Dissertations / Theses on the topic 'Perfectly Matched Layers (PML)'
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Bao, Wentao. "A Simulation and Optimization Study of Spherical Perfectly Matched Layers." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1494166698903702.
Full textErlandsson, 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.
Full textPerfectly 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.
Appelö, Daniel. "Absorbing Layers and Non-Reflecting Boundary Conditions for Wave Propagation Problems." Doctoral thesis, KTH, Numerisk Analys och Datalogi, NADA, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-448.
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Srinivasan, Harish. "FINITE ELEMENT ANALYSIS AND EXPERIMENTAL VERIFICATION OF SOI WAVEGUIDE LOSSES." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_theses/485.
Full textLong, Zeyu. "Introduction of the Debye media to the filtered finite-difference time-domain method with complex-frequency-shifted perfectly matched layer absorbing boundary conditions." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/introduction-of-the-debye-media-to-the-filtered-finitedifference-timedomain-method-with-complexfrequencyshifted-perfectly-matched-layer-absorbing-boundary-conditions(441271dc-d4ea-4664-82e6-90bf93f5c2b7).html.
Full textTomezyk, 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.
Full textIn 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
Silberstein, Éric. "Généralisation de la méthode modale de Fourier aux problèmes de diffraction en optique intégrée : application aux convertisseurs modaux par ingénierie des modes de Bloch." Paris 6, 2002. https://pastel.archives-ouvertes.fr/tel-00003101.
Full textMétral, Jérôme. "Modélisation et simulation numérique de l'écoulement d'un plasma atmosphérique pour l'étude de l'activité électrique des plasmas sur avion." Châtenay-Malabry, Ecole centrale de Paris, 2002. http://www.theses.fr/2002ECAP0868.
Full textA ionized gas (or plasma) has the ability of absorbing or reflecting electromagnetic (radar) waves if its ionization rate is high enough. This is particularly interesting for aeronautics. This study aims at predicting the electric and energetic characteristics of a weakly ionized air plasma in an atmospheric pressure flow. The plasma is described by a two-temperature model, coming from the non-equilibrium description of plasmas. Plasma flow is then described by a two-temperature hydrodynamic system coupled with a collisional model (energy exchanges rates) and a kinetic model (chemical reactions). An algorithm was built to simulate plasma flow in axisymetric geometry. The algorithm is a 2D Lagrange + Projection scheme. The projection step was adapted to multi-components advection, using a second order, non oscillating, and bidimensionnal scheme. This algorithm allows the simulation of experiments concerning atmospheric pressure plasma and then the validation of the model parameters. In a second part, we study the Perfectly Matched Layer (PML) which is a boundary condition to simulate wave propagation in open domains. This method is particularly efficient for electromagnetic problems, and we want to enlarge this approach to aeroacoutics problems (linearized Euler equations). We propose two solutions: a practical approach to avoid numerical oscillations of the solution and a more general approach which consists in a new absorbing layer formulation which leads to well-posed problems
Duru, Kenneth. "Perfectly matched layers for second order wave equations." Licentiate thesis, Uppsala universitet, Avdelningen för teknisk databehandling, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-124538.
Full textRamli, Khairun N. "Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods. Development of hybridised Method of Moments, Finite-Difference Time-Domain method and subgridded Finite-Difference Time-Domain method for precise computation of electromagnetic interaction with arbitrarily complex geometries." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5443.
Full textMinistry of Higher Education Malaysia and Universiti Tun Hussein Onn Malaysia (UTHM)
Ramli, Khairun Nidzam. "Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods : development of hybridised Method of Moments, Finite-Difference Time-Domain method and subgridded Finite-Difference Time-Domain method for precise computation of electromagnetic interaction with arbitrarily complex geometries." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5443.
Full textCigánek, 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.
Full textDuru, Kenneth. "Perfectly Matched Layers and High Order Difference Methods for Wave Equations." Doctoral thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-173009.
