Bibliografias temáticas / Reactive diffusive transport

Literatura científica selecionada sobre o tema "Reactive diffusive transport"

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Publicado: 25 de maio de 2024

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Artigos de revistas sobre o assunto "Reactive diffusive transport"

Zimmerman, R. A., G. Severino e D. M. Tartakovsky. "Hydrodynamic dispersion in a tube with diffusive losses through its walls". Journal of Fluid Mechanics 837 (5 de janeiro de 2018): 546–61. http://dx.doi.org/10.1017/jfm.2017.870.

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Advective–diffusive transport of passive or reactive scalars in confined environments (e.g. tubes and channels) is often accompanied by diffusive losses/gains through the confining walls. We present analytical solutions for transport of a reactive solute in a tube, whose walls are impermeable to flow but allow for solute diffusion into the surrounding medium. The solute undergoes advection, diffusion and first-order chemical reaction inside the tube, while diffusing and being consumed in the surrounding medium. These solutions represent a leading-order (in the radius-to-length ratio) approximation, which neglects the longitudinal variability of solute concentration in the surrounding medium. A numerical solution of the full problem is used to demonstrate the accuracy of this approximation for a physically relevant range of model parameters. Our analysis indicates that the solute delivery rate can be quantified by a dimensionless parameter, the ratio of a solute’s residence time in a tube to the rate of diffusive losses through the tube’s wall.

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Seaïd, Mohammed. "On the Quasi-monotone Modified Method of Characteristics for Transport-diffusion Problems with Reactive Sources". Computational Methods in Applied Mathematics 2, n.º 2 (2001): 186–210. http://dx.doi.org/10.2478/cmam-2002-0012.

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AbstractThis is an attempt to construct a strong numerical method for transportdiffusion equations with nonlinear reaction terms, which relies on the idea of the Modified Method of Characteristics that is explicit but stable and is second-order accurate in time. The method consists in convective-diffusive splitting of the equations along the characteristics. The convective stage of the splitting is straightforwardly treated by a quasi-monotone and conservative modified method of characteristics, while the diffusive-reactive stage can be approximated by an explicit scheme with an extended real stability interval. A numerical comparative study of the new method with Characteristics Crank-Nicholson and Classical Characteristics Runge-Kutta schemes, which are used in many transport-diffusion models, is carried out for several benchmark problems, whose solutions represent relevant transport-diffusion-reaction features. Experiments for transport-diffusion equations with linear and nonlinear reactive sources demonstrate the ability of our new algorithm to better maintain the shape of the solution in the presence of shocks and discontinuities.

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CVETKOVIC, V., J. O. SELROOS e H. CHENG. "Transport of reactive tracers in rock fractures". Journal of Fluid Mechanics 378 (10 de janeiro de 1999): 335–56. http://dx.doi.org/10.1017/s0022112098003450.

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Transport of tracers subject to mass transfer reactions in single rock fractures is investigated. A Lagrangian probabilistic model is developed where the mass transfer reactions are diffusion into the rock matrix and subsequent sorption in the matrix, and sorption on the fracture surface as well as on gauge (infill) material in the fracture. Sorption reactions are assumed to be linear, and in the general case kinetically controlled. The two main simplifying assumptions are that diffusion in the rock matrix is one-dimensional, perpendicular to the fracture plane, and the tracer is displaced within the fracture plane by advection only. The key feature of the proposed model is that advective transport and diffusive mass transfer are related in a dynamic manner through the flow equation. We have identified two Lagrangian random variables τ and β as key parameters which control advection and diffusive mass transfer, and are determined by the flow field. The probabilistic solution of the transport problem is based on the statistics of (τ, β), which we evaluated analytically using first-order expansions, and numerically using Monte Carlo simulations. To study (τ, β)-statistics, we assumed the ‘cubic law’ to be applicable locally, whereby the pressure field is described with the Reynolds lubrication equation. We found a strong correlation between τ and β which suggests a deterministic relationship β∼τ3/2; the exponent 3/2 is an artifact of the ‘cubic law’. It is shown that flow dynamics in fractures has a strong influence on the variability of τ and β, but a comparatively small impact on the relationship between τ and β. The probability distribution for the (decaying) tracer mass recovery is dispersed in the parameter space due to fracture aperture variability.

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Horsch, Georgios M. "Steady, Diffusive-Reactive Transport in Shallow Triangular Domain". Journal of Engineering Mechanics 124, n.º 10 (outubro de 1998): 1135–41. http://dx.doi.org/10.1061/(asce)0733-9399(1998)124:10(1135).

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Stefanovic, Dragoslav L., e Heinz G. Stefan. "Accurate Two-Dimensional Simulation of Advective-Diffusive-Reactive Transport". Journal of Hydraulic Engineering 127, n.º 9 (setembro de 2001): 728–37. http://dx.doi.org/10.1061/(asce)0733-9429(2001)127:9(728).

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Heming, T. A., E. K. Stabenau, C. G. Vanoye, H. Moghadasi e A. Bidani. "Roles of intra- and extracellular carbonic anhydrase in alveolar-capillary CO2 equilibration". Journal of Applied Physiology 77, n.º 2 (1 de agosto de 1994): 697–705. http://dx.doi.org/10.1152/jappl.1994.77.2.697.

