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Статті в журналах з теми "Transferts advectifs"
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Genuchten, Martinus Th van, Feike J. Leij, Todd H. Skaggs, Nobuo Toride, Scott A. Bradford, and Elizabeth M. Pontedeiro. "Exact Analytical Solutions for Contaminant Transport in Rivers." Journal of Hydrology and Hydromechanics 61, no. 3 (2013): 250–59. http://dx.doi.org/10.2478/johh-2013-0032.
Повний текст джерелаАнотація:
Abstract Contaminant transport processes in streams, rivers, and other surface water bodies can be analyzed or predicted using the advection-dispersion equation and related transport models. In part 1 of this two-part series we presented a large number of one- and multi-dimensional analytical solutions of the standard equilibrium advection-dispersion equation (ADE) with and without terms accounting for zero-order production and first-order decay. The solutions are extended in the current part 2 to advective-dispersive transport with simultaneous first-order mass exchange between the stream or river and zones with dead water (transient storage models), and to problems involving longitudinal advectivedispersive transport with simultaneous diffusion in fluvial sediments or near-stream subsurface regions comprising a hyporheic zone. Part 2 also provides solutions for one-dimensional advective-dispersive transport of contaminants subject to consecutive decay chain reactions.
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Genuchten, Martinus Th van, Feike J. Leij, Todd H. Skaggs, Nobuo Toride, Scott A. Bradford, and Elizabeth M. Pontedeiro. "Exact analytical solutions for contaminant transport in rivers 1. The equilibrium advection-dispersion equation." Journal of Hydrology and Hydromechanics 61, no. 2 (2013): 146–60. http://dx.doi.org/10.2478/johh-2013-0020.
Повний текст джерелаАнотація:
Abstract Analytical solutions of the advection-dispersion equation and related models are indispensable for predicting or analyzing contaminant transport processes in streams and rivers, as well as in other surface water bodies. Many useful analytical solutions originated in disciplines other than surface-water hydrology, are scattered across the literature, and not always well known. In this two-part series we provide a discussion of the advection-dispersion equation and related models for predicting concentration distributions as a function of time and distance, and compile in one place a large number of analytical solutions. In the current part 1 we present a series of one- and multi-dimensional solutions of the standard equilibrium advection-dispersion equation with and without terms accounting for zero-order production and first-order decay. The solutions may prove useful for simplified analyses of contaminant transport in surface water, and for mathematical verification of more comprehensive numerical transport models. Part 2 provides solutions for advective- dispersive transport with mass exchange into dead zones, diffusion in hyporheic zones, and consecutive decay chain reactions.
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Peyrillé, Philippe, and Jean-Philippe Lafore. "An Idealized Two-Dimensional Framework to Study the West African Monsoon. Part II: Large-Scale Advection and the Diurnal Cycle." Journal of the Atmospheric Sciences 64, no. 8 (2007): 2783–803. http://dx.doi.org/10.1175/jas4052.1.
Повний текст джерелаАнотація:
The idealized 2D model developed in Part I of this study is used to study the West African monsoon sensitivity to large-scale forcing. Using ECWMF reanalyses, a large-scale forcing is introduced in the 2D model in terms of temperature and humidity advection. A coherent structure of cooling–moistening near the surface and drying–warming in the 2–4-km layer is found in the Saharan heat low region. The effect of the advective forcing is to block the monsoon propagation by strengthening the northerly flux and by an increase of convective inhibition. The heat low thus appears to play a key role in the monsoon northward penetration through its temperature and humidity budget. Ultimately, warmer low levels and/or more moist midlevels in the heat low favor a more northerly position of the ITCZ. A detailed view of the continental diurnal cycle is also presented. Potential temperature and humidity budgets are performed in the deep convective and heat low area. The moistening process to sustain deep convection is made through nocturnal advection at low levels and daytime turbulence that redistributes humidity vertically. The same mechanism occurs in the heat low except that the vertical transfers by turbulence help maintain the dryness of the low levels. A possible mechanism of interaction between the deep convective zone and the Saharan heat low is also proposed that involves gravity waves in the upper troposphere.
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Aderogba, Adebayo Abiodun, and Appanah Rao Appadu. "Classical and Multisymplectic Schemes for Linearized KdV Equation: Numerical Results and Dispersion Analysis." Fluids 6, no. 6 (2021): 214. http://dx.doi.org/10.3390/fluids6060214.
Повний текст джерелаАнотація:
We construct three finite difference methods to solve a linearized Korteweg–de-Vries (KdV) equation with advective and dispersive terms and specified initial and boundary conditions. Two numerical experiments are considered; case 1 is when the coefficient of advection is greater than the coefficient of dispersion, while case 2 is when the coefficient of dispersion is greater than the coefficient of advection. The three finite difference methods constructed include classical, multisymplectic and a modified explicit scheme. We obtain the stability region and study the consistency and dispersion properties of the various finite difference methods for the two cases. This is one of the rare papers that analyse dispersive properties of methods for dispersive partial differential equations. The performance of the schemes are gauged over short and long propagation times. Absolute and relative errors are computed at a given time at the spatial nodes used.
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Sun, Yubiao, Amitesh S. Jayaraman, and Gregory S. Chirikjian. "Approximate solutions of the advection–diffusion equation for spatially variable flows." Physics of Fluids 34, no. 3 (2022): 033318. http://dx.doi.org/10.1063/5.0084789.
Повний текст джерелаАнотація:
The advection–diffusion equation (ADE) describes many important processes in hydrogeology, mechanics, geology, and biology. The equations model the transport of a passive scalar quantity in a flow. In this paper, we have developed a new approach to solve incompressible advection–diffusion equations (ADEs) with variable convective terms, which are essential to study species transport in various flow scenarios. We first reinterpret advection diffusion equations on a microscopic level and obtain stochastic differential equations governing the behavior of individual particles of the species transported by the flow. Then, simplified versions of ADEs are derived to approximate the original ADEs governing concentration evolution of species. The approximation is effectively a linearization of the spatially varying coefficient of the advective term. These simplified equations are solved analytically using the Fourier transform. We have validated this new method by comparing our results to solutions obtained from the canonical stochastic sampling method and the finite element method. This mesh-free algorithm achieves comparable accuracy to the results from discrete stochastic simulation of spatially resolved species transport in a Lagrangian frame of reference. The good consistency shows that our proposed method is efficient in simulating chemical transport in a convective flow. The proposed method is computationally efficient and quantitatively reliable, providing an alternative technique to investigate various advection–diffusion processes.
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Dritschel, David G., and Maarten H. P. Ambaum. "The Diabatic Contour Advective Semi-Lagrangian Model." Monthly Weather Review 134, no. 9 (2006): 2503–14. http://dx.doi.org/10.1175/mwr3202.1.
Повний текст джерелаАнотація:
Abstract This article describes a novel algorithmic development extending the contour advective semi-Lagrangian model to include nonconservative effects. The Lagrangian contour representation of finescale tracer fields, such as potential vorticity, allows for conservative, nondiffusive treatment of sharp gradients allowing very high numerical Reynolds numbers. It has been widely employed in accurate geostrophic turbulence and tracer advection simulations. In the present, diabatic version of the model the constraint of conservative dynamics is overcome by including a parallel Eulerian field that absorbs the nonconservative (diabatic) tendencies. The diabatic buildup in this Eulerian field is limited through regular, controlled transfers of this field to the contour representation. This transfer is done with a fast newly developed contouring algorithm. This model has been implemented for several idealized geometries. In this paper a single-layer doubly periodic geometry is used to demonstrate the validity of the model. The present model converges faster than the analogous semi-Lagrangian models at increased resolutions. At the same nominal spatial resolution the new model is 40 times faster than the analogous semi-Lagrangian model. Results of an orographically forced idealized storm track show nontrivial dependency of storm-track statistics on resolution and on the numerical model employed. If this result is more generally applicable, this may have important consequences for future high-resolution climate modeling.
