1999-01-01
). The low to moderately saline (3-18 wt% NaCl) fluids with higher temperatures (200-550 deg. C), containing traces of O 2 , CH 4 and CO 2 are related to the reactors functioning and cooling with local silicification events. During the last compressional phase, the fluid paleo-circulations are mainly responsible of barren calcite crystallization (δ 13 C= 0 to -5 0/00 vs. PDB). (2) The Toarcian shales from experimental IPSN site in the Tournemire tunnel (Aveyron, France). Four mineral parageneses (calcite, calcite and framboidal pyrite, calcite and cubic pyrite, and calcite and barite) have been distinguished in fractures induced by compressional Pyrenean tectonic activities. The major- and trace-element contents, and the 87 Sr/ 86 Sr isotopic ratios (0.70847-0.70852) of the vein calcite are buffered by the surrounding shales, strongly suggesting short-distance migrations of the elements considered. Low uranium and high iron contents of the vein calcite suggest circulation of reducing fluids. However, an external origin for the carbonate fillings of the main fault, obtained with 87 Sr/ 86 Sr isotopic ratios (0.70841 and 0.70858), and of positive Eu anomalies in the REE patterns, cannot be excluded. This study shows that the competition between chemical aggressiveness of diagenetic fluids and buffering from surrounding rocks, with P-T conditions control determine or regulate the scale of element migration which has been important at Oklo and moderate at Tournemire. (author) [fr
Directory of Open Access Journals (Sweden)
Chenet P. Y.
2006-11-01
transfer, compaction and water flow, hydrocarbon generation, and two-phase migration of fluids. The model reproduces the influence of conductivity variations and of transient heat transfer on paleotemperatures. Quantitative verification of the paleotemperature reconstruction and of the kinetic model of hydrocarbon generation may be obtained from present temperatures and geochemical data. Compaction-driven flows and overpressures are described by coupling a compaction law with Darcy's law for water flow and a criterion for natural hydraulic fracturing. This formulation allows modeling of overpressures in young deltalic sequences (e. g. , the Mahakam delta, Indonesia as well as in old rift basins (e. g. , the North Sea. An adapted two-phase Darcy's law reproduces primary and secondary migration. In particular, the model helps investigate the role of overpressures and fault behavior on hydrocarbon migration and entrapment. Our results confirm that basin models contribute to the synthesis of geological, geophysical, and geochemical data consistently. By defining parameters for petroleum evaluations, these models increase exploration efficiency.
Quinquis, M. E. T.; Buiter, S. J. H.
2014-06-01
Subduction of oceanic lithosphere brings water into the Earth's upper mantle. Previous numerical studies have shown how slab dehydration and mantle hydration can impact the dynamics of a subduction system by allowing a more vigorous mantle flow and promoting localisation of deformation in the lithosphere and mantle. The depths at which dehydration reactions occur in the hydrated portions of the slab are well constrained in these models by thermodynamic calculations. However, computational models use different numerical schemes to simulate the migration of free water. We aim to show the influence of the numerical scheme of free water migration on the dynamics of the upper mantle and more specifically the mantle wedge. We investigate the following three simple migration schemes with a finite-element model: (1) element-wise vertical migration of free water, occurring independent of the flow of the solid phase; (2) an imposed vertical free water velocity; and (3) a Darcy velocity, where the free water velocity is a function of the pressure gradient caused by the difference in density between water and the surrounding rocks. In addition, the flow of the solid material field also moves the free water in the imposed vertical velocity and Darcy schemes. We first test the influence of the water migration scheme using a simple model that simulates the sinking of a cold, hydrated cylinder into a dry, warm mantle. We find that the free water migration scheme has only a limited impact on the water distribution after 1 Myr in these models. We next investigate slab dehydration and mantle hydration with a thermomechanical subduction model that includes brittle behaviour and viscous water-dependent creep flow laws. Our models demonstrate that the bound water distribution is not greatly influenced by the water migration scheme whereas the free water distribution is. We find that a bound water-dependent creep flow law results in a broader area of hydration in the mantle wedge, which
International Nuclear Information System (INIS)
Czarnecki, J.B.; Faunt, C.C.; Gable, C.W.; Zyvoloski, G.A.
