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Old   August 17, 2014, 19:56
Default Age of Air and Source Conflict
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Michael Smith
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Hi all,

I am doing an analysis in a carpark, and want to calculate age of air and CO concentration.

When I run the sim with both setup, I get the CO concentration but age of air doesn't seem to increase (or calcualate) and remains at essentially zero.

If I don't add the source term age of air calculates fine.

Ideas why the source prevents age of air?

Cheers,
Mike
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Old   August 18, 2014, 06:27
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Glenn Horrocks
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Can you post your CCL?
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Old   August 18, 2014, 20:58
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Michael Smith
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See attached.

Thanks!
Attached Files
File Type: zip S141289_Basement AltSol_20140819.zip (7.6 KB, 5 views)
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Old   August 18, 2014, 22:05
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Glenn Horrocks
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It looks like you have not set a source term properly. You have set the source term to "Density", this should be set to 1.0.

Code:
    SUBDOMAIN: AoA
      Coord Frame = Coord 0
      Location = B2519
      SOURCES:
        EQUATION SOURCE: AoA
          Option = Source
          Source = Density
        END
      END
    END
This post is useful: [Indoor Air Quality]How do I calcauate "Age of Air
It worked for me on the benchmark example.
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Old   August 18, 2014, 22:46
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Michael Smith
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Hi Glenn,

Thanks for the advice. So the source term has to be constant (ie, 1) rather than density? Density is the input I got told to use by Leap (Ansys provider). Hmm.

On another note, what did you use to assess the CCL?

Cheers,
Mike
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Old   August 18, 2014, 23:01
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Glenn Horrocks
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Are you sure you are referencing the Density correctly? In fact that is probably your problem - if the Density function is zero then nothing will happen.

I suspect that if you have an incompressible simulation then the density variable is not present. I am not sure about that, but I think that is the case.

The ANSYS guy is probably right, you probably do need to integrate density rather than a constant.

So write a CEL expression which defines the density for the material properties, and then use that variable for the source term.
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Old   August 19, 2014, 02:15
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Michael Smith
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That will be exactly it. I'm assuming the Source "Density" is for air at 25degC, but I have set a custom fluid to allow calculation of CO.

Ok... so how do I specify density for my material to use as a source term?
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Old   August 19, 2014, 03:07
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Glenn Horrocks
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I've just tried a few things and what you have done works fine for me. I used the simple benchmark simulation with a variable composition mixture with both Density and a constant (1) as the source term factor. Both worked fine.

So I recommend you do the same and try to get the benchmark simulation working, as I can confirm it definitely does work for me. Then you can start debugging your simulation.
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Old   August 20, 2014, 22:41
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Michael Smith
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Yip, you're right. A simplified model worked for me with Density as well.

Well that's good, now at least I know it can work, and I've just got something muddled elsewhere!

Thanks Glenn!
Mike
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