Tesis sobre el tema "Layer Finite Element Method"
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Gundu, Krishna Mohan. "hp-Finite Element Method for Photonics Applications". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195940.
Texto completoSevilla, Cárdenas Rubén. "NURBS-Enhanced Finite Element Method (NEFEM)". Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/5857.
Texto completoLa implementació i aplicació de NEFEM a problemes que requereixen una descripció acurada del contorn són, també, objectius prioritaris d'aquesta tesi. Per exemple, la solució numèrica de les equacions de Maxwell és molt sensible a la descripció geomètrica. Es presenta l'aplicació de NEFEM a problemes d'scattering d'ones electromagnètiques amb una formulació de Galerkin discontinu. S'investiga l'habilitat de NEFEM per obtenir solucions precises amb malles grolleres i aproximacions d'alt ordre, i s'exploren les possibilitats de les anomenades malles NEFEM, amb elements que contenen singularitats dintre d'una cara o aresta d'un element. Utilitzant NEFEM, la mida de la malla no està controlada per la complexitat de la geometria. Això implica una dràstica diferència en la mida dels elements i, per tant, suposa un gran estalvi tant des del punt de vista de requeriments de memòria com de cost computacional. Per tant, NEFEM és una eina poderosa per la simulació de problemes tridimensionals a gran escala amb geometries complexes. D'altra banda, la simulació de problemes d'scattering d'ones electromagnètiques requereix mecanismes per aconseguir una absorció eficient de les ones scattered. En aquesta tesi es discuteixen, optimitzen i comparen dues tècniques en el context de mètodes de Galerkin discontinu amb aproximacions d'alt ordre.
La resolució numèrica de les equacions d'Euler de la dinàmica de gasos és també molt sensible a la representació geomètrica. Quan es considera una formulació de Galerkin discontinu i elements isoparamètrics lineals, una producció espúria d'entropia pot evitar la convergència cap a la solució correcta. Amb NEFEM, l'acurada imposició de la condició de contorn en contorns impenetrables proporciona resultats precisos inclús amb una aproximació lineal de la solució. A més, la representació exacta del contorn permet una imposició adequada de les condicions de contorn amb malles grolleres i graus d'interpolació alts. Una propietat atractiva de la implementació proposada és que moltes de les rutines usuals en un codi d'elements finits poden ser aprofitades, per exemple rutines per realitzar el càlcul de les matrius elementals, assemblatge, etc. Només és necessari implementar noves rutines per calcular les quadratures numèriques en elements corbs i emmagatzemar el valor de les funciones de forma en els punts d'integració. S'han proposat vàries tècniques d'elements finits corbs a la literatura. En aquesta tesi, es compara NEFEM amb altres tècniques populars d'elements finits corbs (isoparamètics, cartesians i p-FEM), des de tres punts de vista diferents: aspectes teòrics, implementació i eficiència numèrica. En els exemples numèrics, NEFEM és, com a mínim, un ordre de magnitud més precís comparat amb altres tècniques. A més, per una precisió desitjada NEFEM és també més eficient: necessita un 50% dels graus de llibertat que fan servir els elements isoparamètrics o p-FEM per aconseguir la mateixa precisió. Per tant, l'ús de NEFEM és altament recomanable en presència de contorns corbs i/o quan el contorn té detalls geomètrics complexes.
This thesis proposes an improvement of the classical finite element method (FEM) for an efficient treatment of curved boundaries: the NURBSenhanced FEM (NEFEM). It is able to exactly represent the geometry by means of the usual CAD boundary representation with non-uniform rational Bsplines (NURBS), while the solution is approximated with a standard piecewise polynomial interpolation. Therefore, in the vast majority of the domain, interpolation and numerical integration are standard, preserving the classical finite element (FE) convergence properties, and allowing a seamless coupling with standard FEs on the domain interior. Specifically designed polynomial interpolation and numerical integration are designed only for those elements affected by the NURBS boundary representation.
