# How to integrate variable in a transient simulation?

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 January 8, 2012, 20:38 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,704 Rep Power: 98 Accessing old values in CEL is not supported. But there is an unsupported way to do it, search the forum and hopefully you can find it.

 January 9, 2012, 05:05 #3 New Member   Nic Patkwoski Join Date: Jan 2012 Posts: 4 Rep Power: 6 Hi Glenn, To be fair, I don't actually need to access the old data. It's just a way for me to understand what needs to happen. Were I writing my own code I would use the formulation of eq. 2. to 'accumulate' a variable. I'm surprised that CFX does not support this type of variable accumulation/integration given that every solid-gas reaction rate is determined by a conversion extent which needs to be integrated. Can you suggest search terms...I don't really know what it is called that which I'm looking for. Thanks Nic

January 9, 2012, 05:56
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Glenn Horrocks
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Accessing old values, accumulating over time, time integral - all the same thing and you cannot do it as a supported feature in CFX. This question has been asked many times and all I can recommend is you put in a feature request to ANSYS for it to be included.

You can do it as an unsupported feature. Define an additional variable (say "OldVel") and edit the CCL for the additional variable to include the hidden CCL:

Quote:
 ADDITIONAL VARIABLE: OldVel Option = Definition Tensor Type = SCALAR Units = [m s^-1] Variable Type = Specific Update Loop = TRANS_LOOP END
For further details check this thread:
derivative in CEL expressions

 January 9, 2012, 09:59 #5 New Member   Nic Patkwoski Join Date: Jan 2012 Posts: 4 Rep Power: 6 Hello Glenn, That's it. The trick with the dummy run to initialization the Additional Variables to 0 seem to have worked well. Thanks for the link to the thread. Seems like a pretty standard procedure which should be better documented despite being unsupported. Anyway, thanks for your help. Nic

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