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Alveolar-capillary CO2 equilibration involves diffusive equilibration of CO2 across the blood-gas barrier and chemical equilibration of perfusate CO2-HCO-3-H+ reactions. These processes are governed by different, but related, driving forces and conductances. The present study examined the importance of pulmonary carbonic anhydrase (CA) for diffusive and reactive CO2 equilibration in isolated rat lungs. Lungs were perfused with salines containing membrane-impermeant or -permeant inhibitors of CA. Measurements of CO2 excretion rate, equilibrated venous and arterial PCO2 and pH, and postcapillary pH and PCO2 disequilibria were used, together with our previous model of CO2-HCO-3-H+ reactions and transport in saline-perfused capillaries (Bidani et al. J. Appl. Physiol. 55: 75–83, 1983), to compute the relevant driving forces and conductances. Reactive CO2 equilibration was markedly affected by extracellular (vascular) CA activity but not by the activity of intracellular (cytosolic) CA. The driving force for CO2 diffusion was strongly influenced by vascular CA activity. The conductance for CO2 diffusion was independent of CA activity. The minimum conductance for CO2 diffusion was estimated to be 700–800 ml.min-1.Torr-1. The results indicate that extracellular vascular CA activity influences both diffusive and reactive CO2 equilibration. However, cytosolic CA has no detectable role in alveolar-capillary CO2 equilibration.

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Liu, Jiangjin, Pablo A. García-Salaberri e Iryna V. Zenyuk. "Bridging Scales to Model Reactive Diffusive Transport in Porous Media". Journal of The Electrochemical Society 167, n.º 1 (2 de janeiro de 2020): 013524. http://dx.doi.org/10.1149/2.0242001jes.

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Jungnickel, Christian, David Smith e Stephen Fityus. "Coupled multi-ion electrodiffusion analysis for clay soils". Canadian Geotechnical Journal 41, n.º 2 (1 de abril de 2004): 287–98. http://dx.doi.org/10.1139/t03-092.

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For a well-engineered compacted clay landfill liner, diffusive transport through the liner is the main mass transport mechanism from the landfill. Therefore, accurate estimates of diffusion coefficients for clay liners are essential for the engineering design of liner systems. A long-standing problem has been the effect of ion pairing on the estimation of diffusion coefficients for multicomponent ionic solutions migrating through clay liners. This paper considers the solution of a fully coupled set of transport equations describing the simultaneous diffusion of several ion species through a clayey soil. The analysis takes into account the diffusion coefficient for each ion species, ion pairing (as required by electroneutrality of the solution), and time-dependent first-order ion and (or) ligand exchange reactions with the clay particles. The behaviour of a double-reservoir diffusion cell, often employed for the estimation of diffusion coefficients in the laboratory, is analyzed using the coupled transport model. A detailed theoretical analysis is made of sodium fluoride transport through saturated kaolinitic clay.Key words: multi-ion diffusion, finite element analysis, reactive transport, kaolinite, double-reservoir diffusion cell.

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Kapoor, Rajat, e S. T. Oyama. "Measurement of solid state diffusion coefficients by a temperature-programmed method". Journal of Materials Research 12, n.º 2 (fevereiro de 1997): 467–73. http://dx.doi.org/10.1557/jmr.1997.0068.

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This paper presents a method for determining diffusivities in solids where the diffusing species desorbs or reacts at the external surfaces, and where the diffusivity does not vary appreciably with concentration. The method involves measuring the flux of the diffusive species out of the solid under the influence of a temperature program. A general model is developed, based on nonisothermal Fickian diffusion, which is applicable to solid particles with slab or spherical geometry. The solution is presented both as an analytical expression and as correlation charts of experimentally observable quantities. These charts are contour diagrams of the temperatures of peak diffusion rate with ln(E/R) and ln(D0/h2) as the axes, where E and D0 are the activation energy and pre-exponential terms of the diffusivity expression D = D0 exp(−E/RT), where R is the gas constant, and h the size of the particles. This paper deals exclusively with the case of oxygen diffusion in the vanadium oxide system. In this case, vanadium oxide was reduced in a reactive ammonia stream at conditions in which the surface reaction was fast compared to the diffusive transport process. Using this method the diffusion parameters were found to be D0 = 1.9 × 10−5 cm2 s−1 and E = 101 kJ/mol. The method was checked by varying the crystallite size of the vanadium oxide sample in the range 2h = 0.14−0.29 μm.

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Honjo, Yusuke, e Thuraisamy Thavaraj. "On uncertainty evaluation of contaminant migration through clayey barriers". Canadian Geotechnical Journal 31, n.º 5 (1 de outubro de 1994): 637–48. http://dx.doi.org/10.1139/t94-076.

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This paper presents a methodology to estimate parameters and to make predictions with quantified uncertainty for an advective–diffusive transport of nonreactive species and low-concentration reactive species through saturated porous media. The methodology is put in the framework of inverse and forward analyses. The maximum-likelihood method (or the weighted least square method) is employed in the inverse analysis, whereas the first-order second-moment method is used in the forward analysis. The methodology facilitates the quantification of uncertainty in the estimated parameters as well as in the predictions. A case study consisting of sets of laboratory tests and field data taken from the literature is used to demonstrate the capability of the proposed methodologies. It is generally recognized that the advective–diffusive transport of contaminants is a rather uncertain process in prediction; therefore the methodology proposed in this study should be useful for practising geotechnical engineers. Key words : statistical analysis, contaminant migration, diffusion, clay barrier, inverse analysis, waste disposal.

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Mais fontes

Teses / dissertações sobre o assunto "Reactive diffusive transport"

Ndjaka, Ange. "THERMOPHYSICAL PROCESSES AND REACTIVE TRANSPORT MECHANISMS INDUCED BY CO2 INJECTION IN DEEP SALINE AQUIFERS". Electronic Thesis or Diss., Pau, 2022. http://www.theses.fr/2022PAUU3003.

