Joachim Fetzer

A novel formulation for 3D eddy current problems with moving bodies using a Lagrangian description and BEM-FEM coupling

This paper summarizes the theoretical background of 3D eddy current problems with moving bodies. A novel 3D formulation combining a Lagrangian description and BEM-FEM coupling is subsequently developed. The conducting and permeable bodies are described by the FEM in their respective rest frame, whereas the surrounding space is treated by the BEM in the laboratory frame. The FEM and BEM descriptions are coupled together taking into account the transformation between the different frames. The proposed formulation contains no explicit velocity terms.

An improved algorithm for the BEM-FEM-coupling method using domain decomposition

The BEM-FEM-coupling method has the advantage of the correct representation of infinite space. But there are also disadvantages. The system matrix is non-symmetric and it has a large mean bandwidth. We apply domain decomposition so that the original problem is split into a separate BEM and FEM part. The typical advantages of both methods are preserved so that reduced computer resources are needed. The solution of the overall problem is obtained by iteration. This paper deals only with eddy current problems. >

Three-dimensional transient BEM-FEM coupled analysis of electrodynamic levitation problems

This paper deals with the numerical solution of three-dimensional electromagnetic levitation problems. The transient behaviour is described by the Maxwell equations, by the (possibly nonlinear) constitutive equations, and by the equations of motion. For the solution of the electromagnetic problem the BEM-FEM coupling method is used. An aluminium plate above two coils is presented as an example.

A novel iterative algorithm for the nonlinear BEM-FEM coupling method

A novel iterative algorithm for the application of BEM-FEM coupling to nonlinear magnetic problems is presented. It combines an algorithm for nonlinear solution with an algorithm for memory saving. The resulting iterative method contains a relaxation parameter which is determined adaptively. The proposed algorithm exhibits superior numerical performance compared,to earlier ones.

Comparison of analytical and numerical integration techniques for the boundary integrals in the BEM-FEM coupling considering TEAM workshop problem no. 13

When the BEM-FEM coupling is used for the solution of a boundary value problem the domain is decomposed into a multiple connected BEM subdomain and generally several FEM subdomains. Magnetic materials are treated in the FEM subdomains only. To keep the discretization process simple, the parts containing magnetic materials coincide with the FEM subdomains. The surrounding air space is described with the help of boundary elements. The coupling of both methods is carried out on the surface of the magnetic materials. The solution of problems discretized this way shows that the accuracy of the results strongly depends on the accuracy of the boundary element integral calculation. Therefore either a large number of Gauss points or an analytical integration scheme has to be used for the calculation of the BEM integrals.

Die Kopplung der Randelementmethode und der Methode der finiten Elemente zur Lösung dreidimensionaler elektromagnetischer Feldprobleme auf unendlichem Grundgebiet

ÜbersichtWill man elektromagnetische Probleme, die auf unendlichen Grundgebieten definiert sind, mit Hilfe der Methode der finiten Elemente lösen, so bereitet die Berücksichtigung der unendlichen Grundgebiete Schwierigkeiten. Um diese Schwierigkeiten zu überwinden, kann man beispielsweise zusätzlich infinite Elemente [1] oder sog. “Ballooning-Elemente” [2] verwenden. Eine andere Möglichkeit ist die Kopplung der Methode der finiten Elemente mit der Randelementmethode [4].In diesem Artikel wird die Berechnung elektrostatischer und magnetischer Felder im unendlichen Raum mit Hilfe einer solchen Hybridmethode vorgestellt. Die Probleme werden entweder mit dem skalaren elektrischen Potential ϕ oder mit dem magnetischen Vektorpotential A formuliert. Um die Leistungsfähigkeit des Hybridansatzes zu untersuchen, werden u. a. zwei Beispiele behandelt, und deren Ergebnisse werden mit den nach dem Biot-Savartschen Gesetz gewonnenen Lösungen vergleichen.ContentsIf 3-dimensional electromagnetic problems are solved by finite elements, the computation of the fields for problems involving infinite space causes difficulties. To treat such problems either infinite elements [1] or so called ‘ballooning elements’ [2] can be used. Another possibility is the coupling of finite elements and boundary elements.In this article the calculation of electrostatic and magnetostatic fields in infinite space is presented, utilizing coupled elements. The problems are formulated in terms of potentials. In the electrostatic case the scalar potential ϕ and in the magnetostatic case the vector potentialA is used. To investigate the capability of the coupled elements, among other things two examples have been calculated and compared to their solutions gained with the help of Biot-Savarts law.

Analysis of an actuator with eddy currents and iron saturation: comparison between a FEM and a BEM-FEM coupling approach

This paper deals with the numerical analysis of electromechanical devices. The dynamic characteristics are described by Maxwells equations, by the constitutive equations, and by the equations of motion. For the solution of the electromagnetic problem a comparison between the BEM-FEM coupling method and a pure FEM approach is carried out.

Coupled BEM-FEM methods for 3D field calculations with iron saturation

If electromagnetic problems are solved by finite elements, the computation for problems involving infinite space and/or complicated coil geometries causes difficulties. One possibility to treat such problems is the coupling of finite elements (FEM) and boundary elements (BEM), referred to as BEM-FEM coupling. The physical problem is decomposed into a BEM part, which represents the surrounding space as well as prescribed exciting currents, and a FEM part, which contains the magnetic media. In this paper, the BEM-FEM coupling for magnetostatic problems is derived in detail. For the treatment of nonlinear media the -iteration is presented. As an application example the computation of iron induced effects in superconducting dipole magnets is considered.

The coupling of boundary elements and finite elements for nondestructive testing applications

In this paper, the coupling of finite elements and boundary elements, referred to as BEM-FEM coupling, is used to numerically treat a nondestructive testing (NDT) problem based on eddy currents. BEM-FEM coupling is especially well suited for NDT problems because it greatly reduces the discretization effort. A general formulation for such problems involving FEM and BEM is given. The coupling of both methods is achieved using the boundary conditions on the common boundaries between FEM and BEM domains. Only the conducting parts and the exciting coil are discretized by finite elements. The surrounding air space is taken into account by boundary elements. As an example, problem no. 8 (coil above a crack) of the TEAM workshop (Testing Electromagnetic Analysis Methods) is considered.

Comparison between different formulations for the solution of 3D nonlinear magnetostatic problems using BEM-FEM coupling

Two formulations of the BEM-FEM coupling method for 3D nonlinear magnetostatic problems are developed. Different ways of introducing the Coulomb gauge and handling of the respective boundary terms are discussed. Several iterative methods for the solution of the discretized equations are presented. An example of the TEAM workshop (Testing Electromagnetic Analysis Methods) has been used to examine the numerical behaviour.