In CFD-GEOM, a convenient tool called "Butterfly Faces" allows the user to quickly and automatically create a structured mesh for circular topologies. The resulting mesh consists of 5 structured faces (4 sides and 1 core) inside a circle. Parameters are available to set the size of the core and the mesh density.

Figure 1a. Circle with four edges                                          Figure 1b. Resulting butterfly mesh

To start, create a circle and split it into 4 arcs. Create edges on the arcs, making sure that opposite sides have the same number of grid points. In this case (Figure 1a), 11 grid points have been placed on each arc.

In the "Structured Face Options" panel, select the "Butterfly Face" tool, shown in figure 2.

Figure 2. butterfly mesh tool

Select each edge followed by a middle mouse click. Figure 3 depicts what you should see after picking all four edges.

Figure 3. Edge selection for the butterfly mesh tool

The user has control over the radius of the Major and Minor axes. Note: this radius is measured from the center of the circle. Figure 4 shows the Butterfly faces setting options. Once the major and minor radii have been defined, click Apply and you will get a Butterfly mesh as shown on top of this page in figure 1b.

Figure 4. Butterfly faces setting options

If you have any questions about this tip or would like us to discuss other topics in the future, please let us know.

Regards,
Olivier Demaneuf
ESI CFD Support Team