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Author: Juha Mikael Virtanen
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
This work is concerned with the derivation of adaptive methods for discontinuous Galerkin approximations of linear fourth order elliptic and parabolic partial differential equations. Adaptive methods are usually based on a posteriori error estimates. To this end, a new residual-based a posteriori error estimator for discontinuous Galerkin approximations to the biharmonic equation with essential boundary conditions is presented. The estimator is shown to be both reliable and efficient with respect to the approximation error measured in terms of a natural energy norm, under minimal regularity assumptions. The reliability bound is based on a new recovery operator, which maps discontinuous finite element spaces to conforming finite element spaces (of two polynomial degrees higher), consisting of triangular or quadrilateral Hsieh-Clough-Tocher macroelements. The efficiency bound is based on bubble function techniques. The performance of the estimator within an h-adaptive mesh refinement procedure is validated through a series of numerical examples, verifying also its asymptotic exactness. Some remarks on the question of proof of convergence of adaptive algorithms for discontinuous Galerkin for fourth order elliptic problems are also presented. Furthermore, we derive a new energy-norm a posteriori error bound for an implicit Euler time-stepping method combined with spatial discontinuous Galerkin scheme for linear fourth order parabolic problems. A key tool in the analysis is the elliptic reconstruction technique. A new challenge, compared to the case of conforming finite element methods for parabolic problems, is the control of the evolution of the error due to non-conformity. Based on the error estimators, we derive an adaptive numerical method and discuss its practical implementation and illustrate its performance in a series of numerical experiments.
Author: Juha Mikael Virtanen
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
This work is concerned with the derivation of adaptive methods for discontinuous Galerkin approximations of linear fourth order elliptic and parabolic partial differential equations. Adaptive methods are usually based on a posteriori error estimates. To this end, a new residual-based a posteriori error estimator for discontinuous Galerkin approximations to the biharmonic equation with essential boundary conditions is presented. The estimator is shown to be both reliable and efficient with respect to the approximation error measured in terms of a natural energy norm, under minimal regularity assumptions. The reliability bound is based on a new recovery operator, which maps discontinuous finite element spaces to conforming finite element spaces (of two polynomial degrees higher), consisting of triangular or quadrilateral Hsieh-Clough-Tocher macroelements. The efficiency bound is based on bubble function techniques. The performance of the estimator within an h-adaptive mesh refinement procedure is validated through a series of numerical examples, verifying also its asymptotic exactness. Some remarks on the question of proof of convergence of adaptive algorithms for discontinuous Galerkin for fourth order elliptic problems are also presented. Furthermore, we derive a new energy-norm a posteriori error bound for an implicit Euler time-stepping method combined with spatial discontinuous Galerkin scheme for linear fourth order parabolic problems. A key tool in the analysis is the elliptic reconstruction technique. A new challenge, compared to the case of conforming finite element methods for parabolic problems, is the control of the evolution of the error due to non-conformity. Based on the error estimators, we derive an adaptive numerical method and discuss its practical implementation and illustrate its performance in a series of numerical experiments.
Author: Younis Abid Sabawi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Murat Uzunca
Publisher: Birkhäuser
ISBN: 3319301306
Category : Mathematics
Languages : en
Pages : 111
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Book Description
The focus of this monograph is the development of space-time adaptive methods to solve the convection/reaction dominated non-stationary semi-linear advection diffusion reaction (ADR) equations with internal/boundary layers in an accurate and efficient way. After introducing the ADR equations and discontinuous Galerkin discretization, robust residual-based a posteriori error estimators in space and time are derived. The elliptic reconstruction technique is then utilized to derive the a posteriori error bounds for the fully discrete system and to obtain optimal orders of convergence.As coupled surface and subsurface flow over large space and time scales is described by (ADR) equation the methods described in this book are of high importance in many areas of Geosciences including oil and gas recovery, groundwater contamination and sustainable use of groundwater resources, storing greenhouse gases or radioactive waste in the subsurface.
