Stefan Kurz

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. >

Comparison between different approaches for fast and efficient 3-D BEM computations

Fast methods like the fast multipole method or the adaptive cross approximation technique reduce the memory requirements and the computational costs of the boundary-element method (BEM) to approximately O(N). In this paper, both fast methods are applied in combination with BEM-finite-element method coupling to nonlinear magnetostatic 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.

3D transient analysis of electromechanical devices using parallel BEM coupled to FEM

This paper describes the coupling of the parallel BEM to the FEM within the framework of a preconditioned iterative solver based on domain decomposition. This approach allows to overcome the limitations that arise on a serial computer when a 3D transient analysis of electromechanical devices should be performed. The parallel implementation of different BEM solution tasks is discussed. The numerical modeling of an electromechanical relay is presented as an example, including performance issues.

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.

Discretization of boundary integral equations by differential forms on dual grids

In this paper, some integral equations of electromagnetics are reformulated in terms of differential forms. The integral kernels become double forms. These are forms in one space with coefficients that are forms in another space. The results correspond closely to the usual treatment, but are clearer and more intuitive. Since differential forms possess discrete counterparts, the discrete differential forms, such schemes lend themselves naturally to discretization. As an example, a boundary integral equation for the double curl operator is considered. The discretization scheme generalizes the well-known collocation technique by using de Rham maps. Depending on the integral operator to be discretized, the 1-form valued residual is forced to be zero either over the 1-chains of the primal or the dual grid.

Parallelization of coupled differential and integral methods using domain decomposition

This paper describes the parallel implementation of a preconditioned iterative solver based on the coupling of a differential (FEM) and an integral approach (BEM). Applying a domain decomposition scheme splits the problem into separate FEM and BEM parts and preserves the typical advantages of both methods. In particular, an independent parallelization with respect to the properties of both methods is possible. The limitations regarding computer resources that arise on sequential computers can therefore be overcome. The parallel implementation of the iterative framework is discussed with focus on the mechanisms for sharing and distributing information among the involved processes. A three-dimensional eddy current problem is presented as an example for discussing performance issues.