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Littérature scientifique sur le sujet « Real boundary conditions »

Auteur : Grafiati
Publié le 4 juin 2021
Mis à jour le 14 février 2022

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Articles de revues sur le sujet "Real boundary conditions"

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Котов et P. Kotov. « THE METHOD OF REAL BOUNDARY PROBLEMS DEVELOPING THE REAL BOUNDARY CONDITIONS ». Modeling of systems and processes 9, no 1 (23 septembre 2016) : 11–13. http://dx.doi.org/10.12737/21619.

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An efficient solution to the real equation of heat transfer with deterministic disturbance and informative method of the basic initial-boundary value problems for the unsteady heat propagation with measurable initial and boundary conditions.
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McDonald, Robb. « Geodesic Loewner paths with varying boundary conditions ». Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 476, no 2242 (octobre 2020) : 20200466. http://dx.doi.org/10.1098/rspa.2020.0466.

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Equations of the Loewner class subject to non-constant boundary conditions along the real axis are formulated and solved giving the geodesic paths of slits growing in the upper half complex plane. The problem is motivated by Laplacian growth in which the slits represent thin fingers growing in a diffusion field. A single finger follows a curved path determined by the forcing function appearing in Loewner’s equation. This function is found by solving an ordinary differential equation whose terms depend on curvature properties of the streamlines of the diffusive field in the conformally mapped ‘mathematical’ plane. The effect of boundary conditions specifying either piecewise constant values of the field variable along the real axis, or a dipole placed on the real axis, reveal a range of behaviours for the growing slit. These include regions along the real axis from which no slit growth is possible, regions where paths grow to infinity, or regions where paths curve back toward the real axis terminating in finite time. Symmetric pairs of paths subject to the piecewise constant boundary condition along the real axis are also computed, demonstrating that paths which grow to infinity evolve asymptotically toward an angle of bifurcation of π /5.
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van Rees, Balt C. « Real-time gauge/gravity duality and ingoing boundary conditions ». Nuclear Physics B - Proceedings Supplements 192-193 (juillet 2009) : 193–96. http://dx.doi.org/10.1016/j.nuclphysbps.2009.07.078.

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Konin, A. « Boundary conditions in a real bipolar semiconductor-metal junction ». Lithuanian Journal of Physics 46, no 2 (2006) : 233–35. http://dx.doi.org/10.3952/lithjphys.46214.

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Gnecco, Giorgio, Marco Gori et Marcello Sanguineti. « Learning with Boundary Conditions ». Neural Computation 25, no 4 (avril 2013) : 1029–106. http://dx.doi.org/10.1162/neco_a_00417.

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Kernel machines traditionally arise from an elegant formulation based on measuring the smoothness of the admissible solutions by the norm in the reproducing kernel Hilbert space (RKHS) generated by the chosen kernel. It was pointed out that they can be formulated in a related functional framework, in which the Green’s function of suitable differential operators is thought of as a kernel. In this letter, our own picture of this intriguing connection is given by emphasizing some relevant distinctions between these different ways of measuring the smoothness of admissible solutions. In particular, we show that for some kernels, there is no associated differential operator. The crucial relevance of boundary conditions is especially emphasized, which is in fact the truly distinguishing feature of the approach based on differential operators. We provide a general solution to the problem of learning from data and boundary conditions and illustrate the significant role played by boundary conditions with examples. It turns out that the degree of freedom that arises in the traditional formulation of kernel machines is indeed a limitation, which is partly overcome when incorporating the boundary conditions. This likely holds true in many real-world applications in which there is prior knowledge about the expected behavior of classifiers and regressors on the boundary.
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WEHRHEIM, KATRIN. « BANACH SPACE VALUED CAUCHY–RIEMANN EQUATIONS WITH TOTALLY REAL BOUNDARY CONDITIONS ». Communications in Contemporary Mathematics 06, no 04 (août 2004) : 601–35. http://dx.doi.org/10.1142/s0219199704001410.

