How to access a parameter from a previous timestep

Ridley · June 13, 2010, 04:31

Hi, I have a problem with a CEL-expression, where the density from the previous timestep (transient simulation) is needed for the calculation. Is it possible to access the density from this previous timestep just by using CEL-Code?

Thanks a lot!

Attesz · June 13, 2010, 10:29

hi, you have to use density(current time step -1)@somewhere. search for the syntax code of the current time step (for example, current iteration number is "citern"). i don't know surely, but it should work.

ghorrocks · June 14, 2010, 18:40

Sorry, but the answer is no. It is not possible. This is the biggest failing in CFX CEL. You may be able to use an additional variable and make use of the fact the CEL is updated at the start of a time step and additional variables at the end - but I have not confirmed this works.

Attesz · June 15, 2010, 03:06

I used it by adjusting the RPM's, outlet pressures etc. But as I see, for the flow parameters it is not suitable. It's really a big fail...

ghorrocks · June 15, 2010, 06:55

What is an RPM?

Attesz · June 15, 2010, 06:56

Sorry, Revolutions Per Minute

June 13, 2010, 04:31	How to access a parameter from a previous timestep	#1
Ridley New Member Join Date: Jun 2010 Posts: 6 Rep Power: 15	Hi, I have a problem with a CEL-expression, where the density from the previous timestep (transient simulation) is needed for the calculation. Is it possible to access the density from this previous timestep just by using CEL-Code? Thanks a lot!

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June 13, 2010, 10:29		#2
Attesz Senior Member Attesz Join Date: Mar 2009 Location: Munich Posts: 368 Rep Power: 17	hi, you have to use density(current time step -1)@somewhere. search for the syntax code of the current time step (for example, current iteration number is "citern"). i don't know surely, but it should work.

June 14, 2010, 18:40		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	Sorry, but the answer is no. It is not possible. This is the biggest failing in CFX CEL. You may be able to use an additional variable and make use of the fact the CEL is updated at the start of a time step and additional variables at the end - but I have not confirmed this works.

June 15, 2010, 03:06		#4
Attesz Senior Member Attesz Join Date: Mar 2009 Location: Munich Posts: 368 Rep Power: 17	I used it by adjusting the RPM's, outlet pressures etc. But as I see, for the flow parameters it is not suitable. It's really a big fail...

June 15, 2010, 06:55		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	What is an RPM?

June 15, 2010, 06:56		#6
Attesz Senior Member Attesz Join Date: Mar 2009 Location: Munich Posts: 368 Rep Power: 17	Sorry, Revolutions Per Minute