# pisoFoam Error

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 November 20, 2009, 11:03 pisoFoam Error #1 Member   Join Date: Nov 2009 Location: Munich Posts: 43 Rep Power: 7 Hej all, I recieve this error when I execute pisoFoam: __________________________________________________ ____________________ Calculating averages Time = 0.00142 Courant Number mean: 3.72507e+52 max: 1.36418e+54 DILUPBiCG: Solving for Ux, Initial residual = 0.555198, Final residual = 1.81207e-06, No Iterations 35 DILUPBiCG: Solving for Uy, Initial residual = 0.882337, Final residual = 2.82071e-06, No Iterations 36 DILUPBiCG: Solving for Uz, Initial residual = 0.959453, Final residual = 2.3849e-06, No Iterations 29 DICPCG: Solving for p, Initial residual = 0.685706, Final residual = 0.0341773, No Iterations 70 time step continuity errors : sum local = 2.65701e+50, global = 1.48284e+49, cumulative = 1.38529e+49 DICPCG: Solving for p, Initial residual = 0.684507, Final residual = 9.50829e-07, No Iterations 171 time step continuity errors : sum local = 2.06627e+46, global = -1.52172e+44, cumulative = 1.38528e+49 DILUPBiCG: Solving for k, Initial residual = 0.88271, Final residual = 7.51988e-06, No Iterations 6 bounding k, min: -3.72039e+117 max: 7.6031e+117 average: 2.9493e+116 ExecutionTime = 164.59 s ClockTime = 165 s Calculating averages Time = 0.00143 Courant Number mean: 8.88307e+51 max: 2.84151e+53 DILUPBiCG: Solving for Ux, Initial residual = 0.856534, Final residual = 7.94225e-06, No Iterations 39 DILUPBiCG: Solving for Uy, Initial residual = 0.826641, Final residual = 9.82446e-06, No Iterations 37 DILUPBiCG: Solving for Uz, Initial residual = 0.6356, Final residual = 6.89001e-06, No Iterations 35 DICPCG: Solving for p, Initial residual = 0.702043, Final residual = 0.0343882, No Iterations 78 time step continuity errors : sum local = 6.28092e+51, global = -2.13804e+49, cumulative = -7.5276e+48 DICPCG: Solving for p, Initial residual = 0.778709, Final residual = 8.64955e-07, No Iterations 171 time step continuity errors : sum local = 5.07704e+47, global = -7.17519e+44, cumulative = -7.52832e+48 #0 Foam::error:rintStack(Foam::Ostream&) in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libOpenFOAM.so" #1 Foam::sigFpe::sigFpeHandler(int) in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libOpenFOAM.so" #2 ?? in "/lib/libc.so.6" #3 Foam::PBiCG::solve(Foam::Field&, Foam::Field const&, unsigned char) const in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libOpenFOAM.so" #4 Foam::fvMatrix::solve(Foam::dictionary const&) in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libfiniteVolume.so" #5 Foam::incompressible::LESModels:neEqEddy::correc t(Foam::tmp, Foam::fvPatchField, Foam::volMesh> > const&) in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libincompressibleLESModels.so" #6 Foam::incompressible::LESModel::correct() in "/opt/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libincompressibleLESModels.so" #7 main in "/opt/OpenFOAM/OpenFOAM-1.6/applications/bin/linux64GccDPOpt/pisoFoam" #8 __libc_start_main in "/lib/libc.so.6" #9 _start at /usr/src/packages/BUILD/glibc-2.9/csu/../sysdeps/x86_64/elf/start.S:116 Gleitkomma-Ausnahme __________________________________________________ ____________________ It's running for a while and then it crashes. Could it be, that my Courant Number is much to hight? Or isn't there enough memory? Have I nice weekend, Erik PS: I'll only be back on monday :-)

 November 20, 2009, 15:23 #2 Senior Member     Anton Kidess Join Date: May 2009 Location: Delft, Netherlands Posts: 919 Rep Power: 17 Yes, your simulations are diverging and the Courant number gets way out of hand. As usual, check your boundary and initial conditions, and then your numerical parameters. Time step looks like it's pretty small already, so I'm assuming that's not your problem.