The implementation and application of NEFEM to problems demanding an accurate boundary representation are also primary goals of this thesis. For instance, the numerical solution of Maxwell's equations is highly sensitive to geometry description. The application of NEFEM to electromagnetic scattering problems using a discontinuous Galerkin formulation is presented. The ability of NEFEM to compute an accurate solution with coarse meshes and high-order approximations is investigated, and the possibilities of NEFEM meshes, with elements containing edge or corner singularities, are explored. With NEFEM, the mesh size is no longer subsidiary to geometry complexity, and depends only on the accuracy requirements on the solution, whereas standard FEs require mesh refinement to properly capture the geometry. This implies a drastic difference in mesh size that results in drastic memory savings, and also important savings in computational cost. Thus, NEFEM is a powerful tool for large-scale scattering simulations with complex geometries in three dimensions. Another key issue in the numerical solution of electromagnetic scattering problems is using a mechanism to perform the absorption of outgoing waves. Two perfectly matched layers are discussed, optimized and compared in a high-order discontinuous Galerkin framework.
The numerical solution of Euler equations of gas dynamics is also very sensitive to geometry description. Using a discontinuous Galerkin formulation and linear isoparametric elements, a spurious entropy production may prevent convergence to the correct solution. With NEFEM, the exact imposition of the solid wall boundary condition provides accurate results even with a linear approximation of the solution. Furthermore, the exact boundary representation allows using coarse meshes, but ensuring the proper implementation of the solid wall boundary condition. An attractive feature of the proposed implementation is that the usual routines of a standard FE code can be directly used, namely routines for the computation of elemental matrices and vectors, assembly, etc. It is only necessary to implement new routines for the computation of numerical quadratures in curved elements and to store the value of shape functions at integration points.
Several curved FE techniques have been proposed in the literature. In this thesis, NEFEM is compared with some popular curved FE techniques (namely isoparametric FEs, cartesian FEs and p-FEM), from three different perspectives: theoretical aspects, implementation and performance. In every example shown, NEFEM is at least one order of magnitude more accurate compared to other techniques. Moreover, for a desired accuracy NEFEM is also computationally more efficient. In some examples, NEFEM needs only 50% of the number of degrees of freedom required by isoparametric FEs or p-FEM. Thus, the use of NEFEM is strongly recommended in the presence of curved boundaries and/or when the boundary of the domain has complex geometric details.
Brown, Steven Andrew. "Development of a coupled finite element - boundary element program for a microcomputer". Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45713.
Texto completoMaster of Science
Nishio, Yoshiyuki. "Challenges in applying the PSPG/SUPG Finite element method to the atmosphéric boundary layer". Thesis, La Rochelle, 2021. http://www.theses.fr/2021LAROS017.
Texto completoIn the context of a Chemical, Biological, Radiological, and Nuclear (CBRN) application for the Belgian Defense, the original objective of the work was to simulate a realistic open-air CBRN case (e.g. dispersion after an explosion of particles in a city), by applying the Streamline-Upwind Petrov-Galerkin (SUPG) stabilization on a nite element method (FEM), together with a second phase (i.e. particles). This would be done through the code Cool uid 3, a Domain Speci c Language (DSL) written in C++.However, open-air applications requires to describe the atmospheric bound-ary layer (ABL) correctly. This has never been done using stabilized FEM. Consequently, the challenge of this work is to answer the simple question: How to model an ABL taking advantage of the SUPG stabilization method.To reduce the number of elements produced by a wall-resolved simulation, the ABL was implemented with a wall model and veri ed in 2D, while a few corrections (e.g. grid scalability, stable velocity pro le) could also be adressed.However, the 3D implementation revealed spurious oscillations, suggesting a numerical origin. Although SUPG does provide dissipation, it seemed not su cient enough for such a high Reynolds ow. Consequently, two directions were followed to add numerical dissipation: Firstly, the implementation of an extended version of the SUPG, the Variational MultiScale method (VMS), was initiated. The latter provides a combined framework for stabilization and turbulence modeling. Secondly, two LES formulations, known for their dissipative behavior, were integrated.Having solved the spurious oscillations, the velocity pro le was analyzed. Eventually, the viscous Reynolds number for the ABL domain was reduced to enable the comparison with an available DNS result. Fortunately, rela-tive to the standard no-slip wall condition and to the friction velocity condi-tion, the wall model implementation provided the best result, although not matching.In conclusion, we ascertained two methodologies (LES and SUPG / VMS) that have the potential to approach the ABL ow. The stabilized FEM using SUPG revealed that it is currently not su cient to avoid spurious oscillations in the case of an ABL ow. In contrast, LES provided encouraging results for reduced Reynolds number, supporting that some kind of turbulence model is indispensable. This emphasizes that the implementation of VMS should be promising, although challenging
Ozgun, Ozlem. "Finite Element Modeling Of Electromagnetic Radiation/scattering Problems By Domain Decomposition". Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608290/index.pdf.