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Surfleet, Christopher, and Justin Louen. "The Influence of Hyporheic Exchange on Water Temperatures in a Headwater Stream." Water 10, no. 11 (2018): 1615. http://dx.doi.org/10.3390/w10111615.
Повний текст джерелаАнотація:
A headwater stream in coastal California was used to evaluate the temperature response of effective shade reduction. Spatial distribution of stream water temperatures for summer low-flow conditions (<0.006 m3 s−1) were highly correlated with net radiation and advective heat transfers from hyporheic exchange and subsequent streambed conduction. Using a heat budget model, mean maximum stream water temperatures were predicted to increase by 1.7 to 2.2 °C for 50% and 0% effective shade scenarios, respectively, at the downstream end of a 300 m treatment reach. Effects on mean maximum stream water temperature changes, as water flowed downstream through a 500 m shaded reach below the treatment reach, were reduced by 52 to 30% from the expected maximum temperature increases under the 50% and 0% effective shade scenarios, respectively. Maximum stream water temperature change predicted by net radiation heating alone was greater than measured and heat-budget-estimated temperatures. When the influence of hyporheic water exchange was combined with net radiation predictions, predicted temperatures were similar to measured and heat-budget-predicted temperatures. Results indicate that advective heat transfers associated with hyporheic exchange can promote downstream cooling following stream water temperature increases from shade reduction in a headwater stream with cascade, step-pool, and large woody debris forced-pool morphology.
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Lumpkin, Rick, and Kevin Speer. "Global Ocean Meridional Overturning." Journal of Physical Oceanography 37, no. 10 (2007): 2550–62. http://dx.doi.org/10.1175/jpo3130.1.
Повний текст джерелаАнотація:
Abstract A decade-mean global ocean circulation is estimated using inverse techniques, incorporating air–sea fluxes of heat and freshwater, recent hydrographic sections, and direct current measurements. This information is used to determine mass, heat, freshwater, and other chemical transports, and to constrain boundary currents and dense overflows. The 18 boxes defined by these sections are divided into 45 isopycnal (neutral density) layers. Diapycnal transfers within the boxes are allowed, representing advective fluxes and mixing processes. Air–sea fluxes at the surface produce transfers between outcropping layers. The model obtains a global overturning circulation consistent with the various observations, revealing two global-scale meridional circulation cells: an upper cell, with sinking in the Arctic and subarctic regions and upwelling in the Southern Ocean, and a lower cell, with sinking around the Antarctic continent and abyssal upwelling mainly below the crests of the major bathymetric ridges.
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Ménesguen, C., S. Le Gentil, P. Marchesiello, and N. Ducousso. "Destabilization of an Oceanic Meddy-Like Vortex: Energy Transfers and Significance of Numerical Settings." Journal of Physical Oceanography 48, no. 5 (2018): 1151–68. http://dx.doi.org/10.1175/jpo-d-17-0126.1.
Повний текст джерелаАнотація:
Abstract The increase of computational capabilities led recent studies to implement very high-resolution simulations that gave access to new scale interaction processes, particularly those associated with the transfer of energy from the oceanic mesoscales to smaller scales through an interior route to dissipation, which is still underexplored. In this context, we study spindown simulations of a mesoscale interior vortex, unstable to a mixed baroclinic–barotropic instability. Even though the global energy is almost conserved, some energy is transferred down to dissipation scales during the development of instabilities. However, in our parameter regime, there is no substantial forward energy cascade sustained by unbalanced dynamics. Rather than exploring the physical parameter range, we clarify numerical discretization issues that can be detrimental to the physical solutions and our interpretation of finescale dynamics. Special care is given to determining the effective resolution of the different simulations. We improve it by a factor of 2 in our primitive equation (PE) finite-difference Coastal and Regional Ocean Community (CROCO) model by implementing a fifth-order accurate horizontal advection scheme. We also explore a range of grid aspect ratios dx/dz and find that energy spectra converge for aspect ratios that are close to N/f, the ratio of the stratification N over the Coriolis parameter f. However, convergence is not reached in the PE model when using a fourth-order centered scheme for vertical tracer advection (standard in ROMS-family codes). The scheme produces dispersion errors that trigger baroclinic instabilities and generate spurious submesoscale horizontal features. This spurious instability shows great impact on submesoscale production and energy cascade, emphasizing the significance of numerical settings in oceanic turbulence studies.
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Gutknecht, E., I. Dadou, B. Le Vu, et al. "Nitrogen transfers and air-sea N<sub>2</sub>O fluxes in the upwelling off Namibia within the oxygen minimum zone: a 3-D model approach." Biogeosciences Discussions 8, no. 2 (2011): 3537–618. http://dx.doi.org/10.5194/bgd-8-3537-2011.
Повний текст джерелаАнотація:
Abstract. As regions of high primary production and being often associated to Oxygen Minimum Zones (OMZs), Eastern Boundary Upwelling Systems (EBUS) represent key regions for the oceanic nitrogen (N) cycle. Indeed, by exporting the Organic Matter (OM) and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. Losses of fixed inorganic N, through denitrification and anammox processes and through nitrous oxide (N2O) emissions to the atmosphere, take place in oxygen depleted environments such as EBUS, and alleviate the role of these regions as a source of N. In the present study, we developed a 3-D coupled physical/biogeochemical (ROMS/BioBUS) model for investigating the full N budget in the Namibian sub-system of the Benguela Upwelling System (BUS). The different state variables of a climatological experiment have been compared to different data sets (satellite and in situ observations) and show that the model is able to represent this biogeochemical oceanic region. The N transfer is investigated in the Namibian upwelling system using this coupled model, especially in the Walvis Bay area between 22° S and 24° S where the OMZ is well developed (O2 < 0.5 ml O2 l−1). The upwelling process advects 24.2 × 1010 mol N yr−1 of nitrate enriched waters over the first 100 m over the slope and over the continental shelf. The meridional advection by the alongshore Benguela current brings also nutrient-rich waters with 21.1 × 1010 mol N yr−1. 10.5 × 1010 mol N yr−1 of OM are exported outside of the continental shelf (between 0 and 100-m depth). 32.4% and 18.1% of this OM are exported by advection in the form of Dissolved and Particulate Organic Matters (DOM and POM), respectively, however vertical sinking of POM represents the main contributor (49.5%) to OM export outside of the first 100-m depth of the water column on the continental shelf. The continental slope also represents a net N export (11.1 × 1010 mol N yr−1) between 0 and 100-m depth: advection processes export 14.4% of DOM and 1.8% of POM, and vertical sinking of POM contributes to 83.8%. Between 100 and 600-m depth, water column denitrification and anammox constitute a fixed inorganic N loss of 2.2 × 108 mol N yr−1 on the continental shelf and slope, which will not significantly influence the N transfer from the coast to the open ocean. At the bottom, an important quantity of OM is sequestrated in the upper sediments of the Walvis Bay area. 78.8% of POM vertical sinking at 100-m depth is sequestrated on the shelf sediment. Only 14% of POM vertical sinking reaches the sediment on the slope without being remineralized. From our estimation, the Walvis Bay area (0–100 m), can be a substantial N source (28.7 × 1010 mol N yr−1) for the eastern part of the South Atlantic Subtropical Gyre. Assuming the same area for the South Atlantic Subtropical Gyre as the North Atlantic Subtropical Gyre, this estimation is equivalent to 3.7 × 10−2 mol N m−2 yr−1 for the Walvis Bay area, and 0.38 mol N m−2 yr−1 by extrapolating for the entire Benguela upwelling system. This last estimation is of the same order as other possible N sources sustaining primary production in the subtropical gyres. The continental shelf off Walvis Bay area does not represent more than 1.2% of the world's major eastern boundary regions and 0.006% of the global ocean, its estimated N2O emission (2.9 × 108 mol N2O yr−1), using a parameterization based on oxygen consumption, contributes to 4% of the emissions in the eastern boundary regions, and represents 0.2% of global ocean N2O emission. Hence, even if the Walvis Bay area is a small domain, its N2O emissions have to be taken into account in the atmospheric N2O budget.
