Academic literature on the topic 'Approche à interface diffuse'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Approche à interface diffuse.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Journal articles on the topic "Approche à interface diffuse":

1

ELLIOTT, CHARLES M., and BJÖRN STINNER. "ANALYSIS OF A DIFFUSE INTERFACE APPROACH TO AN ADVECTION DIFFUSION EQUATION ON A MOVING SURFACE." Mathematical Models and Methods in Applied Sciences 19, no. 05 (May 2009): 787–802. http://dx.doi.org/10.1142/s0218202509003620.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
A diffuse interface model for an advection diffusion equation on a moving surface is formulated involving a small parameter ε related to the thickness of the interfacial layer. The coefficient functions degenerate on the boundary of the diffuse interface. In appropriately weighted Sobolev spaces, existence and uniqueness of weak solutions is shown. Using energy methods the convergence of solutions to the diffuse interface model to the solution to the equation on the moving surface as ε → 0 is proved. The approach is intended to be applied to phase field models describing the surface motion. Among other problems we have surfactants on liquid-liquid interfaces and species diffusion on moving grain boundaries in mind.
2

Gránásy, L. "Diffuse Interface Approach to Crystal Nucleation." Materials Science Forum 215-216 (June 1996): 451–58. http://dx.doi.org/10.4028/www.scientific.net/msf.215-216.451.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Gránásy, L. "Diffuse Interface Approach to Vapour Condensation." Europhysics Letters (EPL) 24, no. 2 (October 10, 1993): 121–26. http://dx.doi.org/10.1209/0295-5075/24/2/008.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Rätz, Andreas, and Axel Voigt. "PDE's on surfaces---a diffuse interface approach." Communications in Mathematical Sciences 4, no. 3 (2006): 575–90. http://dx.doi.org/10.4310/cms.2006.v4.n3.a5.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Daher, Ali, Amine Ammar, and Abbas Hijazi. "Nanoparticles migration near liquid-liquid interfaces using diffuse interface model." Engineering Computations 36, no. 3 (April 8, 2019): 1036–54. http://dx.doi.org/10.1108/ec-03-2018-0153.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Purpose The purpose of this paper is to develop a numerical model for the simulation of the dynamics of nanoparticles (NPs) at liquid–liquid interfaces. Two cases have been studied, NPs smaller than the interfacial thickness, and NPs greater than the interfacial thickness. Design/methodology/approach The model is based on the molecular dynamics (MD) simulation in addition to phase field (PF) method, through which the discrete model of particles motion is superimposed on the continuum model of fluids which is a new ide a in numerical modeling. The liquid–liquid interface is modeled using the diffuse interface model. Findings For NPs smaller than the interfacial thickness, the results obtained show that the concentration gradient of one fluid in the other gives rise to a hydrodynamic drag force that drives the NPs to agglomerate at the interface. Whereas, for spherical NPs greater than the interfacial thickness, the results show that such NPs oscillate at the interface which agrees with some experimental studies. Practical implications The results are important in the field of numerical modeling, especially that the model is general and can be used to study different systems. This will be of great interest in the field of studying the behavior of NPs inside fluids and near interfaces, which enters in many industrial applications. Originality/value The idea of superimposing the molecular dynamic method on the PF method is a new idea in numerical modeling.
6

Glasner, Karl. "A diffuse interface approach to Hele Shaw flow." Nonlinearity 16, no. 1 (October 28, 2002): 49–66. http://dx.doi.org/10.1088/0951-7715/16/1/304.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Gránásy, László, and Dieter M. Herlach. "Diffuse interface approach to crystal nucleation in glasses." Journal of Non-Crystalline Solids 192-193 (December 1995): 470–73. http://dx.doi.org/10.1016/0022-3093(95)00430-0.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Millett, Paul C., and Yu U. Wang. "Diffuse-interface field approach to modeling arbitrarily-shaped particles at fluid–fluid interfaces." Journal of Colloid and Interface Science 353, no. 1 (January 2011): 46–51. http://dx.doi.org/10.1016/j.jcis.2010.09.021.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Rätz, Andreas, and Matthias Röger. "A new diffuse-interface approximation of the Willmore flow." ESAIM: Control, Optimisation and Calculus of Variations 27 (2021): 14. http://dx.doi.org/10.1051/cocv/2021013.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Standard diffuse approximations of the Willmore flow often lead to intersecting phase boundaries that in many cases do not correspond to the intended sharp interface evolution. Here we introduce a new two-variable diffuse approximation that includes a rather simple but efficient penalization of the deviation from a quasi-one dimensional structure of the phase fields. We justify the approximation property by a Gamma convergence result for the energies and a matched asymptotic expansion for the flow. Ground states of the energy are shown to be one-dimensional, in contrast to the presence of saddle solutions for the usual diffuse approximation. Finally we present numerical simulations that illustrate the approximation property and apply our new approach to problems where the usual approach leads to an undesired behavior.
10

Boettinger, W. J., J. E. Guyer, C. E. Campbell, and G. B. McFadden. "Computation of the Kirkendall velocity and displacement fields in a one-dimensional binary diffusion couple with a moving interface." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 463, no. 2088 (October 9, 2007): 3347–73. http://dx.doi.org/10.1098/rspa.2007.1904.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
The moving interface problem in a one-dimensional binary α/β diffusion couple is studied using sharp and diffuse interface (Cahn–Hilliard) approaches. With both methods, we calculate the solute field and the Kirkendall marker velocity and displacement fields. In the sharp interface treatment, the velocity field is generally discontinuous at the interphase boundary, but can be integrated to obtain a displacement field that is continuous everywhere. The diffuse interface approach avoids this discontinuity, simplifies the integration and yet gives the same qualitative behaviour. Special features observed experimentally and reported in the literature are also studied with the two methods: (i) multiple Kirkendall planes, where markers placed on the initial compositional discontinuity of the diffusion couple bifurcate into two locations, and (ii) a Kirkendall plane that coincides with the interphase interface. These situations occur with special values of the interdiffusion coefficients and starting couple compositions. The details of the deformation in these special situations are given using both methods and are discussed in terms of the stress-free strain rate associated with the Kirkendall effect.

