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-   -   Gambit: interaction of two sizing functions? (http://www.cfd-online.com/Forums/fluent/39441-gambit-interaction-two-sizing-functions.html)

Ralf Schmidt January 30, 2006 06:43

Gambit: interaction of two sizing functions?
 
Hi!

How does Gambit handel the interaction of two or more sizing function, that are attached to the same volume?.

What about two sizing function, one attached to a volume, the other one attached to a face that belongs to the volume?

The sizing fuctions may have different start size, growth rate and size limit. Say, in the middle between the source of the sizing functions, what is the cell size??

Any Idea?

Ralf

Jason January 30, 2006 09:48

Re: Gambit: interaction of two sizing functions?
 
When there are multiple sizing functions, the sizing function that requires the minimum local mesh size dominates... this is evaluated as Gambit builds the background grid.

So lets say you have two nodes next to one another. One with a small mesh and a high growth rate, the other with a coarser mesh, but a slower growth rate. The mesh will be controlled by the node with the smaller mesh, up until the distance from the nodes where the sizing functions are equal, then the mesh with the smaller growth rate controls the mesh because it is now asking for a smaller mesh.

Hope this helps, and good luck, Jason

Ralf Schmidt January 30, 2006 10:37

Re: Gambit: interaction of two sizing functions?
 
ok... thanks a lot for the explanation!

But, what happend, if the starting size of the second node is larger than the size limit of the first one?? So the sizing functions will never really meet each others.

Or, if the growth rate of one sizing fuction is to small, to meet the cell size of the secons sizing function?

Ok, these are just theoretical questions... thanks anyway

Ralf

Jason January 30, 2006 18:35

Re: Gambit: interaction of two sizing functions?
 
Which ever sizing function is asking for the smallest mesh will dominate. So if the size limit of function A is smaller than the start size of function B, then function A will dominate throughout the domain. Same thing if the growth rate of function A is so small that it's always resulting in a smaller mesh than function B.

All sizing functions are calculated when creating a background grid. Wherever multiple sizing functions overlay, the sizing function that is looking for the smallest mesh size dominates. Size limits continue to the end of the volume (unlike older versions of Gambit which had an "effective distance" that you had to input), so if a sizing function has a small size limit, that size limit will be the maximum mesh size throughout the volume.

Hope this helps, Jason


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