1996-01-01
Development of a preliminary three-dimensional model of the saturated zone at Yucca Mountain, the potential location for a high-level nuclear waste repository, is presented. The development of the model advances the technology of interfacing: (1)complex three-dimensional hydrogeologic framework modeling; (2) fully three-dimensional, unstructured, finite-element mesh generation; and (3) groundwater flow, heat, and transport simulation. The three-dimensional hydrogeologic framework model is developed using maps, cross sections, and well data. The framework model data are used to feed an automated mesh generator, designed to discretize irregular three-dimensional solids,a nd to assign materials properties from the hydrogeologic framework model to the tetrahedral elements. The mesh generator facilitated the addition of nodes to the finite-element mesh which correspond to the exact three-dimensional position of the potentiometric surface based on water-levels from wells. A ground water flow and heat simulator is run with the resulting finite- element mesh, within a parameter-estimation program. The application of the parameter-estimation program is designed to provide optimal values of permeability and specified fluxes over the model domain to minimize the residual between observed and simulated water levels
Globalization and migration: A "unified brain drain" model
Brezis, Elise S.; Soueri, Ariel
2012-01-01
Globalization has led to a vast flow of migration of workers but also of students. The purpose of this paper is to analyze the migration of individuals encompassing decisions already at the level of education. We develop a unified brain drain model that incorporates the decisions of an individual vis - à - vis both education and migration. In the empirical part, this paper addresses international flows of migration within the EU and presents strong evidence of concentration of students in cou...
Busch, H.; Hofer, J.; Chasiotis, A.; Campos, D.
2013-01-01
Human behavior is directed by an implicit and an explicit motivational system. The intrinsic form of the implicit achievement motive has been demonstrated to predict the experience of flow. Thus, this achievement flow motive can be considered an integral component of the autotelic personality,
Theories of international labor migration: an overview.
Stahl, C W
1995-01-01
"Emigration pressures are primarily the result of increasing inequalities between countries which, in turn, are the result of factors internal to less developed countries and their relations with developed countries. Both micro (neoclassical) and macrostructural theories of migration are reviewed. It is argued that the neoclassical theory of migration is often unjustly criticized and is sufficiently robust to incorporate those structural considerations which are at the core of macrostructural theories. Moreover, the neoclassical theory, with slight modification, can incorporate the ¿new economics of migration.' The major empirical problem confronting models of international labor migration is that migration flows are constrained by immigration policy. This policy, in turn, is influenced by various special interest groups. The direction and form of migration flows is conditioned by contemporary and historical relationships between source and destination countries." excerpt
Directory of Open Access Journals (Sweden)
Shymanska Kateryna V.
2017-06-01
Full Text Available The aim of the article is to reveal the influence of geo-economic transformations on the trends in international migration of human resources as an element of the resource potential of countries and regions. The current state of geo-economic transformations is analyzed, and their influence on the processes of international migration of human resources is revealed. The relevance of analyzing international movement of human resources, not labor ones, in building the geo-economic strategy of a country or a regional grouping is justified. The connection between the international migration of human resources and the trends in development of individual countries and regions (oil exporting countries, newly industrialized countries and least developed agrarian countries is determined, the general patterns of migration flows in these countries are described. Furthermore, the topical issues in studying international migration of human resources in the context of the directions of geo-economics identified by scientists are formulated. It is determined that the regional migration policy should contribute to maximizing the benefits of migration of human resources for the development of the region and the use of immigrants in the countries of the region as an economic resource that becomes strategically important under conditions of geo-economic transformations.
MIGRATION IMPACT ON ECONOMICAL SITUATION
Directory of Open Access Journals (Sweden)
Virginia COJOCARU
2016-01-01
Full Text Available This paper presents recent trends and flows of labor migration and its impact on economic and social life. Main aim of this research sets up the influence of the migration on the European economics and its competitiveness. Methods of research are: method of comparison, analysis method, method of deduction, method of statistics, modeling method. The economic impact of migration has been intensively studied but is still often driven by ill-informed perceptions, which, in turn, can lead to public antagonism towards migration. These negative views risk jeopardising efforts to adapt migration policies to the new economic and demographic challenges facing many countries. Migration Policy looks at the evidence for how immigrants affect the economy in three main areas: The labour market, public purse and economic growth. In Europe, the scope of labour mobility greatly increased within the EU/EFTA zones following the EU enlargements of 2004, 2007 and 2014-2015. This added to labour markets’ adjustment capacity. Recent estimates suggest that as much as a quarter of the asymmetric labour market shock – that is occurring at different times and with different intensities across countries – may have been absorbed by migration within a year.
An economic analysis of migration in Mexico.