Дисертації з теми "Transferts advectifs"
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Touze-Foltz, Nathalie. "Modélisation des transferts advectifs dans les étanchéités composites de centres de stockage de déchets." Paris, ENMP, 2001. http://www.theses.fr/2001ENMPA001.
Повний текст джерелаАнотація:
Les géomembranes des étanchéités composites présentent fréquemment des défauts qui constituent des passages préférentiels d'écoulement pour les lixiviats. Plusieurs auteurs ont développe des modèles mathématiques et des équations empiriques pour interpréter les débits de fuite, générés par les transferts advectifs obtenus au laboratoire et les étendre aux conditions de terrain en régime permanent, pour une transmissivité d'interface uniforme, un sol et une interface saturés en eau. La synthèse bibliographique réalisée permet de déterminer les limites de validité des modèles mathématiques et des équations empiriques existantes, pour une transmissivité d'interface uniforme. Il s'avère que la transmissivité d'interface dans les étanchéités composites est non uniforme. Le travail de thèse a donc consiste à étudier l'influence a travers différents outils de cette non-uniformité. Le développement de solutions analytiques basées sur les modèles mathématiques existants tout comme des expérimentations de laboratoire et de terrain ont permis de montrer l'influence de la prise en compte des non-uniformités de l'interface et du positionnement des défauts dans la géomembrane par rapport à celle-ci. Toutes les observations réalisées montrent la nécessité pour progresser dans la connaissance de transferts advectifs de pouvoir disposer d'une cartographie précise de la transmissivité d'interface et des défauts dans la géomembrane, à l'échelle d'un site. Deux méthodes ont d'ailleurs été testées au cours de la thèse pour décrire les états de surface de géomembranes et d'un limon compacté.
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Touze-Foltz, Nathalie. "Modélisation des transferts advectifs dans les étanchéités composites de centres de stockage de déchets." Paris, ENMP, 2001. http://www.theses.fr/2001ENMP1038.
Повний текст джерелаАнотація:
Les géomembranes des étanchéités composites présentent fréquemment des défauts qui constituent des passages préférentiels d'écoulement pour les lixiviats. Plusieurs auteurs ont développé des modèles mathématiques et des équations empiriques pour interpréter les débits de fuite, générés par les transferts advectifs obtenus au laboratoire et les étendre aux conditions de terrain en régime permanent, pour une transmissivité d'interface uniforme, un sol et une interface saturés en eau. La synthèse bibliographique réalisée permet de déterminer les limites de validité des modèles mathématiques et des équations empiriques existantes, pour une transmissivité d'interface uniforme. Il s'avère que la transmissivité d'interface dans les étanchéités composites est non uniforme. Le travail de thèse a donc consiste à étudier l'influence à travers différents outils de cette non-uniformité. Le développement de solutions analytiques basées sur les modèles mathématiques existants tout comme des expérimentations de laboratoire et de terrain ont permis de montrer l'influence de la prise en compte des non-uniformités de l'interface et du positionnement des défauts dans la géomembrane par rapport à celle-ci. Toutes les observations réalisées montrent la nécessité pour progresser dans la connaissance de transferts advectifs de pouvoir disposer d'une cartographie précise de la transmissivité d'interface et des défauts dans la géomembrane, à l'échelle d'un site. Deux méthodes ont d'ailleurs été testées au cours de la thèse pour décrire les états de surface de géomembranes et d'un limon compacté<br>Geomembranes of composite liners often exhibit holes representing preferential advective flow paths for leachate. Various authors have developed mathematical models and empirical equations in order to interpret flow rates due to advective transfers obtained in the laboratory and extrapolate them to field conditions, for steady-state flow, unifrom interface transmissivity, and saturated soils and interfaces. Limits of validity of these mathematical models and empirical equations were determined for a uniform interface transmissivity. But the transmissivity proves to be non-uniform. The work performed thus consisted in studying the influence of this non-uniformity on flow rates thanks to analytical equations and experimental devices. The influence of the respective location of the hole in the geomembrane as well as the spatial repartition of transmissivity. For this latestt point two methods were used during the PhD in order to describe geomembrane and compacted soil surfaces topography
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Bannour, Hajer. "Evalution des transferts advectifs à travers les étanchéités composites géomenbranes-géosynthétiques bentonitiques des barrières de fonds d'installations de stockage de déchets." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU048/document.
Повний текст джерелаАнотація:
L'étanchéité composite géomembrane(GM)-géosynthétique bentonitique (GSB) mise en place dans les barrières de fond d'installations de stockage de déchets non dangereux (ISDnD) peut être sujette à des transferts advectifs liés à l'existence de défauts dans la GM. Les lixiviats peuvent percoler dans le GSB, pénétrer dans le sol et les nappes phréatiques sous-jacentes ce qui peut nuire à l'environnement. Il est donc important de comprendre les mécanismes de transferts dans les étanchéités composites GM-GSB et de les quantifier afin de connaitre, maitriser et minimiser l'impact des transferts advectifs à travers la barrière vers l'environnement. Cependant, l'inaccessibilité de la GM rend difficile l'estimation réelle des fuites à travers l'étanchéité composite. La présente thèse évalue via une démarche expérimentale et numérique les transferts advectifs à travers les étanchéités composites et contribue à améliorer la compréhension des mécanismes de transfert en fonction des sollicitations extérieures. Le but est de bien cerner la problématique des transferts advectifs à travers les étanchéités composites GM-GSB, combler les vides des précédentes études et mettre en évidence les principaux paramètres à prendre en compte (contrainte de confinement, hétérogénéité du GSB, qualité de contact à l'interface GM-GSB, altération chimique et physique des GSB durant leur durée de service sur site). Leur influence sur l'étanchéité de l'ensemble et sur l'évolution des caractéristiques des matériaux utilisés est étudiée. L'approche expérimentale a consisté à acquérir des données sur la rétention d'eau et à introduire la notion des surfaces d'états des GSB sous le confinement généré par les déchets. Il a été démontré que le confinement réduit le gonflement du GSB lors de son hydratation ce qui permet de diminuer sa conductivité hydraulique à saturation. Ce résultat renforce les recommandations appelant à confiner rapidement les GSB après leur mise en place afin qu'ils acquièrent rapidement toutes leurs capacités d'étanchéité. Cette étude expérimentale a été complétée par une quantification numérique des transferts à travers les étanchéités composites en prenant en compte le caractère hétérogène du GSB. Cette étude numérique de prédiction des fuites a fourni de précieux renseignements sur la réduction des débits de fuite qui s'est avérée dépendante des courbes de rétention respectives du géotextile et de la bentonite. En effet, en plus de contenir la bentonite et de promouvoir la résistance aux efforts de traction, le géotextile contribue à la réduction des débits de fuite grâce sa faible perméabilité une fois désaturé. Des expérimentations de mesure du débits de fuites et de quantification de la transmissivité d'interface pour différentes combinaisons d'étanchéités composites GM-GSB ont permis de conclure que ni les sollicitations extérieures conduisant à l'altération chimique, physique et hydraulique des GSB, conduisant à augmenter la conductivité hydraulique du GSB de 4 à 5 ordres de grandeurs, ni la qualité de la GM (en lien avec la rugosité, rigidité, épaisseur) n'affectent significativement les transferts dans les étanchéités composites GM-GSB en régime permanent. Un effet est décelé sur le régime transitoire. Une approche synthétique est enfin donnée et permet une analyse globale des transferts dans les étanchéités composites GM-GSB afin de prévoir au mieux l'impact des transferts dans les barrières vers l'environnement. Il a été