CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

please help me --> FOAM Warning : From function Time::operator++()

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   November 14, 2012, 13:02
Default please help me --> FOAM Warning : From function Time::operator++()
  #1
Senior Member
 
adambarfi's Avatar
 
Mostafa Mahmoudi
Join Date: Jan 2012
Posts: 322
Rep Power: 15
adambarfi is on a distinguished road
Send a message via Yahoo to adambarfi Send a message via Skype™ to adambarfi
hi every body

any body knows what is the meaning of this warning:

Code:
Courant Number mean: 6.18417 max: 57.2403
deltaT = 4.41444e-94
--> FOAM Warning : 
    From function Time::operator++()
    in file db/Time/Time.C at line 982
    Increased the timePrecision from 44 to 45 to distinguish between timeNames at time 0.000971272
Time = 0.000971271576785370013146225787181720079388469458
when this warning appeared, after some iteration the following errors appear:

Code:
#0  Foam::error::printStack(Foam::Ostream&) in "/home/mostafa/OpenFOAM/OpenFOAM-2.1.0/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
#1  Foam::sigFpe::sigHandler(int) in "/home/mostafa/OpenFOAM/OpenFOAM-2.1.0/platforms/linuxGccDPOpt/lib/libOpenFOAM.so"
.
.
.
Thank you
adambarfi is offline   Reply With Quote

Old   November 14, 2012, 13:57
Default
  #2
Senior Member
 
mturcios777's Avatar
 
Marco A. Turcios
Join Date: Mar 2009
Location: Vancouver, BC, Canada
Posts: 740
Rep Power: 28
mturcios777 will become famous soon enough
If you read the warning, its telling you that the time precision had to be increased as your timestep has just become really really REALLY small (10^-94!). Your simulation crashes after for reasons likely related to that.

Your courant number is really huge at that point (56!) so you should really check what's going on in your simulation, as these are only symptoms of a deeper underlying problem.
mturcios777 is offline   Reply With Quote

Old   November 14, 2012, 14:09
Default
  #3
Senior Member
 
adambarfi's Avatar
 
Mostafa Mahmoudi
Join Date: Jan 2012
Posts: 322
Rep Power: 15
adambarfi is on a distinguished road
Send a message via Yahoo to adambarfi Send a message via Skype™ to adambarfi
Quote:
Originally Posted by mturcios777 View Post
If you read the warning, its telling you that the time precision had to be increased as your timestep has just become really really REALLY small (10^-94!). Your simulation crashes after for reasons likely related to that.

Your courant number is really huge at that point (56!) so you should really check what's going on in your simulation, as these are only symptoms of a deeper underlying problem.
Thank you Marco,

I know that the time precision has been really small and my Courant number is huge but I don't understand where is the source of my mistake.

Does it originate from my solver?!!
adambarfi is offline   Reply With Quote

Old   November 14, 2012, 14:18
Default
  #4
Senior Member
 
mturcios777's Avatar
 
Marco A. Turcios
Join Date: Mar 2009
Location: Vancouver, BC, Canada
Posts: 740
Rep Power: 28
mturcios777 will become famous soon enough
That is the source of your problem. Unless you have some amazing numerical schemes and/or implicit methods at work, there is no way that a Courant number that big (or time-step that small) will remain stable for long:

http://en.wikipedia.org/wiki/Implicit_method
http://en.wikipedia.org/wiki/Courant...Lewy_condition

I would recommend looking at the output from your simulation at that point. I can almost guarantee something unphysical is happening.
mturcios777 is offline   Reply With Quote

Old   November 14, 2012, 14:18
Default
  #5
Member
 
Petr Furmanek
Join Date: Jan 2012
Location: Faenza, Italy
Posts: 66
Rep Power: 14
petr.f. is on a distinguished road
At first post some more detailed info (which solver do you use, what are the basic solver settings, characteristics of the solved case.. otherwise we might be as well guessing from crystal ball). It may be caused by a lot of things, e.g.
- does it happen at the beging of your simulation? If yes your initial timestep might be too big...
- what Courant number do you set in controlDict?
- boundary conditions...
petr.f. is offline   Reply With Quote

Old   November 14, 2012, 14:20
Default
  #6
Senior Member
 
mturcios777's Avatar
 
Marco A. Turcios
Join Date: Mar 2009
Location: Vancouver, BC, Canada
Posts: 740
Rep Power: 28
mturcios777 will become famous soon enough
Quote:
Originally Posted by petr.f. View Post
At first post some more detailed info (which solver do you use, what are the basic solver settings, characteristics of the solved case.. otherwise we might be as well guessing from crystal ball). It may be caused by a lot of things, e.g.
- does it happen at the beging of your simulation? If yes your initial timestep might be too big...
- what Courant number do you set in controlDict?
- boundary conditions...
This is also super important. Here are some guidelines to have a better change of having your question answered:

http://www.cfd-online.com/Forums/ope...-get-help.html
mturcios777 is offline   Reply With Quote