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The main purpose of this paper is to give a general regularity result for Cauchy–Riemann equations in complex Banach spaces with totally real boundary conditions. The usual elliptic Lp-regularity results hold true under one crucial assumption: The Banach space is isomorphic to a closed subspace of an Lp-space. (Equivalently, the totally real submanifold is modelled on a closed subspace of an Lp-space.) Secondly, we describe a class of examples of such totally real submanifolds, namely gauge invariant Lagrangian submanifolds in the space of connections over a Riemann surface. These pose natural boundary conditions for the anti-self-duality equation on 4-manifolds with a boundary space-time splitting, leading towards the definition of a Floer homology for 3-manifolds with boundary, which is the first step in a program by Salamon for the proof of the Atiyah–Floer conjecture. The principal part of such a boundary value problem is an example of a Banach space valued Cauchy–Riemann equation with totally real boundary condition.
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Dallos Santos, Dionicio Pastor. « Problems with Mixed Boundary Conditions in Banach Spaces ». Chinese Journal of Mathematics 2017 (15 mars 2017) : 1–8. http://dx.doi.org/10.1155/2017/7838102.

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Using Leray-Schauder degree or degree for α-condensing maps we obtain the existence of at least one solution for the boundary value problem of the following type: φu′′=ft,u,u′, u(T)=0=u′(0), where φ:X→X is a homeomorphism with reverse Lipschitz constant such that φ(0)=0, f:0,T×X×X→X is a continuous function, T is a positive real number, and X is a real Banach space.
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Medková, Dagmar. « The transmission problem with boundary conditions given by real measures ». Annales Polonici Mathematici 92, no 3 (2007) : 243–59. http://dx.doi.org/10.4064/ap92-3-4.

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Nogueira, José Alexandre, et Pedro Leite Barbieri. « Boundary conditions as mass generation mechanism for real scalar fields ». Brazilian Journal of Physics 32, no 3 (septembre 2002) : 798–803. http://dx.doi.org/10.1590/s0103-97332002000400022.

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Frauenfelder, Urs, et Kai Zehmisch. « Gromov compactness for holomorphic discs with totally real boundary conditions ». Journal of Fixed Point Theory and Applications 17, no 3 (29 avril 2015) : 521–40. http://dx.doi.org/10.1007/s11784-015-0229-0.

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Thèses sur le sujet "Real boundary conditions"

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Coussement, Axel. « Direct numerical simulation and reduced chemical schemes for combustion of perfect and real gases ». Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209765.

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La première partie de cette thèse traite du développement du code de simulation numérique directe YWC, principalement du développement des conditions aux limites. En effet, une forte contribution scientifique a été apportée aux conditions aux limites appelées "Three dimensional Navier-Stokes characteristic boundary condtions" (3D-NSCBC). Premièrement, la formulation de ces conditions aux arêtes et coins a été complétée, ensuite une extension de la formulation a été proposée pour supprimer les déformations observées en sortie dans le cas d'écoulements non-perpendiculaires à la frontière.

De plus, ces conditions ont été étendues au cas des gaz réels et une nouvelle définition du facteur de relaxation pour la pression a été proposée. Ce nouveau facteur de relaxation permet de supprimer les déformations observées en sortie pour des écoulements transcritiques.

Les résultats obtenus avec le code YWC ont ensuite été utilisés dans la seconde partie de la thèse pour développer une nouvelle méthode de tabulation basée sur l'analyse en composantes principales. Par rapport aux méthodes existante telles que FPI ou SLFM, la technique proposée, permet une identification automatique des variables à transporter et n'est, de plus, pas lié à un régime de combustion spécifique. Cette technique a permis d'effectuer des calculs d'interaction flamme-vortex en ne transportant que 5 espèces à la place des 9 requises pour le calcul en chimie détaillée complète, sans pour autant perdre en précision.

Finalement, dans le but de réduire encore le nombre d'espèces transportées, les techniques T-BAKED et HT-BAKED PCA ont été introduites. En utilisant une pondération des points sous-représentés, ces deux techniques permettent d'augmenter la précision de l'analyse par composantes principales dans le cadre des phénomènes de combustion.


Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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Gdhaidh, Farouq A. S. « Heat Transfer Characteristics of Natural Convection within an Enclosure Using Liquid Cooling System ». Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/7824.