Texto completoLinß, Torsten. "Layer-adapted meshes for convection-diffusion problems". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1203582105872-58676.
Texto completoMcClain, Stephen Taylor. "A discrete-element model for turbulent flow over randomly-rough surfaces". Diss., Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-04032002-140007.
Texto completoLinß, Torsten. "Layer-adapted meshes for convection-diffusion problems". Doctoral thesis, Technische Universität Dresden, 2006. https://tud.qucosa.de/id/qucosa%3A24058.
Texto completoParikh, Kunal. "Simulation of Rectangular, Single-Layer, Coax-Fed Patch Antennas Using Agilent High Frequency Structure Simulator (HFSS)". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/9663.
Texto completoMaster of Science
Xu, Boqing y 許博卿. "Convolutional perfectly matched layers for finite element modeling of wave propagation in unbounded domains". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208043.
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Civil Engineering
Doctoral
Doctor of Philosophy
Onen, Onursal. "Development Of An Effective Single Layer Micro-perforated Sound Absorber". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12610064/index.pdf.
Texto completoRodriguez, Miranda Juan Carlos 1984. "Estudio y análisis de sistemas lineales generados en problemas de contorno con frontera discontínua a partir de métodos espectrales/hp = Estudo e análise de sistemas lineares gerados nos problemas de contorno com fronteira descontinua a partir de métodos espectrais/hp". [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/306347.
Texto completoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matemática Estatística e Computação Científica
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Resumo: O Método dos Elementos Finitos representou nos últimos anos uma ferramenta fundamental no estudo de problemas de contorno. A evolução desde sua formulação fundamental a partir do Método de Galerkin clássico até sua versão com refinamento hp, se tornou na base dos métodos numéricos mais avançados como é o Método de Galerkin Descontinuo. O Método dos Elementos Finitos de Alta Ordem juntamente com os Métodos Espectrais usados na obtenção de soluções numéricas para problemas de contorno com fronteira descontinua, serão nosso objeto de estudo nesta Dissertação. Desde sua formulação matemática fundamental, por intermédio da escolha apropriada das funções hierárquicas que compõem os espaços de aproximação, assim como a montagem dos sistemas lineares locais e sua respectiva utilização no sistema linear global esparso, cuja solução é obtida pelo método iterativo de Gradiente Conjugado usando diversos Precondicionadores, será o caminho a seguir
Abstract: The Finite Element Method developed in the last decades has been the most important tool in the study of Boundary Value Problems. Your evolution from its fundamental formulation using the Galerkin Method to the hp-adaptive finite element methods (hp-FEM), provided the necessary foundation for more advanced Numerical Methods like the Galerkin Discontinuous Method. The Finite Element Method of Higher Order, together with the Spectral formulation as a numerical method to solve Boundary Problems with Discontinuous Boundary, is the objective of study to this dissertation. The fundamental mathematical formulation of the finite element methods, passing through of to choose of hierarchical basis functions, also the assembly of local linear systems and it posteriorly use to construct a Sparse Linear System, whose solution is obtained for an iterative Preconditioner Gradient Method
Mestrado
Matematica Aplicada
Mestre em Matemática Aplicada
Krause, Martin, Daniel Steinert, Eric Starke, Uwe Marschner, Günther Pfeifer y Wolf-Joachim Fischer. "Piezoelectric two-layer plate for position stabilization". Sage, 2014. https://tud.qucosa.de/id/qucosa%3A35620.
