As it was explained in a previous tip called Understanding cell-splitting in CFD-VisCART and its effect on cell count, a small change in a specified cell size could lead to drastic changes in the cell count due to the cell-splitting rules used by CFD-VisCART. In order to know before hand the exact size of the cells in your domain, the user specifies the level of refinement desired (as opposed to the actual cell size), indicating the maximum number of divisions CFD-VisCART will perform during grid generation. The resulting minimum cell size is calculated using this formula: size_of_boundingbox / 2^{max_division_level}. For instance, Level 2 in X will cut the bounding box into 4 pieces in the X direction.

Figure 1.   Mesh generation panel

As can be seen on Figure 1, next to the Level you choose, the actual minimum size of the Cartesian cell is given. Cell size and division level are stored in the VGD file, therefore older CFD-VisCART versions are able to use the same grid generation settings. It is possible to specify different levels for the initial stair step mesh, the boundary refinement, and each of the sources.

Currently, the maximum level is set by default to 15, but can be changed in the Preferences panel (Figure 2) and increased up to 20. If an old VGD file is read, the maximum level will be automatically increased if needed.

Figure 2.  Preferences panel

If you have any questions about this tip or any other tip or would like to make a suggestion for tip, please feel free to contact the ESI CFD Support Team.

Regards,
Emmanuel Bot
ESI CFD Support Team