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Le stockage du CO2 dans les aquifères salins profonds a été reconnu comme l'une des voies les plus prometteuses pour atténuer les émissions atmosphériques de CO2 et répondre ainsi aux enjeux du changement climatique. Cependant, l’injection du CO2 dans le milieu poreux perturbe considérablement son équilibre thermodynamique. La zone proche du puits d’injection est particulièrement impactée avec une forte réactivité géochimique associée à d’intenses échanges thermiques. Cela a un impact majeur sur l’injectivité du réservoir et l’intégrité du stockage. A ces effets s’ajoute une complexité supplémentaire liée à la présence de deux phases non miscibles : la saumure et le CO2. Ces effets conduisent à des processus Thermo-Hydro-Mécaniques-Chimiques (THMC) fortement couplés, dont les interprétations ne sont pas encore abouties ni formellement implémentées dans les modèles numériques.Ce travail de thèse, associant des mesures expérimentales et des modélisations numériques, porte sur l’étude du couplage entre les gradients thermiques et les processus diffusifs de transport réactif se déroulant dans les aquifères salins, notamment dans la zone proche du puits d’injection. Nous avons étudié les échanges entre une phase froide CO2 anhydre qui s’écoule dans des zones de forte perméabilité, et une phase aqueuse salée chaude piégée dans la porosité de la roche. La stratégie de l'étude commence par une approche simple en milieu libre sans flux de CO2 afin d'étudier la réactivité des solutions salines de différentes compositions chimiques et d’évaluer l'impact d'un gradient thermique sur ce réseau réactionnel.Nous avons développé une cellule expérimentale permettant de superposer 2 à 3 couches de solution de concentration et composition chimique différentes. L’analyse de la lumière diffusée par les fluctuations de non-équilibre de la concentration et de la température permet de remonter aux coefficients de diffusion des sels dans l’eau. Nos résultats sont en bon accord avec les valeurs de la littérature. Pour ce qui est de l’étude du transport réactif diffusif, l’analyse du contraste des images a permis de mettre en évidence le fait que la précipitation de minéral, par mise en contact de deux couches aqueuses de sels réactifs, s’accompagne d’une instabilité convective qui s’estompe dans le temps. La modélisation numérique des résultats expérimentaux avec PHREEQC par une approche de diffusion multi-espèce hétérogène permet de rendre compte des instabilités convectives. Différents gradients de température ont été appliqués au système réactif, tout en conservant une température moyenne de 25 °C. Les observations expérimentales et les interprétations numériques montrent que le gradient de température n'a pas d’influence significative sur le comportement du système.Ensuite, nous avons étudié numériquement le processus de dessiccation (évaporation de l’eau) à l’interface entre une saumure piégée dans la porosité de la roche et du CO2 circulant dans une structure porale drainante, simulant les conditions de l’aquifère du Dogger du bassin parisien. Un modèle couplant l’évaporation de l’eau dans le flux de CO2 et la diffusion multi-espèces hétérogène des sels prévoit l’apparition d’un assemblage minéral au niveau du front d’évaporation, principalement composé d’halite et d’anhydrite. La modélisation de ce phénomène à l’échelle du réservoir nécessite la prise en compte de la vitesse d’évaporation en fonction du taux d’injection du CO2 et de l’évolution de la porosité au niveau de l’interface.Ce travail de thèse a permis de mettre en évidence plusieurs phénomènes physico-chimiques, thermo-physiques et de transport diffusif aux interfaces de phase. Ce qui ouvre de nouvelles perspectives d’amélioration des approches numériques et de modélisation à grande échelle notamment du proche puits d’injection du CO2 et des réservoirs de stockage géologique et soutenir les futurs développements industriels et technologiques pour la transition écologique
CO2 storage in deep saline aquifers has been recognised as one of the most promising ways to mitigate atmospheric CO2 emissions and thus respond to the challenges of climate change. However, the injection of CO2 into the porous medium considerabely disturbs its thermodynamic equilibrium. The near-well injection zone is particularly impacted with a strong geochemical reactivity associated with intense heat exchanges. This has a major impact on injectivity of the reservoir and the integrity of the storage. In addition to these effects, there is the added complexity of the presence of two immiscible phases: brine (wetting fluid) and CO2 (non-wetting fluid). These effects lead to highly coupled Thermo-Hydro-Mechanical-Chemical (THMC) processes, whose interpretations have not yet been completed nor formally implemented into the numerical models.This thesis work, combining experimental measurements and numerical modelling, focuses on the study of the coupling between the thermal gradients and the diffusive reactive transport processes taking place in the deep saline aquifers, particularly in the near-well injection zone. We studied the exchanges between a cold anhydrous CO2 phase flowing in high permeability zones, and a hot salty aqueous phase trapped in the porosity of the rock. The strategy of the study starts with a simple approach in a free medium without CO2 flow, in order to study the reactivity of saline solutions of different chemical compositions, and to evaluate the impact of a thermal gradient on this reaction network.We have developed an experimental cell that allow to superimpose 2 to 3 layers of solution of different concentration and chemical composition. The analysis of the light scattered by the non-equilibrium fluctuations of concentration and temperature allows to obtain the diffusion coefficients of salts in water. Our results are in good agreement with literature values. Regarding the study of diffusive reactive transport, the analysis of the contrast of the images allowed us to highlight the fact that the precipitation of minerals, obtained by superimposing two aqueous layers of reactive, is accompanied by a convective instability that fades with time. Numerical modelling of the experimental results with PHREEQC using a heterogeneous multicomponent diffusion approach has allowed us to account for these convective instabilities. Different temperature gradients were applied to the reactive system, while keeping a mean temperature of 25 °C. The experimental observations and numerical interpretations swhow that the temperature gradient has no significant influence on the behaviour of the system. Subsequently, we numerically studied the desiccation process (evaporation of water) at the interface between a brine trapped in the rock porosity and the CO2 flowing in a draining pore structure, simulating the conditions of the Dogger aquifer of the Paris basin. A model coupling the evaporation of water in the CO2 stream and the heterogeneous multicomponent diffusion of salts predicts the appearance of a mineral assemblage at the evaporation front, mainly composed by halite and anhydrite. Modelling this phenomenon at the reservoir scale would requires taking into account the evaporation rate as a function of the CO2 injection rate and the change in porosity at the interface.This thesis work has made it possible to highlight several physicochemical, thermophysical and diffusive transport phenomena at phase interfaces. This opens up new perspectives for improving numerical approaches and large-scale modelling, in particular of near-well injection of CO2 and geological storage reservoirs, and supports future industrial developments and technologies for the ecological transition

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Seigneur, Nicolas. "A coupled experimental, numerical and statistical homogenization approach towards an accurate feedback relationship between porosity and diffusive properties of model cementitious materials in the field of reactive transport modelling". Doctoral thesis, Universite Libre de Bruxelles, 2016. https://dipot.ulb.ac.be/dspace/bitstream/2013/237928/3/TDM.pdf.