Texto completoBarreira, Luísa. "Estudo numérico do comportamento térmico e mecânico de estruturas em madeira". Master's thesis, Instituto Politécnico de Bragança, Escola Superior de Tecnologia e de Gestão, 2008. http://hdl.handle.net/10198/2086.
Texto completoCui, Xiaoming. "Discontinuous finite/boundary element method for radiative heat transfer with application in laser cancer therapy". Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Fall2005/x%5Fcui%5F121805.pdf.
Texto completoMacLean, Matthew. "A Numerical Study of Internal Flow Effects on Skin Friction Gages". Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/27114.
Texto completoPh. D.
Roos, Hans-Görg y Martin Schopf. "Layer structure and the galerkin finite element method for a system of weakly coupled singularly perturbed convection-diffusion equations with multiple scales". Cambridge University Press, 2015. https://tud.qucosa.de/id/qucosa%3A39046.
Texto completoBharath, Krishna. "Signal and power integrity co-simulation using the multi-layer finite difference method". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28155.
Texto completoCommittee Chair: Madhavan Swaminathan; Committee Member: Andrew F. Peterson; Committee Member: David C. Keezer; Committee Member: Saibal Mukhopadyay; Committee Member: Suresh Sitaraman.
Hrdonka, Štěpán. "Simulace mazání bodových kontaktů metodou konečných prvků". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-377883.
Texto completoZhao, Bo. "THE APPLICATION OF DISCONTINUOUS GALKERIN FINITE ELEMENT TIME-DOMAIN METHOD IN THE DESIGN, SIMULATION AND ANALYSIS OF MODERN RADIO FREQUENCY SYSTEMS". UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/186.
Texto completoYue, Liyang. "Laser cleaning of slotted components". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/laser-cleaning-of-slotted-components(c66c7114-d1d7-40be-a2c9-b99329435a43).html.
Texto completoBhamare, Sagar D. "High Cycle Fatigue Simulation using Extended Space-Time Finite Element Method Coupled with Continuum Damage Mechanics". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352490187.
Texto completoPratt, Phillip Roger. "Analysis of thermo-mechanical characteristics of the LENS[TM] process for steels using the finite element method". Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-12082008-183521.
Texto completoSobczyk, Martin y Thomas Wallmersperger. "Modeling and simulation of a chemically stimulated hydrogel bilayer bending actuator". SPIE, 2017. https://tud.qucosa.de/id/qucosa%3A34887.
Texto completoStafne, Michael Allan. "An Experimental Evaluation of the Experimental Spatial Dynamics Modeling (ESDM) Technique". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/46492.
Texto completoMaster of Science
Birgersson, Fredrik. "Prediction of random vibration using spectral methods". Doctoral thesis, KTH, Aeronautical and Vehicle Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3694.
Texto completoMuch of the vibration in fast moving vehicles is caused bydistributed random excitation, such as turbulent flow and roadroughness. Piping systems transporting fast flowing fluid isanother example, where distributed random excitation will causeunwanted vibration. In order to reduce these vibrations andalso the noise they cause, it is important to have accurate andcomputationally efficient prediction methods available.
The aim of this thesis is to present such a method. Thefirst step towards this end was to extend an existing spectralfinite element method (SFEM) to handle excitation of planetravelling pressure waves. Once the elementary response tothese waves is known, the response to arbitrary homogeneousrandom excitation can be found.
One example of random excitation is turbulent boundary layer(TBL) excitation. From measurements a new modified Chase modelwas developed that allowed for a satisfactory prediction ofboth the measured wall pressure field and the vibrationresponse of a turbulence excited plate. In order to model morecomplicated structures, a new spectral super element method(SSEM) was formulated. It is based on a waveguide formulation,handles all kinds of boundaries and its elements are easily putinto an assembly with conventional finite elements.
Finally, the work to model fluid-structure interaction withanother wave based method is presented. Similar to the previousmethods it seems to be computationally more efficient thanconventional finite elements.
RADAMPOLA, Senanie Sujeewa y senanie s. radampola@mainroads qld gov au. "EVALUATION AND MODELLING PERFORMANCE OF CAPPING LAYER IN RAIL TRACK SUBSTRUCTURE". Central Queensland University. Centre for Railway Engineering, 2006. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20060817.115415.