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In this investigation, a single phase fluid is used to study the coupling between natural convection heat transfer within an enclosure and forced convection through computer covering case to cool the electronic chip. Two working fluids are used (water and air) within a rectangular enclosure and the air flow through the computer case is created by an exhaust fan installed at the back of the computer case. The optimum enclosure size configuration that keeps a maximum temperature of the heat source at a safe temperature level (85℃) is determined. The cooling system is tested for varying values of applied power in the range of 15−40𝑊. The study is based on both numerical models and experimental observations. The numerical work was developed using the commercial software (ANSYS-Icepak) to simulate the flow and temperature fields for the desktop computer and the cooling system. The numerical simulation has the same physical geometry as those used in the experimental investigations. The experimental work was aimed to gather the details for temperature field and use them in the validation of the numerical prediction. The results showed that, the cavity size variations influence both the heat transfer process and the maximum temperature. Furthermore, the experimental results ii compared favourably with those obtained numerically, where the maximum deviation in terms of the maximum system temperature, is within 3.5%. Moreover, it is seen that using water as the working fluid within the enclosure is capable of keeping the maximum temperature under 77℃ for a heat source of 40𝑊, which is below the recommended electronic chips temperature of not exceeding 85℃. As a result, the noise and vibration level is reduced. In addition, the proposed cooling system saved about 65% of the CPU fan power.
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Gdhaidh, Farouq Ali S. « Heat transfer characteristics of natural convection within an enclosure using liquid cooling system ». Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/7824.

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In this investigation, a single phase fluid is used to study the coupling between natural convection heat transfer within an enclosure and forced convection through computer covering case to cool the electronic chip. Two working fluids are used (water and air) within a rectangular enclosure and the air flow through the computer case is created by an exhaust fan installed at the back of the computer case. The optimum enclosure size configuration that keeps a maximum temperature of the heat source at a safe temperature level (85°C) is determined. The cooling system is tested for varying values of applied power in the range of 15-40W. The study is based on both numerical models and experimental observations. The numerical work was developed using the commercial software (ANSYS-Icepak) to simulate the flow and temperature fields for the desktop computer and the cooling system. The numerical simulation has the same physical geometry as those used in the experimental investigations. The experimental work was aimed to gather the details for temperature field and use them in the validation of the numerical prediction. The results showed that, the cavity size variations influence both the heat transfer process and the maximum temperature. Furthermore, the experimental results ii compared favourably with those obtained numerically, where the maximum deviation in terms of the maximum system temperature, is within 3.5%. Moreover, it is seen that using water as the working fluid within the enclosure is capable of keeping the maximum temperature under 77°C for a heat source of 40W, which is below the recommended electronic chips temperature of not exceeding 85°C. As a result, the noise and vibration level is reduced. In addition, the proposed cooling system saved about 65% of the CPU fan power.
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Blondel, Frédéric. « Couplages instationnaires de la vapeur humide dans les écoulements de turbines à vapeur ». Phd thesis, Ecole Centrale de Lyon, 2014. http://tel.archives-ouvertes.fr/tel-00985725.

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Le bon fonctionnement et les performances des turbines à vapeur sont liés à l'état de la vapeur et notamment au taux d'humidité qu'elle contient. EDF souhaite pouvoir maîtriser les phénomènes spécifiques à ces problématiques afin d'améliorer l'utilisation et l'évolution de ses turbines. Le sujet de recherche concerne la modélisation de la formation de l'humidité dans un corps de turbine et l'étude des couplages entre la phase liquide et les instationnarités. Dans ce contexte, la démarche adoptée est la suivante : la présence d'humidité est prise en compte à l'aide d'un modèle homogène, couplé à des modèles de condensation permettant de prendre en compte les phénomènes hors-équilibre thermodynamique : le grossissement et la nucléation des gouttes d'eau dans la vapeur. Pour mener à bien les calculs, des méthodes numériques adaptées aux gaz réels ont été utilisées et testées à l'aide d'un code monodimensionnel avant d'être intégrées dans le code 3D elsA. Deux types de modèles de condensation ont été mis en œuvre, considérant ou non la polydispersion des gouttes dans la vapeur. Les couplages instationnaires entre la condensation et l'écoulement principal ont été étudiés à différents niveaux d'observations (1D, 1D − 3D, 3D). Il a été montré que la méthode des moments apporte une richesse supplémentaire par rapport à un modèle mono-dispersé, et permet de mieux capter les couplages instationnaires entre l'humidité et le champ principal.
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Lee, Chung-Shuo, et 李崇碩. « A Generalized Real-Space Absorbing Boundary Condition for Molecular Dynamics Simulation ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/07157499668541060162.

