In CFD-VisCART, the Cartesian cells can split or grow by a minimum factor of 2 because of the intrinsic cartesian-cell-splitting algorithm. Due to this, in some cases, there is a chance that the mesh could grow from dense (at the wall) to coarse (away from the wall) within a short distance.

In certain applications, it may be desired that the rate of growth of cells be slower to obtain a smoother transition of mesh density, and to avoid creation of larger cells close to the wall. Towards this end, CFD-VisCART 2009.0 provides an option to keep the cell size unchanged for several layers, thus delaying the growth of cells.

This new option is available under the Advanced tab in the Generate Mesh dialogue window as shown below in Figure 1.

Figure 1. Option to keep the cell size unchanged over several cell layers

Figure 2 below compares two meshes generated around a sphere, (a) with the default value of 1 for the above option and (b) with the number of layers equal to 3.

 Figure 2. Minimum number of layers at each refinement level equal to (a) 1 (default) and (b) 3

Please note that using this new option will usually result in an increase in the cell count. In certain cases though, using this option may eliminate the need to create box sources, and thus results in a lower cell count.

If you have any questions on this tip or have suggestions on future tips, please let us know.

Regards,
Santosh Kini ESI CFD Support Team