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-   -   Gambit periodic boundaries vs TGrid (http://www.cfd-online.com/Forums/fluent/29930-gambit-periodic-boundaries-vs-tgrid.html)

AnnaG June 20, 2002 16:16

Gambit periodic boundaries vs TGrid
 
Hi,

I'm creating a periodic geometry in Gambit (v 1.3) that itself is symmetrical - it's an 18 degree pie slice of a 360 degree cylinder that has 20 holes in it. I have created one half of the geometry so that in 9 degrees there is one hole cut in half by one periodic boundary. To create the full geometry, I copy -> reflect then move -> rotate this geometry by 18 degrees.

I have tried 2 approaches to meshing this: 1. mesh the geometry first then check the "copy mesh" option for the reflect operation 2. copy the geometry then apply the mesh using hard-links for face meshes

The problem with 1) is that there are duplicate edges created between the original and reflected-rotated geometry. This problem could easily be solved using TGrid (merge nodes) but I don't have TGrid anymore. Is there a merge-nodes operation in Gambit or another way to get around this? I try to connect the duplicate edges but am not allowed because of the mesh links.

Using option 2) is just not working - I get topology errors that tell me a link could not be made, or that some vertex is already associated with a link, etc. Mesh linking is confusing!

I read Phil's posting dated June 11 on hard linking faces in Gambit and will follow these rules and keep plugging away. Any additional insight would be greatly appreciated.

By the way, I have not been able to get the periodic boundary condition to work in Gambit. To get around this I write them out as walls the use the Fluent text command Grid -> modify-zones -> make-periodic , which ONLY works if the rotational periodicity is about the Z axis.


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