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Old   January 9, 2012, 12:06
Default Problem with fvc::domainIntegrate
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Dear Foamers,

I have encountered a problem with the domainIntegrate function.
I actually don't understand why OpenFOAM gets this result and would be happy about suggestions.
Ok, here is the Problem:
I have created 2 geometries with blockMesh. One is a simple square as a reference and the other one is the same square with a hole cut out and a bump merged into it. (see attached files)

Clearly the domain with the bump should have a larger volume, but the result due to domainIntegrate is exactly the same.
I am using domainIntegrate that way:

Code:
 Info<< "wavesize= " << scale_spaceunit*fvc::domainIntegrate(pos(u-(1e-12))) << endl;
In this case I have given the function u = 1 a constant value.
The result is for both geometries
Quote:
wavesize= (scale_spaceunit*domainIntegrate(pos((u-1e-12)))) [0 0 0 0 0 0 0] 1600
What went wrong here?

Am I misunderstanding the purpose of domainIntegrate? Is volumeIntegrate working better for my purpose? Are there any other functions?

Oh btw. I am using OpenFOAM 2.0.0

I appreciate your time

seb
Attached Images
File Type: jpg square.jpg (42.0 KB, 14 views)
File Type: jpg bump.jpg (69.5 KB, 20 views)
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Old   January 9, 2012, 13:40
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Marco A. Turcios
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Try
Code:
 sum(mesh.V().field())
. Without knowing what is inside your blockMesh files, its possible that the number of cells in your domain might be the same? You could also try
Code:
 domainIntegrate(mesh.V().field())
.
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Old   January 9, 2012, 13:55
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Thank you for the hint.
I am not sure what exactly
Quote:
Code:
 sum(mesh.V().field())
does, but I assume V is a vector field defined on my mesh right? In my case this would be u, but the point is I want to sum up only the cells where u>0 including the cells volume, thats why I use
Code:
pos(u-(1e-12))
I dont see how to incorporate that... Can you point me in a direction?

Also, if both meshes have the same number of cells, the volumes should still be different since I am looking for Volume and not number of cells...

What I am looking for is something like this pseude code:

If u>0:
calculate volume of cell

sum(volumes of all cells where u>0)

greets, seb
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Old   January 9, 2012, 13:59
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Code:
mesh.V().field
is the field that has all the cell volumes. By summing them you obtain the total volume.
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Old   January 14, 2012, 07:21
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Thanks for the hints,

I have realised the problem is actually not in the integration or the volume as such, but seems to be a more general problem. I guess I will just open a new thread, as the topic doesn't really fit anymore...
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