Texto completoSobczyk, Martin y Thomas Wallmersperger. "Modeling and simulation of the electro-chemical behavior of chemically stimulated polyelectrolyte hydrogel layer composites". Sage, 2016. https://tud.qucosa.de/id/qucosa%3A35624.
Texto completoTangirala, Sailesh Kumar. "EXPERIMENTAL AND NUMERICAL INVESTIGATION OF PLASMA-JET FORMING". UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_theses/361.
Texto completoXu, Yingjie. "Prediction of properties and optimal design of microstructure of multi-phase and multi-layer C/SiC composites". Phd thesis, Université de Technologie de Belfort-Montbeliard, 2011. http://tel.archives-ouvertes.fr/tel-00625953.
Texto completoFišer, Jan. "Asynchronní motor s plným rotorem". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-317076.
Texto completoRolseth, Anton y Anton Gustafsson. "Implementation of thermomechanical laser welding simulation : Predicting displacements of fusing A AISI304 T-JOINT". Thesis, Högskolan i Skövde, Institutionen för ingenjörsvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-19946.
Texto completoGanti, Satya Rama Naga Lakshmi. "Characterization and Modelling of Laser Micro-Machined Metallic Terahertz Wire Waveguides". Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1347472107.
Texto completoJukic, Miha. "Finite elements for modeling of localized failure in reinforced concrete". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00997197.
Texto completoErlandsson, Simon. "Evaluation, adaption and implementations of Perfectly Matched Layers in COMSOL Multiphysics". Thesis, KTH, Numerisk analys, NA, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280757.
Texto completoPerfectly matched layer (PML) är en metod som ofta används för vågabsorbering vid randen för problem med partiella differentialekvationer (PDE). I det här examensarbetet presenteras metoder som förenklar användingen av PMLer i COMSOL Multiphysics. Studien kollar på PMLer baserade på komplex-koordinatsträckning med fokus på Helmholtz ekvation och finita elementmetoden (FEM). För att en PML ska fungera måste den sättas upp på rätt sätt med parametrar anpassade efter det givna problemet. Att göra detta är inte alltid enkelt. Teori presenteras och experiment på PMLer görs. Flera metoder för optimisering och adaption av PMLer presenteras. I nuläget kräver appliceringen av PMLer i COMSOL Multiphysics att användaren sätter upp en geometri, ett beräkningsnät och väljer den komplexa koordinatsträckningen. Genom att använda COMSOLs implementation av extra dimensioner är det möjligt att applicera PMLer som randvilkor. I en sådan implementation kan geometri och beräkningsnät skötas av mjukvaran vilket underlättar för användaren.
CARVALHO, OSNI de. "Influência da configuração de bobinagem no comportamento mecânico de cilindros de compósito polimérico". reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9301.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
Doh, Jeung-Hwan y n/a. "Experimental and Theoretical Studies of Normal and High Strength Concrete Wall Panels". Griffith University. School of Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030605.114125.
Texto completoDoh, Jeung-Hwan. "Experimental and Theoretical Studies of Normal and High Strength Concrete Wall Panels". Thesis, Griffith University, 2003. http://hdl.handle.net/10072/366176.
Texto completoThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Engineering
Full Text
Cigánek, Jan. "Hranové konečné prvky v časové oblasti". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218744.
Texto completoNakhaei, Mohsen. "Layer-specific multiscale mechanical modeling of arterial structures with evolving fiber configurations". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEM014.