Dissertations / Theses on the topic "Approche à interface diffuse":

1

Ait-Ali, Takfarines. "Modélisation de la cavitation par une approche à interface diffuse avec prise en compte de la tension de surface." Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0024/document.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
La cavitation est la transformation d'un liquide en vapeur qui est causée par une chute de pression en dessous de la pression de saturation vapeur. Ce phénomène se manifeste le plus souvent dans les turbomachines qui sont en interaction avec des liquides. On peut citer les pompes hydrauliques, les injecteurs, les inducteurs ou encore les hélices de bateaux. Vue les effets néfastes qu'elle engendre : bruit, vibrations, détérioration du métal et baisse des performances (chute des rendements et pertes de charges), sa prise en compte est indispensable dans le design des turbomachines. Cette thèse a pour objectif de modéliser ce phénomène de manière à reproduire la nucléation, la convection et l'implosion des bulles de cavitation. Nous nous basons sur un modèle à interface diffuse (le modèle d'équilibre homogène) sur lequel nous greffons un modèle de tension de surface basé sur les équations de Navier Stokes & Korteweg compressibles. Nous réalisons en somme une étude sur l'influence de la tension de surface sur le phénomène de collapse. Nous utilisons un code de volumes finis dont la discrétisation spatiale est assurée par méthode des moindres carrés mobiles. Combinée à un solveur de Riemann de type SLAU, le modèle numérique permet d'outre passer les difficultés liés à la nature du phénomène de cavitation qui sont principalement les forts gradients qui subsistent à travers l'interface liquide-vapeur. L'autre point traité dans la thèse est la détermination d'un coefficient capillaire numérique qui correspond à une tension de surface réelle en fonction de l'épaisseur de l'interface artificiellement élargie pour un maillage donné
Cavitation is the transformation of a liquid into vapor which is caused by a pressure drop below the vapor saturation pressure. This phenomenon usually occurs in turbine engines that interact with liquids like: hydraulic pumps, injectors, inductors or boat propellers. View its negative effects: noise, vibrations, damage to the metal and decreased performance, it should be included in the design of turbomachinery The main objective of this thesis is to model this phenomenon so as to reproduce the nucleation, convection and the implosion of cavitation bubbles. We rely on a diffuse interface model (the homogeneous equilibrium model) on which we graft a surface tension model based on compressible Navier Stokes & Korteweg equations. We study the influence of surface tension on the bubble collapse. We used a finite volume approach whose spatial discretization is made by moving least squared method. Coupled with a Riemann solver called SLAU, the numerical model can go further difficulties related to the nature of the cavitation phenomenon which is mainly the strong gradients that remain through the liquid-vapor interface. Another issue addressed in this thesis is the determination of a numerical capillary coefficient which corresponds to a real surface tension in function of the thickness of the artificially extended interface for a given mesh
2

Diedhiou, Moussa Mory. "Approche mixte interface nette-diffuse pour les problèmes d'intrusion saline en sous-sol : modélisation, analyse mathématique et illustrations numériques." Thesis, La Rochelle, 2015. http://www.theses.fr/2015LAROS023/document.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Le contexte du sujet est la gestion des systèmes aquifères, en particulier le contrôle de leur exploitation et de leur éventuelle pollution. Comme exemple d'application, nous nous focalisons sur le problème d'eau salée dans les aquifères côtiers. Plus généralement, le travail s'applique à tout écoulement miscible et stratifié dans un milieu poreux faiblement déformable. Le but est d'obtenir un modèle robuste pour modéliser le déplacement des fronts de l'eau salée et de la surface supérieure de l'aquifère. Nous avons proposé une approche mixte entre interface diffuse et interface abrupte ce qui a l'avantage de respecter la réalité physique du problème tout en conservant l'efficacité numérique. De plus, nous réussissons à modéliser ce problème 3D par un modèle dynamique 2D où la 3ème dimension est traitée via l'évolution des fronts d'eau salée et de la surface libre supérieure de l'aquifère en prenant en compte l'épaisseur des zones de transition (transition entre eau salée et eau claire, transition entre zone saturée et zone insaturée). Le modèle est basé sur les lois de conservation dans le domaine de l'eau salée et dans celui de l'eau douce, les deux domaines (à frontière libre) étant couplés par un modèle intermédiaire de changement de phase. De plus, nous avons effectué des simulations numériques pour comparer notre modèle 2D issu de l'approche mixte avec un modèle 3D d'écoulement de deux fluides miscibles en milieu compressible saturé. Puis, des simulations sont faites sur notre modèle 2D pour illustrer son efficacité (cette fois dans le cas insaturé)
The context of the subject is the management of aquifers, in especially the control of their operations and their possible pollution. A critical case is the saltwater intrusion problem in costal aquifers. The goal is to obtain efficient and accurate models to simulate the displacement of fresh and salt water fronts in coastal aquifer for the optimal exploitation of groundwater. More generally, the work applies for miscible and stratified displacements in slightly deformable porous media. In this work we propose an original model mixing abrupt interfaces/diffuse interfaces approaches. The advantage is to adopt the (numerical) simplicity of a sharp interface approach, and to take into account the existence of diffuse interfaces. The model is based on the conservation laws written in the saltwater zone and in the freshwater zone, these two free boundary problems being coupled through an intermediate phase field model. An upscaling procedure let us reduce the problem to a two-dimensional setting. The theoretical analysis of the new model is performed. We also present numerical simulations comparing our 2D model with the classical 3D model for miscible displacement in a confined aquifer. Physical predictions from our new model are also given for an unconfined setting
3