Greenwood, M J; Ladman, J R
1978-07-01
This paper analyzes internal migration in Mexico over the 1960-70 period. A model of the determinants of migration is specified and estimated for aggregated interstate migration flows. Results show that distance serves as a significant deterrent to migration, that higher destination earning levels are attractive to migrants, and that regions with high unemployment rates experience lower rates of inmigration. An unanticipated finding is that regions with higher earning levels have greater rates of outmigration. The data are disaggregated to examine separate migration relationships for each state. The results are that distance is a lesser deterrent for those migrants with more accessible alternatives, that higher earning levels reduce the deterring effects of distance, and that regions with higher earning levels have lower associated elasticities of migration. It is concluded that economic factors have played a crucial role in internal migration and thus in the changing occupational and geographic structure of the Mexican labor force.
Urbanization, Migration, Information
Directory of Open Access Journals (Sweden)
Konstantin Lidin
2016-05-01
Full Text Available In the contemporary world urbanization becomes a large-scale process. Huge flows of people migrate from poorer districts to the cities with a higher level of consumption. It takes migrants about 15-25 years to give up their traditional ascetic way of life. In this period the ‘new citizens’ try to arrange compact settlements with an archaic way of life, insanitary conditions, high criminogenity and an authoritative local self-government. The processes of formation and decay of the ascetic enclave are viewed through the example of the ‘Shanghai’ trading neighborhood in Irkutsk.
National Research Council Canada - National Science Library
Russell, Thomas
2000-01-01
New, improved computational methods for modeling of groundwater flow and transport have been formulated and implemented, with the intention of incorporating them as user options into the DoD Ground...
Energy Technology Data Exchange (ETDEWEB)
Solodov, V G [Kharkov State Automobile and Highway Technical University, Theoretical Mechanics and Hydraulics Department, Kharkov (Ukraine)
1998-12-31
The article describes numerical models and some results of numerical simulation of self-excited oscillatory flow regimes through exhaust diffusers of large steam turbines, operating as a part of compartment (jointly with last stage). The modelling is based on a model of ideal gas flow and full nonstationary 3D formulation and 2nd time and space order explicit Godunov`s scheme. (author) 11 refs.
Energy Technology Data Exchange (ETDEWEB)
Solodov, V.G. [Kharkov State Automobile and Highway Technical University, Theoretical Mechanics and Hydraulics Department, Kharkov (Ukraine)
1997-12-31
The article describes numerical models and some results of numerical simulation of self-excited oscillatory flow regimes through exhaust diffusers of large steam turbines, operating as a part of compartment (jointly with last stage). The modelling is based on a model of ideal gas flow and full nonstationary 3D formulation and 2nd time and space order explicit Godunov`s scheme. (author) 11 refs.
International Nuclear Information System (INIS)
Davis, C.D.
1981-01-01
This work examines a single flat fuel plate bounded by two channels and determines static plate deflections, resultant forces and bending stresses due to pressure differential and hydrodynamic loadings. The classical then reactangular plate equations are used to model the fuel plate. These equations contain as an input the hydrodynamic loading function for modeling the fluid-structural interaction. Two models of the channel flow are developed. One assumes the accelerating potential core flow is laminar with developing two-dimensional laminar boundary layers being formed on the channel walls. The Schlichting entry length solution for developing laminar flow is found to be valid the entire length of the channel. The second model assumes the core flow is fully-developed turbulent the entire length of the channel. Hydrodynamic loading functions are developed for both flow models containing parameters for fluid density, fluid velocity, Reynolds number and channel and plate dimensions. Hence the effects of each parameter can be examined independently. A criterion is developed for predicting ETR fuel plate collapse at high channel flow velocities, 1067 cm/s (420 in/sec) (R/sub e/ = 60,000). The criterion predicts that in order to prevent ETR plate collapse the inlet velocities between channels must not differ by more than 2%
Johannesson, K. H.; Tang, J.