confirmé que le gonflement de la bentonite intervient dans la réduction du débit de fuite à travers les étanchéités composites indépendamment de la forme granulométrique de la bentonite. Par ailleurs, il a été conclu que la phase transitoire durant laquelle une réduction des débits de fuites à travers la barrière d'étanchéité composite est observée, doit être prise en compte dans les calculs de fuites pour une prédiction réaliste et rigoureuse des fuites à travers la barrière<br>Geomembrane (GM)-geosynthetic clay liner placed in bottom landfill barriers could be faced to advective transfers caused by the appearance of GM defects. Leachate could percolate naturally through the GCL; penetrate the soil and the ground water which could result in environmental damage. It's therefore important to understand leakage transfer mechanism though GM-GCL composite liners and quantify them in order to be aware, to master and to minimize advective transfer impact through the barrier to the environment. However, the GM is not accessible in bottom land fill liner which makes it harder to correctly estimate leakage through the composite liner. The present work used to evaluate advective transfer through GM-GCL composite liner via an experimental and numerical approach. This work used also to ameliorate the comprehension of leakage transfer mechanisms as a function of external solicitations compared to the literature. The purpose of this study was thus to properly identify advective transfer problem through composite liner by highlighting the main parameters affecting advective transfers through composite liners (confining stress, heterogeneity of the GCL composition, contact quality at the GM-GCL interface, chemical and physical alteration during its service life). Those parameters influence the whole barrier performances and material characteristics evolution were studied. Experimental program was dealing with acquiring water retention data of GCL by introducing state surface concept under the confining stress generated by the waste. It has been found that confining stress used to reduce GCL swelling facilities while hydrated and consequently lead to the decrease of the saturated hydraulic conductivity. This result emphasizes on landfill conception recommendations based on rapidly covering the GCL in in order to acquiring its watertightness capabilities. This experimental study was reinforced by a numerical computation study dealing with water transfer through composite liner due to a GM defect and a hydraulic head with considering the heterogeneity of the GCL. This numerical study highlighted new phenomena regulating flow rate through composite liners consisting of geotextile deaturation due to high suction performed by the bentonite as part of the GCL. Indeed, in addition to containing the bentonite and providing tensile shear stresses, the geotextile contribute to reduce the flow rate through composite liner thanks to its high hydraulic conductivity while desaturated. Interface transmissivity tests were also carried for different composite liners combinations. Measurements concluded that neither external solicitations resulting from chemical and physical alteration conducting to the increase of the hydraulic conductivity of the GCL nor the quality of the GM (in relation with its roughness, rigidity and thickness) significantly affect advective transfer through composite liners at the steady state. However an effect was highlighted during transient state. A synthetic approach was thus given to summarize composite liners transfers mechanism and anticipate environmental impact of its leakage. It was later confirmed that the bentonite swelling contributes also to flow rate reduction through composite liner regardless of the bentonite nature and granulometry. In addition, it has been concluded that the transient state within which flow rate reduction though has been observed must be taken into consideration to realistically predict flow rate leakage through composite liners
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Chabi, Fatiha. "Etude numérique et expérimentale du transfert de masse, par advection et diffusion en écoulement pulsé, sur des stents actifs." Thesis, Paris, ENSAM, 2016. http://www.theses.fr/2016ENAM0051/document.
Повний текст джерелаАнотація:
La perturbation des écoulements au voisinage de la paroi artérielle équipée d'un stent joue un rôle prépondérant dans l'apparition et le développement des complications liées aux maladies cardiovasculaires (sténose, resténose, thrombose...). La topologie de l'écoulement dans ces régions est très complexe. En effet, au voisinage du stent, des zones de recirculation se forment en amont et aval de chaque branche et les contraintes pariétales y sont très faibles. Des études in vivo et in vitro ont mis en évidence le rôle de ces caractéristiques de l'écoulement intra-stent sur les maladies cardiovasculaires. Pour cela, la bonne estimation des contraintes pariétales et la compréhension du comportement de l'écoulement intra-stent et son rôle dans le transfert du principe actif devraient permettre d'optimiser les traitements (design de la prothèse, principe actif...). L'approche numérique est une voie très utile pour étudier ces phénomènes. Cependant, la bonne précision du calcul dépend du choix du modèle d'écoulement, des conditions aux limites, de la géométrie du stent et de l'artère pour réaliser une simulation pertinente.Nous étudions ici dans un premier temps l'effet du choix du modèle hémodynamique sur les caractéristiques de l'écoulement intra-stent. Trois modèles numériques décrivant l'écoulement coronaire ont été utilisés. Ces modèles sont : un modèle stationnaire "MP", le modèle pulsé simplifié "MPS" et le modèle pulsé complet "MPC" basé sur l'analyse de Womersley. Nous avons ainsi montré l'importance de la prise en compte de l'instationnarité de l'écoulement mais au dépens d'un temps de calcul très accru. Dans un second temps, nous étudions expérimentalement l'écoulement intra-stent en utilisant la technique de mesure "PIV". Cette étude expérimentale a permis de confirmer les résultats numériques précédents. Au final, nous examinons numériquement l'effet de la pulsatilitié de l'écoulement sur les flux massiques libérés par les faces d'une branche de stent actif. Cette étude numérique a mis en exergue l'importance du couplage entre les recirculations et le transfert de masse vers la paroi artérielle<br>The disturbance of the flow in the vicinity of the arterial wall equipped with a stent plays a key role in the onset and development of complications related to cardiovascular diseases (stenosis, restenosis, thrombosis...). The topology of the flow field in the intra-stent zone is very complex. Indeed, in the vicinity of the stent, recirculation zones form upstream and downstream of the stent strut where wall shear stress is very low. In vivo and in vitro studies have demonstrated the role of the in-stent flow features on cardiovascular diseases.The correct estimation of the wall shear stress, the understanding of the behavior of the in-stent flow and its role in the transfer of the drug are expected to help optimize treatments (stent geometry, drug composition...). The numerical approach (CFD) is a useful and versatile way to study these phenomena. However, the accuracy and the relevance of the results depend on the choice of the flow model, the boundary conditions and the stent and artery geometry.Firstly we study in this work the impact of the hemodynamic model on the in-stent flow characteristics. Three numerical models describing the coronary flow are used. These models are: the steady model "MP", the simplified pulsatile model "MPS" and the complete pulsatile model "MPC" based on Womersley's analysis. We show the importance of the pulsatility of the flow but at the expense of a high increase in the computing time. Secondly we study experimentally the in-stent flow using measurement technique "PIV". This experimental study confirms the previous numerical results. Finally we examine numerically the effects of the flow pulsatility on the mass fluxes released by the faces of a drug eluting stent. This numerical study highlights the importance of the coupling between the recirculation zones and the mass transfer into the arterial wall
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Ortega, Ramirez Miriam Patricia. "Analysis of soil structural and transfer properties using pore scale images and numerical modelling." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAU017/document.
