› › A Discontinuous Galerkin Method With Enrichment For Boundary Layers

The Discontinuous Enrichment Method (DEM) for Multi-scale Transport Problems

Author : Irina Kalashnikova

Publisher : Stanford University

Page : 178 pages

File Size : 21,60 MB

Release : 2011

Category :

ISBN :

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Book Description

A discontinuous enrichment method (DEM) for the efficient finite element solution of advection-dominated transport problems in fluid mechanics whose solutions are known to possess multi-scale features is developed. Attention is focused specifically on the two-dimensional (2D) advection-diffusion equation, the usual scalar model for the Navier-Stokes equations. Following the basic DEM methodology [1], the usual Galerkin polynomial approximation is locally enriched by the free-space solutions to the governing homogeneous partial differential equation (PDE). For the constant-coefficient advection-diffusion equation, several families of free-space solutions are derived. These include a family of exponential functions that exhibit a steep gradient in some flow direction, and a family of discontinuous polynomials. A parametrization of the former class of functions with respect to an angle parameter is developed, so as to enable the systematic design and implementation of DEM elements of arbitrary orders. It is shown that the original constant-coefficient methodology has a natural extension to variable-coefficient advection-diffusion problems. For variable-coefficient transport problems, the approximation properties of DEM can be improved by augmenting locally the enrichment space with a "higher-order" enrichment function that solves the governing PDE with the advection field a(x) linearized to second order. A space of Lagrange multipliers, introduced at the element interfaces to enforce a weak continuity of the solution and related to the normal derivatives of the enrichment functions, is developed. The construction of several low and higher-order DEM elements fitting this paradigm is discussed in detail. Numerical results for several constant as well as variable-coefficient advection-diffusion benchmark problems reveal that these DEM elements outperform their standard Galerkin and stabilized Galerkin counterparts of comparable computational complexity by a large margin, especially when the flow is advection-dominated.



The Finite Element Method for Fluid Dynamics

Author : O. C. Zienkiewicz

Publisher : Butterworth-Heinemann

Page : 581 pages

File Size : 21,10 MB

Release : 2013-11-21

Category : Technology & Engineering

ISBN : 0080951376

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Book Description

The Finite Element Method for Fluid Dynamics offers a complete introduction the application of the finite element method to fluid mechanics. The book begins with a useful summary of all relevant partial differential equations before moving on to discuss convection stabilization procedures, steady and transient state equations, and numerical solution of fluid dynamic equations. The character-based split (CBS) scheme is introduced and discussed in detail, followed by thorough coverage of incompressible and compressible fluid dynamics, flow through porous media, shallow water flow, and the numerical treatment of long and short waves. Updated throughout, this new edition includes new chapters on: - Fluid-structure interaction, including discussion of one-dimensional and multidimensional problems - Biofluid dynamics, covering flow throughout the human arterial system Focusing on the core knowledge, mathematical and analytical tools needed for successful computational fluid dynamics (CFD), The Finite Element Method for Fluid Dynamics is the authoritative introduction of choice for graduate level students, researchers and professional engineers. - A proven keystone reference in the library of any engineer needing to understand and apply the finite element method to fluid mechanics - Founded by an influential pioneer in the field and updated in this seventh edition by leading academics who worked closely with Olgierd C. Zienkiewicz - Features new chapters on fluid-structure interaction and biofluid dynamics, including coverage of one-dimensional flow in flexible pipes and challenges in modeling systemic arterial circulation



hp-Version Discontinuous Galerkin Methods on Polygonal and Polyhedral Meshes

Author : Andrea Cangiani

Publisher : Springer

Page : 133 pages

File Size : 33,50 MB

Release : 2017-11-27

Category : Mathematics

ISBN : 3319676733

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Book Description

Over the last few decades discontinuous Galerkin finite element methods (DGFEMs) have been witnessed tremendous interest as a computational framework for the numerical solution of partial differential equations. Their success is due to their extreme versatility in the design of the underlying meshes and local basis functions, while retaining key features of both (classical) finite element and finite volume methods. Somewhat surprisingly, DGFEMs on general tessellations consisting of polygonal (in 2D) or polyhedral (in 3D) element shapes have received little attention within the literature, despite the potential computational advantages. This volume introduces the basic principles of hp-version (i.e., locally varying mesh-size and polynomial order) DGFEMs over meshes consisting of polygonal or polyhedral element shapes, presents their error analysis, and includes an extensive collection of numerical experiments. The extreme flexibility provided by the locally variable elemen t-shapes, element-sizes, and element-orders is shown to deliver substantial computational gains in several practical scenarios.



Direct and Large-Eddy Simulation X

Author : Dimokratis G.E. Grigoriadis

Publisher : Springer

Page : 523 pages

File Size : 18,61 MB

Release : 2017-10-06

Category : Technology & Engineering

ISBN : 3319632124

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Book Description

This book addresses nearly all aspects of the state of the art in LES & DNS of turbulent flows, ranging from flows in biological systems and the environment to external aerodynamics, domestic and centralized energy production, combustion, propulsion as well as applications of industrial interest. Following the advances in increased computational power and efficiency, several contributions are devoted to LES & DNS of challenging applications, mainly in the area of turbomachinery, including flame modeling, combustion processes and aeroacoustics. The book includes work presented at the tenth Workshop on 'Direct and Large-Eddy Simulation' (DLES-10), which was hosted in Cyprus by the University of Cyprus, from May 27 to 29, 2015. The goal of the workshop was to establish a state of the art in DNS, LES and related techniques for the computation and modeling of turbulent and transitional flows. The book is of interest to scientists and engineers, both in the early stages of their career and at a more senior level.