2003-12-01
Groundwater samples were collected in two different types of aquifer (i.e., Carrizo Sand Aquifer, Texas and Upper Floridan carbonate Aquifer, west-central Florida) to study the concentrations, fractionation, and speciation of rare earth elements (REE) along groundwater flow paths in each aquifer. Major solutes and dissolved organic carbon (DOC) were also measured in these groundwaters. The Carrizo Sand aquifer was sampled in October 2002 and June 2003, whereas, to date, we have only sampled the Floridan once (i.e., June 2003). The data reveal no significant seasonal differences in major solute and REE concentrations for the Carrizo. In Carrizo sand aquifer, groundwaters from relatively shallow wells (i.e., less than 167 m) in the recharge zone are chiefly Ca-Na-HCO3-Cl type waters. With flow down-gradient the groundwaters shift composition to the Na-HCO3 waters. pH and alkalinity initially decrease with flow away from the recharge zone before increasing again down-gradient. DOC is generally low (0.65 mg/L) along the flow path. REE concentrations are highest in groundwaters from the recharge zone (Nd 40.5 pmol/kg), and decrease substantially with flow down-gradient reaching relatively low and stable values (Nd 4.1-8.6 pmol/kg) roughly 10 km from the recharge zone. Generally, Carrizo groundwaters exhibit HREE-enriched shale-normalized patterns. The HREE enrichments are especially strong for waters from the recharge zone [(Yb/Nd)SN =1.7-5.6], whereas down-gradient (deep) groundwaters have flatter patterns [(Yb/Nd)SN =0.7-2.5]. All groundwaters have slightly positive Eu anomalies (Eu/Eu* 0.09-0.14) and negative Ce anomalies (Ce/Ce* -0.85 - -0.07). In the Upper Floridan Aquifer, Ca, Mg, SO4, and Cl concentrations generally increase along groundwater flow path, whereas pH and alkalinity generally decrease. DOC is higher (0.64 - 2.29 mg/L) than in the Carrizo and initially increases along the flow path and then decreases down-gradient. LREE (Nd) concentrations generally
Directory of Open Access Journals (Sweden)
Schwarz, C.
2004-06-01
Full Text Available Ringing of birds unveiled many aspects of avian migration and dispersal movements. However, there is even much more to be explored by the use of ringing and other marks. Dispersal is crucial in understanding the initial phase of migration in migrating birds as it is to understand patterns and processes of distribution and gene flow. So far, the analysis of migration was largely based on analysing spatial and temporal patters of recoveries of ringed birds. However, there are considerable biases and pitfalls in using recoveries due to spatial and temporal variation in reporting probabilities. Novel methods are required for future studies separating the confounding effects of spatial and temporal heterogeneity of recovery data and heterogeneity of the landscape as well. These novel approaches should aim a more intensive and novel use of the existing recovery data by taking advantage of, for instance, dynamic and multistate modeling, should elaborate schemes for future studies, and should also include other marks that allow a more rapid data collection, like telemetry, geolocation and global positioning systems, and chemical and molecular markers. The latter appear to be very useful in the delineating origin of birds and connectivity between breeding and non–breeding grounds. Many studies of migration are purely descriptive. However, King and Brooks (King & Brooks, 2004 examine if movement patterns of dolphins change after the introduction of a gillnet ban. Bayesian methods are an interesting approach to this problem as they provide a meaningful measure of the probability that such a change occurred rather than simple yes/no response that is often the result of classical statistical methods. However, the key difficulty of a general implementation of Bayesian methods is the complexity of the modelling —there is no general userfriendly package that is easily accessible to most scientists. Drake and Alisauskas (Drake & Alisauskas, 2004 examine the
Managing International Labour Migration in ASEAN | IDRC ...
International Development Research Centre (IDRC) Digital Library (Canada)
... of managing labour migration flows are varied, however, and in many cases uncoordinated. ... Indonesia, Malaysia, Singapore and Thailand to undertake joint research on ... IDRC invites applications for the IDRC Research Awards 2019.
