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how to define a surface within the domain

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Old   August 8, 2013, 04:30
Default how to define a surface within the domain
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hannes
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Hi,

could anybody give me a hint on if or how it is possible to evaluate for example the mass flow through a given area/surface. The problem I have is how to define the surface within the domain. I know about the possibility to define a cuttingPlane but that extends throughout the entire domain. So I'm actually looking for a method to define a surface with three points or two vectors or so.
Any Ideas?
Thanks a lot
Hannes
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Old   August 13, 2013, 14:17
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Niels Gjoel Jacobsen
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Hi Hanness,

This is partly guessing on my part, but I suppose that you could:

1. Create a faceSet (and subsequently a faceZone)
2. Use a functionObject to evaluate the flux across this faceZone.

Since a faceZone (faceSet) can be everything from 0 to all faces, then you have a lot better control over the area of integrating, than if you were to use a cutting plane.

Kind regards

Niels

P.S. A quick search revealed the following utility, which should do exactly what you want: src/postProcessing/functionObjects/field/fieldValues/faceSource
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Old   August 23, 2013, 04:23
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Hi Niels,

thanks a lot for your support. I created the faceZone accordingly and evaluated the massflow with a swak expression and funkyDoCalc. I also checked with a faceSource in the functions section in the controlDict (and also the swakExpression). Those two give the same values but with opposite sign. How can that be?
However, one more question remains: Is it possible to interpolate on an arbitraty plane/face? As I understand the faceSet-tool just picks the faces which are in a given box and the faces are not neccessarily oriented in the direction of the cut. So is the way to proceed to create a cuttingPlane which interpolates as I understand it and then subsequently identify the faces of the cuttingPlane which are within a given box?

Thanks a lot
Hannes
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