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-   -   Offset warning (http://www.cfd-online.com/Forums/openfoam-meshing/70478-offset-warning.html)

Mercato November 25, 2009 11:35

Offset warning
 
2 Attachment(s)
Hi Foamers,
I have create tube in tube mesh for heat exchanger with setSet. But during chtMultiRegionFoam calculation appear warnig:
Quote:

--> FOAM Warning :
From function directMappedPatchBase::calcMapping() const
in file directMapped/directMappedPolyPatch/directMappedPatchBase.C at line 451
The actual cell/face centres picked up using offset (0 0 0) are not
on a single plane. This might give numerical problems.
At patchface (-0.005366228 6.12 0.006246755) the sampled cell/face (-0.005366229 6.12 0.006246755)
is not on a plane 3.929719e-16 offset from the patch.
You might want to shift your plane offset. Set the debug flag to get a dump of sampled cells.
I guess that this warning gives nonreliable results.
Please, help to fix it up.

Attachment 1600
Attachment 1601

AirS November 27, 2009 08:06

Hi Mercato,
just to tell you that I've got the same error as you... That occurs when I run renumberMesh.
Moreover, how can we do what we are asked for:

"Set the debug flag to get a dump of sampled cells" ?

If you have already solved the problem, I'd appreciate your help.
Thanks.

dakos November 29, 2009 13:24

1 Attachment(s)
Hi Mercato and AirS,

I have the same problem using a mesh I have generated with snappyhexmesh.
The problem, in my case, is in the boundary where some faces are wrong (but i don't know how i can correct them!).

Ciao

AirS November 30, 2009 07:15

Can anyone give me some suggestions about how to set the debug flag to get a dump of sampled cells ?I give you my inputs in constant/polyMesh/boundary :

{
type directMappedPatch;
nFaces 2291;
startFace 1200381;
sampleMode nearestCell;
sampleRegion region0;
samplePatch none;
offset ( 0.766 0 0 ); // Which is the keyword needed here ??
}

Any suggestions are welcome,
Thank you!

AirS December 1, 2009 08:27

I've finally partly solved my problem.
I add the keyword directMappedPatchBase in the controlDict (OpenFOAM-1.6/etc) followed by 1 (Debug switches). So that I can see the suggestions and another file is created: INLET_directMapped.obj. My problem is that I don't understand what it's inside :confused: the first lines being like so:

v -1 -0.08115735 0.112
v -0.2315849597 -0.08110849465 0.1120022489
l 1 2
v -1 -0.08115735 0.13
v -0.231585471 -0.08110835716 0.1299997623
l 3 4

Thanks a lot !

AirS December 2, 2009 07:35

Hi,
When I run decomposePar or renumberMesh I've got this warning:

--> FOAM Warning :
From function directMappedPatchBase::calcMapping() const
in file directMapped/directMappedPolyPatch/directMappedPatchBase.C at line 451
The actual cell/face centres picked up using offset (2 0 0) are not
on a single plane. This might give numerical problems.
At patchface (-1 -0.0811574 0.112) the sampled cell/face (1.00878 -0.0811143 0.111998)
is not on a plane 2.00502 offset from the patch.
You might want to shift your plane offset. Set the debug flag to get a dump of sampled cells.


Since it's just a warning I tried to run pisoFoam to see what happened, and it worked well. My simulation being done, I used reconstructPar and unfortunately I've got the same error. I can't understand how that can be possible actually since everything worked fine with the directMappedPatch boundary during the simulation.
Does anybody have an idea of what I could try to sort this issue out ?

Thanks !


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