Kirov, Nikolay. "Simulation numérique de l’écoulement air-huile dans une enceinte moteur." Electronic Thesis or Diss., Toulouse, ISAE, 2024. http://www.theses.fr/2024ESAE0015.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
La tendance actuelle vers des moteurs d'avion plus puissants et plus économes en carburant crée le besoin de roulements capables de transférer des charges mécaniques plus élevées entre les composants rotatifs et fixes de la machine, à des températures extrêmes et à des régimes moteur plus élevés. Les roulements nécessitent d'être lubrifié en permanence avec une huile spécialisée afin de réduire les frottements, de dissiper la chaleur, d'éloigner les minuscules débris et ainsi d'assurer l'intégrité mécanique du moteur.Les débits massiques d'huile qui en résultent au sein du moteur sont importants et le lubrifiant doit donc être recyclé en permanence via un système de recirculation d'huile. En conséquence, les roulements sont enfermés dans des enceintes, constitués de joints étanchéités et des roulements eux-mêmes. Les enceintes à huile sont essentiellement des chambres étanches adjacentes aux roulements, ou parfois les enfermant, dans lesquelles l'huile éjectée est canalisée après la lubrification. Ils sont généralement scellés avec de l'air sous pression du côté opposé, qui passe à travers un joint labyrinthe afin d'empêcher tout écoulement sortant. En règle générale, une ouverture d'orifice de ventilation est incluse sur le dessus pour permettre à l'air de s'échapper, et une ouverture d'orifice de récupération est située près du bas pour ramener l'huile vers les pompes de récupération d'huile vers le réservoir.À l'intérieur de l'enceinte, l'huile et l'air forment un écoulement complexe à deux phases, dans lequel les effets centrifuges, le cisaillement aérodynamique et les forces de gravité provoquent la dispersion de la majorité de l'huile dans l' enceinte huile et s'accumulent sous forme de film dans les parois extérieures. Un transfert de chaleur de ces parois vers l'huile pré-refroidie à lieu, lui conférant ainsi une fonction secondaire importante : absorber une partie de la chaleur et donc refroidir l'enceinte. Il est cependant important que l'huile des roulements soit collectée et renvoyée au réservoir avant d'atteindre des températures trop élevées, afin d'éviter la cokéfaction ou, pire encore, l'inflammation, qui pourrait déclencher un incendie dans l'enceinte. La physique complexe des écoulements diphasiques conduit à un problème d'optimisation qui ne peut être résolu que via des simulations numériques.À ce jour, une quantité considérable d’incertitude demeure quant à la pratique de modélisation informatique la plus optimale pour une simulation précise, fiable et rentable des chambres de roulements dans différentes conditions de fonctionnement. L'objectif de cette thèse est donc de tester plusieurs approches de modélisation numérique pour la simulation d'un banc d'essai simplifié de enceinte, ici nommé ELUBSYS, pour lequel certaines mesures expérimentales sont disponibles et peuvent être utilisées pour fournir des moyens de validation desdites approches. Il s’agit, à savoir, d’une approche interfaciale multi-fluide à interface diffuse, d’une approche simplifiée Eulerian Integral Thin Film (EITF), d’une approche à phase dispersée Lagrangienne (Disperse Particles Model, DPM) et, enfin, d’une approche couplée EITF-DPM. Au cours de toutes ces investigations, de nouvelles connaissances ont été acquises sur les caractéristiques de l'écoulement, les paramètres d'influence et les performances globales, par rapport aux données expérimentales pour deux configurations de chambres de roulements sous une variété de débits massiques d'huile et de vitesses de rotation de l'arbre.La méthodologie couplée EITF-DPM s'est avérée obtenir une bonne précision pour les mesures de distribution d'épaisseur de film pour un coût contenu et pour une variété de régimes de fonctionnement
The current trend towards more powerful and fuel-efficient aircraft engines produces the need for bearings, capable of transferring higher mechanical loads between rotating and stationary machine components, at extreme temperatures and higher engine speeds. The bearings demand lubrication oil at all times in order to reduce friction, dissipate heat, drive tiny debris away and therefore ensure the mechanical integrity of the engine.The resulting oil mass flow rates within the engine are significant and thus the lubricant must be continuously recycled via an oil recirculation system. As a result, the bearings are encompassed within oil sumps, consisting of chambers, seals and the bearings themselves. The bearing chambers are essentially sealed chambers adjacent to, or sometimes enclosing the bearings, whereby the ejected oil is channeled into after lubrication. They are typically sealed with pressurised air on the opposite side, which is passed through a labyrinth seal in order to provide flow obstruction. Typically, a vent port opening is included on the top for the air to escape, and a scavenge port opening is located near the bottom to lead the oil to the oil scavenge pumps back to the reservoir.While still contained within the bearing chamber, the oil and the air form a complex two-phase flow, whereby centrifugal effects, aerodynamic shear and gravity forces cause the majority of the oil to disperse within the bearing chamber and accumulate as film on its outer stationary walls. Heat transfer from these walls to the pre-cooled oil takes place, therefore giving it an important secondary function - to absorb some of the heat and therefore cool the bearing chamber enclosure. It is important, however, that the oil from the bearings is collected and returned to the reservoir before reaching temperatures that are too high, in order to avoid coking or even worse - ignition, that can start a fire within the bearing chamber. The complex two-phase flow physics lead to an optimisation problem which can only be tackled via numerical simulations.To date, a considerable amount of uncertainty remains concerning the most optimal computational modelling practice for the accurate, reliable and cost-efficient simulation of bearing chambers across different operating conditions. The objective of this thesis, is therefore to test several computational modelling approaches for the simulation of a simplified bearing chamber test rig, hereby named ELUBSYS, for which some experimental measurements are available that can be used to provide means of validation of the said approaches. These are, namely, an interfacial multi-fluid diffuse-interface approach, an Eulerian Integral Thin Film (EITF) approach, a two-way coupled Discrete Parcel Method approach, and, lastly, an EITF-DPM coupled approach. During all of these investigations, new knowledge has been gained for the flow field characteristics, influencing parameters and overall predictory performance, as compared to the experimental data for two bearing chamber configurations under a variety of oil mass flow rates and shaft rotational speeds.The cost-efficient coupled EITF-DPM methodology proposed within this thesis was found to obtain good accuracy for the film thickness distribution measurements for a variety of operating conditions
4

