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Old   June 6, 2011, 06:23
Question extracting value at particular location
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Churamani Prasad
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There is an interface in the YZ plane at x=xo(known value).
A material is present on both sides of the interface which diffuses from the left side to right side. Is it possible to extract the mol concentration/average mol concentratoin (or mass fraction or volume fraction) of the material at the mesh cells lying just to the left and just to the right of the interface using some User-Fortran Code for every time step?/ These extracted values are to be used later....

Or may be at the mesh cells which are within some distance to the interface, like average concentration of the material from x=(xo-dx) to xo, where dx is small (can be 2-5 mesh cells wide)??

Are there any tutorials which demonstrate this type of requirements??

Need help !!
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Old   June 6, 2011, 07:46
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Glenn Horrocks
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Yes, you can extract values as the simulation progresses. Use a transient results file which only has the variables you want. Then you can post-process that in CFD-Post and extract it if necessary for later analysis.
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Old   June 6, 2011, 07:55
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Churamani Prasad
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I have read one paper and I think they have done this, extracting/updating value at particular mesh cells.

Here, is the paper paragraph :
"
The recirculating flow patterns act to refresh the acid
concentration at the interface of the organic and inorganic
segments. In the aqueous segment, the recirculating
flow draws the acid away from the interface along
the centre line. A true representation of movement of
acetic acid from kerosene to water is partitioning 85:1 in
favour of the water phase. The source terms of the scalar
equation representing dissolved acid were calculated
to represent the partitioning movement of acetic acid
across the water/kerosene interface. Fig. 7 illustrates
how the concentration of acid was recalculated for the
mesh cells either side of the fluid interface. In the diagram


a
1 and a2 represent the total mass of acid in water

and kerosene respectively. The numerical expressions
below the mesh cell diagram indicate how


a1 and a2 were

redefined in the source terms of the scalar equation

representing dissolved acid."
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Old   June 6, 2011, 07:59
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Churamani Prasad
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Thanks for the reply..

But the "extracted values" have to be used in the CFX-pre only...not in post...

I have successfully extracted the values of some variables in domains, at boundary, at walls, interfaces..but never at mesh cells near the interface(as i mentioned in my question)
I m going through some materials but unable to do it..
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Old   June 7, 2011, 19:04
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Why don't you use the built in mass transfer stuff at an interface?
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