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Au vu de leurs différentes propriétés, les matériaux cimentaires sont largement considérés dans les différents projets de gestion de déchets radioactifs. Leurs propriétés mécaniques, leurs faibles coefficients de transport ainsi que leur capacité à fixer les principaux radionucléides sont les principaux avantages qui en font un des meilleurs choix pour la conception des barrières ouvragées.Pour les études de sûreté, leur durabilité est capitale. Au cours de la vie d’un tel dépôt,via l’infiltration d’eau ou les interfaces chimiquement agressives avec les argiles, les différents matériaux vont subir des perturbations physicochimiques qui vont altérer leurs structures et potentiellement compromettre leurs fonctions de sûreté. L’étendue de ces perturbations, fondamentale pour l’étude de sûreté, est contrôlée par les propriétés de transport de ces matériaux.Pour modéliser proprement ces phénomènes, il faut pouvoir coupler les évolutions géochimiques des matériaux tout en évaluant le transport à travers ceux-ci. C’est le but de différents codes de transport réactif, qui utilisent une loi de rétroaction pour modifier les propriétés de transport lors d’une modification de microstructure. Le problème est qu’il n’existe pas de loi de rétroaction adaptée aux matériaux cimentaires, qui possèdent une structure poreuse complexe du nanomètre jusqu’à plusieurs micromètres. En général, des lois empiriques de type Archie sont utilisées. Toutefois, même l’utilisation de lois plus sophistiquées ne permet pas de reproduire sensiblement les évolutions liées à la structure porale. Cette loi de rétroaction est probablement la principale raison pour laquelle les résultats de simulation ont du mal à reproduire lesrésultats expérimentaux. Le but de cette thèse est de proposer une meilleure loi de rétroaction et de l’intégrer dans un code de transport réactif.Pour ce faire, trois approches complémentaires ont été mises en oeuvre. La première, expérimentale,consiste en la réalisation des matériaux cimentaires les plus simples possibles :des phases C-S-H pures et une pâte de ciment modèle. Ces matériaux sont ensuite caractérisés finement :leurs propriétés de transport sont évaluées et une description fine de leur microstructure est obtenue. L’approche expérimentale consiste ensuite en la dégradation (par lixiviation et carbonatation sous eau) de la pâte de ciment modèle, afin de comprendre l’impact de ces dégradations sur la microstructure et les propriétés de transport.La deuxième partie, numérique, consiste en l’obtention d’un volume élémentaire représentatif de la pâte de ciment modèle, basée sur les caractérisations expérimentales. Différentes analyses de sensibilité et de propriétés de transport permettent de comprendre les liens entre les différents paramètres et les propriétés effectives. Ensuite, l’approche numérique modélise les dégradations.Ces approches numériques démontrent pourquoi les approches empiriques fonctionnent dans certains cas, et pas dans d’autres.La dernière partie dédiée à la modélisation mathématique développe une approche d’homogénéisation statistique de la diffusion, basée sur une description du phénomène à l’échelle du pore. Cette étude met en évidence des paramètres clés qui contrôlent les propriétés effectives de diffusion.C’est ce pour quoi il est démontré que cette approche, en plus d’être très adaptée aux matériaux cimentaires, est applicable à un large spectre de microstructures. Les paramètres mis en évidences ont intrinsèquement sensibles aux propriétés de percolation et de connectivités de la structure poreuse, qui sont centrales pour la compréhension des propriétés effectives de transport ainsi que l’impact des dégradations. La finalité de la thèse consiste en le couplage de ces différentes approches et en l’incorporation de celles-ci dans un code de transport réactif. Les résultats obtenus en utilisant différentes lois de rétroaction sont comparés entre eux. L’utilisation de lois de rétroaction basée sur l’étude tri-dimensionnelle de la microstructure améliore la comparaison aux résultats expérimentaux.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

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Morgado, Lopes André. "Reactive transport through nanoporous materials". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0560/document.

