CST2013: Which Mesh to Use

For the spatial discretization the Finite Integration Method (FI-Method) is used. The method requires the computational domain to be covered by a mesh. Two different mesh types are available: hexahedral and tetrahedral meshes. In the figure below a single element for each mesh type is displayed.

For the Integral Equation solver a surface mesh will be created.

Setting the mesh type

You select the mesh type for your computation in the respective solver dialog. Please note that almost all CST solvers work with a hexahedral mesh, while only some solvers provide a tetrahedral or surface mesh method.  

Another way to select the mesh type is by using the menu available with Home: MeshGlobal Properties . However, this is just for previewing the mesh. A change of the solver method will change the active mesh type.

Differences between CST surface, hexahedral and tetrahedral meshes.

CST hexahedral meshes:

• In general, hexahedral meshes do not conform to material jumps; please note that this is not necessary because CST provides the Perfect Boundary Approximation? (PBA) and the Thin Sheet Technology (TST) in combination with hexahedral meshes.

• If the CST Multilevel Subgridding Scheme (MSS) is used, refinement can be local with respect to all coordinate directions. Otherwise, refinement can be local with respect to one coordinate direction, i.e. in order to account for details of the model whole  mesh planes will be inserted.

• Hexahedral meshing is very robust even for most complex imported geometries.

• Hexahedral meshes without MSS? are highly structured and lead to very fast computations.

In contrast, CST tetrahedral and surface meshes

• are conform to solid-boundaries and consequently conform to material jumps.

• The mesh refinement can be local with respect to all coordinate directions, i.e. single elements can be refined.

• Surface meshing leads to a smaller number of unknowns.

Which mesh type is most appropriate for a given simulation task?

It is difficult to provide a general statement on how to decide which mesh type should be applied for a given problem. However, as a rule of thumb, using CST hexahedral meshes (without MSS?) will often lead to faster computations because the solver can take advantage of their additional structure. Moreover, hexahedral meshing is very robust concerning complex geometries. This may be important if you must deal with imported structures.

However, if your problem setting includes strongly local details in the geometry or solution, structured hexahedral meshes may produce a large overhead in the number of elements for the part of the computational domain that does not need a fine mesh. For these types of problems, tetrahedral meshes or hexahedral meshes with MSS? are more suitable because they offer more flexibility.

Verification by comparison

You can get crucial benefit by the use of all, a surface, a tetrahedral and a hexahedral mesh for the same problem: The results can be compared. This yields an additional validity check for your numerical results.

Note that this is not a time-consuming task. In contrast to the use of different software tools for validation you can use different solver methods in the same CST software without setting up your computational model again!