Newbie Heat Transfer Problem

[petroo]

Hello Matthias,

It would be better if the mesher cleaned up the duplicate surfaces and created a continuous mesh. Do you know if Salome can handle this problem?

I'd say yes, it does. I create my structured walls by piling boxes on each other in Salomé, then creating a partition of the various boxes, then creating respective groups in this partition to be able to attribute different (intermediate) surfaces with BC in Elmer later on. The whole process is described rather well in http://www.elmerfem.org/wiki/index.php/ ... e_to_Elmer .

The UNV mesh that is exported for the complete calculational domain, consisting of all participating bodies, carries the body indexes over to Elmer, and the junctions between them consist of only one surface. The UNV net can be directly loaded into Elmer, but beware of potential "locale" issues, namely the necessity to exchange "." against ",". For this, see some other thread here.

There is the necessity to decompose individual surfaces again in ElmerGUI, though. Here an angle value of 70° always worked for my basically rectangular geometries.

All in all, I feel Salomé to be more practical, and presently we are trying to go the whole way round from parametric geometry definition to scalar values extraction to couple the simulation to an evolutionary black-box optimizer module on the longer run.

Regards,

Peter

[raback]

Hi

I try avoid proposing ElmerGrid for the mesh generation but for stacked 3D objects it could really be a viable option. There is a possibility to do selected extrusion which might be enough at least for academic studies. The ElmerGrid manual has some example on this and I could ellaborate on the logic if it turns out to be intractable.

-Peter

[mzenker]

Hi Peter ("petroo"),

thank you for the reply. I still have some questions:

1) can Salome import STEP (or IGES) format?
2) what happens if I do the following:
* create two boxes in Salome with different sizes, each one having its own set of boundary surfaces
* put them one on top of the other, so that the outer face of the smaller box is a subset of the outer face of the larger one. I now have an interface consisting of a double surface
* mesh the geometry
Are all nodes at the interface merged, so that there can be a heat flow between the boxes?
3) More important, if I import those boxes (or a more complex geometry with adjacent bodies) from CAD (e.g. Solidworks export in STEP format) and mesh them, do I get a mesh with merged nodes at the interfaces?

If the answer to all these questions is "yes", I will consider switching to Salome, since for gmsh the answer for 2) and 3) is "no" (with a "yes" for 1), however).

Best regards,

Matthias

[petroo]

Hi Matthias,

1) can Salome import STEP (or IGES) format?

According to the import options it can read both. But I did not do it myself, so this is no final answer from this side.

2) what happens if I do the following:
* create two boxes in Salome with different sizes, each one having its own set of boundary surfaces
* put them one on top of the other, so that the outer face of the smaller box is a subset of the outer face of the larger one. I now have an interface consisting of a double surface
* mesh the geometry
Are all nodes at the interface merged, so that there can be a heat flow between the boxes?

As a picture may tell more than a thousand words, here is a setup I am investigating at the moment:

Cut through a brick wall (with a depicted heat spread in a transient calculation), consisting of isolated tiles, embedded in mortar, and heated by a rather thin patch volume on top.

Ziegelwand-Cut.jpg (82.05 KiB) Viewed 4382 times

This setup was completely defined in Salomé, with the bricks being repetitively multiplied from just one and being treated by elmer as one spatially distributed object with identical body conditions. You plant the interior volumes inside another existing one (here: the wall's outline), and Salomé takes care of the meshing later. The different volume indexes are conserved and transported to Elmer as a multi-volumes mesh.

3) More important, if I import those boxes (or a more complex geometry with adjacent bodies) from CAD (e.g. Solidworks export in STEP format) and mesh them, do I get a mesh with merged nodes at the interfaces?

Sorry, this is out of my depth. I would *expect* this to work, at least if you do the (somewhat confusing) partitioning and grouping on the imported bodies.

If the answer to all these questions is "yes", I will consider switching to Salome, since for gmsh the answer for 2) and 3) is "no" (with a "yes" for 1), however).

Well, don't expect it to be a simple system. In my notion at least, it is not. But once you geht acquainted with it, it offers quite a lot of features. I guess I used only a very tiny bit of it so far, presumably due to a lack of theoretical education on the very basics of meshing etc..

Regards,

Peter

[mzenker]

Hi Peter,

thank you for your answer. I still have some doubts about how Salome treats duplicate surfaces - the best thing would be to try it myself.
But I have just visited the Salome website and found that the Windows version seems to be still experimental and buggy. Since I have to use Windows at work, I would need Salome to be reasonably stable on this platform. Do you have experience with Salome under Windows?

Matthias

P.S.: Maybe we should start a new thread under "external tools"?

[petroo]

Hello Matthias,

I still have some doubts about how Salome treats duplicate surfaces - the best thing would be to try it myself.

Yes, I'd think so, too.

Do you have experience with Salome under Windows?

Sorry, but my computer is fully climatized. I don't open Windows (except in rare circumstances)

Maybe we should start a new thread under "external tools"?

Feel free to do so, but w/r/to Windows I won't be able to contribute.

I overhauled the already existing "Salomé to Elmer" tutorial in the Elmer Wiki (http://www.elmerfem.org/wiki/index.php/ ... e_to_Elmer) a bit further, and I'd say it is now a bit more readable and reflects my state of knowlegde on this behalf. Did you take a look on it?

Regards,

Peter