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please help me --> FOAM Warning : From function Time::operator++() |
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November 14, 2012, 13:02 |
please help me --> FOAM Warning : From function Time::operator++()
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#1 |
Senior Member
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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 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" . . . |
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November 14, 2012, 13:57 |
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#2 |
Senior Member
Marco A. Turcios
Join Date: Mar 2009
Location: Vancouver, BC, Canada
Posts: 740
Rep Power: 28 |
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. |
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November 14, 2012, 14:09 |
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#3 | |
Senior Member
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Quote:
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?!! |
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November 14, 2012, 14:18 |
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#4 |
Senior Member
Marco A. Turcios
Join Date: Mar 2009
Location: Vancouver, BC, Canada
Posts: 740
Rep Power: 28 |
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. |
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November 14, 2012, 14:18 |
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#5 |
Member
Petr Furmanek
Join Date: Jan 2012
Location: Faenza, Italy
Posts: 66
Rep Power: 14 |
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... |
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November 14, 2012, 14:20 |
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#6 | |
Senior Member
Marco A. Turcios
Join Date: Mar 2009
Location: Vancouver, BC, Canada
Posts: 740
Rep Power: 28 |
Quote:
http://www.cfd-online.com/Forums/ope...-get-help.html |
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November 14, 2012, 14:40 |
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#7 | |||
Senior Member
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Quote:
Quote:
Quote:
I think I made a mistake somewhere in my solver, but I don't know where!!!!! |
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November 14, 2012, 15:18 |
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#8 |
Member
Petr Furmanek
Join Date: Jan 2012
Location: Faenza, Italy
Posts: 66
Rep Power: 14 |
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)... |
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November 16, 2012, 05:35 |
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#9 |
Senior Member
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Dear petr,
I attach the log file |
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November 19, 2012, 06:20 |
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#10 |
Member
Petr Furmanek
Join Date: Jan 2012
Location: Faenza, Italy
Posts: 66
Rep Power: 14 |
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...
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November 19, 2012, 07:12 |
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#11 | |
Senior Member
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Quote:
I will do it. another question: any body knows how can I change the transport and viscosity model? |
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