Thieulot, Cedric
2016-04-01
Many Finite Element geodynamical codes (Fullsack,1995; Zhong et al., 2000; Thieulot, 2011) are based on bi/tri-linear velocity constant pressure element (commonly called Q1P0), because of its ease of programming and rather low memory footprint, despite the presence of (pressure) checkerboard modes. However, it is long known that the Q1P0 is not inf-sup stable and does not lend itself to the use of iterative solvers, which makes it a less than ideal candidate for high resolution 3D models. Other attempts were made more recently (Burstedde et al., 2013; Le Pourhiet et al., 2012) with the use of the stabilised Q1Q1 element (bi/tri-linear velocity and pressure). This element, while also attractive from an implementation and memory standpoint, suffers a major drawback due to the artificial compressibility introduced by the polynomial projection stabilization. These observations have shifted part of the community towards the Finite Difference Method while the remaining part is now embracing infsup stable second order elements [May et al., 2015; Kronbichler,2012). Rather surprinsingly, a third option exists when it comes to first order elements in the form of the stabilised Q1P0 element, but virtually no literature exists concerning its use for geodynamical applications. I will then recall the specificity of the stabilisation and will carry out a series of benchmark experiments and geodynamical tests to assess its performance. While being shown to work as expected in benchmark experiments, the stabilised Q1P0 element turns out to introduce first-order numerical artefacts in the velocity and pressure solutions in the case of buoyancy-driven flows. Burstedde, C., Stadler, G., Alisic, L., Wilcox, L. C., Tan, E., Gurnis, M., & Ghattas, O. (2013). Largescale adaptive mantle convection simulation. Geophysical Journal International, 192(3), 889906. Fullsack, P. (1995). An arbitrary LagrangianEulerian formulation for creeping flows and its application in
International Nuclear Information System (INIS)
Vidal, Guilherme A.M.; Vieira, Tiago A.S.; Castro, Higor F.P.
2017-01-01
With the advancement and development of computational tools, the studies of thermofluidodynamic behavior in nuclear fuel elements have been developed in recent years. Of the devices present in these elements, the spacing grids received more attention. They have kept the fuel rods equally spaced and have fins that aim to improve the heat transfer process between the water and the fuel element. Therefore, the grids present an important structural and thermal function. This work was carried out with the purpose of verifying and validating simulations of spacer grids using OpenFOAM (2017) software of Computational Fluid Dynamics (CFD). The simulations were validated using results obtained through the commercial CFD program, Ansys CFX, and experiments available in the literature and obtained in test sections assembled on the Water-Air Circuit (CCA) of the CDTN thermo-hydraulic laboratory
Lagrangian finite element method for 3D time-dependent non-isothermal flow of K-BKZ fluids
DEFF Research Database (Denmark)
Román Marín, José Manuel; Rasmussen, Henrik K.
2009-01-01
equation is replaced with a temperature dependent pseudo time. The spatial coordinate system attached to the particles is discretized by 10-node quadratic tetrahedral elements using Cartesian coordinates. The temperature and the pressure are discretized by 10-node quadratic and linear interpolation...... utilizing an implicit variable step backwards differencing (BDF2) scheme, obtaining second order convergence of the temperature in time. A quadratic interpolation in time is applied to approximate the time integral in the K-BKZ equation. This type of scheme ensures third order accuracy with respect......, respectively, in the tetrahedral particle elements. The spatial discretization of the governing equations follows a mixed Galerkin finite element method. This type of scheme ensures third order accuracy with respect to the discretization of spatial dimension. The temperature equation is solved in time...
International Nuclear Information System (INIS)
Pot, G.; Laurence, D.; Rharif, N.E.; Leal de Sousa, L.; Compe, C.
1995-12-01
This paper deals with the introduction of a second moment closure turbulence model (Reynolds Stress Model) in an industrial finite element code, N3S, developed at Electricite de France.The numerical implementation of the model in N3S will be detailed in 2D and 3D. Some details are given concerning finite element computations and solvers. Then, some results will be given, including a comparison between standard k-ε model, R.S.M. model and experimental data for some test case. (authors). 22 refs., 3 figs
Colbourne, A. A.; Blythe, T. W.; Barua, R.; Lovett, S.; Mitchell, J.; Sederman, A. J.; Gladden, L. F.
2018-01-01
Nuclear magnetic resonance rheology (Rheo-NMR) is a valuable tool for studying the transport of suspended non-colloidal particles, important in many commercial processes. The Rheo-NMR imaging technique directly and quantitatively measures fluid displacement as a function of radial position. However, the high field magnets typically used in these experiments are unsuitable for the industrial environment and significantly hinder the measurement of shear stress. We introduce a low field Rheo-NMR instrument (1 H resonance frequency of 10.7MHz), which is portable and suitable as a process monitoring tool. This system is applied to the measurement of steady-state velocity profiles of a Newtonian carrier fluid suspending neutrally-buoyant non-colloidal particles at a range of concentrations. The large particle size (diameter > 200 μm) in the system studied requires a wide-gap Couette geometry and the local rheology was expected to be controlled by shear-induced particle migration. The low-field results are validated against high field Rheo-NMR measurements of consistent samples at matched shear rates. Additionally, it is demonstrated that existing models for particle migration fail to adequately describe the solid volume fractions measured in these systems, highlighting the need for improvement. The low field implementation of Rheo-NMR is complementary to shear stress rheology, such that the two techniques could be combined in a single instrument.