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Le but de cette thèse est d’étudier le comportement des asphaltènes dans des condition de hydrotraitement, y compris les propriétés de transport et d’adsorption. La chromatographie d'exclusion stérique inverse (ISEC) ainsi que la spectroscopie d'impédance sont utilisées pour déterminer des paramètres topologiques de solides poreux d’alumine (porosité, taille de pores, tortuosité). Des coefficients de diffusion effectifs de polystyrènes de différentes tailles sont aussi étudiés par chromatographie liquide en conditions non-adsorbantes: les molécules de petites tailles pénètrent plus profondément dans le milieu poreux donc elles prennent plus de temps pour traverser la colonne, tandis que les molécules ayant une taille supérieure à la taille du pore ne sondent que la macroporosité. Avec l'utilisation des méthodes dynamique et «peak parking», il est possible de modéliser le transport des molécules de différentes tailles, et cela aidera à prédire le comportement de molécules d’une taille quelconque. Les colonnes ont été assemblées au laboratoire à partir de poudres et de monolithes d’alumine. Les caractéristiques d'adsorption des asphaltènes modèles sont déterminées et comparées avec une fraction d’asphaltènes extraite d’un brut. Un phénomène de dimérisation ainsi qu’une très forte adsorption sur la surface de l’alumine sont observés avec la molécule modèle. La méthode dynamique a été utilisée avec des colonnes courtes dans des conditions de saturation. Une influence apparente du débit dans l’importance et le mécanisme d’adsorption a pu être constatée
This work aims to study the complex behaviors of asphaltenes within the hydrotreatment catalytic porous system including transport properties and adsorption. Inverse size-exclusion chromatography (ISEC) and impedance spectroscopy are used to determine the topological characteristics of different alumina porous solids (porosity, pore size, tortuosity). The effective diffusion coefficient of polystyrenes of different sizes was studied via chromatography in non-adsorbing conditions. Elution peaks are used to determine the effect of molecule size on the accessible pore volume and the transport properties therein: molecules of relatively small sizes penetrate further into the porous medium, thus taking more time to navigate the chromatographic setup, while larger molecules traverse much faster, through the macroporosity. The liquid chromatography technique is divided in two different methods. Both methods yield diffusion coefficient values which are modelled, predicting the behavior of molecules of any size. Columns were assembled manually from alumina powders or monoliths. A synthesized asphaltene model molecule was used and its adsorption behavior was determined and compared to an asphaltene fraction recovered from crude oil. The asphaltene model molecule shows a dimerization behavior as well as extremely strong interactions with the alumina surface. Dynamic method was attempted in short alumina columns at saturation conditions and an apparent influence of the flow rate on the extent and mechanics of adsorption was observed

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Pfeifer, Peter, e Chen Hou. "Diffusion-Reaction in space-filling networks". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184563.

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Kaganovskii, Yuri, Andrey A. Lipovskii, Emma Mogilko, Valentina Zhurikhina e Michael Rosenbluh. "Kinetics of bulk nano-clustering in silver-doped glasses during reactive hydrogen diffusion". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193695.

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Agliari, Elena, Raffaella Burioni, Davide Cassi e Franco M. Neri. "Autocatalytic reaction-diffusion processes in restricted geometries". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192966.

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Kuzovkov, Vladimir, Guntars Zvejnieks, Olaf Kortlüke e Niessen Wolfgang von. "Forced oscillations in self-oscillating surface reaction models". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195406.

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Kosztolowicz, Tadeusz, e Katarzyna D. Lewandowska. "Subdiffusive reaction front in the enamel caries process". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196978.

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Starting with the equation describing subdiffusion associated with chemical reactions for one-static reactant, we show that the reaction front X f evolves in time as x f ~ t α/2 with α < 1. The equation is applied to the carious lesion which is caused by the chemical reactions of diffusing acid molecules or pure hydrogen ions with static hydroxyapatite in the tooth enamel. Comparing our theoretical results with the already published experimental ones, we conclude that in some cases the transport process of the acids in the tooth enamel appears to be subdiffusive and should be described by the subdiffusion-reaction equation with the fractional time derivative.

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Sinder, Michael, Zeev Burshtein e Joshua Pelleg. "Reaction fronts and ambipolar chemical diffusion in oxide crystals". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-198684.

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Agliari, Elena, Raffaella Burioni, Davide Cassi e Franco M. Neri. "Autocatalytic reaction-diffusion processes in restricted geometries". Diffusion fundamentals 7 (2007) 1, S. 1-8, 2007. https://ul.qucosa.de/id/qucosa%3A14157.

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Livros sobre o assunto "Reactive diffusive transport"

Jäger, Willi, Rolf Rannacher e Jürgen Warnatz, eds. Reactive Flows, Diffusion and Transport. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-28396-6.

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C, Helgeson Harold, e United States. Dept. of Energy. Office of Scientific and Technical Information., eds. Multi-phase reactive transport theory. Washington, D.C. : The Commission: Available from GPO Sales Program, Division of Technical Information and Document JControl, U.S. Nuclear Regulatory Commission, 1995.

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Sergei, Fedotov, e Horsthemke W. (Werner) 1950-, eds. Reaction-transport systems: Mesoscopic foundations, fronts, and spatial instabilities. Heidelberg: Springer, 2010.

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Periodic precipitation: A microcomputer analysis of transport and reaction processes in diffusion media, with software development. Oxford [England]: Pergamon, 1991.

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1940-, Jäger W., Rannacher Rolf e Warnatz J, eds. Reactive flows, diffusion and transport: From experiments via mathematical modeling to numerical simulation and optimization : final report of SFB (Collaborative Research Center) 359. Berlin: Springer, 2007.

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Warnatz, J., Rolf Rannacher e Willi Jäger. Reactive Flows, Diffusion and Transport: From Experiments via Mathematical Modeling to Numerical Simulation and Optimization. Springer, 2016.

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(Editor), Willi Jäger, Rolf Rannacher (Editor) e Jürgen Warnatz (Editor), eds. Reactive Flows, Diffusion and Transport: From Experiments via Mathematical Modeling to Numerical Simulation and Optimization. Springer, 2006.

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Reactive Flows, Diffusion and Transport: From Experiments Via Mathematical Modeling to Numerical Simulation and Optimization. Springer London, Limited, 2007.

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Henisch, H. K. Periodic Precipitation: A Microcomputer Analysis of Transport and Reaction Processes in Diffusion Media, with Software Development. Elsevier Science & Technology Books, 2014.

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Capítulos de livros sobre o assunto "Reactive diffusive transport"

Ewing, Richard E., e Hong Wang. "Eulerian-Lagrangian Localized Adjoint Methods for Variable-Coefficient Advective-Diffusive-Reactive Equations in Groundwater Contaminant Transport". In Advances in Optimization and Numerical Analysis, 185–205. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-015-8330-5_12.

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Méndez, Vicenç, Sergei Fedotov e Werner Horsthemke. "Reaction–Diffusion Fronts". In Reaction–Transport Systems, 123–53. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11443-4_4.