Повний текст джерелаАнотація:
.Dans cette thèse, il a été étudié la structure des milieux poreux, en particulier sur des sols sableux et un paquet virtuel de sphères; Sur la base de références bibliographiques, nos propres outils ont été créés pour calculer la porosité, la surface spécifique et la distribution de la taille des pores. Nous avons construit un algorithme pour résoudre l'équation de diffusion de l'advection directement sur la structure du milieu poreux (en utilisant un résultat d'image 3D du scan $ mu $ CT du support poreux). Nous avons utilisé l'opérateur de division pour calculer la partie advective avec une méthode de volume fini (FV), mettant en œuvre un schéma de réduction de la variation totale (TVD). La partie diffusion a été calculée en utilisant une méthode de FV et avec l’aide du logiciel MUMPS pour résoudre le système linéaire résultant. A partir du champ de concentration obtenu avec l’algorithme et suivant une méthode de moyenne volumique, nous avons calculé les propriétés macroscopiques de: dispersivité et coefficient de dispersion à Pe = 223,23,2.3,0,23 pour un échantillon de sable de Fontainbleau NE34. Nous avons observé que ces résultats dépendent de la qualité de l'image 3D. Les propriétés structurelles et de transport ont été étudiées à l'aide d'images 3D à différentes résolutions. Les images à différentes résolutions ont été appelées images redimensionnées, elles ont été générées numériquement et prises directement à partir du micro CT scan. Comme premier résultat, nous avons proposé un critère basé sur la distribution de la taille des pores pour déterminer si une résolution d'image 3D convient ou non au calcul de la perméabilité d'un matériau granulaire avec une méthode de volume fini (FV). Dans un deuxième résultat, nous avons montré comment les propriétés des macros de transport de soluté sont moins affectées par une détérioration de la résolution que la propriété d’écoulement de la perméabilité (les deux cas sont calculés par une méthode FV). Et comme troisième résultat, nous avons montré qu'une image numérique redimensionnée préserve davantage le comportement des propriétés macroscopiques qu'une image réelle redimensionnée<br>In this thesis it was studied the structure of the porous media, particularly on a sandy soils and a virtual pack of spheres; based on bibliographic references here were generated our own tools to compute the porosity, specific surface and pore size distribution. We built an algorithm to solve advection diffusion equation directly on the porous media structure (using a 3D image result of the $mu $ CT scan of the porous media). We used the splitting operator to compute the advective part with a Finite Volume (FV) method, implementing a Total Variation Diminishing (TVD) scheme. The diffusion part was computed using with a FV method with the assistance of the MUMPS software to solve the resulting linear system. From the concentration field obtained with the algorithm and following a volume averaging method, we computed the macroscopic properties of: dispersivity and dispersion coefficient at Pe=223,23,2.3,0.23 for a sample of Fontainbleau NE34 sand. We observing that these results depend on the quality of the 3D image, structural and transport properties were studied using 3D images at different resolutions. The images at different resolutions were called rescaled images, and they were generated numerically and taken directly from the micro CT scan. As a first result we proposed a criterion based on the pore size distribution to assess if a 3D image resolution is suitable or not for permeability computation of a granular material with a finite volume (FV) method. As a second result we showed how the solute transport macro properties are less affected by a deterioration of the resolution than the flow property of permeability (both cases computed through a FV method). And as a third result we showed that a numerical rescaled image preserve the behavior of the macroscopic properties more than a real rescaled image
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Zambaux, Julie-Anne. "Influence des déformations successives alternées de la paroi sur l'accroissement des performances d'échange d'un tube : application aux échangeurs multifonctionnels." Thesis, Valenciennes, 2014. http://www.theses.fr/2014VALE0036/document.
Повний текст джерелаАнотація:
Les travaux de thèse sont consacrés à l’étude numérique de l’application de macro-déformations successives alternées a la paroi d’un tube. La modification de l’écoulement du fait des déformations permet de modifier ses propriétés en termes de transfert thermique et de mélange. L’objectif de l’étude d’un tel dispositif est entre autre de l’appliquer pour des configurations d’échangeurs multifonctionnels, qui sont à la fois échangeurs de chaleur et réacteurs chimiques. L’étude s’intéresse principalement aux écoulements laminaires. Les calculs sont réalisés avec le code ANSYS Fluent. L’étude est tout d’abord consacrée à la caractérisation de l’écoulement secondaire créé par les déformations ainsi qu’à l’influence des différents paramètres de déformation. Afin d’améliorer le mélange dans l’écoulement, l’étude d’une configuration coaxiale déformée a été envisagée (cette géométrie correspond de plus à une configuration d’écoulement utilisée dans l’industrie). Deux configurations annulaires ont été considérées. Dans un premier temps, les déformations pariétales ont été appliquées aux tubes interne et externe : différents déphasages longitudinaux et angulaires entre ces deux déformations ont été étudiés pour optimiser les performances thermo-hydrauliques. La seconde configuration combine des déformations sur la paroi externe et un swirl sur la paroi interne de la géométrie. Cette configuration particulière permet en régime laminaire d’augmenter significativement le mélange du fait de l’apparition d’advection chaotique dans l’écoulement. Cette dernière géométrie est appliquée dans le cas d’un échangeur solaire à concentration et permet d’améliorer les performances par rapport à un tube lisse dans des conditions similaires. La dernière partie de l’étude est consacrée à une validation expérimentale des résultats numériques lorsque les déformations sont appliquées à une plaque. Des mesures par PIV et LDA ont été réalisées pour mesurer la vitesse locale de l’écoulement<br>The work presented here is focused on the numerical study of specific successive wall deformations in alternate directions, applied to a tubular geometry. Those deformations help modifying the flow structure and thus its heat transfer and mixing properties. One of the main aims of the study is to apply those deformations to multifunctional exchangers which are heat exchangers and chemical reactors at the same time. The study is mainly focused on laminar flows and all the numerical calculations were performed using the CFD code ANSYS Fluent. The first step of the study is to assess the secondary flow created by the wall deformations. The influence of several deformation geometrical parameters has also been studied. In order to enhance the mixing in the deformed tube, the wall deformations have been applied to coaxial configurations (often used in the industry). Two kinds of annular configurations have been evaluated. At first, the wall deformations are applied to the external and internal walls of the coaxial tube. The effect on the heat transfer enhancement of the longitudinal and angular phase-shifting between the two deformations has been specifically assessed. The second configuration considered combines the alternate deformations on its external walls and a swirled internal wall. This particular annular configuration creates chaotic advection in laminar flows, therefore helping increasing the mixing. This geometry is used as a solar captor and helps increasing the global performances when compared with a smooth tube usually used. The last part of the presented work is focused on the experimental validation of the numerical results. Techniques such as PIV and LDA are used to measure local velocity fields in a plane duct with alternate deformations applied to its lower wall
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Roque, António José Pereira Mendes. "Transfert advectif et diffusif de polluants inorganiques dans les barrières d'étanchéité minérales présentes dans les centres de stockage de déchets." Lyon, INSA, 2001. http://www.theses.fr/2001ISAL0034.