Texto completoArterial tissues are made of variously organized collagen and elastin networks and exhibit a highly nonlinear anisotropic behavior with the ability to sustain large reversible strains and to undergo a load-induced progressive morphological rearrangement of the microstructure. In the present study motivated by these specificities of arterial mechanics, we developed a detailed multi-scale model of the arterial wall. The framework of finite strain continuum micromechanics was employed in an incremental approach to compute stress, strain, and fiber reorientations. The extensions of Eshelby’s matrix-inclusion problem allowed for deriving analytical expressions for the concentration tensors, which relate the macroscopic strain rate tensor to phase-averaged strain rate and vorticity. The model accounts for the universal patterns across different scales in the two mechanically significant layers of arteries, namely the adventitia and the media. Furthermore, the multi-scale constitutive model was implemented in a non-linear finite element formulation to solve the structural model of the artery. The model was validated against different experimental data sets on arterial samples from different species. The results show that the model is able to estimate the contribution of each component into the macroscopic response of the tissue for different loading and can predict both the macroscopic response and microscopic fiber kinematics accurately. We submit that such model would help in predicting the evolution of the mechanical tissue response overtime during, for instance, remodeling and growth or damage
Golshan, Roozbeh. "Residual-based Variational Multiscale LES with Wall-modeling for Oceanic Boundary Layers in Shallow Water". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5489.
Texto completoKaragoz, Cem. "Analysis Of Flexible Pavements Incorporating Nonlinear Resilient Behavior Of Unbound Granular Layers". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605320/index.pdf.
Texto completoSchopf, Martin. "Error analysis of the Galerkin FEM in L 2 -based norms for problems with layers". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-143439.
Texto completoClement, Adrien. "Étude hydroacoustique de la réponse d'une structure à une excitation de couche limite turbulente". Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0033/document.
Texto completoThe following work consist in the study of the vibroacoustic response of a structure submerged in fluid, under a turbulent boundary layer flow, the response of the structure is driven by the low wavenumber behaviour, for a small Mach number. This work aims at providing better means of predicting the noise radiated in such setups, mainly regarding stealthiness of ships and submarines and noise radiated by outer structures.A numerical modal analysis based on the (u,p,φ) formulation available in the finite element software Code_Aster is performed. The pressure induced by the boudary layer is then described as a sum of plane waves and several harmonical analysis are performed on the reduced problem, projected on the (u,p,φ) modal basis, one for each term of the sum. This allows us to account for the fluid-structure interaction (inertial and acoustic) in confined and infinite fluid domains. Most numerical models found in scientific papers are making the assumption of a light fluid, or a fluid loaded plate, thus not taking clearly into account the fluid-strucure interaction or only the inertialpart. Here the interaction due to the acoustic field radiated by the plate is fully accounted for.The validity of the proposed numerical method is assesed and numerical results are compared to data obtained from an experimental setup used within a hydrodynamic tunnel. Numerically, a good reproduction of the behaviour of the plate is obtained, both in terms of displacement and spectral levels. The acoustic levels are also compared to their numerical counterparts at the position of the transducer. Moreover, an experimantal analysis is performed, for backward and forward steps of height smaller than the thickness of the boundary layer, in order to investigate the influence of such configurations on the boundary layer excitation and on the vibroacoustic response
Kadlec, Radim. "Analýza elektromagnetické vlny na rozhraní heterogenního prostředí". Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233658.
Texto completoTomezyk, Jérôme. "Résolution numérique de quelques problèmes du type Helmholtz avec conditions au bord d'impédance ou des couches absorbantes (PML)". Thesis, Valenciennes, 2019. http://www.theses.fr/2019VALE0017/document.
