Explicit CEL variables

juanluisfb · November 16, 2022, 09:25

Hi everybody,

Anyone knows how can you use explicit variables in CEL? Or, is it possible to access variables or properties of previous time steps?

Thank you.

ghorrocks · November 16, 2022, 17:28

What do you mean by explicit variables? Example = 10[m/s]+2*Velocity is an explicit variable.

Can you access variables from previous time steps? This is not supported, but there is a unsupported method of doing it: see
Update Loop = TRANS_LOOP
Why the Trans_Loop trick does not work? No old time value obtained!

Note it is pretty unreliable and does not work in every case (that is why it is unsupported)

Alternately you can write some user fortran to do it.

Opaque · November 16, 2022, 17:38

adding to Glenn's question:

what are you trying to achieve that needs variables at previous timesteps?

juanluisfb · November 17, 2022, 10:17

I have a CEL expression that have to be evaluated with variables at the previous step. An example of this could be a temperature ON/OFF control.

ghorrocks · November 17, 2022, 18:15

It would be good if you described what you are actually trying to do because there usually is a better way of doing it.

But to answer your question: You cannot do temperature on/off control in a steady state simulation as it will never converge. If you want to do it in a transient simulation you can try the TRANS_LOOP approach or a user fortran routine, as previously suggested.

November 16, 2022, 09:25	Explicit CEL variables	#1
juanluisfb New Member Juan Luis Join Date: Mar 2013 Posts: 4 Rep Power: 13	Hi everybody, Anyone knows how can you use explicit variables in CEL? Or, is it possible to access variables or properties of previous time steps? Thank you.

November 16, 2022, 17:28		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	What do you mean by explicit variables? Example = 10[m/s]+2*Velocity is an explicit variable. Can you access variables from previous time steps? This is not supported, but there is a unsupported method of doing it: see Update Loop = TRANS_LOOP Why the Trans_Loop trick does not work? No old time value obtained! Note it is pretty unreliable and does not work in every case (that is why it is unsupported) Alternately you can write some user fortran to do it. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

November 16, 2022, 17:38		#3
Opaque Senior Member Join Date: Jun 2009 Posts: 1,880 Rep Power: 33	adding to Glenn's question: what are you trying to achieve that needs variables at previous timesteps? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

November 17, 2022, 18:15		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	It would be good if you described what you are actually trying to do because there usually is a better way of doing it. But to answer your question: You cannot do temperature on/off control in a steady state simulation as it will never converge. If you want to do it in a transient simulation you can try the TRANS_LOOP approach or a user fortran routine, as previously suggested. Opaque likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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November 17, 2022, 10:17		#4
juanluisfb New Member Juan Luis Join Date: Mar 2013 Posts: 4 Rep Power: 13	I have a CEL expression that have to be evaluated with variables at the previous step. An example of this could be a temperature ON/OFF control.