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2020 | Book

The Isogeometric Boundary Element Method

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About this book

This book discusses the introduction of isogeometric technology to the boundary element method (BEM) in order to establish an improved link between simulation and computer aided design (CAD) that does not require mesh generation. In the isogeometric BEM, non-uniform rational B-splines replace the Lagrange polynomials used in conventional BEM. This may seem a trivial exercise, but if implemented rigorously, it has profound implications for the programming, resulting in software that is extremely user friendly and efficient. The BEM is ideally suited for linking with CAD, as both rely on the definition of objects by boundary representation. The book shows how the isogeometric philosophy can be implemented and how its benefits can be maximised with a minimum of user effort. Using several examples, ranging from potential problems to elasticity, it demonstrates that the isogeometric approach results in a drastic reduction in the number of unknowns and an increase in the quality of the results. In some cases even exact solutions without refinement are possible. The book also presents a number of practical applications, demonstrating that the development is not only of academic interest. It then elegantly addresses heterogeneous and non-linear problems using isogeometric concepts, and tests them on several examples, including a severely non-linear problem in viscous flow. The book makes a significant contribution towards a seamless integration of CAD and simulation, which eliminates the need for tedious mesh generation and provides high-quality results with minimum user intervention and computing.

Table of Contents

Frontmatter
Chapter 1. Introduction
Abstract
In this chapter, the motivation behind the book and an introduction to the boundary element method, including historical notes, are given. A glossary of terms and the notation used is presented.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 2. The Boundary Integral Equations
Abstract
In this chapter it is shown how differential equations are transferred into integral equations. The differential equations considered range from flow problems to elasticity. Fundamental solutions are also presented.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 3. Basis Functions, B-splines
Abstract
The chapter provides an introduction to B-spline basis functions, their properties and refinement procedures. We examine various features that distinguish B-splines from the classical functions used in numerical simulations, i.e., Lagrange polynomials. The discussion of bivariate tensor product splines focuses on performing local refinement using (truncated) hierarchical B-spline techniques.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 4. Description of the Geometry
Abstract
We provide insight into the representation of geometric objects in CAD. In particular, this chapter covers the generalisation of B-splines to NURBS, the interaction of control points and their patches, and the concept of trimmed surfaces. After presenting the concept of (B-rep) solid models, we outline various aspects relevant to their application in the context of analysis.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 5. Getting Geometry Information from CAD Programs
Abstract
The long-term goal of isogeometric analysis is to integrate design and analysis. Hence, it is worth to take a brief look at how information can be extracted from CAD systems. The following discussion is by no means complete, but we aim to highlight some aspects of this topic. The chapter starts with general considerations for exchanging data between different computer software systems. Next, we provide a brief introduction to the Standard for the Exchange of Product Model Data (STEP). Finally, the idea of Bézier extraction is presented.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 6. Numerical Treatment of Integral Equations
Abstract
In this chapter, methods are presented for the numerical solution of the integral equations. This includes discretisation and the fast and efficient solution of the system of equations.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 7. Numerical Integration
Abstract
The integrals in the discretised integral equations involve Kernel basis function products and can only be evaluated analytically for low-order basis functions and for simple geometries. For practical problems, they have to be evaluated numerically. In this chapter, details are presented on how the integration can be carried out accurately and efficiently.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 8. Steady State Potential Problems
Abstract
Steady state potential problems are problems where the primary variable is a scalar and the results are independent of time. The chapter discusses the implementation and shows examples ranging from confined to unconfined seepage problems.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 9. Static Linear Solid Mechanics
Abstract
In this chapter, we discuss the implementation for static linear solid mechanics. On several examples in 2-D and 3-D, we investigate the efficiency of the implementation and the accuracy that can be obtained.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 10. Simulation with Trimmed Models
Abstract
Trimmed surfaces introduce several challenges for analysis, and their treatment is the focus of this chapter. The following techniques are problem-independent in principle. As examples, we consider their application in the context of isogeometric BEM simulations of the problem types presented in the previous chapters, i.e., potential problems and linear elasticity.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 11. Body Force Effects
Abstract
With boundary integral equations alone we cannot consider effects that occur inside the domain and therefore can only deal with linear problems and homogeneous domains, with effects on the boundary only. In this chapter, we introduce effects inside the domain, also known as body forces.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 12. Treatment of Inhomogeneities/Inclusions
Abstract
The BEM relies on the availability of fundamental solutions of the governing differential equations, which are only available for homogeneous domains. As this would restrict the practical application of the method, we explore here the possibility of considering inhomogeneities.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 13. Material Non-linear Behaviour
Abstract
This chapter deals with the implementation of non-linear material behavior, in particular plasticity.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 14. Applications in Geomechanics
Abstract
The BEM is ideally suited for applications in geomechanics because it can handle infinite domain problems without truncation. This chapter shows how the theory outlined so far can be applied to practical problems, in this case the simulation of underground excavations.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 15. Viscous Flow Problems
Abstract
In this chapter, we discuss the implementation of the isogeometric BEM for steady state viscous incompressible flows.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 16. Time Dependent Problems
Abstract
Here we re-introduce time effects. Which can be either transient or harmonic. We discuss transient problems for potential flow in 2-D first and then show an example of a harmonic problem, namely acoustics.
Gernot Beer, Benjamin Marussig, Christian Duenser
Chapter 17. Summary and Outlook
Abstract
This chapter summarizes the contents of the book and provides an outlook of future developments.
Gernot Beer, Benjamin Marussig, Christian Duenser
Backmatter
Metadata
Title
The Isogeometric Boundary Element Method
Authors
Prof. Dr. Gernot Beer
Dr. Benjamin Marussig
Prof. Dr. Christian Duenser
Copyright Year
2020
Electronic ISBN
978-3-030-23339-6
Print ISBN
978-3-030-23338-9
DOI
https://doi.org/10.1007/978-3-030-23339-6

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