[Migration mobility and movement of the population].
Zaslavska, T; Ribakovski, L
1983-01-01
"The functions of migration are reviewed from the viewpoint of the demographic situation in the USSR (by regions, sex, age, education, profession, labour and social activity, nationality, rural-urban, etc.). Some effects of migration on fertility are shown. The authors investigate the role of the economic functions of migration for the process of professional mobility. The territorial mobility of the population is analysed on a wider scale as a part of the social mobility in the socialist society. In connection with this, some problems of the migration policy as an element of the demographic policy of the USSR are outlined." (summary in ENG, RUS) excerpt
Bubble dynamics in microchannels: inertial and capillary migration forces
Rivero-Rodriguez, Javier; Scheid, Benoit
2018-05-01
This work focuses on the dynamics of a train of unconfined bubbles flowing in microchan- nels. We investigate the transverse position of a train of bubbles, its velocity and the associated pressure drop when flowing in a microchannel depending on the internal forces due to viscosity, inertia and capillarity. Despite the small scales of the system, inertia, referred to as inertial migration force, play a crucial role in determining the transverse equilibrium position of the bubbles. Beside inertia and viscosity, other effects may also affect the transverse migration of bubbles such as the Marangoni surface stresses and the surface deformability. We look at the influence of surfactants in the limit of infinite Marangoni effect which yields rigid bubble interface. The resulting migration force may balance external body forces if present such as buoyancy, Dean or magnetic ones. This balance not only determines the transverse position of the bubbles but, consequently, the surrounding flow structure, which can be determinant for any mass/heat transfer process involved. Finally, we look at the influence of the bubble deformation on the equilibrium position and compare it to the inertial migration force at the centred position, explaining the stable or unstable character of this position accordingly. A systematic study of the influence of the parameters - such as the bubble size, uniform body force, Reynolds and capillary numbers - has been carried out using numerical simulations based on the Finite Element Method, solving the full steady Navier-Stokes equations and its asymptotic counterpart for the limits of small Reynolds and/or capillary numbers.
Energy Technology Data Exchange (ETDEWEB)
Ashwal, L.D.; Morgan, P.; Kelley, S.A.; Percival, J.A.
1987-10-01
We have measured concentrations of heat producing elements (Th, U, and K) in 58 samples representative of the main lithologies in a 100 km transect of the Superior Province of the Canadian Shield, from the Michipicoten (Wawa) greenstone belt, near Wawa, Ontario, through a domal gneiss terrane of amphibolite grade, to the granulite belt of the Kapuskasing Structural Zone, near Foleyet. (orig./SHOE).
Thomson, S.L.; Tack, J.W.; Verkerke, Gijsbertus Jacob
2007-01-01
A computational model for exploring the design of a voice-producing voice prosthesis, or voice-producing element (VPE), is presented. The VPE is intended for use by laryngectomized patients who cannot benefit from current speech rehabilitation techniques. Previous experiments have focused on the
Assessment of fluid-to-fluid modelling of critical heat flux in horizontal 37-element bundle flows
International Nuclear Information System (INIS)
Yang, S.K.