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碩士
國立臺灣大學
土木工程學研究所
101
A non-reflection boundary condition is essential for any molecular dynamics simulation involving wave transition. In the past, the Fourier transform was applied to derive the absorbing boundary condition for a n-dimensional system. The method is powerful but only valid for boundaries with a simple geometry, e.g., a simple edge boundary in a two-dimensional domain. Our goal is to develop a generalized absorbing boundary condition for boundaries with complex geometry. In this thesis, we used the model of “virtual atoms” and the equations of motion of these “virtual atoms” to derive a generalized absorbing boundary condition. We studied a one-dimensional atomic chain to verify our method, and to discuss the convergence properties of our results in comparison with analytical solutions. In addition, we studied two kinds of boundaries: side and corner of a square lattice in two dimensions, and the results agreed very well with previous studies. These case studies confirm the accuracy of the proposed method. The generalized absorbing boundary condition is developed in the real space thus can be applied to any dimension, any regular lattice and any geometric boundary in the future.
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Livres sur le sujet "Real boundary conditions"

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Guenther, B. D. Modern Optics Simplified. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198842859.001.0001.

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This textbook is designed for use in a standard physics course on optics at the sophomore level. The book is an attempt to reduce the complexity of coverage found in Modem Optics to allow a student with only elementary calculus to learn the principles of optics and the modern Fourier theory of diffraction and imaging. Examples based on real optics engineering problems are contained in each chapter. Topics covered include aberrations with experimental examples, correction of chromatic aberration, explanation of coherence and the use of interference theory to design an antireflection coating, Fourier transform optics and its application to diffraction and imaging, use of gaussian wave theory, and fiber optics will make the text of interest as a textbook in Electrical and bioengineering as well as Physics. Students who take this course should have completed an introductory physics course and math courses through calculus Need for experience with differential equations is avoided and extensive use of vector theory is avoided by using a one dimensional theory of optics as often as possible. Maxwell’s equations are introduced to determine the properties of a light wave and the boundary conditions are introduced to characterize reflection and refraction. Most discussion is limited to reflection. The book provides an introduction to Fourier transforms. Many pictures, figures, diagrams are used to provide readers a good physical insight of Optics. There are some more difficult topics that could be skipped and they are indicated by boundaries in the text.
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Chapitres de livres sur le sujet "Real boundary conditions"

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Schwab, Daniela, Stefan Ingwersen, Alois Peter Schaffarczyk et Michael Breuer. « Aerodynamic Boundary Layer Investigation on a Wind Turbine Blade under Real Conditions ». Dans Research Topics in Wind Energy, 203–8. Berlin, Heidelberg : Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-54696-9_30.

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Hetmaniuk, Ulrich, et Charbel Farhat. « A Blended Fictitious/Real Domain Decomposition Method for Partially Axisymmetric Exterior Helmholtz Problems with Dirichlet Boundary Conditions ». Dans Lecture Notes in Computational Science and Engineering, 1–26. Berlin, Heidelberg : Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-642-56118-4_1.

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Opitz, Mark, Dominic Bertling et Nico Liebers. « FAUST : MATERIAL CHARACTERIZATION OF LOW-COST FOAM MATERIALS UNDER REAL BOUNDARY PROCESS CONDITIONS FOR RTM LARGE-SCALE PRODUCTION ». Dans Technologies for economical and functional lightweight design, 221–33. Berlin, Heidelberg : Springer Berlin Heidelberg, 2019. http://dx.doi.org/10.1007/978-3-662-58206-0_21.

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Heber, Lars, Julian Schwab et Horst E. Friedrich. « Design of a Thermoelectric Generator for Heavy-Duty Vehicles : Approach Based on WHVC and Real Driving Vehicle Boundary Conditions ». Dans Energy and Thermal Management, Air-Conditioning, and Waste Heat Utilization, 206–21. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-00819-2_15.

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Haidn, Oskar J., Nikolaus A. Adams, Rolf Radespiel, Thomas Sattelmayer, Wolfgang Schröder, Christian Stemmer et Bernhard Weigand. « Collaborative Research for Future Space Transportation Systems ». Dans Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 1–30. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_1.

