relaxation factor for coupling in FSI simulation

taedeneo · September 10, 2009, 09:40

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, 19:22

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, 04:09

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

ghorrocks · September 11, 2009, 08:29

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, 09:40	relaxation factor for coupling in FSI simulation	#1
taedeneo New Member Join Date: Apr 2009 Posts: 13 Rep Power: 17	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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
BCs in an FSI simulation of a flexble pipe	vivekcfd	OpenFOAM	10	January 8, 2010 05:14
FSI simulation is DEAD SLOW	Lance	CFX	6	September 12, 2009 10:00
FSI Simulation unsing ANSYS Multifield	k_buz	CFX	2	April 6, 2009 18:40
FSI TWO-WAY SIMULATION	Smagmon	CFX	1	March 6, 2009 14:24
Restart of FSI simulation	V. Kumar	CFX	3	July 20, 2006 14:23

September 10, 2009, 19:22		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	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, 04:09		#3
taedeneo New Member Join Date: Apr 2009 Posts: 13 Rep Power: 17	Hi Ghorrock, Thanks for your reply. Could you give me some guideline of how to do the scripting? Cheers

September 11, 2009, 08:29		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	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".