Most models have certain parts or regions where the grid density needs to be higher than other areas to accommodate for steep curvatures, sharply changing topology, etc.  If the grid is not refined in these areas, it could lead to the generation of “bad cells” including Negative Volumes, Small Volumes, Degenerate Faces and Skewed Cells. CFD-VisCART V2008 and onward is capable of displaying these cells, if they are generated, to help the user identify the regions where the grid may need to be refined or modified.

Once the grid has been generated and the grid quality detection/improvement performed, any existing “bad cells” in the grid will automatically be displayed. In addition , the explorer window will give a detailed statistical report of the grid quality.

The toolbar below the graphics window has icons to Blank-UnBlank the display of these bad cells, as shown in figure 1.

Figure 1.  Icons to Blank-Unblank bad cells (bottom toolbar)

Figure 2.  Visual display of bad cells

In CFD-VisCART version 2009.4, a new display option "Show Only Faces Near Bad Cells" (see figure 3) was added to hide all the other geometries in the model except the surfaces near the bad cells. This makes it easier for the user to visualize the bad cells and the adjoining geometry.

Figure 3.  Icon to only show the faces near bad cells (top toolbar)

Regards,
Santosh Kini
ESI CFD Support Team