2006-01-01
Fluid-to-fluid modelling laws of critical heat flux (CHF) available in the literature were reviewed. The applicability of the fluid-to-fluid modelling laws was assessed using available data ranging from low to high mass fluxes in horizontal 37-element bundles simulating a CANDU fuel string. Correlations consisting of dimensionless similarity groups were derived using modelling fluid data (Freon-12) to predict water CHF data in horizontal 37-element bundles with uniform and non-uniform axial-heat flux distribution (AFD). The results showed that at mass fluxes higher than ∼4,000 kg/m 2 s (water equivalent value), the vertical fluid-to-fluid modelling laws of Ahmad (1973) and Katto (1979) predict water CHF in horizontal 37-element bundles with non-uniform AFD with average errors of 1.4% and 3.0% and RMS errors of 5.9% and 6.1%, respectively. The Francois and Berthoud (2003) fluid-to-fluid modelling law predicts CHF in non-uniformly heated 37-element bundles in the horizontal orientation with an average error of 0.6% and an RMS error of 10.4% over the available range of 2,000 to 6,200 kg/m 2 s. (author)
Energy Technology Data Exchange (ETDEWEB)
Zhou, Jing [Idaho National Lab. (INL), Idaho Falls, ID (United States); Huang, Hai [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mattson, Earl [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wang, Herb F. [Univ. of Wisconsin, Madison, WI (United States); Haimson, Bezalel C. [Univ. of Wisconsin, Madison, WI (United States); Doe, Thomas W. [Golder Associates Inc., Redmond, VA (United States); Oldenburg, Curtis M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Dobson, Patrick F. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2017-02-01
Aimed at supporting the design of hydraulic fracturing experiments at the kISMET site, ~1500 m below ground in a deep mine, we performed pre-experimental hydraulic fracturing simulations in order to estimate the breakdown pressure, propagation pressure, fracture geometry, and the magnitude of induced seismicity using a newly developed fully coupled three-dimensional (3D) network flow and quasi-static discrete element model (DEM). The quasi-static DEM model, which is constructed by Delaunay tessellation of the rock volume, considers rock fabric heterogeneities by using the “disordered” DEM mesh and adding random perturbations to the stiffness and tensile/shear strengths of individual DEM elements and the elastic beams between them. A conjugate 3D flow network based on the DEM lattice is constructed to calculate the fluid flow in both the fracture and porous matrix. One distinctive advantage of the model is that fracturing is naturally described by the breakage of elastic beams between DEM elements. It is also extremely convenient to introduce mechanical anisotropy into the model by simply assigning orientation-dependent tensile/shear strengths to the elastic beams. In this paper, the 3D hydraulic fracturing model was verified against the analytic solution for a penny-shaped crack model. We applied the model to simulate fracture propagation from a vertical open borehole based on initial estimates of rock mechanical properties and in-situ stress conditions. The breakdown pressure and propagation pressure are directly obtained from the simulation. In addition, the released elastic strain energies of individual fracturing events were calculated and used as a conservative estimate for the magnitudes of the potential induced seismic activities associated with fracturing. The comparisons between model predictions and experimental results are still ongoing.
Energy Technology Data Exchange (ETDEWEB)
Kobler, Johannes, E-mail: johannes.kobler@umweltbundesamt.a [Umweltbundesamt, Spittelauer Laende 5, 1090 Vienna (Austria); Fitz, Walter J.; Dirnboeck, Thomas; Mirtl, Michael [Umweltbundesamt, Spittelauer Laende 5, 1090 Vienna (Austria)
2010-03-15
Anthropogenic trace element emissions have declined. However, top soils all over the world remain enriched in trace elements. We investigated Pb and Cd migration in forest soils of a remote monitoring site in the Austrian limestone Alps between 1992 and 2004. Large spatial variability masked temporal changes in the mineral soil of Lithic Leptosols (Skeltic), whereas a significant reduction of Pb concentrations in their forest floors occurred. Reductions of concentrations in the less heterogeneous Cambisols (Chromic) were significant. In contrast, virtually no migration of Pb and Cd were found in Stagnosols due to their impeded drainage. Very low element concentrations (<1 mug l{sup -1}) in field-collected soil solutions using tension lysimeters (0.2 mum nylon filters) imply that migration largely occurred by preferential flow as particulate-bound species during intensive rainfall events. Our results indicate that the extent of Pb and Cd migration in soils is largely influenced by soil type. - Comparison between soil solid phase and soil solution concentrations imply that trace element migration largely occurred by preferential flow as particulate-bound species.
Directory of Open Access Journals (Sweden)
Reddy G.J.
2017-02-01
Full Text Available An unsteady magnetohydromagnetic natural convection on the Couette flow of electrically conducting water at 4°C (Pr = 11.40 in a rotating system has been considered. A Finite Element Method (FEM was employed to find the numerical solutions of the dimensionless governing coupled boundary layer partial differential equations. The primary velocity, secondary velocity and temperature of water at 4°C as well as shear stresses and rate of heat transfer have been obtained for both ramped temperature and isothermal plates. The results are independent of the mesh (grid size and the present numerical solutions through the Finite Element Method (FEM are in good agreement with the existing analytical solutions by the Laplace Transform Technique (LTT. These are shown in tabular and graphical forms.
