"divergence detected in AMG solver: omega"

Sidewinder · June 14, 2010, 05:13

I am having a problem with my simulation for university. I keep getting this error:

divergence detected in AMG solver: omega

I have tried changing the relaxation factors for the turbulence and the specific dissipation rate. But to no success. the gas is compressbile and I have specified a mass flow inlet and a pressure outlet. I am using the k-omega model for this simulation.
But i cant seem to get away from this error. I am thinking to turn off the energy equation.

Does enybody have some help or hints for me? I would greatly appreciate it.

Thanks!

arunintn · March 6, 2012, 16:41

Hi,
I have the same error. I'm doing analysis on T106A turbine blade simuli. I think you have the solution for that. If it so please let me know what is the solution.
Thank you

arjun3020 · March 7, 2012, 00:11

in URF go to advance settings, and change the cycle to F.

arunintn · March 7, 2012, 03:45

Quote:

Originally Posted by arjun3020

in URF go to advance settings, and change the cycle to F.

thanks for replying.. I have another problem divergence detected in AMG solver: Temperature". I like to know this troubleshooting method. I quit new to CFD.

arjun3020 · March 8, 2012, 23:57

Reduce URf for temperature. and check all Boundary conditions. hope it will help.

arunintn · March 9, 2012, 05:50

I solved the problem.. I made some mistake in boundary.. thank you for you help

arjun3020 · March 10, 2012, 00:15

Ok... these are common errors with fluent, to resolve it 1. check URF.
2. Check BC
3. Change advance cycle to F.

wujinlao5 · March 10, 2012, 05:33

hi ,man
there are 5 to 6 dropdown list in urf advance setting ,x-momnetum\y-momnetum...
when you say " change cycle to F" for this problem, which one do you refer to?
dont tell me it is the omega relevant one.

Quote:

Originally Posted by arjun3020

Ok... these are common errors with fluent, to resolve it 1. check URF.
2. Check BC
3. Change advance cycle to F.

faudiS8 · June 9, 2012, 10:02

I've the same problem
what do you mean by advanced cycle while there is not such a thing in Under relaxation factors section!?
Thanks for clarification

arunintn · June 10, 2012, 02:07

Quote:

Originally Posted by faudiS8

I've the same problem
what do you mean by advanced cycle while there is not such a thing in Under relaxation factors section!?
Thanks for clarification

you need to find this option in advanced settings and you'll get a pop-up window.

My case i don't need to switch on energy equation because i'm not finding temperature. My problem converged after i switched off the energy equation. If possible you can tell me what you are doing?

faudiS8 · June 10, 2012, 03:35

Quote:

Originally Posted by arunintn

you need to find this option in advanced settings and you'll get a pop-up window.

My case i don't need to switch on energy equation because i'm not finding temperature. My problem converged after i switched off the energy equation. If possible you can tell me what you are doing?

hi
I'm modeling combustion and when I change the density calculation method to ideal gas this problem happens. How do I cope with? I let incompressible ideal gas method to iterate enough (about 300) and then it's residuals are little enough. So by changing to ideal gas method, it converges.
but it's still a question for me!
where is the advanced setting option in the window you say!?
Do we talk about the following link's window!?(Under relaxation window)
http://hpce.iitm.ac.in/website/Manua...ution_Controls

thanks alot

arunintn · June 10, 2012, 04:02

I have attached a picture file. I think you can find now. Pleas let me know your fluent version. I'm using Fluent 13.

I like to say URF is is an advanced settings. Try to be careful when you work in that.

faudiS8 · June 10, 2012, 07:57

goood!

I found out why! I use Fluent 6.3.26! the last dedicate fluent version

)
Ansys in 13 version change it too much! Also I think This option- means F cycle- is available for multigrid, isn't it?
by the way....thank you for your attachment!

faudiS8 · June 27, 2012, 04:31

hi every body
the problem i found! for changing the solver scheme to F-cycle in fluent 6.3.26 you may go to this path:
Solve>Control>Multigrids...>
here a window will be opened and you may change to F-cycle.

