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-   -   Minus Volume of cells (http://www.cfd-online.com/Forums/cfx/18488-minus-volume-cells.html)

di bonga March 29, 2001 06:54

Minus Volume of cells
 
Hi,

I've got a real problem with minus volume in the geo file. What is actually a minus volume? is the cell twisted or what? Is there a way in CFX-Build to check the grids for minus volume ? I have checked the quad elements at the critical faces and i think it looks OK, at least to me:). I also have tried to create the hex mesh and verify the cells for the twist factor and none of the cells in the suspected solid has twist factor more than 46degree. Rearranging the mesh structure by using various configuration doesnt help at all. The only option I know is to change the block shapes which means changing the whole block structures in order to have better grid form, but that is too much pain...!!

Thanks di

jon lewin March 30, 2001 06:44

Re: Minus Volume of cells
 
Are you running in cylindrical co-ordinates?

HPM April 8, 2001 13:38

Re: Minus Volume of cells
 
This usually happens in complex geometries when one is trying to efine small elements in the vicinity of the walls. The cell "collapses", one of its walls collides with the other creating a negative volume. If you correct the growth ratio at the particular trouble-making cell, it is easily sorted.


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