Globalization of international migration: Social challenges and policy implication
Directory of Open Access Journals (Sweden)
I A Aleshkovski
2017-12-01
Full Text Available In the second half of the XX century, the humankind witnessed the insurmountable and irreversible power of globalization processes, which influence all spheres of social life and establish a global system of interdependency between countries and nations. Globalization within impetuous changes in global political, social and economic systems has determined dramatic shifts in the international migration processes that lead to the new stage of migration history. In nowadays globalized world, international migration has become a reality for almost all corners of the globe. The author considers features of the recent trends of international migration: the unprecedented growth of the international migration flows; the widening geography of international migration that involves nearly all countries of the world; qualitative changes in the structure of international migration flows; the key role of economic migration; the permanent growth and structural intricateness of irregular migration; the increasing scale and geographical widening of forced migration; the growing importance of international migration for the demographic development of the world, countries of both origin and destination. All these trends combined prove that the international migration patterns have become more complex. The author analyzes the legal framework of the international migration processes, and gives recommendations on the ways to improve the control and regulation of migration processes. Specific issues related to the social challenges of international migration are also discussed in the article.
Erdbrink, C.D.; Krzhizhanovskaya, V.V.; Sloot, P.M.A.; Klijn, F.; Schweckendiek, T.
2012-01-01
Operation of flood barrier gates is sometimes hampered by flow-induced vibrations. Although the physics is understood for specific gate types, it remains challenging to judge dynamic gate behaviour for unanticipated conditions. This paper presents a hybrid modelling system for predicting vibrations
Czech Academy of Sciences Publication Activity Database
Barczi, T.; Trávníčková, Tereza; Havlica, Jaromír; Kohout, M.
2015-01-01
Roč. 38, č. 7 (2015), s. 1195-1202 ISSN 0930-7516 R&D Projects: GA ČR(CZ) GAP105/12/0664 Institutional support: RVO:67985858 Keywords : granular mixing * DEM * flow patterns Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.385, year: 2015
Nakagawa, Hiroko; Yuno, Tomoji; Itho, Kiichi
2009-03-01
Recently, specific detection method for Bacteria, by flow cytometry method using nucleic acid staining, was developed as a function of automated urine formed elements analyzer for routine urine testing. Here, we performed a basic study on this bacteria analysis method. In addition, we also have a comparison among urine sediment analysis, urine Gram staining and urine quantitative cultivation, the conventional methods performed up to now. As a result, the bacteria analysis with flow cytometry method that uses nucleic acid staining was excellent in reproducibility, and higher sensitivity compared with microscopic urinary sediment analysis. Based on the ROC curve analysis, which settled urine culture method as standard, cut-off level of 120/microL was defined and its sensitivity = 85.7%, specificity = 88.2%. In the analysis of scattergram, accompanied with urine culture method, among 90% of rod positive samples, 80% of dots were appeared in the area of 30 degrees from axis X. In addition, one case even indicated that analysis of bacteria by flow cytometry and scattergram of time series analysis might be helpful to trace the progress of causative bacteria therefore the information supposed to be clinically significant. Reporting bacteria information with nucleic acid staining flow cytometry method is expected to contribute to a rapid diagnostics and treatment of urinary tract infections. Besides, the contribution to screening examination of microbiology and clinical chemistry, will deliver a more efficient solution to urine analysis.
Globalisation and international migration in Asia.
Hugo, G
1998-03-01
"The present paper attempts to summarise the major contemporary trends in international migration in Asia and how this is related to the rapid demographic transition occurring across most of the region. The diversity of types of mobility is one of the striking features of Asian international migration and developments in each major type [are] discussed in the paper. It is then argued that there are elements within the Asian migration system that give it a momentum which to some extent operates outside of the influence of economic and political trends. Finally some emerging issues in Asian international migration are briefly addressed. These include the scale and effects of remittances, the feminisation of migration, undocumented migration, increasing government involvement and brain drain issues." (EXCERPT)
DEFF Research Database (Denmark)
Christensen, Max la Cour; Villa, Umberto; Engsig-Karup, Allan Peter
2017-01-01
associated with non-planar interfaces between agglomerates, the coarse velocity space has guaranteed approximation properties. The employed AMGe technique provides coarse spaces with desirable local mass conservation and stability properties analogous to the original pair of Raviart-Thomas and piecewise......We study the application of a finite element numerical upscaling technique to the incompressible two-phase porous media total velocity formulation. Specifically, an element agglomeration based Algebraic Multigrid (AMGe) technique with improved approximation proper ties [37] is used, for the first...... discontinuous polynomial spaces, resulting in strong mass conservation for the upscaled systems. Due to the guaranteed approximation properties and the generic nature of the AMGe method, recursive multilevel upscaling is automatically obtained. Furthermore, this technique works for both structured...