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question on nonuniform BC

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Old   August 7, 2009, 04:58
Default question on nonuniform BC
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grig
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Hi, I have a question about setting up nonuniform BC's in OF. Namely, when specifying the whole list of values, are these numbers assigned to the points in the center of each boundary cell face or are these values assigned for the whole boundary cell face? Thanks
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Old   August 11, 2009, 03:06
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grig
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Does anyone have an idea? I am new to OF and this would really help... I would also ask if blockMesh can be used to create unstructured grids? Sorry if the questions seem lame. Thanks!
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Old   August 11, 2009, 03:53
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Henrik Rusche
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Dear Grig,

1) Yes, blockMesh can be used to create unstructured grids using the the mergePatchPairs keyword. You can find an example in

$FOAM_TUT/simpleFoam/pitzDaily3Block/constant/polyMesh/blockMeshDict

But I am not sure whether this is what you are after.

2) Yes, the values are assigned at the face centers and in order of the face list. If you have a function that describes your boundary, you either write your own BC or use "groovyBC":

http://www.cfd-online.com/Forums/ope...burb-mesh.html

If you have the values at some arbitrary points, you may want to use "timeVaryingMappedFixedValue" used here:

$FOAM_TUT/simpleFoam/pitzDailyExptInlet

Henrik
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Old   August 11, 2009, 04:00
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grig
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Thank you very much for the reply. So, if the values are assigned for the face center, than are they also interpolated over the whole boundary cell face during solving?! I am asking this because I want to implement a certain velocity value in a particular boundary cell and it seems to me that the values shown in paraFoam are 4 times lower all the time?!
I will have a look at the mergePatchPairs example.

Thank you again!
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Old   August 11, 2009, 04:13
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Henrik Rusche
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Dear Grig,

with cell and faces your are at the atomic level of the finite volume method which assumes that that face and cell values are uniform.

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Old   August 11, 2009, 04:19
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grig
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Ok, then there must be some other problem because, talking specifically, I assigned to only one boundary (wall) cell a velocity of 10 m/s, but when I visualize in paraFoam it shows around 2.5. This why I am a bit puzzled...

Best,
Grig
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Old   August 11, 2009, 07:39
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Henrik Rusche
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Dear Grig,

make sure that you plot the cell values. That's the fat icon rather than the pointy one in paraview's field selector. Each cell/face should then get a unique color - no shading.

Alternatively, have a look into the output files to work out what the exact value is.

Henrik
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Old   August 11, 2009, 08:07
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grig
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Thanks, I will have a look. Best, Grig.
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Old   May 26, 2010, 10:56
Default help about groovyBC
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Joseph
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Hi sir/madam
i simulated polymer in extruder(screw mill) by ViscoElastic fluidFoam,Jovani. According to my geometry, velocity vectors in boundary condition are changed .As result i should code variables condition in 0File>> U>> movingWalls.do you know that GroovyBC was compiled to OpenFoam as defualt or i have to compile it?and how to compile groovyBC to OpenFoam v.1.6?if anybody coded one geometry by groovyBC this is thanksful to sent it me by tamsilian@gmail.com.
Thanks in advanced your help
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