Meshing for conjugate heat transfer

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tpa
Posts: 49
Joined: Fri Mar 16, 2012 11:35 pm

Meshing for conjugate heat transfer

Post by tpa »

Hello.

I am now experimenting with the coupling between Code Saturne and Syrthes. Up to now I have used both tools seperatly with some success. My question here is how to mesh correctly for this coupling to work. My case is based on fluid-solid heat exchange.

I have constructed the Study folder with "code_saturne create -s test -c FLUID --syrthes SOLID" as recommended in the "3 2D disks" example.

For such a study I need two separate 3D meshes. I use Salomé as mesher. I want the fluid boundary zones well represented and I assume that the common surface where heat exchange will take place should be compatible (have nodes in common). In my study the fluid layer is thin compared to the dimensions in the solid.

My approach in Salomé has been to make two volumes in Salomé and combine them in a "Glue" as this will enable meshing the entire domain in a single operation in the mesh module - and thus assure common nodes/surface elements on the coupling surface.

In the MESH module I make one meshes with two sub-meshes one for the solid with one mesh density and another for the fluid with higher density end boundary layers. The assembled mesh looks as I want it to - my problem is that I can not save the sub-meshes and their corresponding groups separately.

I tried to delete one sub-mesh and its groups and then save, followed by reloading the mesh and doing likewise with the other sub-mesh by the meshes saved this way seem not "clean" and do not work correctly in uncoupled runs with code_saturne and syrthes respectively - which is my way of testing the meshes and the setups.

How do I construct this mesh preparation suitably? What do you do?

For the testing I use a relative simple geometry but my target study will have complex geometry so I am interested in leaving the work to the mesher and avoid too much manual manipulation.

Thank you for reading and responding.

(Platform: Linux Mint + code_saturne 7.0.6 + syrthes 5.0 + salomé mesh 8.5.0)
Yvan Fournier
Posts: 4107
Joined: Mon Feb 20, 2012 3:25 pm

Re: Meshing for conjugate heat transfer

Post by Yvan Fournier »

Hello,

This is mostly a SALOME meshing question.

Did you assign different volume groups to the two sections ? That should help exporting only one part of the mesh separately, or at worse, duplicate the mesh, and remove one volume group from the first copy and export it, and remove the other group from the other copy and export it separately.

Best regards,

Yvan
tpa
Posts: 49
Joined: Fri Mar 16, 2012 11:35 pm

Re: Meshing for conjugate heat transfer

Post by tpa »

Hello Yvan. Thank you for answering.

As I wanted boundary layer meshing of the fluid I went with the fluid mesh as one sub-mesh and the solid as another submesh. After defining groups from geometry I saved the hdf, deleted one submesh and groups and exported. Then I reloaded the hdf and did similarly with the other part of the mesh.
I also tried to export it all in one .med and then import the full mesh, manipulate and export. I exported to MED and also tried UNV. The UNV format is read by Syrthes but the description file is empty. When I import MED of the manipulated mesh the description file falsely claims the boundary face meshes to be volume groups instead of surface groups. If I make a mesh and export to MED as one would normally do all is good.
It is a bit of a mystery what goes on.

Maybe I should try a single mesh with boundary layers also in the solid where they in principle wont harm. My concern is that if I mesh the solid this way the mesh will become unnecessary big.

You are probably right that it may be a Salome issue.
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