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Sanwald, S., J. v. Saldern, U. Riedel, C. Schulz, J. Warnatz e J. Wolfram. "Transport and Diffusion in Boundary Layers of Turbulent Channel Flow". In Reactive Flows, Diffusion and Transport, 419–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-28396-6_16.

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von Rohden, C., A. Hauser, K. Wunderle, J. Ilmberger, G. Wittum e K. Roth. "Lake Dynamics: Observation and High-Resolution Numerical Simulation". In Reactive Flows, Diffusion and Transport, 599–619. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-28396-6_23.

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Méndez, Vicenç, Sergei Fedotov e Werner Horsthemke. "Reaction–Diffusion Fronts in Complex Structures". In Reaction–Transport Systems, 183–208. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11443-4_6.

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Méndez, Vicenç, Sergei Fedotov e Werner Horsthemke. "Reactions and Transport: Diffusion, Inertia, and Subdiffusion". In Reaction–Transport Systems, 33–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11443-4_2.

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Quarteroni, Alfio. "Diffusion-transport-reaction equations". In Numerical Models for Differential Problems, 315–65. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-49316-9_13.

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Quarteroni, Alfio. "Diffusion-transport-reaction equations". In Numerical Models for Differential Problems, 291–338. Milano: Springer Milan, 2014. http://dx.doi.org/10.1007/978-88-470-5522-3_12.

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Méndez, Vicenç, Sergei Fedotov e Werner Horsthemke. "Turing Instabilities in Reaction–Diffusion Systems with Temporally or Spatially Varying Parameters". In Reaction–Transport Systems, 333–44. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11443-4_11.

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Viehland, Larry A. "Ab Initio Calculations of Transport Coefficients". In Gaseous Ion Mobility, Diffusion, and Reaction, 155–218. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-04494-7_6.

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Trabalhos de conferências sobre o assunto "Reactive diffusive transport"

Travascio, Francesco, e Wei Yong Gu. "A New Fluorescence Photobleaching Method for Determining Solute Diffusive-Reactive Properties in Biological Tissues". In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19397.

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Bothe, Dieter, Alexander Lojewski e Hans-Joachim Warnecke. "Direct Numerical Simulation of Reactive Mixing in a T-Shaped Micro-Reactor". In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37507.

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The large area-to-volume ratio of micro-reactors gives prospect of better yield and selectivity than for conventional designs, since diffusive fluxes of mass and heat in micro-devices scale with the area, while the rate of changes corresponding to sources and sinks are proportional to the volume. Indeed, theoretical considerations of the scaling behavior support the fact that micro-reactors allow for faster chemical reactions and provide better thermal control; cf., e.g., [1]. For applications in Chemical Reaction Engineering, the mixing of chemical species is of special interest, since it is an essential condition for chemical reactions to occur. Avoiding large pressure drops, laminar flow fields with secondary flows are chosen to increase the contact area between the inflowing educts. In this laminar but complex flow, the mixing state is determined by the interplay of convective and diffusive transport phenomena and, hence, a thorough CFD-simulation of yield and selectivity of such a reacting flow requires the resolution of the finest length scales of both the velocity and the concentration field. In order to reduce the numerical complexity we employ a simplified mathematical model of the relevant convection-diffusion-reaction equations similar to the parabolized Navier-Stokes system.

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Palanisamy, Barath, Yu-Wei Su, Anna Garrison, Brian Paul e Chih-hung Chang. "Cadmium Sulfide Nanoparticle Synthesis Using Oscillatory Flow Mixing". In ASME 2011 International Manufacturing Science and Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/msec2011-50276.

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Microchannel mixers enable faster mixing times compared with batch stir mixing leading to the promise of higher throughput, better yields and less solvent usage for the solution-phase reactive precipitation of inorganic nanoparticles. However, reliance on diffusive transport for subsecond mixing requires channel dimensions in the tens of micrometers. These channel dimensions make diffusive micromixers vulnerable to clogging. In this paper, an oscillatory flow mixing strategy is explored to increase the contact area between reagents within larger microchannels. Forward and reverse oscillatory signals are designed to pump reactants through a 450 μm high serpentine microchannel to increase advection within the flow. Computational fluid dynamics simulations are performed to provide insight into flow behavior and nanoparticle morphology. Quantification of mixing performance is proposed using mixing quality and particle residence time metrics. Experimental validation is pursued through the reactive precipitation of CdS quantum dots using a reverse oscillatory mixing setup. Transmission electron microscopy provides insights into the particle size distribution and particle crystallinity.

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Travascio, Francesco, Chun Yuh Huang e Wei Yong Gu. "Transport of Insulin-Like Growth Factor 1 in Intervertebral Disc: Effect of Binding Interactions and Inhomogeneous Distribution of Binding Proteins in Annulus Fibrosus and Nucleus Pulposus". In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19469.

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The intervertebral disc (IVD), being the largest avascular structure in human body, receives nourishment from the vascular network present near its periannular surface and at cartilage endplates (CEPs). It is believed that insufficient nutritional supply is a major cause for disc degeneration [1]. Understanding the mechanisms of solute transport in IVD is crucial for elucidating the etiology of disc degeneration, and to develop strategies for tissue repair (in vivo), and tissue engineering (in vitro). Transport in IVD is complex and involves a series of electromechanical, chemical, and biological coupled events. This study focused on the implications of solute-tissue reversible binding reactions on transport phenomena in the disc. A two dimensional (2D) finite element model was developed to predict diffusive-reactive transport in IVD. The numerical model was used to simulate transport of insulin-like growth factor 1 (IGF-1) in IVD, in the presence of binding interactions between IGF-1 and IGF-binding proteins (IGFBP-3) located on the extracellular matrix (ECM) of the disc.

