# Age of Air and Source Conflict

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 August 17, 2014, 19:56 Age of Air and Source Conflict #1 New Member   Michael Smith Join Date: Dec 2013 Location: Canberra, Australia Posts: 18 Rep Power: 5 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

 August 18, 2014, 06:27 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,739 Rep Power: 106 Can you post your CCL?

August 18, 2014, 20:58
#3
New Member

Michael Smith
Join Date: Dec 2013
Location: Canberra, Australia
Posts: 18
Rep Power: 5
See attached.

Thanks!
Attached Files
 S141289_Basement AltSol_20140819.zip (7.6 KB, 10 views)

 August 18, 2014, 22:05 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,739 Rep Power: 106 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: http://www.cfd-online.com/Forums/cfx...e-age-air.html It worked for me on the benchmark example.

 August 18, 2014, 22:46 #5 New Member   Michael Smith Join Date: Dec 2013 Location: Canberra, Australia Posts: 18 Rep Power: 5 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

 August 18, 2014, 23:01 #6 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,739 Rep Power: 106 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.

 August 19, 2014, 02:15 #7 New Member   Michael Smith Join Date: Dec 2013 Location: Canberra, Australia Posts: 18 Rep Power: 5 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?

 August 19, 2014, 03:07 #8 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 13,739 Rep Power: 106 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.

 August 20, 2014, 22:41 #9 New Member   Michael Smith Join Date: Dec 2013 Location: Canberra, Australia Posts: 18 Rep Power: 5 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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