Isogeometric analysis of boundary integral equations: High-order collocation methods for the singular and hyper-singular equations

2016 ◽  
Vol 26 (08) ◽  
pp. 1447-1480 ◽  
Author(s):  
Matthias Taus ◽  
Gregory J. Rodin ◽  
Thomas J. R. Hughes
Keyword(s):  
Integral Equations ◽  
Isogeometric Analysis ◽  
Computer Aided Design ◽  
Boundary Integral Equations ◽  
Boundary Integral ◽  
High Order ◽  
Collocation Methods ◽  
Algebraic Equations ◽  
Integration Schemes ◽  
Linear Algebraic Equations

Isogeometric analysis is applied to boundary integral equations corresponding to boundary-value problems governed by Laplace’s equation. It is shown that the smoothness of geometric parametrizations central to computer-aided design can be exploited for regularizing integral operators to obtain high-order collocation methods involving superior approximation and numerical integration schemes. The regularization is applicable to both singular and hyper-singular integral equations, and as a result one can formulate the governing integral equations so that the corresponding linear algebraic equations are well-conditioned. It is demonstrated that the proposed approach allows one to compute accurate approximate solutions which optimally converge to the exact ones.

Numerical solution of integral equations for the three-dimensional scalar diffraction problems

2018 ◽  
Author(s):  
С.И. Смагин ◽  
А.А. Каширин
Keyword(s):  
Numerical Solution ◽  
Integral Equations ◽  
Acoustic Waves ◽  
Boundary Integral Equations ◽  
Three Dimensional ◽  
Boundary Integral ◽  
Special Method ◽  
Algebraic Equations ◽  
Linear Algebraic Equations ◽  
Wide Range

Рассматриваются задачи дифракции (трансмиссии) стационарных акустических волн на трехмерных однородных включениях. Методами теории потенциала для них получены два слабо сингулярных граничных интегральных уравнения Фредгольма первого рода с одной неизвестной функцией, каждое из которых эквивалентно исходной задаче. Интегральные уравнения аппроксимируются системами линейных алгебраических уравнений, которые затем решаются численно итерационным методом обобщенных минимальных невязок GMRES. При дискретизации этих уравнений используется специальный метод осреднения интегральных операторов со слабыми особенностями в ядрах, позволяющий получать системы с легко вычисляемыми коэффициентами. Метод допускает эффективное распараллеливание и позволяет проводить расчеты в широком диапазоне волновых чисел. Приводятся результаты вычислительных экспериментов, позволяющие судить о возможностях предлагаемого подхода. Purpose. The purpose of the article is to develop efficient algorithms for numerical solution of the diffraction (transmission) problem of stationary acoustic waves on threedimensional homogeneous inclusions. Methods. By using the combinations of simple and double layer potentials, two Fredholm boundary integral equations of the first kind with one unknown function are obtained for these potentials, each of which is equivalent to the original problem. When sampling these equations, a special method of averaging integral operators with weak singularities in the kernels is applied. Outcomes. The obtained integral equations are approximated by systems of linear algebraic equations with easily-calculated coefficients, which are then solved numerically by means of the generalized method of minimal residuals (GMRES). A series of computing experiments for numerical solution of particular stationary three-dimensional diffraction problems of acoustic waves has been conducted. Conclusions. Computing experiments have shown that the proposed numerical method possesses high accuracy in finding approximate solutions of these problems. It allows both effective parallelization and ability to perform calculations in a wide range of wave numbers and can be used to solve other problems of mathematical physics, formulated in the form of boundary integral equations.

Calculation of the Magnetization of Permanent Magnets, Based on the Method for Solving the Inverse Problem Using Parallel Calculations

2021 ◽  
Vol 64 (1) ◽  
pp. 13-21
Author(s):  
Petr Denisov ◽  
◽  
Anna Balaban ◽  
Keyword(s):  
Inverse Problem ◽  
Permanent Magnets ◽  
Parallel Implementation ◽  
Boundary Integral Equations ◽  
Boundary Integral ◽  
Tikhonov Regularization Method ◽  
Field Pattern ◽  
Algebraic Equations ◽  
Linear Algebraic Equations ◽  
The Matrix

The article proposes the modification of a technique for assessing the magnetization of permanent magnets from the known field pattern. The identification method is based on solving an ill-conditioned system of linear algebraic equations by the Tikhonov regularization method. The method of boundary integral equations based on scalar potentials is used to compile the matrix of coefficients. The article presents the algorithm that uses parallel computations when performing the most time-consuming operations to reduce the time for solving the inverse problem. In order to check the proposed method, a program was developed that allows to simulate the measurement process: to calculate the direct problem and find the magnetic induction at the points of the air gap, then introduce the error into the "measurement results" and solve the inverse problem. The results of nu-merical experiments that allow us to evaluate the advantages of parallel implementation using the capabilities of modern multi-core processors are presented.

Buckling of Plates by Boundary Elements

1998 ◽  
Author(s):  
Jauhorng Lin ◽  
Roger C. Duffield ◽  
Hui-Ru Shih
Keyword(s):  
Integral Equations ◽  
Weighting Function ◽  
Boundary Integral Equations ◽  
Boundary Integral ◽  
Plane Boundary ◽  
Load Factor ◽  
Algebraic Equations ◽  
Plate Buckling ◽  
Element Method

Abstract This investigation is concerned with the determination of a solution to the onset of instability of elastic plate subjected to non-uniform edge loads and/or displacements using boundary element method. In this study, the in-plane stress distribution was taken to be unknown due to non-uniform external in-plane boundary loading and/or displacements. The fundamental solution which is used to solve plate bending problems was used as the weighting function in the solution to the plate buckling problem. With this approach, the resulting integral equations still retained some domain integral terms which were then converted to boundary integral terms by means of the dual reciprocity method. With the introduction of proper shape functions, the boundary integral equations were transformed into a set of simultaneous algebraic equations expressed in a standard eigenvalue matrix format. A number of examples were studied to obtain the critical load factor and the critical buckling load. Results were then compared with analytical solutions and numerical results obtained by means of the finite element method, to illustrate the accuracy and applicability of the proposed solution procedures for solving plate buckling problems.

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