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Abstract This chapter book summarizes the major achievements of the five topical focus areas, Structural Cooling, Aft-Body Flows, Combustion Chamber, Thrust Nozzle, and Thrust-Chamber Assembly of the Collaborative Research Center (Sonderforschungsbereich) Transregio 40. Obviously, only sample highlights of each of the more than twenty individual projects can be given here and thus the interested reader is invited to read their reports which again are only a summary of the entire achievements and much more information can be found in the referenced publications. The structural cooling focus area included results from experimental as well as numerical research on transpiration cooling of thrust chamber structures as well as film cooling supersonic nozzles. The topics of the aft-body flow group reached from studies of classical flow separation to interaction of rocket plumes with nozzle structures for sub-, trans-, and supersonic conditions both experimentally and numerically. Combustion instabilities, boundary layer heat transfer, injection, mixing and combustion under real gas conditions and in particular the investigation of the impact of trans-critical conditions on propellant jet disintegration and the behavior under trans-critical conditions were the subjects dealt with in the combustion chamber focus area. The thrust nozzle group worked on thermal barrier coatings and life prediction methods, investigated cooling channel flows and paid special attention to the clarification and description of fluid-structure-interaction phenomena I nozzle flows. The main emphasis of the focal area thrust-chamber assembly was combustion and heat transfer investigated in various model combustors, on dual-bell nozzle phenomena and on the definition and design of three demonstrations for which the individual projects have contributed according to their research field.
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Wang, Fang, Bingyu Wang, Yong Han, Qian Peng, Fan Li et Adam Wittek. « Reconstruction of Real-World Car-to-Pedestrian Accident Using Computational Biomechanics Model : Effects of the Choice of Boundary Conditions of the Brain on Brain Injury Risk ». Dans Computational Biomechanics for Medicine, 15–30. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-75589-2_3.

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Meerkerk, Ingmar van, Maria Zwanenburg et Maartje van Eerd. « PART II : The role of participation, in particular through self-organizing networksCHAPTER 8 : Enabling and constraining conditions for boundary-spanning in community-led urban regeneration : A conceptual model ». Dans Urban Governance in the Realm of Complexity, 169–94. The Schumacher Centre, Bourton on Dunsmore, Rugby, Warwickshire CV23 9QZ, UK, : Practical Action Publishing Ltd, 2017. http://dx.doi.org/10.3362/9781780449685.008.

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Sethuramalingam, Ramamoorthy, et Abhishek Asthana. « Design Improvement of Water-Cooled Data Centres Using Computational Fluid Dynamics ». Dans Springer Proceedings in Energy, 105–13. Cham : Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63916-7_14.

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AbstractData centres are complex energy demanding environments. The number of data centres and thereby their energy consumption around the world is growing at a rapid rate. Cooling the servers in the form of air conditioning forms a major part of the total energy consumption in data centres and thus there is an urgent need to develop alternative energy efficient cooling technologies. Liquid cooling systems are one such solution which are in their early developmental stage. In this article, the use of Computational Fluid Dynamics (CFD) to further improve the design of liquid-cooled systems is discussed by predicting temperature distribution and heat exchanger performance. A typical 40 kW rack cabinet with rear door fans and an intermediate air–liquid heat exchanger is used in the CFD simulations. Steady state Reynolds-Averaged Navier–Stokes modelling approach with the RNG K-epsilon turbulence model and the Radiator boundary conditions were used in the simulations. Results predict that heat exchanger effectiveness and uniform airflow across the cabinet are key factors to achieve efficient cooling and to avoid hot spots. The fundamental advantages and limitations of CFD modelling in liquid-cooled data centre racks were also discussed. In additional, emerging technologies for data centre cooling have also been discussed.
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Ono, Tomoya, et Kikuji Hirose. « Implementation for Systems under Various Boundary Conditions ». Dans First-Principles Calculations in Real-Space Formalism, 57–77. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2005. http://dx.doi.org/10.1142/9781860946530_0005.

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Kaimal, J. C., et J. J. Finnigan. « Flow Over Changing Terrain ». Dans Atmospheric Boundary Layer Flows. Oxford University Press, 1994. http://dx.doi.org/10.1093/oso/9780195062397.003.0007.