Cordesse, Pierre. "Contribution to the study of combustion instabilities in cryotechnic rocket engines : coupling diffuse interface models with kinetic-based moment methods for primary atomization simulations." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASC016.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Gardiens de l’espace, les lanceurs de fusée font l’objet d’une amélioration continue et concurrentielle, grâce à des campagnes de tests expérimentaux et numériques. Les simulations prédictives sont devenues indispensables pour accroître notre compréhension de la physique. Ajustables, elles se prêtent parfaitement à la conception et l’optimisation, en particuliers de la chambre de combustion, pour garantir la sureté et maximiser l’efficacité. L’atomisation primaire est l’un des phénomènes déterminants de la combustion du combustible et de l’oxydant, pilotant à la fois la distribution de gouttes et les potentielles instabilités hautes-fréquences en conditions sous-critiques. Elle couvre un large spectre de topologies d’écoulement diphasique, depuis ceux de type phases séparées jusqu’à la phase dispersée, en passant par une région mixte caractérisée par la complexité de la physique à petites échelles et de la topologie de l’écoulement. Les modèles d’ordre réduit constituent de bons candidats pour réaliser des simulations numériques prédictives et relativement peu coûteuses en ressource de calcul sur des configurations industrielles. Cependant, jusqu’à présent ils ne décrivent correctement que la dynamique des grandes échelles et doivent donc être couplés à des modèles de phase dispersée nécessitant un réglage minutieux de paramètres pour prédire la formation du spray. Afin de décrire à la fois les régions mixte et dispersée, l’amélioration de la hiérarchie de modèles d’ordre réduit repose sur quelques principes clefs au cœur de la thèse ci-présente et fournit des problèmes interdisciplinaires faisant appel tant à l’analyse mathématique et la modélisation physique de ces systèmes d’EDP qu’à leur discrétisation numérique et leur implémentation dans des codes de CFD à des fins industriels. Grâce d’une part à l’extension de la théorie des équations de conservation supplémentaires à des systèmes impliquant des termes non-conservatifs et d’autre part à un formalisme de thermodynamique multi-fluide tenant compte des effets non-idéaux, nous proposons de nouvelles pistes pour définir une entropie de mélange strictement convexe et consistante avec le système d’équation et les lois de pression, dans le but de permettre la symmétrisation entropique des modèles diphasiques, de prouver leur hyperbolicité et d’obtenir des termes sources généraux. De plus, en rompant avec la vision géométrique de l’interface, nous proposons une description multi-échelle de l’interface pour décrire un mélange multi-fluide comportant une dynamique interfaciale complexe. Le Principe de Moindre Action a permis de dériver un modèle bifluide à une vitesse couplant grandes et petites échelles de l’écoulement. Nous avons ensuite développé une stratégie de séparation d’opérateurs basée sur la discrétisation par Volumes Finis, et nous avons implémenté le nouveau modèle dans le logiciel industriel multiphysique de CFD, CEDRE, de l’ONERA afin d’évaluer numériquement ce dernier. Enfin, nous avons construit et analysé les fondations d’une hiérarchie de cas tests accessibles à la DNS tout en étant au plus proche de configurations industrielles, dans le but d’évaluer les résultats de simulations du nouveau modèle ou de tout autre modèle à venir
Gatekeepers to the open space, launchers are subject to intense and competitive enhancements, through experimental and numerical test campaigns. Predictive numerical simulations have become mandatory to increase our understanding of the physics. Adjustable, they provide early-stage optimization processes, in particular of the combustion chamber, to guaranty safety and maximize efficiency. One of the major physical phenomenon involved in the combustion of the fuel and oxidizer is the jet atomization, which pilotes both the droplet distributions and the potential high-frequency instabilities in subcritical conditions. It encompasses a large sprectrum of two-phase flow topologies, from separated phases to disperse phase, with a mixed region where the small scale physics and topology of the flow are very complex. Reduced-order models are good candidates to perform predictive but low CPU demanding simulations on industrial configurations but have only been able so far to capture large scale dynamics and have to be coupled to disperse phase models through adjustable and weakly reliable parameters in order to predict spray formation. Improving the hierarchy of reduced order models in order to better describe both the mixed region and the disperse region requires a series of building blocks at the heart of the present work and give on to complex problems in the mathematical analysis and physical modelling of these systems of PDE as well as their numerical discretization and implementation in CFD codes for industrial uses. Thanks to the extension of the theory on supplementary conservative equations to system of non-conservation laws and the formalism of the multi-fluid thermodynamics accounting for non-ideal effects, we give some new leads to define a strictly convex mixture entropy consistent with the system of equations and the pressure laws, which would allow to recover the entropic symmetrization of two-phase flow models, prove their hyperbolicity and obtain generalized source terms. Furthermore, we have departed from a geometric approach of the interface and proposed a multi-scale rendering of the interface to describe multi-fluid flow with complex interface dynamics. The Stationary Action Principle has returned a single velocity two-phase flow model coupling large and small scales of the flow. We then have developed a splitting strategy based on a Finite Volume discretization and have implemented the new model in the industrial CFD software CEDRE of ONERA to proceed to a numerical verification. Finally, we have constituted and investigated a first building block of a hierarchy of test-cases designed to be amenable to DNS while close enough to industrial configurations in order to assess the simulation results of the new model but also to any up-coming models
5

Villanueva, Walter. "Diffuse-Interface Simulations of Capillary Phenomena." Doctoral thesis, Stockholm : Kungl. tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4402.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Schaubeck, Stefan [Verfasser], and Helmut [Akademischer Betreuer] Abels. "Sharp interface limits for diffuse interface models / Stefan Schaubeck. Betreuer: Helmut Abels." Regensburg : Universitätsbibliothek Regensburg, 2013. http://d-nb.info/1047236966/34.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Marth, Wieland. "Hydrodynamic Diffuse Interface Models for Cell Morphology and Motility." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-204651.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
In this thesis, we study mathematical models that describe the morphology of a generalized biological cell in equilibrium or under the influence of external forces. Within these models, the cell is considered as a thermodynamic system, where streaming effects in the cell bulk and the surrounding are coupled with a Helfrich-type model for the cell membrane. The governing evolution equations for the cell given in a continuum formulation are derived using an energy variation approach. Such two-phase flow problems that combine streaming effects with a free boundary problem that accounts for bending and surface tension can be described effectively by a diffuse interface approach. An advantage of the diffuse interface approach is that models for e.g. different biophysical processes can easily be combined. That makes this method suitable to describe complex phenomena such as cell motility and multi-cell dynamics. Within the first model for cell motility, we combine a biological network for GTPases with the hydrodynamic Helfrich-type model. This model allows to account for cell motility driven by membrane protrusion as a result of actin polymerization. Within the second model, we moreover extend the Helfrich-type model by an active gel theory to account for the actin filaments in the cell bulk. Caused by contractile stress within the actin-myosin solution, a spontaneous symmetry breaking event occurs that lead to cell motility. In this thesis, we further study the dynamics of multiple cells which is of wide interest since it reveals rich non-linear behavior. To apply the diffuse interface framework, we introduce several phase field variables to account for several cells that are coupled by a local interaction potential. In a first application, we study white blood cell margination, a biological phenomenon that results from the complex relation between collisions, different mechanical properties and lift forces of red blood cells and white blood cells within the vascular system. Here, it is shown that inertial effects, which can become of relevance in various parts of the cardiovascular system, lead to a decreasing tendency for margination with increasing Reynolds number. Finally, we combine the active polar gel theory and the multi-cell approach that is capable of studying collective migration of cells. This hydrodynamic approach predicts that collective migration emerges spontaneously forming coherently-moving clusters as a result of the mutual alignment of the velocity vectors during inelastic collisions. We further observe that hydrodynamics heavily influence those systems. However, a complete suppression of the onset of collective migration cannot be confirmed. Moreover, we give a brief insight how such highly coupled systems can be treated numerically using finite elements and how the numerical costs can be limited using operator splitting approaches and problem parallelization with OPENMP
Diese Dissertation beschäftigt sich mit mathematischen Modellen zur Beschreibung von Gleichgewichts- und dynamischen Zuständen von verallgemeinerten biologischen Zellen. Die Zellen werden dabei als thermodynamisches System aufgefasst, bei dem Strömungseffekte innerhalb und außerhalb der Zelle zusammen mit einem Helfrich-Modell für Zellmembranen kombiniert werden. Schließlich werden durch einen Energie-Variations-Ansatz die Evolutionsgleichungen für die Zelle hergeleitet. Es ergeben sie dabei Mehrphasen-Systeme, die Strömungseffekte mit einem freien Randwertproblem, das zusätzlich physikalischen Einflüssen wie Biegung und Oberflächenspannung unterliegt, vereinen. Um solche Probleme effizient zu lösen, wird in dieser Arbeit die Diffuse-Interface-Methode verwendet. Ein Vorteil dieser Methode ist, dass es sehr einfach möglich ist, Modelle, die verschiedenste Prozesse beschreiben, miteinander zu vereinen. Dies erlaubt es, komplexe biologische Phänomene, wie zum Beispiel Zellmotilität oder auch die kollektive Bewegung von Zellen, zu beschreiben. In den Modellen für Zellmotilität wird ein biologisches Netzwerk-Modell für GTPasen oder auch ein Active-Polar-Gel-Modell, das die Aktinfilamente im Inneren der Zellen als Flüssigkristall auffasst, mit dem Multi-Phasen-Modell kombiniert. Beide Modelle erlauben es, komplexe Vorgänge bei der selbst hervorgerufenen Bewegung von Zellen, wie das Vorantreiben der Zellmembran durch Aktinpolymerisierung oder auch die Kontraktionsbewegung des Zellkörpers durch kontraktile Spannungen innerhalb des Zytoskelets der Zelle, zu verstehen. Weiterhin ist die kollektive Bewegung von vielen Zellen von großem Interesse, da sich hier viele nichtlineare Phänomene zeigen. Um das Diffuse-Interface-Modell für eine Zelle auf die Beschreibung mehrerer Zellen zu übertragen, werden mehrere Phasenfelder eingeführt, die die Zellen jeweils kennzeichnen. Schließlich werden die Zellen durch ein lokales Abstoßungspotential gekoppelt. Das Modell wird angewendet, um White blood cell margination, das die Annäherung von Leukozyten an die Blutgefäßwand bezeichnet, zu verstehen. Dieser Prozess wird dabei bestimmt durch den komplexen Zusammenhang zwischen Kollisionen, den jeweiligen mechanischen Eigenschaften der Zellen, sowie deren Auftriebskraft innerhalb der Adern. Die Simulationen zeigen, dass diese Annäherung sich in bestimmten Gebieten des kardiovaskulären Systems stark vermindert, in denen die Blutströmung das Stokes-Regime verlässt. Schließlich wird das Active-Polar-Gel-Modell mit dem Modell für die kollektive Bewegung vom Zellen kombiniert. Dies macht es möglich, die kollektive Bewegung der Zellen und den Einfluss von Hydrodynamik auf diese Bewegung zu untersuchen. Es zeigt sich dabei, dass der Zustand der kollektiven gerichteten Bewegung sich spontan aus der Neuausrichtung der jeweiligen Zellen durch inelastische Kollisionen ergibt. Obwohl die Hydrodynamik einen großen Einfluss auf solche Systeme hat, deuten die Simulationen nicht daraufhin, dass Hydrodynamik die kollektive Bewegung vollständig unterdrückt. Weiterhin wird in dieser Arbeit gezeigt, wie die stark gekoppelten Systeme numerisch gelöst werden können mit Hilfe der Finiten-Elemente-Methode und wie die Effizienz der Methode gesteigert werden kann durch die Anwendung von Operator-Splitting-Techniken und Problemparallelisierung mittels OPENMP
8

