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-   -   Multi-Region Meshing Problem (http://www.cfd-online.com/Forums/star-ccm/86045-multi-region-meshing-problem.html)

boathead March 13, 2011 07:21

Multi-Region Meshing Problem
 
1 Attachment(s)
I am trying to mesh separate regions in the attached geometry (the top box represents a combustor, the bottom box represents a cooling plenum and the tubes represent holes in the combustor wall). The fluid flows through the bottom of the cooling plenum, up through the tubes and out the right hand side of the top box.

During the creation of the geometry, when extruding each region I selected the imprint option so as to keep each region separate and not merged into one. I then created a part for each region. I selected all the parts and applied a new region to each part with the option to create interfaces switched on.

I can apply a polyhedral mesh to the entire domain (without any errors messages) but a mesh is created over the end of each tube on both sides (the combustor and cooling plenum) so fluid cannot pass through.

I have been scratching my head over this for a while now so any help would be much appreciated to help get rid of the mesh over each tube end.

Cheers

Jonny6001 March 13, 2011 08:19

Hi, I don't exactly follow how you have split the geometry. From what I can gather, you have each section individual.
This means that the mesher will treat each one separately, fully closing the region during the meshing.

The easiest method in my opinion would be to get the CAD exactly as you want before importing in to Star. There are numerous ways of doing it within Star but I prefer the dedicated CAD environment.

If you could post more info such as the tree structure and the way each region is used, I could possibly help further.

Thanks.

nickd March 20, 2011 18:25

I think what you need is an in-place interface. If you have a look at the tutorial on the rotating fan it shows you how to do it. It seems a little strange as you have walls that you turn into interfaces to allow the flow through.
Nick
just to give you a bit more info:
If you highlight the surface of both parts (select one, then press ctrl and select the second) and then right-click, it will give you the option of creating an interface between the two. Do this then select in-place interface and it will create another node on the tree. THe process will allow fluid to pass straight through the intersection as if it wasn't there.

boathead March 27, 2011 14:36

Volumetric control issue
 
I have managed to sort out the interface issue thanks. I did not manage to get the polyhedral mesh and trimmed mesh to produce conformal meshes across the interfaces between the boxes and the tubes. I have dropped that idea now and am sticking with a single region.

I am however having problems with applying volumetric controls to the upper box (either with the trimmed or polyhedral meshes). When I apply the vol ctrl it basically either crashes STAR or if it does work, makes the entire domain look the same rather than having the original mesh with the refined bit in the vol ctrl?

Fresh May 29, 2012 11:40

Quote:

Originally Posted by nickd (Post 300247)
I think what you need is an in-place interface. If you have a look at the tutorial on the rotating fan it shows you how to do it. It seems a little strange as you have walls that you turn into interfaces to allow the flow through.
Nick
just to give you a bit more info:
If you highlight the surface of both parts (select one, then press ctrl and select the second) and then right-click, it will give you the option of creating an interface between the two. Do this then select in-place interface and it will create another node on the tree. THe process will allow fluid to pass straight through the intersection as if it wasn't there.

What shall i do if the geometry with two parts neighbouring to each other but has only one surface between them? e.g. a rotating turbine in a wind tunnel?
And if the region is rotating, the mesher within STARCCM seems not be able to deal with multiple regions. how should i mesh them while maintain a good mesh quality?

Cheers,

John


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