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This book presents theoretical fundamentals and applications of a new numerical model that has the ability to simulate wave propagation. Coverage examines linear waves in ideal fluids and elastic domains. In addition, the book includes a numerical simulation of wave propagation based on scalar and vector wave equations, as well as fluid-structure interaction and soil-structure interaction.
In Exact non-reflecting boundary conditions by Keller and Givoli, an exact boundary condition is devised for the numerical solution of the reduced wave equation in an infinite domain, using the finite element region without error. This work has been extended to other equations, including those for elastic waves, and small test problems have shown that method is very effective.
This book presents state-of-the-art theory and the application of dynamic and transient infinite elements for simulating the far fields of infinite domains involved in many of scientific and engineering problems.
An informative look at the theory, computer implementation, and application of the scaled boundary finite element method This reliable resource, complete with MATLAB, is an easy-to-understand introduction to the fundamental principles of the scaled boundary finite element method. It establishes the theory of the scaled boundary finite element method systematically as a general numerical procedure, providing the reader with a sound knowledge to expand the applications of this method to a broader scope. The book also presents the applications of the scaled boundary finite element to illustrate its salient features and potentials. The Scaled Boundary Finite Element Method: Introduction to Theory and Implementation covers the static and dynamic stress analysis of solids in two and three dimensions. The relevant concepts, theory and modelling issues of the scaled boundary finite element method are discussed and the unique features of the method are highlighted. The applications in computational fracture mechanics are detailed with numerical examples. A unified mesh generation procedure based on quadtree/octree algorithm is described. It also presents examples of fully automatic stress analysis of geometric models in NURBS, STL and digital images. Written in lucid and easy to understand language by the co-inventor of the scaled boundary element method Provides MATLAB as an integral part of the book with the code cross-referenced in the text and the use of the code illustrated by examples Presents new developments in the scaled boundary finite element method with illustrative examples so that readers can appreciate the significant features and potentials of this novel method—especially in emerging technologies such as 3D printing, virtual reality, and digital image-based analysis The Scaled Boundary Finite Element Method: Introduction to Theory and Implementation is an ideal book for researchers, software developers, numerical analysts, and postgraduate students in many fields of engineering and science.
Many engineering problems (e.g. soil-structure interaction, medical imaging and nondestructive evaluation) encounter the phenomena of wave propagation. Among these problems some involve domains of infinite extent. Standard numerical methods such as finite element and finite difference methods cannot handle the unbounded domain as they are designed for the analysis of bounded domains. In order to solve an unbounded-domain problem, the domain is truncated around a region of interest, and absorbing boundary conditions (ABCs) are applied on the truncation boundary. These ABCs are expected to absorb outgoing waves and mimic the effect of the truncated exterior. Continued-fraction absorbing boundary conditions (CFABCs) are a class of highly efficient ABCs for modeling acoustic wave absorption into unbounded domains. The current versions of CFABCs are applicable only to non-dispersive scalar wave equation and are not effective for dispersive or elastic wave propagation problems. This dissertation contains extensions of CFABCs to dispersive and elastic wave propagation problems. The main difficulty in the case of dispersive wave propagation is that evanescent waves have significant presence and are not treated accurately by original CFABCs. In the first part of the dissertation, CFABCs are modified to effectively absorb propagating as well as evanescent waves. This is achieved with the help of special padding elements that absorb the evanescent waves and standard CFABC elements that are effective in absorbing propagating waves. Called the "padded CFABC", this combination is shown to be a highly efficient and accurate ABC for dispersive wave equations. Numerical results are presented to illustrate the effectiveness of these ABCs. The second part of the dissertation involves the extension of CFABCs to elastic wave propagation problems. Elastic wave propagation is inherently complex because of the strong coupling of pressure and shear waves that propagate at different speeds.
This book presents two distinct aspects of wave dynamics – wave propagation and diffraction – with a focus on wave diffraction. The authors apply different mathematical methods to the solution of typical problems in the theory of wave propagation and diffraction and analyze the obtained results. The rigorous diffraction theory distinguishes three approaches: the method of surface currents, where the diffracted field is represented as a superposition of secondary spherical waves emitted by each element (the Huygens–Fresnel principle); the Fourier method; and the separation of variables and Wiener–Hopf transformation method. Chapter 1 presents mathematical methods related to studying the problems of wave diffraction theory, while Chapter 2 deals with spectral methods in the theory of wave propagation, focusing mainly on the Fourier methods to study the Stokes (gravity) waves on the surface of inviscid fluid. Chapter 3 then presents some results of modeling the refraction of surf ace gravity waves on the basis of the ray method, which originates from geometrical optics. Chapter 4 is devoted to the diffraction of surface gravity waves and the final two chapters discuss the diffraction of waves by semi-infinite domains on the basis of method of images and present some results on the problem of propagation of tsunami waves. Lastly, it provides insights into directions for further developing the wave diffraction theory.
Partial Differential Equations and Boundary Value Problems with Maple, Second Edition, presents all of the material normally covered in a standard course on partial differential equations, while focusing on the natural union between this material and the powerful computational software, Maple. The Maple commands are so intuitive and easy to learn, students can learn what they need to know about the software in a matter of hours - an investment that provides substantial returns. Maple's animation capabilities allow students and practitioners to see real-time displays of the solutions of partial differential equations. This updated edition provides a quick overview of the software w/simple commands needed to get started. It includes review material on linear algebra and Ordinary Differential equations, and their contribution in solving partial differential equations. It also incorporates an early introduction to Sturm-Liouville boundary problems and generalized eigenfunction expansions. Numerous example problems and end of each chapter exercises are provided. Provides a quick overview of the software w/simple commands needed to get started Includes review material on linear algebra and Ordinary Differential equations, and their contribution in solving partial differential equations Incorporates an early introduction to Sturm-Liouville boundary problems and generalized eigenfunction expansions Numerous example problems and end of each chapter exercises
This book covers advanced topics in dynamic modeling of soil-foundation interaction, as well as the response of elastic semi-infinite media from an applications viewpoint. Advanced concepts such as solutions for analysis of elastic semi-infinite mediums, fluid motion in porous media, and nonlinearities in dynamic behavior are explained in great detail. Related theories and numerical analysis for vertical vibration, and rocking vibration of a rigid rectangular mass-less plate, and horizontal vibration of a rigid mass-less plate are presented. Throughout the book, a strong emphasis is placed on applications, and a laboratory model for elastic half-space medium is provided.
Most existing arch dams have been designed for seismic loading by static methods involving the use of seismic coefficients. Although there are no known examples of arch dams which have been seriously damaged by earthquakes, the need for more realistic seismic analyses is now well recognized, not only for new dams but especially in the context of the safety evaluation of existing dams. Fortunately, with the finite element method, engineers have a powerful tool for modeling the complex geometry and the nonlinear material behavior of a dam. However, there is still a major complication in the analysis procedure, namely the interaction of the dam with the reservoir and with the foundation during an earthquake. Interaction is a wave propagation problem involving transmitting boundaries. The State of the Art in engineering practice is to neglect wave propagation by modeling the water as incompressible and the foundation as massless. More advanced analysis methods using compressible water and foundation with mass have been available for some time. However, these methods are restricted to linear models, because they work in the frequency domain. On the other hand, there are also advanced nonlinear models for dams, but they can only be used in the time domain, usually with simple transmitting boundaries. In this report, which is based on an a doctoral thesis, rigorous transmitting boundaries in the time domain are developed which permit combining compressible water with n- linear dam behavior. The new numerical model is based on a systems-theory approach.