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-   -   splitting regions and defining BC in conjugate heat transfer (http://www.cfd-online.com/Forums/openfoam-pre-processing/127171-splitting-regions-defining-bc-conjugate-heat-transfer.html)

skuznet December 5, 2013 00:51

splitting regions and defining BC in conjugate heat transfer
 
Hello!
I'm trying to understand the conjugate heat transfer cases multiRegionHeater from OF tutorial and planeWass2D from
HTML Code:

http://openfoamwiki.net/index.php/Getting_started_with_chtMultiRegionSimpleFoam_-_planeWall2D
.
The Allrun script calles programms
Code:

blockMesh
which creates mesh in /constant/polyMesh folder
Code:

topoSet
which defines different regions in folder sets and file cellZones.
It looks like files in folder sets contains cell labels corresponding to each region.
What is stored in the file cellzones?
Then
Code:

splitMeshRegions -cellZones -overwrite
is called and creates a number of files. Can anyone explain me or give me a link with explanation what exactly this program do and how boundary conditions between regions are defined?

styx December 5, 2013 03:59

hi,
the command topoSet uses the file topoSetDict in the system-folder. It creates the folder sets with the cellZones. The cellZones are volume-regions in the mesh, e.g. topAir, wall.

with "splitMeshRegions -cellZones -overwrite" the Mesh is split in several Regions on the basis of the created cellZones. the new boundaries are get names like bottomAir_to_wall. But the interaction between the regions is not yet defined.

The boundary conditions between the regions are defined with the command changeDictionary which uses the changeDictionaryDict.
The boundary condition of the temperature e.g. in regoin bottomAir changes and the interaction between bottomAir_to_wall is defined:

bottomAir_to_wall
{
type mappedWall;
nFaces 100;
startFace 16040;
sampleMode nearestPatchFace;
sampleRegion wall;
samplePatch wall_to_bottomAir; //interacting boundary in region wall
offsetMode uniform;
offset (0 0 0);
}

Try to run the changeDictionary and have a look at the boundary files in planeWall2D before and after.



Andreas

skuznet December 6, 2013 22:29

Andreas,

thank you for your answer, it is very helpful.

Do I have to define boundary conditions between two regions with same properties - solid1-solid2 or fluid1-fluid2?

styx December 9, 2013 05:42

yes, you also have to define boundary conditions between two solids or fluids.

In the tutorial /heatTransfer/chtMultiRegionsSimpleFoam/multiRegionHeater you can see this. There e.g ist the boundary condition between two solid regions (heater and leftSolid)


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