Author: Z. J. Wang
Publisher: World Scientific
ISBN: 9814313181
Category : Science
Languages : en
Pages : 471
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Book Description
This book consists of important contributions by world-renowned experts on adaptive high-order methods in computational fluid dynamics (CFD). It covers several widely used, and still intensively researched methods, including the discontinuous Galerkin, residual distribution, finite volume, differential quadrature, spectral volume, spectral difference, PNPM, and correction procedure via reconstruction methods. The main focus is applications in aerospace engineering, but the book should also be useful in many other engineering disciplines including mechanical, chemical and electrical engineering. Since many of these methods are still evolving, the book will be an excellent reference for researchers and graduate students to gain an understanding of the state of the art and remaining challenges in high-order CFD methods.
Author: Shmuel Agmon
Publisher: American Mathematical Soc.
ISBN: 0821849107
Category : Mathematics
Languages : en
Pages : 225
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Book Description
This book, which is a new edition of a book originally published in 1965, presents an introduction to the theory of higher-order elliptic boundary value problems. The book contains a detailed study of basic problems of the theory, such as the problem of existence and regularity of solutions of higher-order elliptic boundary value problems. It also contains a study of spectral properties of operators associated with elliptic boundary value problems. Weyl's law on the asymptotic distribution of eigenvalues is studied in great generality.
Author: Bernardo Cockburn
Publisher: Springer Science & Business Media
ISBN: 3642597211
Category : Mathematics
Languages : en
Pages : 468
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Book Description
A class of finite element methods, the Discontinuous Galerkin Methods (DGM), has been under rapid development recently and has found its use very quickly in such diverse applications as aeroacoustics, semi-conductor device simula tion, turbomachinery, turbulent flows, materials processing, MHD and plasma simulations, and image processing. While there has been a lot of interest from mathematicians, physicists and engineers in DGM, only scattered information is available and there has been no prior effort in organizing and publishing the existing volume of knowledge on this subject. In May 24-26, 1999 we organized in Newport (Rhode Island, USA), the first international symposium on DGM with equal emphasis on the theory, numerical implementation, and applications. Eighteen invited speakers, lead ers in the field, and thirty-two contributors presented various aspects and addressed open issues on DGM. In this volume we include forty-nine papers presented in the Symposium as well as a survey paper written by the organiz ers. All papers were peer-reviewed. A summary of these papers is included in the survey paper, which also provides a historical perspective of the evolution of DGM and its relation to other numerical methods. We hope this volume will become a major reference in this topic. It is intended for students and researchers who work in theory and application of numerical solution of convection dominated partial differential equations. The papers were written with the assumption that the reader has some knowledge of classical finite elements and finite volume methods.
Author: Ibrahim Al Balushi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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"This thesis concentrates on the error analysis of B-spline based finite-element methods for three fourth-order elliptic partial differential equations subject to essential boundary conditions. The first being the biharmonic equation with square-integrable right-hand side and the second and third are models for quasi-geostrophic equations (QGE) simulating large-scale wind-driven oceanic currents. The goal of this thesis is two-fold. On one hand, we derive and analyze error estimators for the purpose of adaptive h-refinement. The earliest effort was concerned with the linear Stommel-Munk. We note that a second-order treatment has been done in 2009 by Juntunen and Stenberg where the analysis hinges on a so-called saturation assumption to relate the numerical error with the discrete error between two refinements. We carry out a similar analysis for the fourth-order PDE. In the nonlinear SQGE we perform the error analysis without a saturation assumption making this work novel in two ways: The treatment requires dealing with the nonlinear convective term and the reliability proofs are saturation-assumption free. The second goal of this thesis is concerned with the convergence and optimality of Nitschetype adaptive methods for the biharmonic equation. Such a study for general second order elliptic order equations has been