Old   November 14, 2012, 14:40
Default
  #7
Senior Member
 
adambarfi's Avatar
 
Mostafa Mahmoudi
Join Date: Jan 2012
Posts: 322
Rep Power: 15
adambarfi is on a distinguished road
Send a message via Yahoo to adambarfi Send a message via Skype™ to adambarfi
Quote:
Originally Posted by petr.f. View Post
At first post some more detailed info (which solver do you use, what are the basic solver settings, characteristics of the solved case.. otherwise we might be as well guessing from crystal ball). It may be caused by a lot of things, e.g.
- does it happen at the beging of your simulation? If yes your initial timestep might be too big...
- what Courant number do you set in controlDict?
- boundary conditions...
I'm using a modified viscoelasticFluidFoam that I made it. a solver that can solve natural convection in a viscoelastic fluid.

Quote:
- does it happen at the beging of your simulation? If yes your initial timestep might be too big...
No, it happen at 7.38s.

Quote:
- what Courant number do you set in controlDict?
my maxCo is 0.3

I think I made a mistake somewhere in my solver, but I don't know where!!!!!
adambarfi is offline   Reply With Quote

Old   November 14, 2012, 15:18
Default
  #8
Member
 
Petr Furmanek
Join Date: Jan 2012
Location: Faenza, Italy
Posts: 66
Rep Power: 14
petr.f. is on a distinguished road
Well, if you made a mistake in your solver, much more information would be needed (perhaps the whole code?).

But, if I were you, I would observe, where the time step begins to decrease significantly (in order of magnitude), set this moment as an end of the simulation and researched behaviour of all the variables (p, U, T, K, epsilon or omega respectively)...
petr.f. is offline   Reply With Quote

Old   November 16, 2012, 05:35
Default
  #9
Senior Member
 
adambarfi's Avatar
 
Mostafa Mahmoudi
Join Date: Jan 2012
Posts: 322
Rep Power: 15
adambarfi is on a distinguished road
Send a message via Yahoo to adambarfi Send a message via Skype™ to adambarfi
Dear petr,
I attach the log file
Attached Files
File Type: gz log.tar.gz (16.9 KB, 13 views)
adambarfi is offline   Reply With Quote

Old   November 19, 2012, 06:20
Default
  #10
Member
 
Petr Furmanek
Join Date: Jan 2012
Location: Faenza, Italy
Posts: 66
Rep Power: 14
petr.f. is on a distinguished road
Hi Mostafa, I've checked your log and it seems that problems begin to appear after approx. 10 iterations Just to be sure, I would try much smaller time step for the beginning (~ 1e-5, but I don't know any details about your simulation...). But because the divergence begins so quickly, I would guess there might be some error in the code... Anyway, I've seen a post about visco-elastic simulations in openfoam not so long ago - http://www.cfd-online.com/Forums/ope...fluidfoam.html . Try to find some hints there...
petr.f. is offline   Reply With Quote

Old   November 19, 2012, 07:12
Default
  #11
Senior Member
 
adambarfi's Avatar
 
Mostafa Mahmoudi
Join Date: Jan 2012
Posts: 322
Rep Power: 15
adambarfi is on a distinguished road
Send a message via Yahoo to adambarfi Send a message via Skype™ to adambarfi
Quote:
Originally Posted by petr.f. View Post
Hi Mostafa, I've checked your log and it seems that problems begin to appear after approx. 10 iterations Just to be sure, I would try much smaller time step for the beginning (~ 1e-5, but I don't know any details about your simulation...). But because the divergence begins so quickly, I would guess there might be some error in the code... Anyway, I've seen a post about visco-elastic simulations in openfoam not so long ago - http://www.cfd-online.com/Forums/ope...fluidfoam.html . Try to find some hints there...
thank you petr,
I will do it.

another question:
any body knows how can I change the transport and viscosity model?
adambarfi 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
[blockMesh] error message with modeling a cube with a hold at the center hsingtzu OpenFOAM Meshing & Mesh Conversion 2 March 14, 2012 10:56
Could you please help me about the VTKFoam liugx212 OpenFOAM Pre-Processing 5 February 13, 2008 12:31
OpenFoam 14 installation problem gfcoppola OpenFOAM Installation 20 November 2, 2007 14:38
Droplet Evaporation Christian Main CFD Forum 2 February 27, 2007 07:27
Warning 097- AB Siemens 6 November 15, 2004 05:41


All times are GMT -4. The time now is 06:48.