Dunbar, Oliver. "A diffuse interface model of surfactants in multi-phase flow." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/99133/.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
We investigate a free boundary problem arising in fluid dynamics, by modelling multiple incompressible fluids over subdomains with different material quantities, and in the presence of surface tension reducing chemicals known as surfactants. We construct a free energy for this system, and we require it obey the second law of thermodynamics, leading to the formulation of an energy minimisation problem (the sharp problem). This problem is degenerate, so we regularise it by constructing a new energy of Ginzburg-Landau type, parametrised by a (small) constant ε > 0 and when ε → 0 the sharp problem is recovered in the sense of Γ-convergence. This multi-phase energy is formed from a multiwell potential and gradient term, and the minimisers are known as phase field variables. The phase field variables approximate characteristic functions of the subdomains, and the model is rewritten as functions of them. Beneficially, the energy analysis can be repeated as before to obtain a diffuse interface model. We construct and perform numerical analysis of a novel discretisation scheme for a Cahn-Hilliard Navier-Stokes system. Here we create a fractional-theta coupling scheme which is importantly proved to be of second order in time. The key property of this scheme is that it uses weighted operator splitting to separate the different nonlinearities that appear in a Cahn-Hilliard Navier-Stokes system. That is, the Cahn-Hilliard multiwell potential, the incompressibility condition and the convection. We discuss stability and the extension to surfactants. We implement the novel scheme in DUNE (Distributed Unified Numerics Environment), a finite element package and use simulation to run tests to validate the stability and consistency of the schemes, convergence of the diffuse interface model with respect to its parametrisation, and flexibility for the code development.
9

Lam, Kei Fong. "Diffuse interface models of soluble surfactants in two-phase fluid flows." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/62686/.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Surface active agents (surfactants) reduce the surface tension of fluid interfaces and, via surface tension gradients, can lead to tangential forces resulting in the Marangoni effect. Biological systems take advantage of their impact on fluids with interfaces, but surfactants are also important for industrial applications such as processes of emulsification or mixing. Surfactants can be soluble in at least one of the fluid phases and the exchange of surfactants between the bulk phases and the fluid interfaces is governed by the process of adsorption and desorption. One can compute the interfacial surfactant density from the bulk surfactant density by assuming that the interface is in equilibrium with the adjacent bulk phase and imposing a closure relation (known as adsorption isotherm) between the two quantities. The assumption (known as instantaneous adsorption) is valid when the process of adsorption to the interface is fast compared to the kinetics in the bulk phases. However, it is not valid in the context of ionic surfactant systems, or when the diffusion is not limited to a thin layer. In this thesis, we derive two types of mathematical models for two-phase flow with a soluble surfactant that can account for both instantaneous and non-instantaneous adsorption. The first type is a sharp interface model, in which the interface is modelled by moving hypersurfaces. While the second type is a phase field model, in which the interface is a region of small, nonzero thickness where there is some microscopic mixing of the two fluids. Both types of models are shown to satisfy energy inequalities which guarantee thermodynamical consistency. Via a formal asymptotic analysis, we show the phase field models are related to sharp interface models in the limit that the interfacial width tends to zero. Flexibility with respect to the choice of bulk and surface free energies allows us to realise various isotherms and relations of state between surface tension and surfactant. We present some numerical simulations to support the asymptotic analysis and display the effectiveness of the our approach. As a first step towards an analysis of our models, we consider sharp interface and phase field models for soluble surfactants in a static situation. The surfactant equations become a linear elliptic coupled bulk-surface partial differential equation, and our main result is the rigorous convergence of the weak solution of the phase field models to the weak solution of the sharp interface models.
10

Aland, Sebastian, Sabine Egerer, John Lowengrub, and Axel Voigt. "Diffuse interface models of locally inextensible vesicles in a viscous fluid." Elsevier, 2014. https://htw-dresden.qucosa.de/id/qucosa%3A32307.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
We present a new diffuse interface model for the dynamics of inextensible vesicles in a viscous fluid with inertial forces. A new feature of this work is the implementation of the local inextensibility condition in the diffuse interface context. Local inextensibility is enforced by using a local Lagrange multiplier, which provides the necessary tension force at the interface. We introduce a new equation for the local Lagrange multiplier whose solution essentially provides a harmonic extension of the multiplier off the interface while maintaining the local inextensibility constraint near the interface. We also develop a local relaxation scheme that dynamically corrects local stretching/compression errors thereby preventing their accumulation. Asymptotic analysis is presented that shows that our new system converges to a relaxed version of the inextensible sharp interface model. This is also verified numerically. To solve the equations, we use an adaptive finite element method with implicit coupling between the Navier-Stokes and the diffuse interface inextensibility equations. Numerical simulations of a single vesicle in a shear flow at different Reynolds numbers demonstrate that errors in enforcing local inextensibility may accumulate and lead to large differences in the dynamics in the tumbling regime and smaller differences in the inclination angle of vesicles in the tank-treading regime. The local relaxation algorithm is shown to prevent the accumulation of stretching and compression errors very effectively. Simulations of two vesicles in an extensional flow show that local inextensibility plays an important role when vesicles are in close proximity by inhibiting fluid drainage in the near contact region.