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Jarrahbashi, Dorrin, Sayop Kim e Caroline L. Genzale. "Simulation of Combustion Recession After End-of-Injection at Diesel Engine Conditions". In ASME 2016 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icef2016-9433.

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Recent experimental observations show that lifted diesel flames tend to propagate back towards the injector after the end of injection under conventional high-temperature combustion conditions. Earlier studies have referred to this phenomenon as “flashback,” but more recently the term “combustion recession” has been adopted to reflect findings that the process appears dominated by “auto-ignition” reactions upstream of the lifted flame after the end of injection. Since this process is only initiated after the end of injection, it is also closely linked to the end-of-injection entrainment wave and its impact on the transient mixture-chemistry evolution upstream of the lift-off length. A few recent studies have explored the physics of combustion recession with experimental and simplified modeling approaches, but the details of the chemical kinetics and convective-diffusive transport of reactive scalars in this phenomenon are still largely unexplored. There are also uncertainties in the capability of engine computational fluid dynamics (CFD) simulations to accurately capture entrainment wave and combustion recession phenomena. In this study, highly-resolved numerical simulations have been employed to explore the mixing and combustion of a diesel spray after the end of injection and the influence of modeling choices on the prediction of these phenomena. The simulations are centered on a temperature sweep around the Engine Combustion Network (ECN) Spray-A conditions, from 800–1000 K, where different combustion recession behaviors are observed experimentally. Reacting spray simulations are performed in the open-source CFD software OpenFOAM, using a Reynolds-Averaged Navier-Stokes (RANS) approach with a traditional Lagrangian-Eulerian coupled formulation for two-phase mixture transport. Two reduced chemical kinetics models for n-dodecane by Yao et al. and Cai et al. are used to evaluate the impact of low-temperature chemistry and mechanism formulation on predictions of combustion recession behavior. Observations from the numerical simulations are consistent with recent findings that a two-stage auto-ignition sequence drives the combustion recession process; self-sustained reacting mixtures arise in distinct regions that are spatially separated from the lifted flame. Simulations with two different chemical mechanisms indicate that low-temperature chemistry reactions drive the likelihood for second-stage ignition and combustion recession that in turn strongly influence local entrainment in these mixtures and likelihood of combustion recession.

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Nishimiya, Yuusaku, Tetsuya Asai e Yoshihito Amemiya. "Reaction-Diffusion Devices Using Minority-Carrier Transport in Semiconductors". In 2001 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 2001. http://dx.doi.org/10.7567/ssdm.2001.p-1-3.

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Shewchun, John, Ming-Chia Lai e Santosh A. Bhaskarachari. "An Electronic Model for Transport in Fuel Cell Systems". In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59552.

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Existing descriptions for the current-voltage characteristics of a fuel cell are based on classical thermodynamics, which treat the cell as a simple reversible chemical reaction ( A + B ↔ C + D). The cell voltage is given through the Nernst equation in terms of the concentrations of the reacting species. However, cell current can only be expressed phenomenologically through voltage losses due to charge and mass transport, which are termed “polarizations.” The main component of the cell current (the operating region) is controlled by the diffusion gradients at the two porous electrodes (anode and cathode) and is expressed through Fick’s law.

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Nelson, George J., Comas Haynes e William Wepfer. "A Fractal Approach for Modeling SOFC Electrode Mass Transport". In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12870.

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Fractal modeling approaches are common in the study of porous media and may be applied to describe pore surface morphology and network topology within a porous medium. Fractal structures can serve as templates for the pore structure and allow for the more detailed examination of diffusion phenomena within pore structures. In the present work a fractal pore morphology model is applied toward modeling diffusion within the electrochemically active region of an SOFC electrode. The porous electrode is separated into bulk and electrochemically active regions. Within the bulk electrode a one-dimensional model is applied based on the dusty-gas formalism assuming volume average microstructural parameters. The electrochemically active region is modeled using a two-dimensional finite element model based on a Koch pore cross-section as a fractal template. This fractal model is compared to a one-dimensional transport model applying the common assumption of a planar reaction zone. Performance variations that may exist for electrodes with the same average bulk properties are investigated in initial studies. These studies allow for exploration of the merits of fractal approaches in modeling diffusive transport within porous SOFC electrodes.

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Yang, Guogang, Wei Wei, Jinliang Yuan, Danting Yue e Xinrong Lv. "Analysis of Transport Processes and Chemical Reaction in Combustion Duct of Compact Methane Reformer". In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22420.

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A composite combustion duct in compact methane reformers consists of a gas flow channel, porous layer and solid plates. There are various transport processes appeared, such as gas flow in the channel, multi-component species convection/diffusion in the porous layer, and heat transfer. They are further coupled by methane catalytic combustion in the porous layer, which affects the reformer overall performance and reliability. By three dimensional CFD approach, the reacting gas flow and heat transfer processes were numerically studied. The reformer conditions such as mass balances associated with the chemical reaction and gas permeation to/from the porous layer are implemented in the calculation. The results reveal that the catalytic combustion reaction is confined in a thin porous catalyst area close to fuel gas flow duct. Transport processes of the fuel gas species and temperature distribution are significantly affected by the reactions.

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Ben Abdallah, Ramzi, Vishal Sethi, Pierre Q. Gauthier, Andrew Martin Rolt e David Abbott. "A Detailed Analytical Study of Hydrogen Reaction in a Novel Micromix Combustion System". In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76586.