Full textDorostkar, Ali. "Applications of the perfectly matched layers in a discontinuous fluid media." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-176541.
Full textMORVARIDI, MARYAM. "Flexural Wave Propagation in Microstructured Media. Perfectly Matched Layers and Elastic Metamaterials." Doctoral thesis, Università degli Studi di Cagliari, 2018. http://hdl.handle.net/11584/255943.
Full textLee, Patrick. "Modélisation d'un injecteur laser-plasma pour l'accélération multi-étages." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS180/document.
Full textLaser Wakefield Acceleration (LWFA) relies on the interaction between an intense laser pulse and an under-dense plasma. This interaction generates a plasma wave with a strong accelerating field, which is three orders of magnitude higher than the one of the conventional accelerator; more compact accelerator is therefore theoretically possible. In the design of a future accelerator, a high quality electron bunch with a high charge, low energy spread and low emittance has to be accelerated to high energies. A solution for this is a multi-stage accelerator, which consists of an injector, a transport line and accelerator stages. This research work focuses on the modelling of the injector using the PIC code Warp and on the numerical methods such as the Lorentz-boosted frameto speedup calculations and the Perfectly Matched Layer (PML) to ensure the precision in numerical calculations. The outcome of this thesis has demonstrated the efficiency of the PML in the high-order FDTD and the pseudo-spectral solvers. Besides, it has also demonstrated the convergence of the results performed in simulations using the Lorentz-boosted frame technique. This technique speeds up simulations by a large factor (36) while preserving their accuracy. The modelling work in this thesis has allowed analysis and understanding of experimental results, as well as prediction of results for future experiments. This thesis has also shown ways to optimize the injector to deliver an electron bunch that conforms with the specifications of future accelerators
Pelteku, Altin E. "Development of an electromagnetic glottal waveform sensor for applications in high acoustic noise environments." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0114104-142855/.
Full textKeywords: basis functions; perfectly matched layers; PML; neck model; parallel plate resonator; finite element; circulator; glottal waveform; multi-transmission line; dielectric properties of human tissues; radiation currents; weighted residuals; non-acoustic sensor. Includes bibliographical references (p. 104-107).
Xu, Boqing, and 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
Peynaud, Emilie. "Rayonnement sonore dans un écoulement subsonique complexe en régime harmonique : analyse et simulation numérique du couplage entre les phénomènes acoustiques et hydrodynamiques." Thesis, Toulouse, INSA, 2013. http://www.theses.fr/2013ISAT0019/document.
Full textThis thesis deals with the numerical simulation of time harmonic acoustic propagation in an arbitrary mean flow in an unbounded domain. Our approach is based on an equation equivalent to the linearized Euler equations called the Galbrun equation. It is derived from a mixed Eulerian-Lagrangian formulation and results in a single equation whose only unknown is the perturbation of the Lagrangian displacement. A direct solution using finite elements is unstable but this difficulty can be overcome by using an augmented equation which is constructed by adding a new unknown, the vorticity, defined as the curl of the displacement. This leads to a set of equations coupling a wave like equation with a time harmonic transport equation which allows the use of perfectly matched layers (PML) at artificial boundaries to bound the computational domain. The first part of the thesis is a study of the time harmonic transport equation and its approximation by means of a discontinuous Galerkin scheme, the difficulties coming from the oscillating behaviour of its solutions. Once these difficulties have been overcome, it is possible to deal with the resolution of the acoustic propagation problem. The approximation method is based on a mixed continuous-Galerkin and discontinuous-Galerkin finite element scheme. The well-posedness of both the continuous and discrete problems is established and the convergence of the approximation under some mean flow conditions is proved. Finally a numerical implementation is achieved and numerical results are given which confirm the validity of the method and also show that it is relevant in complex cases, even for unstable flows
Vinoles, Valentin. "Problèmes d'interface en présence de métamatériaux : modélisation, analyse et simulations." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLY009/document.