Books on the topic "Approche à interface diffuse":

1

Mauri, Roberto. Multiphase Microfluidics: The Diffuse Interface Model. Vienna: Springer Vienna, 2012.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
2

Mauri, Roberto, ed. Multiphase Microfluidics: The Diffuse Interface Model. Vienna: Springer Vienna, 2012. http://dx.doi.org/10.1007/978-3-7091-1227-4.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Mauri, Roberto. Multiphase microfluidics: The diffuse interface model. Wien: Springer Verlag, 2012.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
4

B, McFadden Geoffrey, Wheeler A. A, and National Institute of Standards and Technology (U.S.), eds. Diffuse-interface methods in fluid mechanics. Gaithersburg, MD: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 1997.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
5

B, McFadden Geoffrey, Wheeler A. A, and National Institute of Standards and Technology (U.S.), eds. Diffuse-interface methods in fluid mechanics. Gaithersburg, MD: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 1997.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
6

B, McFadden Geoffrey, Wheeler A. A, and National Institute of Standards and Technology (U.S.), eds. Diffuse-interface methods in fluid mechanics. Gaithersburg, MD: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 1997.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
7

B, McFadden Geoffrey, Wheeler A. A, and National Institute of Standards and Technology (U.S.), eds. Diffuse-interface methods in fluid mechanics. Gaithersburg, MD: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 1997.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
8

B, McFadden Geoffrey, Wheeler A. A, and National Institute of Standards and Technology (U.S.), eds. Diffuse-interface methods in fluid mechanics. Gaithersburg, MD: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 1997.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
9

A, Wheeler A., and National Institute of Standards and Technology (U.S.), eds. On the Gibbs adsorption equation and diffuse interface models. Gaithersburg, MD: U.S. Dept. of Commerce, Technology Administration, National Institute of Standards and Technology, 2001.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
10

United States. National Aeronautics and Space Administration., ed. DIFFUSE-INTERFACE METHODS IN FLUID MECHANICS... NASA/CR-97-206424... DEC. 30, 1997. [S.l: s.n., 1998.

Find full text
APA, Harvard, Vancouver, ISO, and other styles

Book chapters on the topic "Approche à interface diffuse":

1

Magiera, Jim, and Christian Rohde. "Analysis and Numerics of Sharp and Diffuse Interface Models for Droplet Dynamics." In Fluid Mechanics and Its Applications, 67–86. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09008-0_4.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
AbstractThe modelling of liquid–vapour flow with phase transition poses many challenges, both on the theoretical level, as well as on the level of discretisation methods. Therefore, accurate mathematical models and efficient numerical methods are required. In that, we focus on two modelling approaches: the sharp-interface (SI) approach and the diffuse-interface (DI) approach. For the SI-approach, representing the phase boundary as a co-dimension-1 manifold, we develop and validate analytical Riemann solvers for basic isothermal two-phase flow scenarios. This ansatz becomes cumbersome for increasingly complex thermodynamical settings. A more versatile multiscale interface solver, that is based on molecular dynamics simulations, is able to accurately describe the evolution of phase boundaries in the temperature-dependent case. It is shown to be even applicable to two-phase flow of multiple components. Despite the successful developments for the SI approach, these models fail if the interface undergoes topological changes. To understand merging and splitting phenomena for droplet ensembles, we consider DI models of second gradient type. For these Navier–Stokes–Korteweg systems, that can be seen as a third order extension of the Navier–Stokes equations, we propose variants that are more accessible to standard numerical schemes. More precisely, we reformulate the capillarity operator to restore the hyperbolicity of the Euler operator in the full system.
2

Clarke, David R. "The Intergranular Film in Silicon Nitride Ceramics: A Diffuse Interface Approach." In Tailoring of Mechanical Properties of Si3N4 Ceramics, 291–301. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-0992-5_21.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Garcke, Harald, Michael Hinze, and Christian Kahle. "Diffuse Interface Approaches in Atmosphere and Ocean—Modeling and Numerical Implementation." In Mathematics of Planet Earth, 287–307. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05704-6_9.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Chen, Ching-Yao, and Ting-Shiang Lin. "Interfacial Instability of a Non-magnetized Drop in Ferrofluids Subjected to an Azimuthal Field: A Diffuse-Interface Approach." In Advances in Computational Fluid-Structure Interaction and Flow Simulation, 181–92. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-40827-9_14.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Pecenko, A., and J. G. M. Kuerten. "The Diffuse Interface Method with Korteweg Approach for Isothermal, Two-Phase Flow of a Van der Waals Fluid." In Direct and Large-Eddy Simulation VII, 479–84. Dordrecht: Springer Netherlands, 2010. http://dx.doi.org/10.1007/978-90-481-3652-0_71.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Lamorgese, Andrea G., Dafne Molin, and Roberto Mauri. "Diffuse Interface (D.I.) Model for Multiphase Flows." In Multiphase Microfluidics: The Diffuse Interface Model, 1–72. Vienna: Springer Vienna, 2012. http://dx.doi.org/10.1007/978-3-7091-1227-4_1.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Park, Jang Min, Roberto Mauri, and Patrick D. Anderson. "Phase separation of viscous ternary liquid mixtures." In Multiphase Microfluidics: The Diffuse Interface Model, 73–91. Vienna: Springer Vienna, 2012. http://dx.doi.org/10.1007/978-3-7091-1227-4_2.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Thiele, Uwe. "Dewetting and decomposing films of simple and complex liquids." In Multiphase Microfluidics: The Diffuse Interface Model, 93–127. Vienna: Springer Vienna, 2012. http://dx.doi.org/10.1007/978-3-7091-1227-4_3.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Plapp, Mathis. "Phase-Field Models." In Multiphase Microfluidics: The Diffuse Interface Model, 129–75. Vienna: Springer Vienna, 2012. http://dx.doi.org/10.1007/978-3-7091-1227-4_4.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Porceddu, I., S. Corda, F. Pasian, and R. Smareglia. "The Interstellar Space Mosaic: A User Interface for Accessing ISM Data World-wide distributed." In The Diffuse Interstellar Bands, 121–28. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0373-2_13.