extensively studied when essential boundary conditions are prescribed into the discrete space. The first convergence proof for the Poisson problem was given by D ̈orfler in 1996 and improved on by Morin, Nochetto, and Siebert in 2000 where some stringent conditions on the domain partitions were removed. Those ideas were soon to be extended to general second order linear elliptic problems by Mekchay and Nochetto, and finally a convergence analysis in a Hilbert space setting was given by Morin, Siebert and Veeser. The first analysis of convergence rates and quasi-optimality for the Poisson problem is pioneered by Binev, Dahmen and DeVore in 2004 and also by Stevenson where he removed an artificial coarsening step. Those ideas were applied to symmetric second order linear elliptic problems by Casc ́on, Kreuzer, Nochetto and Siebert and further generalized by Feischl, Führer and Praetorius to non-symmetric linear problems as well as to strongly monotone nonlinear operators. We add that all aforementioned literature consider boundary condition conforming finite-element spaces in that those discrete spaces satisfy the boundary conditions. For completeness, we do the same for the biharmonic problem. As far as non-conforming methods are concerned, to the best of our knowledge, no such study has been made for Nitsche’s method before the appearance of our work, not even for the Poisson problem. The closest situation we have is that of discontinuous Galerkin methods for symmetric second order elliptic problems which we draw our inspiration from. The convergence and quasi-optimality of discontinuous Galerkin methods was studied by Bonito, Andrea and Nochetto in 2010"--
Author: G. Duvant
Publisher: Springer Science & Business Media
ISBN: 3642661653
Category : Mathematics
Languages : en
Pages : 415
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Book Description
1. We begin by giving a simple example of a partial differential inequality that occurs in an elementary physics problem. We consider a fluid with pressure u(x, t) at the point x at the instant t that 3 occupies a region Q oflR bounded by a membrane r of negligible thickness that, however, is semi-permeable, i. e., a membrane that permits the fluid to enter Q freely but that prevents all outflow of fluid. One can prove then (cf. the details in Chapter 1, Section 2.2.1) that au (aZu azu aZu) (1) in Q, t>o, -a - du = g du = -a z + -a z + -a z t Xl X X3 z l g a given function, with boundary conditions in the form of inequalities u(X,t»o => au(x,t)/an=O, XEr, (2) u(x,t)=o => au(x,t)/an?:O, XEr, to which is added the initial condition (3) u(x,O)=uo(x). We note that conditions (2) are non linear; they imply that, at each fixed instant t, there exist on r two regions r~ and n where u(x, t) =0 and au (x, t)/an = 0, respectively. These regions are not prescribed; thus we deal with a "free boundary" problem.
Author: Vít Dolejší
Publisher: Springer
ISBN: 3319192671
Category : Mathematics
Languages : en
Pages : 575
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Book Description
The subject of the book is the mathematical theory of the discontinuous Galerkin method (DGM), which is a relatively new technique for the numerical solution of partial differential equations. The book is concerned with the DGM developed for elliptic and parabolic equations and its applications to the numerical simulation of compressible flow. It deals with the theoretical as well as practical aspects of the DGM and treats the basic concepts and ideas of the DGM, as well as the latest significant findings and achievements in this area. The main benefit for readers and the book’s uniqueness lie in the fact that it is sufficiently detailed, extensive and mathematically precise, while at the same time providing a comprehensible guide through a wide spectrum of discontinuous Galerkin techniques and a survey of the latest efficient, accurate and robust discontinuous Galerkin schemes for the solution of compressible flow.
Author: Zhi Jian Wang
Publisher: World Scientific
ISBN: 9814464694
Category : Science
Languages : en
Pages : 471
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Book Description
This book consists of important contributions by world-renowned experts on adaptive high-order methods in computational fluid dynamics (CFD). It covers several widely used, and still intensively researched methods, including the discontinuous Galerkin, residual distribution, finite volume, differential quadrature, spectral volume, spectral difference, PNPM, and correction procedure via reconstruction methods. The main focus is applications in aerospace engineering, but the book should also be useful in many other engineering disciplines including mechanical, chemical and electrical engineering. Since many of these methods are still evolving, the book will be an excellent reference for researchers and graduate students to gain an understanding of the state of the art and remaining challenges in high-order CFD methods.