Повний текст джерелаАнотація:
Le présent travail vise à contribuer à une meilleure connaissance de la performance hydro-géochimique des sols dont les caractéristiques géotechniques sont proches de celles des sols habituellement utilisés pour la construction des barrières d'étanchéité minérales présentes dans les Centres de Stockage de Déchets (CSD), et ainsi à une meilleure conception et à un meilleur dimensionnement des dispositifs d'étanchéité sur la base de la détermination de la conductivité hydraulique, du coefficient de diffusion effective et de la capacité de rétention des sols. Nous présentons l'étude de la phénoménologie des interactions sol-eau-électrolyte, dans le but de contribuer à une meilleure compréhension du fonctionnement du système sol-lixiviat. Nous décrivons les principaux processus physiques, chimiques et biologiques de rétention des polluants inorganiques dans les sols et présentons pour quelques polluants inorganiques les mécanismes de rétention responsables de leur retardement dans les sols. Nous indiquons les principaux processus de transport des polluants à travers les barrières d'étanchéité minérales ainsi que la formulation mathématique correspondante. Les principes fondamentaux de la perméabilité et de la diffusion dans les sols ainsi que les méthodes de mesure en laboratoire de la conductivité hydraulique et du coefficient de diffusion effective sont présentés. Les caractéristiques des lixiviats produits dans les CSD de déchets ménagers et assimilés sont données ainsi qu'une base de données relative à la composition chimique de ces lixiviats. Ces données ont permis de sélectionner les espèces chimiques inorganiques et les concentrations chimiques représentatives de la composition chimique des lixiviats réels afin de préparer des lixiviats synthétiques : acide et neutre à légèrement alcalin. Nous décrivons la méthodologie qui a conduit au prélèvement de trente échantillons dans les principales formations argileuses portugaises et procédons à la caractérisation des sols. Les résultats obtenus dans les essais sont analysés ainsi que leur traitement statistique à travers des méthodes de corrélation linéaire et d'analyses multivariées, dans le but de sélectionner les échantillons représentatifs de l'échantillonnage global. Les essais de perméabilité en laboratoire ont été réalisés avec des équipements et dispositifs spécialement conçus pour la détermination de la conductivité hydraulique des éprouvettes et du temps de transfert d'espèces chimiques inorganiques à travers les sols par advection et pour l'étude des effets des lixiviats acide et neutre à légèrement alcalin sur l'intégrité des sols à long terme. Nous avons procédé, en plus de l'étude du transport d'espèces chimiques par advection, à l'étude du transport d'espèces chimiques à travers les sols par diffusion. Pour ce faire, des équipements et dispositifs spécifiques pour l'étude du transport des polluants par diffusion pure ont été conçus<br>This work is intended to contribute to understand better the hydro-geochemical performance of fine-grained soils with geotechnical properties similar to those of soils that are currently used in the construction of compacted clay liners existing in the landfills. Therefore, the work is expected to contribute to improve the design and dimensioning of confinement systems based on the determination of the hydraulic conductivity, the effective diffusion coefficient and the capacity of retention of fine-grained soils. We begin by studying of the phenomenology of soil-water-electrolyte interactions, with a view to contribute to understand better the operation of the soil-leachate system. Subsequently, we describe the main physical, chemical and biological processes of retention of inorganic pollutants in the soils, and we present for some inorganic pollutants the mechanisms of retention that are responsible for their retardation in the soils. In addition, we indicate the main processes of pollutant transport through compacted clay liners, as well as the corresponding mathematical formulation. W e also refer to the fundamental principles of permeability and diffusion in the soils as well as the methods used in laboratory for measuring the hydraulic conductivity and the effective diffusion coefficient. W e present the characteristics of leachates produced in municipal solid landfills, as well as a data base concerning the chemical composition of these leachates. These data were used as supporting basis to the selection of inorganic chemical species and of chemical concentrations representative of the chemical composition of real leachates, with a view to prepare both acid and neutral to moderately alkaline leachates. We present the methodology that has led to collecting thirty samples from the main Portuguese clayey formations and we characterise the soils. The results obtained in the tests are analysed and we perform their statistical processing using linear regression and multivariate analysis methods, in order to select representative samples of the overall sampling. W e carry out permeability tests in laboratory with equipment and apparatuses that were specifically designed for: i) determining the hydraulic conductivity of specimens; ii) determining the time of advective transport of inorganic chemical species through the sampling soils; iii) studying the effects of both ac id and neutral to moderately alkaline leachates on the long-term integrity of soils. We carry out, other than the study on the advective transport of chemical species, a study on the diffusive transport of inorganic chemical species through the sampling soils. For the purpose, we designed equipment and apparatuses that were specifically intended to study the transport of pollutants by pure diffusion
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Davies, Kevin L. "Declarative modeling of coupled advection and diffusion as applied to fuel cells." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51814.
Повний текст джерелаАнотація:
The goal of this research is to realize the advantages of declarative modeling for complex physical systems that involve both advection and diffusion to varying degrees in multiple domains. This occurs, for example, in chemical devices such as fuel cells. The declarative or equation-based modeling approach can provide computational advantages and is compatible with physics-based, object-oriented representations. However, there is no generally accepted method of representing coupled advection and diffusion in a declarative modeling framework.
This work develops, justifies, and implements a new upstream discretization scheme for mixed advective and diffusive flows that is well-suited for declarative models. The discretization scheme yields a gradual transition from pure diffusion to pure advection without switching events or nonlinear systems of equations. Transport equations are established in a manner that ensures the conservation of material, momentum, and energy at each interface and in each control volume. The approach is multi-dimensional and resolved down to the species level, with conservation equations for each species in each phase. The framework is applicable to solids, liquids, gases, and charged particles. Interactions among species are described as exchange processes which are diffusive if the interaction is inert or advective if it involves chemical reactions or phase change.
The equations are implemented in a highly modular and reconfigurable manner using the Modelica language. A wide range of examples are demonstrated—from basic models of electrical conduction and evaporation to a comprehensive model of a proton exchange membrane fuel cell (PEMFC). Several versions of the PEMFC model are simulated under various conditions including polarization tests and a cyclical electrical load. The model is shown to describe processes such as electro-osmotic drag and liquid pore saturation. It can be scaled in complexity from 4000 to 32,000 equations, resulting in a simulation times from 0.2 to 19 s depending on the level of detail. The most complex example is a seven-layer cell with six segments along the length of the channel. The model library is thoroughly documented and made available as a free, open-source software package.
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Hadad, Waseem Al. "Thermique des mini-canaux : comportement instationnaire et approche convolutive." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0121/document.
Повний текст джерелаАнотація:
Un modèle semi-analytique permettant de simuler le transfert thermique conjugué dans un mini/macro canal plan soumis à des sources de chaleur surfaciques localisées sur les faces externes et variantes en fonction du temps, a été présenté et vérifié. Plus le diamètre hydraulique du canal est petit, plus la caractérisation expérimentale interne (mesure des températures et des flux) en régime thermique permanent ou transitoire à l'aide des capteurs internes est délicate. Une méthode non-intrusive permettant d'estimer les conditions internes à partir des mesures de température par thermographie infrarouge sur les faces externes et d'un modèle semi-analytique, a été effectuée. Comme le coefficient de transfert convectif forcé classique perd son sens en régime instationnaire, une approche alternative basée sur une fonction de transfert, valable pour un système linaire et invariant dans le temps a été mise en œuvre. Cette fonction peut être calculée analytiquement (uniquement pour une géométrie simple) ou estimée expérimentalement (géométrie complexe). Grâce au caractère intrinsèque de cette fonction de transfert, deux capteurs virtuels ont été conçus : capteur virtuel de température et détecteur d'encrassement permettent respectivement d'estimer les températures internes et de détecter l'encrassement qui peut avoir lieu dans l'échangeur à partir des mesures de températures sur les faces externes<br>A semi-analytical model allowing to simulate the transient conjugate heat transfer in mini/macro plane channel subject to a heat source(s) localized on the external face(s), was presented and verified. The developed model takes into account advection-diffusion in the fluid and conduction in the solid. As the hydraulic diameter of the channel becomes small, the internal experimental characterization (measurement of temperature and heat flux) using internal sensors become tricky because internal sensors located may compromise the structural integrity of the whole system. A non-intrusive method for estimating the internal conditions from infrared temperature measurements on the external faces using the semi-analytical model was performed. Since the classic convective heat transfer coefficient loses its meaning in transient state, an alternative approach based on a transfer function, valid for Linear Time-Invariant (LTI) systems, was highlighted. This function can be calculated analytically only for a simple geometry. For complex geometries it can be estimated experimentally. Thanks to intrinsic character of this function, two characterization methods were designed. The first to estimate the temperature at a point from a measurement at another point in the system (virtual temperature sensor). The second method concerns the detection of fouling layers that may appear in the heat exchanger from temperature measurements on the external faces
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Ghanem, Akram. "Intensification des transferts : typologies par régime d'écoulement et critères de performance d'échangeurs/réacteurs multifonctionnels." Ecole centrale de Nantes, 2013. http://www.theses.fr/2013ECDN0034.
