The theory and application of numerical methods for unstructured meshes has been improved significantly in recent years. Because meshes can be placed arbitrarily in space, unstructured meshes can provide much higher spatial resolution than structured meshes.

Unstructured meshes have some advantages such as flexibility in fitting complicated domains, rapid growth from small to large elements, and relatively easy refinement and coarsening.

Regarding the modeling, the import of the geometry from a CAD system and the automatic unstructured mesh generation drastically reduces the manpower required for CFD pre-processing tasks.

CFD-GEOM has the capability to generate semi-structured boundary layer meshes.

The benefits of this new option are the following:

• Resolve “near-wall” effects with unstructured mesh clustering
• More accurate boundary layer predictions (e.g. lift, drag, pressure drop, heat transfer, etc.)

Figure 1.  Unstructured boundary layer mesh in CFD-GEOM

The procedure to define the boundary layer mesh is the following:

1. Under the Mesh tab, select Unstructured Meshing Options → Boundary Layer Meshing
2. Select the Shell where you want boundary layers and select "Activate Boundary Layer"



Figure 2.  Boundary layer meshing tool	Figure 3.  Boundary layer meshing options



3. Specify Boundary Layer parameters (Initial Thickness, Growth Factor, and Number of Layers)
4. If certain surfaces should or should not have boundary layers, select the surface(s) and Enable/Disable boundary layers on that surface(s) by selecting the appropriate button. Clicking the Globally Activate/Deactivate button will activate/deactivate Boundary Layers on all the shells present in the model.
5. Now that the boundary layer has been activated and the parameters specified, simply generate the tetrahedral mesh. The boundary layers will automatically be generated during tetrahedral meshing.

Before generating the boundary layer mesh, you can view the size and distribution of the layers. For each surface where the boundary layers option is activated, CFD-GEOM will draw a line perpendicular to that surface, allowing you to preview the boundary layer mesh, as shown in Figure 4.

Figure 4.  Preview of the boundary layer mesh

Note that boundary layers are available in V2008.0+ versions of CFD-GEOM.

Regards,
ESI CFD Support Team