 November 23, 2009, 08:49 #3 Member   Join Date: Nov 2009 Location: Munich Posts: 43 Rep Power: 7 Hi akidess, thx for your help. The courant number depends on the speed, the timestep and the cell size, right? But how can I improve the courant number? I have already tried even smaler time steps and also a smaler inital speed U, but with the same result. What else could I do to make the calculation converging?

November 23, 2009, 19:13
#4
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Alberto Passalacqua
Join Date: Mar 2009
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Quote:
 Originally Posted by sErik Hi akidess, thx for your help. The courant number depends on the speed, the timestep and the cell size, right? But how can I improve the courant number? I have already tried even smaler time steps and also a smaler inital speed U, but with the same result. What else could I do to make the calculation converging?
Info on CFL: http://en.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_condition

About your case, it would be useful to know some more details on the case and the numerical setup (fvSchemes, essentially).

Best,
__________________
Alberto Passalacqua

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Last edited by alberto; November 23, 2009 at 19:14. Reason: Corrected link

November 23, 2009, 20:53
#5
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Anton Kidess
Join Date: May 2009
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Quote:
 Originally Posted by sErik The courant number depends on the speed, the timestep and the cell size, right? But how can I improve the courant number? I have already tried even smaler time steps and also a smaler inital speed U, but with the same result. What else could I do to make the calculation converging?
Changing the initial speed will not do a lot to fix your problem. A Courant number of ~e+52 is unphysical anyways.. As I said, check your boundary conditions and physical parameters, then come back here with more information on the problem (like Alberto said, fvSchemes would be good to look at).

November 24, 2009, 04:33
#6
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Thank you very much, I really appreciate your help!

My case is about a pipe flow with a tube in the middle.

This is my fvSchemes file:
Quote:
 FoamFile { version 2.0; format ascii; class dictionary; location "system"; object fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes { default steadyState; } gradSchemes { default Gauss linear; } divSchemes { default none; div(phi,U) Gauss upwind; div(phi,T) Gauss upwind; div(phi,k) Gauss upwind; div(phi,epsilon) Gauss upwind; div(phi,R) Gauss upwind; div(R) Gauss linear; div((nuEff*dev(grad(U).T()))) Gauss linear; } laplacianSchemes { default none; laplacian(nuEff,U) Gauss linear corrected; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(kappaEff,T) Gauss linear corrected; laplacian(DkEff,k) Gauss linear corrected; laplacian(DepsilonEff,epsilon) Gauss linear corrected; laplacian(DREff,R) Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } fluxRequired { default no; p ; }
I've just copied the file from the tutorial. I'm not so sure about the impact/meaning of every entry.

There are the initial conditions for U:
Quote:
 dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { inlet { type fixedValue; referenceField uniform (0.1 0 0); value uniform (0.1 0 0); } outlet { type inletOutlet; inletValue uniform (0 0 0); value uniform (0 0 0); } frontAndBack { type fixedValue; value uniform (0 0 0); } lowerWall { type fixedValue; value uniform (0 0 0); } upperWall { type fixedValue; value uniform (0 0 0); } Rohrelement_NASTRAN { type fixedValue; value uniform (0 0 0); } }
And this one for p:
Quote:
 inlet { type zeroGradient; } outlet { type fixedValue; value uniform 0; } frontAndBack { type zeroGradient; } lowerWall { type zeroGradient; } upperWall { type zeroGradient; } Rohrelement_NASTRAN { type zeroGradient; } }
And here are the boundary conditions:
Quote:
 6 ( frontAndBack { type wall; nFaces 266; startFace 49933; } inlet { type patch; nFaces 154; startFace 50199; } outlet { type patch; nFaces 367; startFace 50353; } lowerWall { type wall; nFaces 100; startFace 50720; } upperWall { type wall; nFaces 100; startFace 50820; } Rohrelement_NASTRAN { type wall; nFaces 3541; startFace 50920; } )
To be honest, I'm not sure about all the effects of the "type-statements" like, "wall" or "patch" in the boundary conditions or "patch", "inletOutlet" for the initial conditions - or other statements for the cases. Wwhich/how many statements are there acually, with what kind of consequences? Is there a description or something like that, where I can figure out the effects on the solution?

Sorry for the long post.

Last edited by sErik; November 24, 2009 at 06:07.

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