Numerical Methods and Analysis of Multiscale Problems

Author : Alexandre L. Madureira

Publisher : Springer

Page : 129 pages

File Size : 17,26 MB

Release : 2017-02-15

Category : Mathematics

ISBN : 3319508660

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Book Description

This book is about numerical modeling of multiscale problems, and introduces several asymptotic analysis and numerical techniques which are necessary for a proper approximation of equations that depend on different physical scales. Aimed at advanced undergraduate and graduate students in mathematics, engineering and physics – or researchers seeking a no-nonsense approach –, it discusses examples in their simplest possible settings, removing mathematical hurdles that might hinder a clear understanding of the methods. The problems considered are given by singular perturbed reaction advection diffusion equations in one and two-dimensional domains, partial differential equations in domains with rough boundaries, and equations with oscillatory coefficients. This work shows how asymptotic analysis can be used to develop and analyze models and numerical methods that are robust and work well for a wide range of parameters.



New Results in Numerical and Experimental Fluid Mechanics XI

Author : Andreas Dillmann

Publisher : Springer

Page : 735 pages

File Size : 22,1 MB

Release : 2017-10-29

Category : Technology & Engineering

ISBN : 3319645196

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Book Description

This book gathers contributions to the 20th biannual symposium of the German Aerospace Aerodynamics Association (STAB) and the German Society for Aeronautics and Astronautics (DGLR). The individual chapters reflect ongoing research conducted by the STAB members in the field of numerical and experimental fluid mechanics and aerodynamics, mainly for (but not limited to) aerospace applications, and cover both nationally and EC-funded projects. Special emphasis is given to collaborative research projects conducted by German scientists and engineers from universities, research-establishments and industries. By addressing a number of cutting-edge applications, together with the relevant physical and mathematics fundamentals, the book provides readers with a comprehensive overview of the current research work in the field. Though the book’s primary emphasis is on the aerospace context, it also addresses further important applications, e.g. in ground transportation and energy.



Robust Numerical Methods for Singularly Perturbed Differential Equations

Author : Hans-Görg Roos

Publisher : Springer Science & Business Media

Page : 599 pages

File Size : 17,51 MB

Release : 2008-09-17

Category : Mathematics

ISBN : 3540344675

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Book Description

This new edition incorporates new developments in numerical methods for singularly perturbed differential equations, focusing on linear convection-diffusion equations and on nonlinear flow problems that appear in computational fluid dynamics.



Discontinuous Galerkin Methods

Author : Bernardo Cockburn

Publisher : Springer Science & Business Media

Page : 468 pages

File Size : 26,64 MB

Release : 2012-12-06

Category : Mathematics

ISBN : 3642597211

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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.



Modeling and Computation of Boundary-Layer Flows

Author : Tuncer Cebeci

Publisher : Springer

Page : 502 pages

File Size : 31,99 MB

Release : 2009-09-02

Category : Science

ISBN : 9783540807315

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Book Description

This second edition of the book, Modeling and Computation of Boundary-Layer Flows^ extends the topic to include compressible flows. This implies the inclusion of the energy equation and non-constant fluid properties in the continuity and momentum equations. The necessary additions are included in new chapters, leaving the first nine chapters to serve as an introduction to incompressible flows and, therefore, as a platform for the extension. This part of the book can be used for a one semester course as described below. Improvements to the incompressible flows portion of the book include the removal of listings of computer programs and their description, and their incor poration in two CD-ROMs. A listing of the topics incorporated in the CD-ROM is provided before the index. In Chapter 7 there is a more extended discussion of initial conditions for three-dimensional flows, application of the characteristic box to a model problem and discussion of flow separation in three-dimensional laminar flows. There are also changes to Chapter 8, which now includes new sections on Tollmien-Schlichting and cross-flow instabilities and on the predic tion of transition with parabolised stability equations, and Chapter 9 provides a description of the rational behind interactive boundary-layer procedures.



Unified Transform for Boundary Value Problems

Author : Athanasios S. Fokas

Publisher : SIAM

Page : 290 pages

File Size : 29,8 MB

Release : 2015-01-01

Category : Mathematics

ISBN : 1611973821

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Book Description

This book describes state-of-the-art advances and applications of the unified transform and its relation to the boundary element method. The authors present the solution of boundary value problems from several different perspectives, in particular the type of problems modeled by partial differential equations (PDEs). They discuss recent applications of the unified transform to the analysis and numerical modeling of boundary value problems for linear and integrable nonlinear PDEs and the closely related boundary element method, a well-established numerical approach for solving linear elliptic PDEs. The text is divided into three parts. Part I contains new theoretical results on linear and nonlinear evolutionary and elliptic problems. New explicit solution representations for several classes of boundary value problems are constructed and rigorously analyzed. Part II is a detailed overview of variational formulations for elliptic problems. It places the unified transform approach in a classic context alongside the boundary element method and stresses its novelty. Part III presents recent numerical applications based on the boundary element method and on the unified transform.