Full text
APA, Harvard, Vancouver, ISO, and other styles

Conference papers on the topic "Approche à interface diffuse":

1

Patel, Samarth C., John Griffin, Emma M. Schmidt, Brandon Runnels, and John M. Quinlan. "A Diffuse Interface Approach to Modeling Acoustic Wave-Droplet Interactions." In AIAA SCITECH 2024 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2024. http://dx.doi.org/10.2514/6.2024-1659.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Sun, Ying, and Christoph Beckermann. "Phase-Field Simulation of Solidification With Density Change." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-60875.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Phase-field models of solidification with convection often assume the existence of a single (mixture) velocity at any location inside the diffuse interface, and the phase-field, φ, is advected by this mixture velocity. In this paper, the advection of the phase-field is examined for a one-dimensional normal flow to a solidification front induced by a density difference between the solid and liquid. It is found that the results from a phase-field model that assumes a single velocity inside the diffuse interface are generally not in agreement with the sharp interface condition for the kinetic undercooling of the front in the presence of unequal densities, regardless of the interface width. By introducing a two-phase approach, where the solid and liquid are assumed to coexist inside the diffuse interface with different velocities, good agreement with the sharp interface condition is obtained irrespective of the density ratio between the two phases.
3

Navah, Farshad, Marc-Étienne Lamarche-Gagnon, Florin Ilinca, Martin Audet, Marjan Molavi-Zarandi, and Vincent Raymond. "Development of a Topology Optimization Framework For Cooling Channel Design in Die Casting Molds." In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-73363.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Abstract This work is concerned with the development of a framework for the efficient design of cooling channels via two different topology optimization paradigms: a diffuse and a sharp. Each approach relies on a distinct thermo-fluid modeling and features a specific material distribution mode, i.e. fraction-based (diffuse) versus interface-based (sharp). The two models are described and the corresponding solvers are validated. A gradient-based optimization methodology is adopted and the details of the adjoint-based gradient computation are introduced. Finally, examples of cooling channel design optimization are presented and discussed.
4

Mohaghegh, Fazlolah, and H. S. Udaykumar. "Efficiency of Diffuse and Sharp Interface Strongly Coupled Fluid Structure Interaction Methods in Fixed and Moving Boundaries." In ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7668.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Efficiency of different types of immersed boundary methods in the fluid structure interaction (FSI) analysis is studied for different cases. Two different formulations of smoothed profile method (SPM) [1, 2] as diffuse interface approaches are compared with the ghost fluid method (GFM) [3, 4] as sharp interface method (SIM) [5]. First, the original SPM which has two pressure Poisson equations (SPM2P) is modified to a novel formulation for SPM with only one pressure Poisson equation (SPM1P) and then validated. The efficiency study is performed for SPM1P, SPM2P and SIM. The results show that when the solid object is fixed, the explicit solution of SIM is faster than the two SPMs. However, when the solid is moving and strongly coupled formulations is used, SPM1P will be the fastest method. It is shown that the efficiency of the strongly coupled formulations depends on the number of subiterations required in each time step to reach the converged implicit solution. SPM1P and SPM2P need less number of subiterations in comparison with SIM and they are faster. When the added mass effect is high, the efficiency of SPM becomes more noticeable as the required number of subiterations is significantly less in SPM. Finally, SPM1P is faster than SPM2P in all cases however, the accuracy of SPM2P in predicting the flow pattern is better than SPM1P.
5

Cazé, Joris, Fabien Petitpas, Eric Daniel, Sébastien Le Martelot, and Matthieu Queguineur. "Modeling and Simulation of the Cavitation Phenomenon in a Turbopump: A Multiphase Approach." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-78025.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Abstract In this study, cryogenic flows in rocket engine that may undergo a phase change because of a loss of pressure in pump, or any depressurization process are considered. We proposed a well-posed mathematical representation for this kind of flow as well as the numerical model for seeking the solutions. The two important points addressed in this study are: the compressibility of the phases and the use of a rotating reference frame. The compressibility effects are quite essentials to obtain a physical and realistic cavitation model through the equation of state of the fluids (liquid and vapor), while the moving reference frame being the way we chose to model the pump motion. The model we develop is based on conservation equations of mass, momentum and energy for each phase plus a non-conservative equation evolution for the volume fraction. The description of the flow is based on the diffuse interface method: the interfaces appear naturally in the flow (interfaces between vapor and liquid for example) and do not require any interface tracking method. The phase change process is based on a stiff relaxation procedure using thermodynamic equilibrium considerations. Results related to a pump application are then presented using the open-source platform ECOGEN where the present numerical method is implemented. The model is able to produce a quite realistic pump characteristic curve where the relationship between the pump overpressure and its operating mass flow rate is expressed. In these first calculations it will be shown that cavitation may occur in some regions of the flow and that the multiphase approach is suited for this study.
6

Steinhausen, Christoph, Grazia Lamanna, Bernhard Weigand, Rolf Stierle, Joachim Groß, Andreas Preusche, and Andreas Dreizler. "Experimental Investigation of Droplet Injections in the Vicinity of the Critical Point: A comparison of different model approaches." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4635.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
The disintegration process of liquid fuel within combustion chambers is one of the most important parameters forefficient and stable combustion. Especially for high pressures exceeding the critical value of the injected fluids the mixing processes are not fully understood yet. Recently, different theoretical macroscopic models have been introduced to understand breakdown of the classical two phase regime and predict the transition from evaporation to a diffuse-mixing process. In order to gain deeper insight into the physical processes of this transition, a parametric study of free-falling n-pentane droplets in an inert nitrogen atmosphere is presented. Atmospheric conditions varied systematically from sub- to supercritical values with respect to the fluid properties. An overlay of a diffuse lighted image with a shadowgram directly in the optical setup (front lighted shadowgraphy) was applied to simultaneously detect the presence of a material surface of the droplet as well as changes in density gradients in the surrounding atmosphere. The experimental investigation illustrates, that the presence of a material surface cannot be shown by a direct shadowgram. However, reflections and refractions caused by diffuse ambient illumination are able to indicate the presence of a material surface. In case of the supercritical droplet injections in this study, front lighted shadowgraphy clearly revealed the presence of a material surface, even when the pre-heated droplets are released into a supercritical atmosphere. This detection of the droplet interface indicates, that the droplet remains subcritical in the region of interest, even though it is injected into a supercritical atmosphere. Based on the adiabatic mixing assumption recent Raman-scattering results in the wake of the droplet are re-evaluated to compute the temperature distribution. Presented experimental findings as well as the re-evaluation of recent Raman scattering results are compared to thermodynamic models to predict the onset of diffuse-mixing and supercritical disintegration of the droplet. Additionally, a one dimensional evaporation model is used to evaluate the validity of the adiabatic mixing assumption in the estimation of the droplet temperature. The presented findings contribute to the understanding of recent theoretical models for prediction of spray and droplet disintegration and the onset of diffuse-mixing processes.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4635
7