Texto completoIn this thesis, we propose wavenumber explicit convergence analyses of some finite element methods for time-harmonic Maxwell's equations with impedance boundary condition and for the Helmholtz equation with Perfectly Matched Layer (PML). We first study the regularized formulation of time-harmonic Maxwell's equations with impedance boundary conditions (where we add a ∇ div-term to the original equation to have an elliptic problem) and keep the impedance boundary condition as an essential boundary condition. For a smooth domain, the wellposedness of this formulation is well-known. But the well-posedness for convex polyhedral domain has been not yet investigated. Hence, we start the first chapter with the proof of the well-posedness in this case, which is based on the fact that the variational space is embedded in H¹. In order to perform a wavenumber explicit error analysis of our problem, a wavenumber explicit stability estimate is mandatory. We then prove such an estimate for some particular configurations. In the second chapter, we describe the corner and edge singularities for such problem. Then we deduce the regularity of the solution of the original and the adjoint problem, thus we have all ingredients to propose a explicit wavenumber convergence analysis for h-FEM with Lagrange element. In the third chapter, we consider a non conforming hp-finite element approximation for domains with a smooth boundary. To perform a wavenumber explicit error analysis, we split the solution of the original problem (or its adjoint) into a regular but oscillating part and a rough component that behaves nicely for large frequencies. This result allows to prove convergence analysis for our FEM, again explicit in the wavenumber. The last chapter is dedicated to the Helmholtz equation with PML. The Helmholtz equation in full space is often used to model time harmonic acoustic scattering problems, with Sommerfeld radiation condition at infinity. Adding a PML is a way to reduce the infinite domain to a finite one. It corresponds to add an artificial absorbing layer surrounding a computational domain, in which scattered wave will decrease very quickly. We first propose a wavenumber explicit stability result for such problem. Then, we propose two numerical discretizations: an hp-FEM and a multiscale method based on local subspace correction. The stability result is used to relate the choice of the parameters in the numerical methods to the wavenumber. A priori error estimates are shown. At the end of each chapter, we perform numerical tests to confirm our theoritical results
Hall, Braydon Day. "The Dynamic Analysis of a Composite Overwrapped Gun Barrel with Constrained Viscoelastic Damping Layers Using the Modal Strain Energy Method". DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1972.
Texto completoMa, Yue. "Modèles compacts électro-thermiques du premier ordre et considération de bruit pour les circuits 3D". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI042/document.
Texto completoThree Dimensional (3D) Integration and Packaging has been successful in mainstream devices to increase logic density and to reduce data movement distances. It solves the fundamental limits of scaling e.g. increasing delay in interconnections, development costs and variability. Most memory devices shipped today have some form of chip-stacking involved. But because of the power dissipation limits of ICs, today’s MPU’s operating frequency has been limited to a few GHz. The aim of the thesis is to provide a global design method for the 3D integrated circuit in electrical, thermal, electro-thermal and also noise field. To this end, the research question is as follows: How to realize the 3D IC design, how to manage VLS 3D IC and how to solve the thermal issues in the 3D IC. In this context, the simulation methods for substrate and also relative connectivity (TSV, RDL, Micro strip and circuits embedded into the substrate) are proposed. In order to satisfy the research demand, a 3D-TLE and a substrate impedance are programmed in Matlab, which can automatically extract from any contacts; impedance, of arbitrary shape and arbitrary material. The extractor is 100% compatible with SPICE core simulator, and verified with measurement results and FEM simulation results. And as for a demo, a 26 GHz frequency and 2GHz bandwidth RF filter is propose in this work. Another electro-thermal simulator is also programmed and verified with ADS. As a solution to the local heat dissipation, flat heat pipe (FHP) is proposed as a prospective component. The heat-pipe model is verified with FEM simulation. The substrates noise analysis method and electrical and thermos-mechanical keep-out-of-zone (KOZ) calculation methods are also presented
Zouhar, Petr. "Predikce tvaru čela šířící se únavové trhliny". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241674.
Texto completoBhuddi, Ajit. "Approche ondulatoire pour la description numérique du comportement vibroacoustique large bande des conduites avec fluide interne". Thesis, Tours, 2015. http://www.theses.fr/2015TOUR4046/document.
Texto completoIn this work, a wave finite element (WFE) method is proposed to predict the sound radiation of finite axisymmetric fluid-filled pipes immersed in an external acoustic fluid of infinite extent, The Sommerfeld radiation condition is taken into account by means of a perfectly matched layer (PML) around the external fluid. Within the WFE framework, the fluid-filled pipe, the surrounding fluid and the PML constitute a multiphysics waveguide that is discretized by means of a periodic finite element mesh, and is treated as an assembly of identical subsystems of small length. Wave modes are computed from the FE model of a multi-physics subsystem and used as a representation basis to assess the vibroacoustic behavior of the finite waveguide at a low computational cost. Numerical experiments are carried out in the cases of axisymmetric pipes of either homogeneous or multi-layered crosssections, The accuracy and efficiency of the proposed approach are dearly highlighted in comparison with the conventional FE method