# bouyantBoussinesqSimpleFoam continuity error

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August 6, 2012, 05:48
bouyantBoussinesqSimpleFoam continuity error
#1
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Mojtaba Amiraslanpour
Join Date: Jun 2011
Location: Zanjan, Iran
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Quote:
 SIMPLE: convergence criteria field p_rgh tolerance 0.01 field U tolerance 0.0001 field T tolerance 0.01 field "(k|epsilon|omega)" tolerance 0.001 Starting time loop Time = 1 DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.0169481, No Iterations 1 DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 0.0186144, No Iterations 1 DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 0.0176119, No Iterations 1 DILUPBiCG: Solving for T, Initial residual = 1, Final residual = 0.0291332, No Iterations 1 --> FOAM FATAL ERROR: Continuity error cannot be removed by adjusting the outflow. Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow. Total flux : 2.05531 Specified mass inflow : 0.529467 Specified mass outflow : 0 Adjustable mass outflow : 1.82776e-17 From function adjustPhi(surfaceScalarField& phi, const volVectorField& U,const volScalarField& p in file cfdTools/general/adjustPhi/adjustPhi.C at line 116. FOAM exiting
p
Quote:
 dimensions [0 2 -2 0 0 0 0]; internalField uniform 0; boundaryField { wall { type zeroGradient; } air-inlet { type zeroGradient; } out_flow { type fixedValue; value uniform 0.9; } }
U
Quote:
 internalField uniform (0 0 0); boundaryField { wall { type fixedValue; value uniform (0 0 0); } air-inlet { type fixedValue; value uniform (0 -1 0); } out_flow { type zeroGradient; } }
What is the problem?
Regards

Last edited by Mojtaba.a; August 6, 2012 at 06:11.

 August 6, 2012, 06:15 #2 Senior Member     Mojtaba Amiraslanpour Join Date: Jun 2011 Location: Zanjan, Iran Posts: 233 Rep Power: 7 I just solved the problem. I hadn't worked with potentialFoam. I know it was a stupid question. But for those who are beginner in openFOAM like me: 1) make a copy of your current case 2) use potentialFoam to run the case. in this step you initialize your values. 3) copy 0/U file into your own case. 4) start solving. best ~

 April 20, 2013, 01:23 #3 Senior Member     Mostafa Mahmoudi Join Date: Jan 2012 Posts: 314 Rep Power: 6 hi everybody, I have the same problem. first, I ran potentialFoam and it says that no continuity error exists. then I changed the solver to buoyantBoussinesqSimpleFoam and ran it. but the following error appeared agian: Code: ```[1] --> FOAM FATAL ERROR: [1] Continuity error cannot be removed by adjusting the outflow. Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow. Total flux : 0.0582779 Specified mass inflow : 1.08721e-09 Specified mass outflow : 0 Adjustable mass outflow : 0 [1] [1] [1] From function adjustPhi(surfaceScalarField& phi, const volVectorField& U,const volScalarField& p [1] in file cfdTools/general/adjustPhi/adjustPhi.C at line 118. [1] FOAM parallel run exiting [1]``` my U bcs: Code: ```dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { fixedWalls { type fixedValue; value uniform (0 0 0); } openW { type zeroGradient; } hot { type fixedValue; value uniform (0 0 0); } fb { type empty; } }``` my p bcs: Code: ```dimensions [0 2 -2 0 0 0 0]; internalField uniform 0; boundaryField { hot { type fixedValue; value uniform 0; } openW { type fixedValue; value uniform 0; } fixedWalls { type fixedValue; value uniform 0; } fb { type empty; } }``` anybody knows what should I do? thanks a lot Mostafa

 April 20, 2013, 01:57 #4 Senior Member     Mostafa Mahmoudi Join Date: Jan 2012 Posts: 314 Rep Power: 6 hi again, it seems my problem was solved!!!! I changed my zeroGradient velocity BC to fixedValue and waited to openFoam solved it in some iterations, then I changed it to zeroGradient again. there is no continuity error I think the reason is when a model is solved by BCs different from the original BCs, actually the results are used as the initialize values for the next run. do I right????

 April 20, 2013, 11:12 #5 Senior Member     Mostafa Mahmoudi Join Date: Jan 2012 Posts: 314 Rep Power: 6 NO, It didn't work. this way fixed my BC as fixedValue. when I ran the potentialFoam the following results appeared: Code: ```Create time Create mesh for time = 0 Reading field p Reading field U Calculating potential flow DICPCG: Solving for p, Initial residual = 0, Final residual = 0, No Iterations 0 DICPCG: Solving for p, Initial residual = 0, Final residual = 0, No Iterations 0 continuity error = 0 Interpolated U error = 0 ExecutionTime = 5.27 s ClockTime = 5 s End``` I think there is a problem, it added the phi but it didn't change my BCs. please help me

April 20, 2013, 12:25
#6
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Mojtaba Amiraslanpour
Join Date: Jun 2011
Location: Zanjan, Iran
Posts: 233
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Quote:
 Originally Posted by adambarfi hi everybody, I have the same problem. first, I ran potentialFoam and it says that no continuity error exists. then I changed the solver to buoyantBoussinesqSimpleFoam and ran it. but the following error appeared agian: . . . thanks a lot Mostafa
Dear Mostafa,
You do not have any velocity inlet or pressure inlet in order to make your case work.
after defining a velocity inlet, I prefer to use zeroGradient BC for walls and inflow, and a fixed Value 0 BC for outflow in pressure dictionary.
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 April 20, 2013, 12:56 #7 Senior Member     Mostafa Mahmoudi Join Date: Jan 2012 Posts: 314 Rep Power: 6 thank you, Mojtaba I have solved this case before, with this difference that the recent geometry is longer than later geometry. I increased grid number but the error was appeared, but when I decrease it, it worked. already I'm running it. I hope it return correct results. but I don't understand why this error appears????? thanks again. Mostafa

April 20, 2013, 13:01
#8
Senior Member

Mojtaba Amiraslanpour
Join Date: Jun 2011
Location: Zanjan, Iran
Posts: 233
Rep Power: 7
Quote:
 Originally Posted by adambarfi with this difference that the recent geometry is longer than later geometry
What do you mean by this?
You mean by decreasing number of grids you are able to run the case, but increasing it, causes the error?
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If you can't explain it simply, you don't understand it well enough. "Richard Feynman"

 April 20, 2013, 14:59 #9 Senior Member     Mostafa Mahmoudi Join Date: Jan 2012 Posts: 314 Rep Power: 6 yes, I think when I increase the grids the cumulative continuity error increases, while the grids are decreased this error decrease also.

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