Full textWe are interested in transmission problems between dielectrics and metamaterials, that is to say media with unusual electromagnetic properties such as negative constants at some frequencies. These media are often made of periodic assemblies of resonant micro-structures and in this case the homogenization theory can justify mathematically these effective properties. A preliminary part deals with these problems in the harmonic domain and in geometry with separation of variables.Analytical computations are done and reveal in the so-called critical cases some mathematical diffculties: the solutions do not have the standard regularity and the problem can even be ill-posed.The first part examines these transmission problems in the time domain for which metamaterials are modelled by dispersive models (Drude model or Lorentz model for instance). The diffculties reside in the choice of a discretization scheme but especially in the construction of absorbing conditions. The method used here is the use of Perfectly Matched Layers (PMLs). Since classical PMLs are unstable for these models due to the presence of backward waves, we propose a new class of PMLs for which we conduct a stability analysis. The latter allows us to build stable PMLs. They are then used to simulate the long-time behaviour of a transmission problem; we illustrate the fact that the limit amplitude principle can be faulted because of interface resonances.The second part aims to overcome these phenomena by coming back to the classical homogenization in the harmonic domain, for dissipative media. For transmission problems, it is known that models resulting from this method lose accuracy due to the presence of boundary layers at the interface. We propose an enriched model at the interface: by combining the method of two-scale homogenization and that of matched asymptotic expansions, we build non-standard transmission conditions involving tangential derivatives along the interface (Laplace-Beltrami operators). This requires to solve cell problems and non-standardproblems in infinite periodic bands. An error analysis confirms the improvement of the accuracy of the model and numerical simulations show the effectiveness of these new conditions. Finally, this approach is formally reproduced in the case of high contrast materials which behave like metamaterials. We show that these new conditions regularise the transmission problem in the critical cases
Rejiba, Fayçal. "Modélisation de la propagation des ondes électromagnétiques en milieux hétérogènes : application au radar sol." Paris 6, 2002. http://www.theses.fr/2002PA066313.
Full textLaurens, Sophie. "Approximation de haute précision des problèmes de diffraction." Phd thesis, Université Paul Sabatier - Toulouse III, 2010. http://tel.archives-ouvertes.fr/tel-00475286.
Full textLjung, Jonathan. "Parametric Studies of Soil-Steel Composite Bridges for Dynamic Loads, a Frequency Domain Approach using 3D Finite Element Modelling." Thesis, KTH, Bro- och stålbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254343.
Full textMa, Congcong. "The research of acoustic resonance in the waveguide associated with Galbrun equation." Electronic Thesis or Diss., Compiègne, 2020. http://www.theses.fr/2020COMP2560.
Full textIn a two-dimensional open system, when the acoustic wave spreads in the tube with the presence of an obstacle, there will be the amplification of sound pressure around the obstacle. Trapped mode exists surrounding the obstacle below and above the cut-off frequency, and they bring considerable damage to the system in the form of such as noise, stability and security issues. In the previous research, they mainly concentrated on the solving of Helmholtz equation, which means that the variation of non-potential flow was not taken into consideration. The objective of this paper is to numerically compute the trapped mode with the presence of non-potential flow. Firstly, the theoretical framework of this thesis is stated. The mixed Galbrun equation, as well as boundary conditions and the associated energy properties, is represented. And then the perfectly matched layer associated with Galbrun equation is introduced. Secondly, for the analysis of trapped mode, there are already a lot of literature on numerical and physical aspects, but they have studied the trapped mode all associated with Helmholtz equation, which is primarily suitable for the case of without flow or uniform mean flow. Hence, a numerical calculation model involved with Galbrun equationwith the uniform mean flow is proposed and the obtained results are compared with those given in references. Finally, in order to consider the effects of non-potential flow. A coupling method of sound field and flow field associated with Galbrun equation is developed, and the trapped mode is captured through scanning the frequency. At the same time, the effects of various parameters of obstacles on the trapped mode are also studied
Spa, Carvajal Carlos. "Time-domain numerical methods in room acoustics simulations." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7565.