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The micrometeorologist setting out to find a field site that satisfies the requirements of horizontal homogeneity will soon be reminded that most of the earth’s surface is not flat and that most of the flat bits are inconveniently heterogeneous. This is what forced the location of early pioneering experiments to remote sites such as Kansas, Minnesota, or Hay (Chapter 1), where the elusive conditions could be realized. Vital as these experiments were to the development of our understanding, they are merely the point of departure for applications to arbitrary terrain. The components of arbitrariness are two: changes in the land surface and hills. In this chapter we discuss the first of these, flow over changing surface conditions; in Chapter 5 we look at flow over hills. In the real world, the two conditions often occur together — in farmland it is the hills too steep to plow that are left covered with trees — but we separate them here to clarify the explication of phenomena and because treating them in combination would exceed the state of the art. We simplify the problem of horizontal heterogeneity still further and discuss mainly single changes in surface conditions from one extensive uniform surface to another. Furthermore, the change will typically be at right angles to the wind direction so the resulting flow field is two-dimensional. Although multiple changes are now receiving theoretical attention (Belcher et al., 1990; Claussen, 1991), there exist as yet no experimental data for comparison. Two types of surface change may be distinguished at the outset: change in surface roughness, which produces a change in surface momentum flux with a direct effect upon the wind field, and change in the surface availability of some scalar. Those of most interest are the active scalars, heat and moisture. (These are called active because their fluxes and concentrations affect stability and thereby turbulent mixing and momentum transfer, as we saw in Chapters 1 and 3.) We shall discover significant differences in flow behavior according to whether the wind blows from a smooth to a rough surface or a rough to a smooth surface.
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Actes de conférences sur le sujet "Real boundary conditions"

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Wilson, Andrew, et Paul Steen. « Boundary Conditions for Real Gas Puff Loads ». Dans IEEE Conference Record - Abstracts. 2005 IEEE International Conference on Plasma Science. IEEE, 2005. http://dx.doi.org/10.1109/plasma.2005.359320.

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Sriramulu, Yoganandam, Senthil Kanagaraj, Manikandan R et Karthikeyan KJ. « Determination of Climatic Boundary Conditions for Vehicular Real Driving Emission Tests ». Dans WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States : SAE International, 2019. http://dx.doi.org/10.4271/2019-01-0758.

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Xu, Tian, et Yong Lei. « Identification of Young’s Modulus and Equivalent Spring Constraint Boundary Conditions of the Object With Incomplete Displacement Boundary Conditions ». Dans ASME 2020 15th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/msec2020-8396.

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Abstract In endoscopic surgery, the surgical navigation needs to calculate the internal deformation of the soft tissue by biomechanical model which needs to determine the elastic properties and boundary conditions. However, these information cannot be obtained accurately in a real operation scenario. For example, only a limited portion of a liver surface can be observed in a hepatic surgery under endoscope while its elastic properties remain unknown. In addition, simple boundary conditions such as fixed constraints and free-force constraints are not physically adequate to simulate the elastic effect of ligaments attached to the liver. Biomechanical models of the soft tissue have been thoroughly studied in recent years. In these studies, boundary conditions play an important role in identification of elastic properties for mechanical model based methods. But they rarely combine these unknown conditions together to construct the model, and instead set boundary conditions or elastic properties as known for simplification. In this paper, we present a novel method to identify the Young’s modulus and equivalent spring constraint boundary conditions of a partially observed soft object with incomplete boundary conditions. The spring constraint boundary condition is applied to alternate the conventional displacement boundary conditions (e.g. free constraint and fixed constraint) and an inverse algorithm based on the standard finite element method (FEM) and Gauss-Newton (GN) method is developed, which takes external forces and displacements of observable nodes as inputs. A series of numerical simulation experiments are implemented and the analysis of simulation results show the feasibility of the proposed method.
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Coull, John D., et Nicholas R. Atkins. « The Influence of Boundary Conditions on Tip Leakage Flow ». Dans ASME 2013 Turbine Blade Tip Symposium. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/tbts2013-2057.

