Relevant bibliographies by topics / Diffuse-Interface approach

Academic literature on the topic 'Diffuse-Interface approach'

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Published: 7 July 2024

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Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers

Journal articles on the topic "Diffuse-Interface approach":

1

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.

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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.

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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.

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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.

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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.

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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.

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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.
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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.

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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.
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Galina, Reshetova, and Romenski Evgeniy. "Diffuse interface approach to modeling wavefields in a saturated porous medium." Applied Mathematics and Computation 398 (June 2021): 125978. http://dx.doi.org/10.1016/j.amc.2021.125978.

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Brannick, J., C. Liu, T. Qian, and H. Sun. "Diffuse Interface Methods for Multiple Phase Materials: An Energetic Variational Approach." Numerical Mathematics: Theory, Methods and Applications 8, no. 2 (May 2015): 220–36. http://dx.doi.org/10.4208/nmtma.2015.w12si.

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AbstractIn this paper, we introduce a diffuse interface model for describing the dynamics of mixtures involving multiple (two or more) phases. The coupled hydrodynamical system is derived through an energetic variational approach. The total energy of the system includes the kinetic energy and the mixing (interfacial) energies. The least action principle (or the principle of virtual work) is applied to derive the conservative part of the dynamics, with a focus on the reversible part of the stress tensor arising from the mixing energies. The dissipative part of the dynamics is then introduced through a dissipation function in the energy law, in line with Onsager's principle of maximum dissipation. The final system, formed by a set of coupled time-dependent partial differential equations, reflects a balance among various conservative and dissipative forces and governs the evolution of velocity and phase fields. To demonstrate the applicability of the proposed model, a few two-dimensional simulations have been carried out, including (1) the force balance at the three-phase contact line in equilibrium, (2) a rising bubble penetrating a fluid-fluid interface, and (3) a solid particle falling in a binary fluid. The effects of slip at solid surface have been examined in connection with contact line motion and a pinch-off phenomenon.
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Kajzer, Adam, and Jacek Pozorski. "Diffuse interface models for two-phase flows in artificial compressibility approach." Journal of Physics: Conference Series 1101 (October 2018): 012013. http://dx.doi.org/10.1088/1742-6596/1101/1/012013.

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Journal articles

Dissertations / Theses on the topic "Diffuse-Interface approach":

1

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.

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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
2

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.

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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
3

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.

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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
4

Frisani, Angelo 1980. "Direct Forcing Immersed Boundary Methods: Finite Element Versus Finite Volume Approach." Thesis, 2012. http://hdl.handle.net/1969.1/148236.

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Two immersed boundary methods (IBM) for the simulation of conjugate heat transfer problems with complex geometries are introduced: a finite element (IFEM) and a finite volume (IFVM) immersed boundary methods are discussed. In the IFEM a projection approach is presented for the coupled system of time-dependent incompressible Navier-Stokes equations (NSEs) and energy equation in conjunction with the immersed boundary method for solving fluid flow and heat transfer problems in the presence of rigid objects not represented by the underlying mesh. The IBM allows solving the flow for geometries with complex objects without the need of generating a body-fitted mesh. Dirichlet boundary constraints are satisfied applying a boundary force at the immersed body surface. Using projection and interpolation operators from the fluid volume mesh to the solid surface mesh (i.e., the “immersed” boundary) and vice versa, it is possible to impose the extra constraint to the NSEs as a Lagrange multiplier in a fashion very similar to the effect pressure has on the momentum equations to satisfy the divergence-free constraint. The IFEM approach presented shows third order accuracy in space and second order accuracy in time when the simulation results for the Taylor-Green decaying vortex are compared to the analytical solution. For the IFVM a ghost-cell approach with sharp interface scheme is used to enforce the boundary condition at the fluid/solid interface. The interpolation procedure at the immersed boundary preserves the overall second order accuracy of the base solver. The developed ghost-cell method is applied on a staggered configuration with the Semi-Implicit Method for Pressure-Linked Equations Revised algorithm. Second order accuracy in space and first order accuracy in time are obtained when the Taylor-Green decaying vortex test case is compared to the IFVM analytical solution. Computations were performed using the IFEM and IFVM approaches for the two-dimensional flow over a backward-facing step, two-dimensional flow past a stationary circular cylinder, three-dimensional flow past a sphere and two and three-dimensional natural convection in an enclosure with/without immersed body. The numerical results obtained with the discussed IFEM and IFVM were compared against other IBMs available in literature and simulations performed with the commercial computational fluid dynamics code STAR-CCM+/V7.04.006. The benchmark test cases showed that the numerical results obtained with the implemented immersed boundary methods are in good agreement with the predictions from STAR-CCM+ and the numerical data from the other IBMs. The immersed boundary method based of finite element approach is numerically more accurate than the IBM based on finite volume discretization. In contrast, the latter is computationally more efficient than the former.