Full textEn aquesta Tesi hem centrat el nostre anàlisis en els mètodes basats en el comportament ondulatori dins del domini temporal. Més concretament, estudiem en detall les formulacions més importants del mètode de Diferències Finites, el qual s'utilitza en moltes aplicacions d'acústica de sales, i el recentment proposat mètode PseudoEspectral de Fourier. Ambdós mètodes es basen en la formulació discreta de les equacions analítiques que descriuen els fenòmens acústics en espais tancats.
Aquesta obra contribueix en els aspectes més importants en el càlcul numèric de respostes impulsionals: la propagació del so, la generació de fonts i les condicions de contorn de reactància local.
Room acoustics is the science concerned to study the behavior of sound waves in enclosed rooms. The acoustic information of any room, the so called impulse response, is expressed in terms of the acoustic field as a function of space and time. In general terms, it is nearly impossible to find analytical impulse responses of real rooms. Therefore, in the recent years, the use of computers for solving this type of problems has emerged as a proper alternative to calculate the impulse responses.
In this Thesis we focus on the analysis of the wavebased methods in the timedomain. More concretely, we study in detail the main formulations of FiniteDifference methods, which have been used in many room acoustics applications, and the recently proposed Fourier PseudoSpectral methods. Both methods are based on the discrete formulations of the analytical equations that describe the sound phenomena in enclosed rooms.
This work contributes to the main aspects in the computation of impulse responses: the wave propagation, the source generation and the locallyreacting boundary conditions.
Kucukcoban, Sezgin. "The inverse medium problem in PML-truncated elastic media." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-12-2183.
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Thakur, Tapan. "Wave motion simulation using spectral elements and a hybrid PML formulation." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3547.
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Fathi, Arash. "Full-waveform inversion in three-dimensional PML-truncated elastic media : theory, computations, and field experiments." Thesis, 2015. http://hdl.handle.net/2152/30515.
Full textKang, Jun Won 1975. "A mixed unsplit-field PML-based scheme for full waveform inversion in the time-domain using scalar waves." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-05-1263.
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Lee, Seung Ha. "Application of the perfectly matched layers for seismic soil-structure interaction analysis in the time domain." Thesis, 2006. http://hdl.handle.net/10125/20488.
Full text楊崇文. "P-adaptive Hierarchal Finite Element Analysis of Unbounded Electromagnetic Wave Problems Terminated with Perfectly Matched Layers." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/86298526022545601807.
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電機工程學系
92
There are many numerical methods for solving electromagnetic wave problems, such as finite element method, finite difference time domain method, and method of moment. For solving unbounded electromagnetic wave problems with finite element method, the computational domain must be truncated by an absorbing boundary. Typically, the error of these problems involves boundary and discretization error. The boundary error is a function of the efficiency of the absorbing boundary condition. Perfectly matched layers were found to provide better accuracy than traditional absorbing boundary condition. The discretization error can be reduced by using h-adaptive finite element method or p-adaptive finite element method. Generally, the p-adaptive finite element method is more efficient than the h-adaptive finite element method, because it does not require a re-meshing at each iteration. Unfortunately, the conventional p-adaptive finite element method requires that the polynomial order of elements in the whole domain must be identical. This makes inefficiency usage of degrees of freedom in the model. Hierarchal finite element method allows that the order of elements in the domain be different so that the degrees of freedom can be efficiently re-distributed. The discretization error and the boundary error can be reduced efficiently by using p-adaptive hierarchal finite element analysis both in the finite element and the perfectly matched layers regions. Up until now, there is no research in combining p-adaptive finite element method with the perfectly matched layers. This thesis proposes an efficient approach to reduce both boundary and discertization error by combining the p-adaptive hierarchal finite element method with the perfectly matched layers.
Tsuji, Paul Hikaru. "Fast algorithms for frequency domain wave propagation." 2012. http://hdl.handle.net/2152/19533.
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