The example inductor geometry presented in the next subsection and the coaxial geometry from Section 6.1 are discretized with the three-dimensional tetrahedron mesh generation software Netgen [110]. Netgen is able to combine the generation of very small elements in regions, where high resolution is needed with large elements, where the field does not change strongly. This advantage of Netgen makes high frequency simulations with pronounced skin effect possible at all. In the skin effect area a feasible field approximation can be guaranteed only if a very fine mesh is generated. Generating such a mesh in the entire simulation domain will push unnecessarily the memory limits. Thus it is very efficient to generate a coarse mesh in the remaining area.
Netgen uses different different geometry description formats. For the applications in this work the constructive solid geometry (CSG) format is preferred. It is very convenient for the description of small or medium size structures like the coaxial structure or the spiral inductor presented in the example section. The geometry is defined by Eulerian operations (union, intersection, and complement) from primitives. The primitives are generic volume elements like cubes, cylinders, spheres, or even half-spaces defined by an arbitrary point in the boundary plane and an outward normal vector. If CSG input is used, Netgen starts with the computation of the corner points. Then the edges are defined and meshed into segments. Next, the faces are generated by an advancing front algorithm [111]. After optimization of the surface mesh the volume inside is filled with tetrahedrons by a fast Delaunay algorithm [112]. Finally the volume mesh is optimized.