Повний текст джерелаАнотація:
Le concept d’échangeur réacteur multifonctionnel (ERM) recouvre l’ensemble des systèmes efficaces pour réaliser une ou plusieurs opérations unitaires sur les fluides industriels. L'objectif de ce travail est de caractériser les performances de différentes configurations d’ERM en termes de mélange et de transfert de chaleur par des techniques numériques et expérimentales. Une démarche d'efficacité énergétique est adoptée pour évaluer la faisabilité de chaque configuration selon des critères de performance. Dans le régime laminaire, l'advection chaotique produite dans les réacteurs "Split-And-Recombine" (SAR) favorise le mélange par diffusion. Les caractéristiques de l'écoulement et les capacités de transfert de chaleur sont étudiées dans deux configurations SAR. Les propriétés de mélange dans ces configurations sont sensiblement supérieures aux autres géométries et une augmentation des transferts convectifs jusqu’à 20 fois supérieure est constatée. Dans le régime transitionnel ou inertiel, les géométries avec des surfaces modifiées et des inserts sont les plus efficaces. La qualité du mélange dans deux réacteurs ondulés et dans un tube muni d'inserts hélicoïdaux est évaluée. Ici nous avons montré que l’intensification relative du mélange par rapport au tube vide est supérieure à un facteur 100 dans ces configurations. Dans le régime turbulent, l'intensification des transferts convectifs par les générateurs de vortex trapézoïdaux est quantifiée dans le mélangeur statique et l'échangeur de chaleur ‘High-Efficiency Vortex’ (HEV) par des mesures thermiques expérimentales. L’amélioration maximale des transferts convectifs est de l’ordre de 12 fois par rapport au tube vide<br>The concept of multifunctional heat exchanger/reactor (MHE/R) includes all systems efficient for the realization of one or several unitary operations on industrial fluids with high productivity and reduced energy expenditures. The aim of the present work is to characterize the performance of different MHE/R configurations in terms of mixing and heat transfer using numerical and experimental techniques. An energy efficiency approach is adopted to evaluate the feasibility of each configuration based on common performance criteria. In the laminar regime, chaotic advection produced in the Split-And-Recombine (SAR) reactors promotes mixing by diffusion. Flow characteristics, heat transfer capacities, and mixing qualities are investigated in two SAR configurations. Superior mixing qualities are observed in these devices and convective heat transfer is enhanced up to 20 folds compared to classical geometries. In the transitional or inertial regime, modified surface geometries and tube inserts are most efficient in process intensification. Mixing enhancement in two corrugated channel reactors with different radii of curvature and a tube fitted with helical inserts is assessed by chemical probe. Mixing intensification relative to an empty tube reaches as high as 100 folds in the laminar regime. In the turbulent regime, convective heat transfer intensification produced by the trapezoidal vortex generator is quantified in the High-Efficiency Vortex (HEV) static mixer and heat exchanger by experimental thermal measurements. Convective heat transfer in this geometry attains values around 12 times higher than those recorded in a classical plain tube configuration
Книги з теми "Transferts advectifs"
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E, Hobbs Bruce, and Ord Alison 1955-, eds. Convective and advective heat transfer in geological systems. Springer, 2008.
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2
Bennett, Ted D. Transport by advection and diffusion: Momentum, heat, and mass transfer. John Wiley & Sons, Inc., 2013.
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3
Bennett, Ted D. Transport by advection and diffusion: Momentum, heat, and mass transfer. John Wiley & Sons, Inc., 2013.
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4
Convective And Advective Heat Transfer In Geological Systems. Springer, 2008.
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Hobbs, Bruce E., Chongbin Zhao, and Alison Ord. Convective and Advective Heat Transfer in Geological Systems. Springer, 2010.
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6
Hobbs, Bruce E., Chongbin Zhao, and Alison Ord. Convective and Advective Heat Transfer in Geological Systems. Springer, 2009.
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7
Convective and Advective Heat Transfer in Geological Systems. Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-79511-7.
Повний текст джерелаЧастини книг з теми "Transferts advectifs"
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Rumynin, Vyacheslav G. "Models for Assessment of Transverse Diffusive and Advective Transfer in Regional Two-Layer Systems." In Theory and Applications of Transport in Porous Media. Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-1306-2_5.
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Kono, Yohei, Yoshihiko Susuki, and Takashi Hikihara. "Modeling of Advective Heat Transfer in a Practical Building Atrium via Koopman Mode Decomposition." In Lecture Notes in Control and Information Sciences. Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-35713-9_18.
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Zhao, Lei, Linlin Zhang, and Songtao Hu. "The Exploration on Heat Transfer Models for Borehole Heat Exchanger in the Soil with Groundwater Advection." In Lecture Notes in Electrical Engineering. Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-39581-9_69.
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Davydova, M. A., N. N. Nefedov, and S. A. Zakharova. "Asymptotically Lyapunov-Stable Solutions with Boundary and Internal Layers in the Stationary Reaction-Diffusion-Advection Problems with a Small Transfer." In Finite Difference Methods. Theory and Applications. Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-11539-5_23.
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Katopodes, Nikolaos D. "Advective Mass Transfer." In Free-Surface Flow. Elsevier, 2019. http://dx.doi.org/10.1016/b978-0-12-815489-2.00004-6.
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Rubin, Yoram. "An Overview of Stochastic Tools for Modeling Transport of Tracers in Heterogeneous Media." In Applied Stochastic Hydrogeology. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195138047.003.0012.
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Spatial variability and the uncertainty in characterizing the flow domain play an important role in the transport of contaminants in porous media: they affect the pathlines followed by solute particles, the spread of solute bodies, the shape of breakthrough curves, the spatial variability of the concentration, and the ability to quantify any of these accurately. This chapter briefly reviews some basic concepts which we shall later employ for the analysis of solute transport in heterogeneous media, and also points out some issues we shall address in the subsequent chapters. Our exposition in chapters 8-10 on contaminant transport is built around the Lagrangian and the Eulerian approaches for analyzing transport. The Eulerian approach is a statement of mass conservation in control volumes of arbitrary dimensions, in the form of the advection-dispersion equation. As such, it is well suited for numerical modeling in complex flow configurations. Its main difficulties, however, are in the assignment of parameters, both hydrogeological and geochemical, to the numerical grid blocks such that the effects of subgrid-scale heterogeneity are accounted for, and in the numerical dispersion that occurs in advection-dominated flow situations. Another difficulty is in the disparity between the scale of the numerical elements and the scale of the samples collected in the field, which makes the interpretation of field data difficult. The Lagrangian approach focuses on the displacements and travel times of solute bodies of arbitrary dimensions, using the displacements of small solute particles along streamlines as its basic building block. Tracking such displacements requires that the solute particles do not transfer across streamlines. Since such mass transfer may only occur due to pore-scale dispersion, Lagrangian approaches are ideally suited for advection-dominated situations. Let us start by considering the displacement of a small solute body, a particle, as a function of time. “Small” here implies that the solute body is much smaller than the characteristic scale of heterogeneity. At the same time, to qualify for a description of its movement using Darcy’s law, the solute body also needs to be larger than a few pores. The small dimension of the solute body ensures that it moves along a single streamline and that it does not disintegrate due to velocity shear.
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Ferrari, Andrea. "Tutorial on Advection Schemes for Interface Volume Capturing Techniques." In Encyclopedia of Two-Phase Heat Transfer and Flow III. WORLD SCIENTIFIC, 2018. http://dx.doi.org/10.1142/9789813229440_0003.
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Nagorskiy, Petr Mikhailovich, Mikhail Vsevolodovich Kabanov, and Konstantin Nikolaevich Pustovalov. "The Influence of Smoke From Forest Fires on the Meteorological and Electrical Characteristics of the Atmosphere." In Predicting, Monitoring, and Assessing Forest Fire Dangers and Risks. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1867-0.ch014.
Повний текст джерелаАнотація:
The impact of smoke from forest fires in western Siberia on meteorological, atmospheric electric, and aerological variables has been analyzed. The anomalous distribution of water vapor in the atmosphere associated with the peculiarities of the evaporation regime and the absence of advective moisture transfer over the southern regions of Western Siberia during the fires. With an increase in the height of the homogeneous surface smoke layer with an unchanged aerosol optical thickness, the cooling of the earth's surface and heating of the atmosphere was weakened. The smoke plume spreads predominantly in the middle of the troposphere, creating aerosol layers elevated above the ground, the lower part of which had a negative volume charge. The effect of diurnal variations in the electrical field in the near-surface layer, differs from the known similar effects.