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Most of the current understanding of tip leakage flows has been derived from detailed cascade experiments. However, the cascade model is inherently approximate since it is difficult to simulate the boundary conditions present in a real machine, particularly the secondary flows convecting from the upstream stator row and the relative motion of the casing and blade. This problem is further complicated when considering the high pressure turbine rotors of aero engines, where the high Mach numbers must also be matched in order to correctly model the aerodynamics and heat transfer. More realistic tests can be performed on high-speed turbines, but the experimental fidelity and resolution achievable in such set-ups is limited. In order to examine the differences between cascade models and real-engine behavior, the influence of boundary conditions on the tip leakage flow in an unshrouded high pressure turbine rotor is investigated using RANS calculations. This study examines the influence of the rotor inlet condition and relative casing motion. A baseline calculation with a simplified inlet condition and no relative endwall motion exhibits similar behavior to cascade studies. Only minor changes to the leakage flow are induced by introducing either a more realistic inlet condition or relative casing motion. However when both of these conditions are applied simultaneously the pattern of leakage flow is very different, with ingestion of flow over much of the early suction surface. The paper explores the physical processes driving this change and the impact on leakage losses and modeling requirements.
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Harris, Zachary, Joshua Bittle et Ajay Agrawal. « Role of Inlet Boundary Conditions on Fuel-Air Mixing at Supercritical Conditions ». Dans ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-3004.

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Abstract Advanced engine design and alternative fuels present the possibility of fuel injection at purely supercritical conditions in diesel engines and gas turbines. The complex interactions that govern this phenomenon still need significant research for reliable modeling efforts. Boundary conditions for fuel injection are critical to accurate simulation. However, the flow inside the injector itself is often omitted to reduce the computational efforts, and thus, velocity, mass flux, or total pressure is specified at the injector exit (or domain inlet), often with an assumed top hat profile and assumed turbulence levels. Past studies have shown that such simplified inlet boundary treatment has minimal effects on the results for fuel injection in the compressed liquid phase. However, the validity of this approach at supercritical fuel injection conditions has not been assessed so far. In this study, comprehensive real-gas and binary fluid mixing models have been implemented for computational fluid dynamic (CFD) analysis of fuel-air mixing at supercritical conditions. The model is verified using prior CFD results from the literature. Next, the model is used to investigate the effects of the shape of axial velocity and mass fraction profiles at the inlet boundary with the goal to improve the comparison of predictions to experimental data. Results show that the boundary conditions have a significant effect on the predictions, and none of the cases match precisely with experimental data. The study reveals that the physical location of the inlet boundary might be difficult to infer correctly from the experiments and highlights the need for high-quality, repeatable measurements at supercritical conditions to support the development of relevant high-fidelity models for fuel-air mixing.
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Song, Zhihang, Bruce T. Murray et Bahgat Sammakia. « Prediction of Hot Aisle Partition Airflow Boundary Conditions ». Dans ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73049.

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The integration of a simulation-based Artificial Neural Network (ANN) with a Genetic Algorithm (GA) has been explored as a real-time design tool for data center thermal management. The computation time for the ANN-GA approach is significantly smaller compared to a fully CFD-based optimization methodology for predicting data center operating conditions. However, difficulties remain when applying the ANN model for predicting operating conditions for configurations outside of the geometry used for the training set. One potential remedy is to partition the room layout into a finite number of characteristic zones, for which the ANN-GA model readily applies. Here, a multiple hot aisle/cold aisle data center configuration was analyzed using the commercial software FloTHERM. The CFD results are used to characterize the flow rates at the inter-zonal partitions. Based on specific reduced subsets of desired treatment quantities from the CFD results, such as CRAC and server rack air flow rates, the approach was applied for two different CRAC configurations and various levels of CRAC and server rack flow rates. Utilizing the compact inter-zonal boundary conditions, good agreement for the airflow and temperature distributions is achieved between predictions from the CFD computations for the entire room configuration and the reduced order zone-level model for different operating conditions and room layouts.
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Cayeux, Eric. « On the Importance of Boundary Conditions for Real-Time Transient Drill-String Mechanical Estimations ». Dans IADC/SPE Drilling Conference and Exhibition. Society of Petroleum Engineers, 2018. http://dx.doi.org/10.2118/189642-ms.

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Karkar, Sami, et Manuel Collet. « Nonreciprocal Acoustics Using Programmable Boundary Conditions : From Boundary Control and Active Metamaterials to the Acoustic Diode ». Dans ASME 2017 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/smasis2017-3797.