Books on the topic "Diffuse-Interface approach":

1

The Diffuse Interface Approach in Materials Science. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/3-540-36409-9.

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Emmerich, Heike. Diffuse Interface Approach in Materials Science: Thermodynamic Concepts and Applications of Phase-Field Models. Springer London, Limited, 2004.

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Emmerich, Heike. Diffuse Interface Approach in Materials Science: Thermodynamic Concepts and Applications of Phase-Field Models. Springer Berlin / Heidelberg, 2011.

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Emmerich, Heike. The Diffuse Interface Approach in Materials Science: Thermodynamic Concepts and Applications of Phase-Field Models (Lecture Notes in Physics Monographs). Springer, 2003.

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Wright, A. G. The optical interface to PMTs. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780199565092.003.0003.

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The optical interface between a light source and a detector is important. In most practical realizations the aim should be to collect the maximum light possible. Lens systems seldom do this efficiently, especially where the light source is diffuse. Underlying any attempt at concentrating or guiding light is subject to a fundamental limitation referred to as étendue (phase space cannot be squeezed). Light collection from small volume scintillators of high refractive index may approach 50 %, while collection from large-area scintillators is typically less than a few per cent. Incorporation of wavelength-shifting light guides and fibres leads to enhanced performance. Efficiency measurements by the author in terms of photoelectrons per keV are presented for selected configurations. Optical recycling derived from total internal reflection provides enhancement in effective quantum efficiency by a factor of up to 10. Concepts such as escape cones, adiabatic light guides, and trapped light are covered in detail.

Book chapters on the topic "Diffuse-Interface approach":

1

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.

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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.

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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.
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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.

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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.

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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.

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Dally, Tim, Carola Bilgen, Marek Werner, and Kerstin Weinberg. "Cohesive Elements or Phase-Field Fracture: Which Method Is Better for Dynamic Fracture Analyses?" In Modeling and Simulation in Engineering - Selected Problems. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.92180.

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Numerical techniques to simulate crack propagation can roughly be divided into sharp and diffuse interface methods. Two prominent approaches to quantitative dynamic fracture analysis are compared here. Specifically, an adaptive cohesive element technique and a phase-field fracture approach are applied to simulate Hopkinson bar experiments on the fracture toughness of high-performance concrete. The experimental results are validated numerically in the sense of an inverse analysis. Both methods allow predictive numerical simulations of crack growth with an a priori unknown path and determine the related material parameter in a quantitative manner. Reliability, precision, and numerical costs differ however.
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Li, D. Y., and L. Q. Chen. "Computer Simulation of Microstructural Evolution Under External Stresses." In Computer-Aided Design of High-Temperature Materials, 212–28. Oxford University PressNew York, NY, 1999. http://dx.doi.org/10.1093/oso/9780195120509.003.0017.

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Abstract Coherent microstructures and their stability are influenced by both external and internal stresses. During thermo-mechanical processes such as constrained aging, external stresses are applied to modify microstructures for improved performance. This article summarizes our recent computational studies on microstructural evolution under applied stresses or strains, using a diffuse-interface phase-field approach. The coupling between an applied stress and the transformation strain in a coherent twophase microstructure and its variation with different constraints are discussed.

