Mesh Generation

FEMGEN has fast and efficient mesh generation algorithms. Information about point coordinates, line types etc specified in the definition of the geometry, and also information about how the geometric objects are connected is stored in the database. During the mesh generation process, elements are described in terms of nodes, but also the connection between the geometry and mesh is established.

Nodal point coordinates are calculated according to the following rules:

• Coordinates on lines are calculated according to the line type. Nodes are placed exactly on the line, which means that no artificial splitting of the line is necessary.
• Coordinates interior to a surface are either interpolated from the border using a Coons patch mapping, or by rotating (sweeping) a surface.
• If requested the nodes can then be projected onto a given shape (for example, a cylinder).
• Coordinates interior to a body are interpolated from the defining surfaces.
• Mid-side nodes are interpolated between the corner nodes but taking into consideration curved lines and projection. (The exception to this is that graded spline lines and intersections may have mid-side nodes not exactly at the mid-side point).

The order of generation is:

• If splines and/or intersections are defined, nodes are first generated along these.
• Nodes and elements are generated and numbered, first on lines in the order that they were defined, then on surfaces and finally on bodies.

The local numbering follows that of the geometry. For example, on a surface the elements are numbered in the same sense as the surface is defined.

Element types may be specified by the user or supplied by FEMGEN . Default element types are created and deleted according to the following rules:

• When the first surface is created all default (program generated) beam elements are deleted.
• When the first body is created all default beam and surface elements types will be deleted.
• Deleted element types are not reinstated when bodies and surfaces are deleted.