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Liquid hydrogen is considered a technically feasible fuel for all gas turbine applications including propulsion systems [1]. However, the exceptional combustion properties of hydrogen will make fundamental changes to gas turbine combustion systems essential. Micromixing, with a novel cross-flow fuel-injection feature and a large plurality of injection holes offers miniaturised diffusive combustion without the risk of auto-ignition or flashback. A detailed analytical study has been performed to explore combustion behaviour of hydrogen in the micro-diffusion combustor concept. The aims are to investigate a broad range of analytical tools and sensitivities related to hydrogen micromix combustion numerical modelling. Comparative studies based on a number of RANS and LES simulations were carried out to down-select suitable numerical models for species transport, turbulence, chemistry and thermochemistry. Simulation results were found to be particularly sensitive to the species diffusion effects. The study was then extended to identify proper thermal boundary conditions capable of replicating experimental work. A thorough discussion of the findings is provided. The study has generated a novel micromix-injector geometry promising to yield ultra-low NOx emissions. This paper sheds light on the difficulties encountered in modelling the combustion of a gaseous fuel (hydrogen) in a novel micro-diffusion combustion chamber and suggests effective approaches to overcome them. It also identifies additional benefits related to hydrogen as a fuel.

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Relatórios de organizações sobre o assunto "Reactive diffusive transport"

Helgeson, Harold, e Hans-Rudolf Wenk. Diffusion/Dispersion Transport of Chemically Reacting Species. Office of Scientific and Technical Information (OSTI), junho de 2014. http://dx.doi.org/10.2172/1133358.

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Tartakovsky, Daniel. Stochastic Analysis of Advection-diffusion-Reactive Systems with Applications to Reactive Transport in Porous Media. Office of Scientific and Technical Information (OSTI), agosto de 2013. http://dx.doi.org/10.2172/1149536.

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Karniadakis, George Em. Final Technical Report - Stochastic Analysis of Advection-Diffusion-reaction Systems with Applications to Reactive Transport in Porous Media - DE-FG02-07ER24818. Office of Scientific and Technical Information (OSTI), março de 2014. http://dx.doi.org/10.2172/1122803.

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Wang, Chi-Jen. Analysis of discrete reaction-diffusion equations for autocatalysis and continuum diffusion equations for transport. Office of Scientific and Technical Information (OSTI), janeiro de 2013. http://dx.doi.org/10.2172/1226552.

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Helgeson, H. C. [Diffusion/dispersion transport of chemically reacting species]. Progress report, FY 1992--1993. Office of Scientific and Technical Information (OSTI), julho de 1993. http://dx.doi.org/10.2172/10166586.

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Lichtner, P. C., e H. C. Helgeson. Advective-diffusive/dispersive transport of chemically reacting species in hydrothermal systems. Final report, FY83-85. Office of Scientific and Technical Information (OSTI), junho de 1986. http://dx.doi.org/10.2172/5055237.

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Kirchhoff, Helmut, e Ziv Reich. Protection of the photosynthetic apparatus during desiccation in resurrection plants. United States Department of Agriculture, fevereiro de 2014. http://dx.doi.org/10.32747/2014.7699861.bard.

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In this project, we studied the photosynthetic apparatus during dehydration and rehydration of the homoiochlorophyllous resurrection plant Craterostigmapumilum (retains most of the photosynthetic components during desiccation). Resurrection plants have the remarkable capability to withstand desiccation, being able to revive after prolonged severe water deficit in a few days upon rehydration. Homoiochlorophyllous resurrection plants are very efficient in protecting the photosynthetic machinery against damage by reactive oxygen production under drought. The main purpose of this BARD project was to unravel these largely unknown protection strategies for C. pumilum. In detail, the specific objectives were: (1) To determine the distribution and local organization of photosynthetic protein complexes and formation of inverted hexagonal phases within the thylakoid membranes at different dehydration/rehydration states. (2) To determine the 3D structure and characterize the geometry, topology, and mechanics of the thylakoid network at the different states. (3) Generation of molecular models for thylakoids at the different states and study the implications for diffusion within the thylakoid lumen. (4) Characterization of inter-system electron transport, quantum efficiencies, photosystem antenna sizes and distribution, NPQ, and photoinhibition at different hydration states. (5) Measuring the partition of photosynthetic reducing equivalents between the Calvin cycle, photorespiration, and the water-water cycle. At the beginning of the project, we decided to use C. pumilum instead of C. wilmsii because the former species was available from our collaborator Dr. Farrant. In addition to the original two dehydration states (40 relative water content=RWC and 5% RWC), we characterized a third state (15-20%) because some interesting changes occurs at this RWC. Furthermore, it was not possible to detect D1 protein levels by Western blot analysis because antibodies against other higher plants failed to detect D1 in C. pumilum. We developed growth conditions that allow reproducible generation of different dehydration and rehydration states for C. pumilum. Furthermore, advanced spectroscopy and microscopy for C. pumilum were established to obtain a detailed picture of structural and functional changes of the photosynthetic apparatus in different hydrated states. Main findings of our study are: 1. Anthocyan accumulation during desiccation alleviates the light pressure within the leaves (Fig. 1). 2. During desiccation, stomatal closure leads to drastic reductions in CO2 fixation and photorespiration. We could not identify alternative electron sinks as a solution to reduce ROS production. 3. On the supramolecular level, semicrystalline protein arrays were identified in thylakoid membranes in the desiccated state (see Fig. 3). On the electron transport level, a specific series of shut downs occur (summarized in Fig. 2). The main events include: Early shutdown of the ATPase activity, cessation of electron transport between cyt. bf complex and PSI (can reduce ROS formation at PSI); at higher dehydration levels uncoupling of LHCII from PSII and cessation of electron flow from PSII accompanied by crystal formation. The later could severe as a swift PSII reservoir during rehydration. The specific order of events in the course of dehydration and rehydration discovered in this project is indicative for regulated structural transitions specifically realized in resurrection plants. This detailed knowledge can serve as an interesting starting point for rationale genetic engineering of drought-tolerant crops.

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Reaction kinetics and transport properties of the CaO-SO sub 2 -O sub 2 system in absence of intra-particle diffusion. Office of Scientific and Technical Information (OSTI), janeiro de 1991. http://dx.doi.org/10.2172/6375681.

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