Conference papers on the topic "Diffuse-Interface approach":

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.

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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.

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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.
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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.

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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.
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Chen, Yuqi, James M. McDonough, and Kaveh A. Tagavi. "A Hyperbolic Phase-Field Approach for Solidification With Supercooling." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-1026.

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Abstract This report concerns the solidification of a “supercooled” liquid, whose temperature is initially below the equilibrium melt temperature, Tm of the solid. A new approach, the phase-field method, will be applied for this Stefan problem with supercooling, which simulates the solidification process of a pure material into a supercooled liquid in a spherical region. The advantage of the phase-field method is that it bypasses explicitly tracking the freezing front. In this approach the solid-liquid interface is treated as diffuse, and a dynamic equation for the phase variable is introduced in addition to the equation for heat flow. Thus, there are two coupled partial differential equations for temperature and phase field. In the reported study, an implicit numerical scheme using finite-difference techniques on a uniform mesh is employed to solve both Fourier phase-field equations and non-Fourier (known as damped wave or telegraph) phase-field equations. The latter gurantees a finite speed of propagation for the solidification front. Both Fourier (parabolic) and non-Fourier (hyperbolic) Stefan problems with supercooling are satisfactorily simulated and their solutions compared in the present work.
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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.

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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.
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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.

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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.
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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.

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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.
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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.

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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.
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Pastor, J. M., J. M. Desantes, J. M. García-Oliver, A. Pandal, B. Naud, K. Matusik, D. Duke, A. Kastengren, C. Powell, and D. P. Schmidt. "Modelling and validation of near-field Diesel spray CFD simulations based on the Σ -Y model." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4715.

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Diesel spray modelling still remains a challenge, especially in the dense near-nozzle region. This region is difficultto experimentally access and also to model due to the complex and rapid liquid and gas interaction. Modelling approaches based on Lagrangian particle tracking have struggled in this area, while Eulerian modelling has proven particularly useful. An interesting approach is the single-fluid diffuse interface model known as Σ-Y, based on scale separation assumptions at high Reynolds and Weber numbers. Liquid dispersion is modelled as turbulent mixing of a variable density flow. The concept of surface area density is used for representing liquid structures, regardless of the complexity of the interface.In this work, an implementation of the Σ-Y model in the OpenFOAM CFD library is applied to simulate the ECN Spray A in the near nozzle region, using both RANS and LES turbulence modelling. Assessment is performed with measurements conducted at the Advanced Photon Source at Argonne National Laboratory (ANL). The ultra-small- angle x-ray scattering (USAXS) technique has been used to measure the interfacial surface area, and x-rayradiography to measure the fuel dispersion, allowing a direct evaluation of the Σ-Y model predictions.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4715
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Landis, Chad M. "Phase Field Modeling of Ferroelectric Domain Wall Interactions With Charge Defects." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-16184.

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The overall objective of this work is to develop a theoretical model that can track the evolution of the domain structures in ferroelectric crystals, which are responsible for the non-linear electromechanical behavior of these materials. To this end, a continuum thermodynamics framework is devised, and the theory falls into the class of phase-field or diffuse-interface modeling approaches. Here a set of micro-forces and governing balance laws are postulated and applied within the second law of thermodynamics to identify the appropriate material constitutive relationships. The approach is shown to yield the commonly accepted Ginzburg-Landau equation for the evolution of the polarization order parameter. Within the theory a form for the free energy is postulated that can be applied to fit the general elastic, piezoelectric and dielectric properties of a ferroelectric material near its spontaneously polarized state. Thereafter, a principle of virtual work is specified for the theory and is implemented to devise a finite element formulation. The theory and numerical methods are used to investigate the interactions of 180° and 90° domain walls with an array of charge defects and to determine the electromechanical pinning strength of the array on the walls.

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