relaxation factor for coupling in FSI simulation

taedeneo · September 10, 2009, 08:40

Hi All,
I am currently working on a project in FSI which I need to use non-constant value for under relaxation factors of the coupling. For Example, I want to use relaxation factors of 0.1 for the first few stagger iterations and then change it to 1. I have tried putting in an expression to tell the solver to do what I want above but CFX returns an error saying that only numeric value can be used. Is there anyway to do this? Also, I thought if it cannot be inserted in the CFX-pre(CCL), then maybe it can be done by going into the MMS and overwrite the value at the beginning of each stagger iteration. However, I am trying browsing the data location of the relaxation factor of the coupling but I couldn't find anything since I don't know its solver name and not even sure that the value is stored in MMS of CFX. Any idea would be appreciated!

Cheers
taedeneo

ghorrocks · September 10, 2009, 18:22

The easiest way sounds like stopping the simulation, resetting the URF and restarting. This can all be scripted so it still can run efficiently.

taedeneo · September 11, 2009, 03:09

Hi Ghorrock,
Thanks for your reply. Could you give me some guideline of how to do the scripting?
Cheers

ghorrocks · September 11, 2009, 07:29

The documentation discusses starting the CFX solver from the command line. This gives you all the solver run-time options. Then probably use a CCL file to change the things you wish. Look for the commands "cfx5cmds" and "cfx5solve".

September 10, 2009, 08:40	relaxation factor for coupling in FSI simulation	#1
taedeneo New Member Join Date: Apr 2009 Posts: 13 Rep Power: 16	Hi All, I am currently working on a project in FSI which I need to use non-constant value for under relaxation factors of the coupling. For Example, I want to use relaxation factors of 0.1 for the first few stagger iterations and then change it to 1. I have tried putting in an expression to tell the solver to do what I want above but CFX returns an error saying that only numeric value can be used. Is there anyway to do this? Also, I thought if it cannot be inserted in the CFX-pre(CCL), then maybe it can be done by going into the MMS and overwrite the value at the beginning of each stagger iteration. However, I am trying browsing the data location of the relaxation factor of the coupling but I couldn't find anything since I don't know its solver name and not even sure that the value is stored in MMS of CFX. Any idea would be appreciated! Cheers taedeneo

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September 10, 2009, 18:22		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	The easiest way sounds like stopping the simulation, resetting the URF and restarting. This can all be scripted so it still can run efficiently.

September 11, 2009, 03:09		#3
taedeneo New Member Join Date: Apr 2009 Posts: 13 Rep Power: 16	Hi Ghorrock, Thanks for your reply. Could you give me some guideline of how to do the scripting? Cheers

September 11, 2009, 07:29		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,697 Rep Power: 143	The documentation discusses starting the CFX solver from the command line. This gives you all the solver run-time options. Then probably use a CCL file to change the things you wish. Look for the commands "cfx5cmds" and "cfx5solve".