update the pyhsicaltimestep during a steady-state-run

mvoss · April 3, 2009, 08:18

hey,

i am doing a mesh study and i am facing really slow convergence within the highest/finest mesh . So i could increase my timestep.
According to the other runs on the coarser meshes i know that i can increase my phsyical timestep bit by bit.
So i linked the physicaltimestep with an expression,like:

"Timestep*Factor(CITERN)"
to increase it depending on my iterationnumber.

Tried it with the AutoTimeScale--> No problem. Updating the value means updating the factor means new timescale.

But with PhysicalTimeScale the solver doesn't update the value for the timescale, so my function isn't working.

Any idea how i can force the solver to update the value for the physical timescale automatically? Maybe smth. like an ExpertOption.

Best regards,
neewbie

Martijn · April 3, 2009, 08:27

I think this has to be done in Fortran. Probably in a similar way as described in "Junction Box Example 3: Timestep Control" in the help function of CFX-11.

Jasmine · April 6, 2009, 00:09

Em... It confused me.
For steady-state simulation, why does time step need to be defined in CFX?

ghorrocks · April 6, 2009, 01:48

Hi:

neewbie - your CEL is almost right. The variable name is "citern" in lower case. It is case sensitive. Look in the documentation for the exact naming of variables.

Martijn - No need for fortran. CEL should be fine.

Jasmine - CFX uses a timestep to advance the simulation, even in a steady state simulation. Read the documentation on this or do a search on past posts on this issue.

Glenn Horrocks

mvoss · April 6, 2009, 03:08

hi,

thanks for the response.
I used the capital letters only for entering the post... in the expression i wrote "citern".
Btw. the expression did well with the AutoTimeScale but not with the Physical... which is not loose because why should the solver update a value which is ought to be fixed over the run.
Any further ideas?

neewbie

April 3, 2009, 08:18	update the pyhsicaltimestep during a steady-state-run	#1
mvoss Senior Member Matthias Voß Join Date: Mar 2009 Location: Berlin, Germany Posts: 449 Rep Power: 20	hey, i am doing a mesh study and i am facing really slow convergence within the highest/finest mesh . So i could increase my timestep. According to the other runs on the coarser meshes i know that i can increase my phsyical timestep bit by bit. So i linked the physicaltimestep with an expression,like: "Timestep*Factor(CITERN)" to increase it depending on my iterationnumber. Tried it with the AutoTimeScale--> No problem. Updating the value means updating the factor means new timescale. But with PhysicalTimeScale the solver doesn't update the value for the timescale, so my function isn't working. Any idea how i can force the solver to update the value for the physical timescale automatically? Maybe smth. like an ExpertOption. Best regards, neewbie

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April 3, 2009, 08:27		#2
Martijn New Member Martijn Join Date: Mar 2009 Posts: 14 Rep Power: 17	I think this has to be done in Fortran. Probably in a similar way as described in "Junction Box Example 3: Timestep Control" in the help function of CFX-11.

April 6, 2009, 00:09		#3
Jasmine Member ^_^ Join Date: Mar 2009 Posts: 36 Rep Power: 17	Em... It confused me. For steady-state simulation, why does time step need to be defined in CFX?

April 6, 2009, 01:48		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,690 Rep Power: 143	Hi: neewbie - your CEL is almost right. The variable name is "citern" in lower case. It is case sensitive. Look in the documentation for the exact naming of variables. Martijn - No need for fortran. CEL should be fine. Jasmine - CFX uses a timestep to advance the simulation, even in a steady state simulation. Read the documentation on this or do a search on past posts on this issue. Glenn Horrocks

April 6, 2009, 03:08		#5
mvoss Senior Member Matthias Voß Join Date: Mar 2009 Location: Berlin, Germany Posts: 449 Rep Power: 20	hi, thanks for the response. I used the capital letters only for entering the post... in the expression i wrote "citern". Btw. the expression did well with the AutoTimeScale but not with the Physical... which is not loose because why should the solver update a value which is ought to be fixed over the run. Any further ideas? neewbie