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In this communication, we first introduce the concept of programmable boundary conditions, and then use it to design a nonreciprocal acoustic device: an effective, broadband, acoustic diode. Previous works showed that, using sufficiently small transducers, an active acoustic metasurface can be realized: a smart active acoustic skin with tunable acoustic properties. Using distributed control, these properties can be adapted or reconfigured in real-time. Or, it can even depend on the acoustic field itself, allowing for a programming of the (meta)surface properties: a programmable boundary condition. For instance, a partial derivative equation depending on the acoustic quantities can be imposed, in a discretized form, at the surface of such a programmable boundary. This type of non-standard boundary conditions have been shown to provide the necessary basis for nonreciprocal propagation for a plane wave interacting with a boundary with non grazing incidence, ie. for wavevectors that possess a component normal to the boundary. This restriction may appear problematic when the wavevector is then parallel to the boundary, e.g. when dealing with plane waves in a 1D waveguide, as in an acoustic diode. An acoustic diode, or acoustic isolator, is a nonreciprocal device that let acoustic power pass only in one direction, hence breaking the reciprocity of normal acoustic propagation. We propose a new model of acoustic diode, based on active components: a continuous, distributed source inside the domain. However, based on the modeling of parietal sources in ducts, in the low frequency range, we show that the boundary control approach and the distributed domain sources are equivalent. The only difference is that, in the case of the programmable boundary condition, the near-field of the boundary also contains a component normal to the boundary. Hence our acoustic diode can be realized in practice using programmable boundary conditions. Moreover, the acoustic diode is effective on a broad frequency range, since it can work both on the fundamental mode (plane waves) and on higher-order mode of the waveguide.
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Salih, Saif, Daniel DelVescovo, Christopher P. Kolodziej, Toby Rockstroh et Alexander Hoth. « Defining the Boundary Conditions of the CFR Engine Under RON Conditions for Knock Prediction and Robust Chemical Mechanism Validation ». Dans ASME 2018 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icef2018-9640.

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In order to establish a pathway to evaluate chemical kinetic mechanisms (detailed or reduced) in a real engine environment, a GT Power model of the well-studied Cooperative Fuels Research (CFR) engine was developed and validated against experimental data for primary reference fuel blends between 60 and 100 under RON conditions. The CFR engine model utilizes a predictive turbulent flame propagation sub-model, and implements a chemical kinetic solver to solve the end-gas chemistry. The validation processes were performed simultaneously for thermodynamic and chemical kinetic parameters to match IVC conditions, burn rate, and knock prediction. A recently published kinetic mechanism was implemented in GT-Power, and was found to over-predict the low temperature heat release for iso-octane and PRF blends, leading to advanced knock onset phasing compared to experiments. Three reaction rates in the iso-octane and n-heptane pathways were tuned in the kinetic mechanism in order to match experimental knock-point values, yielding excellent agreement in terms of the knock onset phasing, burn rate, and the thermodynamic conditions compared to experiments. This developed model provides the initial/boundary conditions of the CFR engine under RON conditions, including IVC temperature and pressure, MFB profile, residual fraction and composition. The conditions were then correlated as a function of CFR engine compression ratio, and implemented in a 0-D SI engine model in Chemkin Pro in order to demonstrate an application of the current work. The Chemkin Pro and GT-Power simulations provided nearly identical results despite significant differences in heat transfer models and chemical kinetic solvers. This work provides the necessary framework by which robust chemical kinetic mechanisms can be developed, evaluated, and tuned, based on the knocking tendencies in a real engine environment for PRF blends.
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Gamino, Marcus, Samuel Abankwa et Raresh Pascali. « FSI Methodology for Analyzing VIV on Subsea Piping Components With Practical Boundary Conditions ». Dans ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10419.

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A general assumption in performing vortex-induced vibration (VIV) analysis of pipeline free spans is both ends of the free span are fixed and/or pinned in order to simplify computational simulations; however, DNV Recommended Practice F105 states that these boundary conditions must adequately represent the pipe-soil interaction and the continuality of the pipeline. A computational methodology is developed to determine the effects of pip-soil interaction at the ends of a free span. Three-dimensional fluid-structure interaction (FSI) simulations are performed by coupling the computational fluid dynamics (CFD) codes from STAR-CCM+ with the finite element analysis (FEA) codes from ABAQUS. These FSI simulations in combination with separate coupled Eulerian-Lagrangian (CEL) simulations are modeled to mimic real word conditions by setting up boundary conditions to factor in the effects of pipe-soil interaction at the ends of the span. These simulations show a mitigation of overall stresses to the free spans; as a result, the integration of pipe-soil interaction in free span assessment may prove cost effective in the prevention of unnecessary corrective action.
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