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Nurgaliev, Ildus Saetgalievich. "Solar Energy in Agro-Ecologic Micrometeorology Measurements." In Handbook of Research on Renewable Energy and Electric Resources for Sustainable Rural Development. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-3867-7.ch006.
Повний текст джерелаАнотація:
New approach to the measurements in agro-ecologic micrometeorology is suggested on the bases of renewable solar panels for energy supply to instruments at the remote sites and new turbulent model of the flow of the gases. Analytical dynamic model of the turbulent multi-component flow in the three-layer boundary system is presented. Turbulence is simulated by the non-zero vorticity, but not only. Other mathematical aspects of the turbulence are an introducing new model of the material point and considering a torsion of their trajectories. The generalized advection-diffusion-reaction equation is derived for an arbitrary number of components in the flow. The flows in the layers are objects for matching requirements on the boundaries between the layers. Different types of transport mechanisms are dominant on the different levels of the layers and space scales. The same models of mass and energy transfer are instrumental in simulation rural electrification concepts in general on the bases renewable sources.
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Yury, Yanilkin, Shmelev Vladimir, and Kolobyanin Vadim. "A Monotonic Method of Split Particles." In Recent Advances on Numerical Simulations [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97044.
Повний текст джерелаАнотація:
The problem of correct calculation of the motion of a multicomponent (multimaterial) medium is the most serious problem for Lagrangian–Eulerian and Eulerian techniques, especially in multicomponent cells in the vicinity of interfaces. There are two main approaches to solving the advection equation for a multicomponent medium. The first approach is based on the identification of interfaces and determining their position at each time step by the concentration field. In this case, the interface can be explicitly distinguished or reconstructed by the concentration field. The latter algorithm is the basis of widely used methods such as VOF. The second approach involves the use of the particle or marker method. In this case, the material fluxes of substances are determined by the particles with which certain masses of substances bind. Both approaches have their own advantages and drawbacks. The advantages of the particle method consist in the Lagrangian representation of particles and the possibility of” drawbacks. The main disadvantage of the particle method is the strong non-monotonicity of the solution caused by the discrete transfer of mass and mass-related quantities from cell to cell. This paper describes a particle method that is free of this drawback. Monotonization of the particle method is performed by spliting the particles so that the volume of matter flowing out of the cell corresponds to the volume calculated according to standard schemes of Lagrangian–Eulerian and Eulerian methods. In order not to generate an infinite chain of spliting, further split particles are re-united when certain conditions are met. The method is developed for modeling 2D and 3D gas-dynamic flows with accompanying processes, in which it is necessary to preserve the history of the process at Lagrangian points.
Тези доповідей конференцій з теми "Transferts advectifs"
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Chalhub, D. J. M. N., L. A. Sphaier, and L. S. de B. Alves. "Hybrid Eigenfunction-Discretization Methodology for Solving Convective Heat Transfer Problems." In ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ht2012-58336.
Повний текст джерелаАнотація:
This paper presents a novel methodology for the solution of problems that include diffusion and advection effects, as naturally occur in convective heat transfer problems. The methodology is based on writing the unknown temperature field in terms of eigenfunction expansions, as traditionally carried-out with the Generalized Integral Transform Technique (GITT). However, a different approach is used for handling advective derivatives. Rather than transforming the advection terms as done in traditional GITT solutions, upwind discretization schemes (UDS) are used prior to the integral transformation. With the introduction of upwind approximations, numerical diffusion is introduced, which can be used to reduce unwanted oscillations that arise at higher Péclet values. This combined methodology is termed the GITT-UDS for convective problems. The procedure is illustrated for a simple case of one-dimensional Burgers’ equation with temperature-dependent velocities. Numerical results are calculated, showing that augmenting the upwind approximation parameter can effectively reduce solution oscillations for higher Péclet values.
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Lefevre, A., Jose Paulo Barbosa Mota, Antonio Jose Silveiro Rodrigo, and Esteban Saatdjian. "Chaotic advection and heat transfer enhancement in Stokes flows." In International Heat Transfer Conference 12. Begellhouse, 2002. http://dx.doi.org/10.1615/ihtc12.3220.
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Marschewski, Julian, Patrick Ruch, Bruno Michel, and Dimos Poulikakos. "Enhancement of Mass and Heat Transfer Using Herringbone-Inspired Microstructures for Application in Microfluidic Redox Flow Cells." In ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icnmm2016-7920.
Повний текст джерелаАнотація:
Enhancing advection is of uttermost importance in many laminar microfluidic devices in order to thin boundary layers which limit both mass and heat transfer. We address this challenge by integrating herringbone-inspired flow promoters in channels for microfluidics. Due to the small dimensions of microchannels, microfluidic devices typically experience a purely laminar flow regime and are thus limited by diffusion. By augmenting diffusion limited transport to the wall of species and heat with advective transport mechanisms, the performance per unit area of microfluidic devices can be significantly improved. In the present contribution, we demonstrate that herringbone microstructures are a very promising class of flow promoters to passively increase both mass transfer in chemical reactions as well as heat transfer within the same device. This combined use of the same passive flow promoter microstructure is for example attractive for on-chip microfluidic redox flow cells for microprocessor power delivery with integrated cooling by using the same electrolyte as an energy carrier and as a coolant.
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Chu, Vincent H., and Wihel Altai. "ADVECTION AND DIFFUSION SIMULATIONS USING LAGRANGIAN BLOCKS." In Proceedings of CHT-12. ICHMT International Symposium on Advances in Computational Heat Transfer. Begellhouse, 2012. http://dx.doi.org/10.1615/ichmt.2012.cht-12.270.
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Mechitoua, N., and P. L. Viollet. "MODELLING OF ADVECTIVE AND RADIATIVE HEAT TRANSFER IN TURBULENT FLOWS APPLICATION TO FURNACE COMPUTATIONS." In International Heat Transfer Conference 9. Begellhouse, 1990. http://dx.doi.org/10.1615/ihtc9.1490.
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Luo, Huan-Lin. "THE UNSTEADY ONE-DIMENSIONAL ADVECTION MODELLING USING CCMC SCHEME." In CHT'97 - Advances in Computational Heat Transfer. Proceedings of the International Symposium. Begellhouse, 1997. http://dx.doi.org/10.1615/ichmt.1997.intsymliqtwophaseflowtranspphencht.290.
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Ranalli, Joseph, and Esther E. M. Peerlings. "Downscaling of Spatial Irradiance Based on Cloud Advection using Transfer Functions." In 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). IEEE, 2021. http://dx.doi.org/10.1109/pvsc43889.2021.9518748.
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Sun, Yong Kweon, and Yong Kyun Kim. "ENHANCEMENT OF HEAT TRANSFER BY CHAOTIC ADVECTION IN A SINGLE SCREW EXTRUDER WITH A STAGGERED FLIGHT GEOMETRY." In International Heat Transfer Conference 11. Begellhouse, 1998. http://dx.doi.org/10.1615/ihtc11.2030.
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Jurcisinova, E., M. Jurcisin, and R. Remecky. "Passive vector advection in the turbulent velocity field with finite correlation time: two-loop approximation." In Turbulence, Heat and Mass Transfer 6. Proceedings of the Sixth International Symposium On Turbulence, Heat and Mass Transfer. Begellhouse, 2009. http://dx.doi.org/10.1615/ichmt.2009.turbulheatmasstransf.1330.
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Moreira, Davidson M., Marco Tulio de Vilhena, D. Buske, and Tiziano Tirabassi. "Analytical Solution for the Transient Two-Dimensional Advection-Diffusion Equation Considering Nonlocal Closure of the Turbulent Diffusion." In Turbulence, Heat and Mass Transfer 5. Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer. Begellhouse, 2006. http://dx.doi.org/10.1615/ichmt.2006.turbulheatmasstransf.1530.
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