CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

fluent divergence for no reason

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   March 22, 2016, 09:11
Angry fluent divergence for no reason
  #1
Member
 
Join Date: Mar 2016
Posts: 73
Rep Power: 10
sufjanst is on a distinguished road
hello everyone,

i am working on a cfd simulation of a combustion chamber.
The mesh passed the Mesh Check in Fluent and Icem and the quality is good.
I use a Delaunay Mesh and profiles as Inlet Boundaries.
The Case initialiazed and works pretty good. The residuals seem to converge. But I have a big problem. It happens sometimes when I save my case and data that fluent diverges for no reason.

For example:
I saved a case and data file at iteration 500 and one at iteration 1000.
After Saving the Case and Data files of iteration files 1000 the solver does not work anymore and says:

# Divergence detected in AMG solver: x-momentum -> Increasing relaxation sweeps!
# You may try the enhanced divergence recovery with (rpsetvar 'amg/protective-enhanced? #t)

absolute pressure limited to 5.000000e+10 in 249 cells on zone 72

turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 12954 cells

Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: x-momentum
Divergence detected in AMG solver: y-momentum
Divergence detected in AMG solver: z-momentum
Divergence detected in AMG solver: pressure correction
Divergence detected in AMG solver: species-0
Divergence detected in AMG solver: species-1
Divergence detected in AMG solver: temperature
Error at host: floating point exception

Error at Node 0: floating point exception

Error at Node 1: floating point exception

Error at Node 2: floating point exception

Error at Node 3: floating point exception

Error at Node 4: floating point exception

Error at Node 5: floating point exception

Error at Node 6: floating point exception

Error at Node 7: floating point exception

Error at Node 8: floating point exception

Error at Node 9: floating point exception

Error at Node 10: floating point exception

Error at Node 11: floating point exception

Error: floating point exception
Error Object: #f


The weird thing is, that the case and data files of iteration 500 do not work as well! It seems like fluent does not want to work anymore and I have to start my calculation from the beginning without saving any case and data files.

Does anyone have a solution for that problem?

I use Fluent 16 in parallel mode with 12 cores and double precision.

Thank you very much

sufjanst
sufjanst is offline   Reply With Quote

Old   March 23, 2016, 09:06
Default
  #2
New Member
 
Join Date: Feb 2016
Posts: 8
Rep Power: 10
PeterPete is on a distinguished road
hello sufjanst,

i have/had a similar problem and was not able to find a solution. Does this happen with all your calculations or just one? Every time this happened to me i had to reset the setup in order to get it to work again.

cheers
peterpete
PeterPete is offline   Reply With Quote

Old   March 23, 2016, 16:08
Default
  #3
Senior Member
 
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,739
Rep Power: 66
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
I've also had a similar issue where it starts doing all sorts of stupid things after you save a file but will run forever if you do not save. Maybe this is the same as your problem.

I was only able to solve it by completely starting over a fresh new simulation (importing a new mesh, re-doing all my settings, and just everything). I tried using a settings file to import the old settings onto a new mesh and that also did not work. Re-initializing, and patching also did not fix anything. It seems like there is a way for the settings to get corrupted and cause the simulation to crash that is not easy to fix.

The only real way to avoid it is to save backup .cas files in case this happens (which I never do).
LuckyTran is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fluent running GPGPU throws up divergence error but not in parallel without GPGPU rsdsaurav FLUENT 0 December 16, 2014 02:57
problem in using parallel process in fluent 14 aydinkabir88 FLUENT 1 July 10, 2013 02:00
Fluent jobs through pbs ibnkureshi FLUENT 5 June 9, 2011 13:43
Fluent strange behaviour (occasional divergence) muketa FLUENT 0 March 18, 2010 04:55
Reason of divergence ? Brayton Main CFD Forum 3 December 2, 2000 22:34


All times are GMT -4. The time now is 07:38.