De Bellis, Lisa, Ravi S. Prasher, and Patrick E. Phelan. "Predicting Thermal Boundary Resistance Using Monte Carlo Simulation." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0708.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Abstract The Acoustic Mismatch Model (AMM) and the Diffuse Mismatch Model (DMM) have traditionally been used to predict the thermal boundary resistance, Rb, across the interface of two adjoining materials at temperatures well below the Debye temperatures of the materials in question. Both models, however, fall short when compared to experimental data. The development of these models involves limiting assumptions in order to simplify the mathematical evaluation. A Monte Carlo (MC) Model is proposed and developed as a compliment to the AMM and DMM models. Using the statistical approach eliminates the need of addressing complicated expressions, thereby allowing us to lift some of the limiting assumptions. Furthermore, for the first time, the AMM and DMM are combined into a single, mixed model which determines Rb based on a net heat transfer calculated from both specular and diffuse transmission. As expected, the results in this instance lay between those of the AMM and DMM models.
8

Majidi, Sahand, and Asghar Afshari. "Adaptive Mesh Simulations of Supersonic Liquid Jets Spreading in Quiescent Gaseous Media." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21846.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Propagation and evolution of supersonic liquid jets in quiescent gaseous media is studied numerically using a computational fluid dynamics (CFD) tool. A wave propagation method finite-volume solver is employed to discretize and solve the time-dependent two-dimensional Euler equations based on diffuse interface approach. The developed flow solver is implemented in the adaptive mesh refinement code (AMROC) to improve the ability of the solver to capture inherent characteristics of compressible multiphase flow including shocks and contact discontinuities. Several benchmark problems are simulated to evaluate the performance of the numerical tool. Simulations of a supersonic liquid jet flow in gaseous environment are conducted by developed flow solver. The results indicate that our numerical methodology can be considered as a promising approach to study high speed liquid jets.
9

Michopoulos, John G., Athanasios P. Iliopoulos, John C. Steuben, Andrew J. Birnbaum, Yao Fu, and Jeong-Hoon Song. "Towards Computational Synthesis of Microstructural Crystalline Morphologies for Additive Manufacturing Applications." In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-68149.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Powder-based additive manufacturing technologies introduce severe variations in microstructure in terms of grain size and aspect ratio that, coupled with porosity, can result in dramatic effects on the functional (mechanical, thermal, fatigue, fracture etc.) performance of as-produced parts. In the context of Integrated Computational Materials Engineering (ICME), it is essential develop a computationally efficient approach for generating synthetic microstructural morphologies that reflect these process-induced features. In the present paper, we employ two methodologies for computing the evolution of metal solidification at the microstructural level as a function of process parameters associated with additive manufacturing. The first method is the Continuum Diffuse Interface Model (CDM) applied to an arbitrary material system, and the second, the Multi-Phase Field Model (MPFM) applied to pure nickel (Ni). We present examples of microstructures generated by these methods within the context of additive manufacturing.
10

Kazemiabnavi, Saeed, Prashanta Dutta, and Soumik Banerjee. "Ab Initio Modeling of the Electron Transfer Reaction Rate at the Electrode-Electrolyte Interface in Lithium-Air Batteries." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-40239.

Full text
APA, Harvard, Vancouver, ISO, and other styles
Abstract:
Lithium-air batteries are very promising energy storage systems for meeting current demands in electric vehicles. However, the performance of these batteries is highly dependent on the electrochemical stability and physicochemical properties of the electrolyte such as ionic conductivity, vapor pressure, static and optical dielectric constant, and ability to dissolve oxygen and lithium peroxide. Room temperature ionic liquids, which have high electrical conductivity, wide electrochemical stability window and also low vapor pressure, are considered potential electrolytes for these batteries. Moreover, since the physicochemical and electrochemical properties of ionic liquids are dependent on the structure of their constitutive cations and anions, it is possible to tune these properties by choosing from various combinations of cations and anions. One of the important factors on the performance of lithium-air batteries is the local current density. The current density on each electrode can be obtained by calculating the rate constant of the electron transfer reactions at the surface of the electrode. In lithium-air batteries, the oxidation of pure lithium metal into lithium ions happens at the anode. In this study, Marcus theory formulation was used to calculate the rate constant of the electron transfer reaction in the anode side using the respective thermodynamics data. The Nelsen’s four-point method of separating oxidants and reductants was used to evaluate the inner-sphere reorganization energy. In addition, the Conductor-like Screening Model (COSMO) which is an approach to dielectric screening in solvents has been implemented to investigate the effect of solvent on these reaction rates. All calculations were done using Density Functional Theory (DFT) at B3LYP level of theory with a high level 6-311++G** basis set which is a Valence Triple Zeta basis set with polarization and diffuse on all atoms (VTZPD) that gives excellent reproducibility of energies. Using this methodology, the electron transfer rate constant for the oxidation of lithium in the anode side was calculated in an ionic liquids electrolyte. Our results present a novel approach for choosing the most appropriate electrolyte(s) that results in enhanced current densities in these batteries.

Reports on the topic "Approche à interface diffuse":

1

Anderson, D. M., G. B. McFadden, and A. A. Wheeler. Diffuse-interface methods in fluid mechanics. Gaithersburg, MD: National Institute of Standards and Technology, 1997. http://dx.doi.org/10.6028/nist.ir.6018.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Anderson, D. M., and G. B. McFadden. A diffuse-interface description of fluid systems. Gaithersburg, MD: National Institute of Standards and Technology, 1996. http://dx.doi.org/10.6028/nist.ir.5887.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

McFadden, G. B., and A. A. Wheeler. On the Gibbs adsorption equation and diffuse interface models. Gaithersburg, MD: National Institute of Standards and Technology, 2001. http://dx.doi.org/10.6028/nist.ir.6732.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Garcia-Cardona, Cristina, Ekaterina Merkurjev, Andrea L. Bertozzi, Arjuna Flenner, and Allon G. Percus. Fast Multiclass Segmentation using Diffuse Interface Methods on Graphs. Fort Belvoir, VA: Defense Technical Information Center, February 2013. http://dx.doi.org/10.21236/ada580102.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Wheeler, A. A., and G. B. McFadden. On the notion of a *-vector and a stress tensor for a general class of anisotropic diffuse interface models. Gaithersburg, MD: National Institute of Standards and Technology, 1996. http://dx.doi.org/10.6028/nist.ir.5848.

Full text
APA, Harvard, Vancouver, ISO, and other styles

To the bibliography