Note: I would appreciate any one who help me to find out the exact mechanism change by this method. In the other words I want to know how this mechanism works, why it diverges, and what does this scheme change do. I heard of a CFD book by someone like choe(?!?) on this. but i'm not sure.

June 14, 2010, 05:13	"divergence detected in AMG solver: omega"	#1
Sidewinder New Member Jon Join Date: Mar 2010 Posts: 10 Rep Power: 16	I am having a problem with my simulation for university. I keep getting this error: divergence detected in AMG solver: omega I have tried changing the relaxation factors for the turbulence and the specific dissipation rate. But to no success. the gas is compressbile and I have specified a mass flow inlet and a pressure outlet. I am using the k-omega model for this simulation. But i cant seem to get away from this error. I am thinking to turn off the energy equation. Does enybody have some help or hints for me? I would greatly appreciate it. Thanks! Last edited by Sidewinder; June 17, 2010 at 05:01.

June 10, 2012, 07:57		#13
faudiS8 New Member Fariborz Soroush Join Date: Oct 2009 Location: Tehran, Iran Posts: 14 Rep Power: 16	goood! I found out why! I use Fluent 6.3.26! the last dedicate fluent version) Ansys in 13 version change it too much! Also I think This option- means F cycle- is available for multigrid, isn't it? by the way....thank you for your attachment!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Divergence detected in AMG solver: pressure correction	jimmer	FLUENT	2	August 7, 2010 06:47
AMG solver _divergence detected	Shamoon	FLUENT	6	March 11, 2009 07:59
Error: divergence detected in AMG solver: temperat	Rubén	FLUENT	3	December 11, 2007 11:48
user subroutine error	CFDUSER	CFX	2	December 9, 2006 06:31
user defined function	cfduser	CFX	0	April 29, 2006 10:58

March 6, 2012, 16:41		#2
arunintn Member Arun Join Date: Mar 2012 Location: Vellore,TN,India Posts: 43 Rep Power: 14	Hi, I have the same error. I'm doing analysis on T106A turbine blade simuli. I think you have the solution for that. If it so please let me know what is the solution. Thank you

March 7, 2012, 00:11		#3
arjun3020 Member arjun Join Date: Oct 2011 Location: Tokyo, JAPAN Posts: 66 Rep Power: 14	in URF go to advance settings, and change the cycle to F.

March 8, 2012, 23:57		#5
arjun3020 Member arjun Join Date: Oct 2011 Location: Tokyo, JAPAN Posts: 66 Rep Power: 14	Reduce URf for temperature. and check all Boundary conditions. hope it will help.

March 9, 2012, 05:50		#6
arunintn Member Arun Join Date: Mar 2012 Location: Vellore,TN,India Posts: 43 Rep Power: 14	I solved the problem.. I made some mistake in boundary.. thank you for you help

March 10, 2012, 00:15		#7
arjun3020 Member arjun Join Date: Oct 2011 Location: Tokyo, JAPAN Posts: 66 Rep Power: 14	Ok... these are common errors with fluent, to resolve it 1. check URF. 2. Check BC 3. Change advance cycle to F.

June 9, 2012, 10:02		#9
faudiS8 New Member Fariborz Soroush Join Date: Oct 2009 Location: Tehran, Iran Posts: 14 Rep Power: 16	I've the same problem what do you mean by advanced cycle while there is not such a thing in Under relaxation factors section!? Thanks for clarification

June 27, 2012, 04:31		#14
faudiS8 New Member Fariborz Soroush Join Date: Oct 2009 Location: Tehran, Iran Posts: 14 Rep Power: 16	hi every body the problem i found! for changing the solver scheme to F-cycle in fluent 6.3.26 you may go to this path: Solve>Control>Multigrids...> here a window will be opened and you may change to F-cycle. Note: I would appreciate any one who help me to find out the exact mechanism change by this method. In the other words I want to know how this mechanism works, why it diverges, and what does this scheme change do. I heard of a CFD book by someone like choe(?!?) on this. but i'm not sure.