[tian]

Hi Vishal,

can you give me a hint where did you find in the OpenFOAM code T.relax()? Thanks

Bye
Thomas

[lhcamilo]

Hello Thomas

it seems that I got here a little late, the link that you have posted has reached its limit, could you perhaps mail me the file?

thanks

leo

[tian]

Hi,

try this one:

http://rapidshare.com/files/20600643...eFoam.tar.html

Bye
Thomas

[lhcamilo]

thanks

[nandiganavishal]

Hi Tian,

I found such a relaxation technique mentioned by Prof Hrv.. in this forum

I would like to know precisely what each one exactly does in openFOAM... and which is more advantageous...

http://www.cfd-online.com/cgi-bin/Op...ow.cgi?1/10111

Regards

Vishal

[chiven]

Hi, dear Foamers, I also meet the same problem when use simpleFoam to do a simple case. I have try some suggestions in this thread, but fails. any other comments?

Thank you very much. have a nice day.
Chiven


Time = 8
DILUPBiCG: Solving for Ux, Initial residual = 0.0154965, Final residual = 3.56285e-05, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.00436824, Final residual = 3.31732e-05, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.00323331, Final residual = 3.00037e-05, No Iterations 1
GAMG: Solving for p, Initial residual = 0.961782, Final residual = 0.00929941, No Iterations 3
time step continuity errors : sum local = 1.72947e+25, global = 2.12055e+19, cumulative = 2.12055e+19
DILUPBiCG: Solving for epsilon, Initial residual = 0.999551, Final residual = 0.0140238, No Iterations 1
bounding epsilon, min: -1.97709e+32 max: 1.13481e+50 average: 7.81416e+44
DILUPBiCG: Solving for k, Initial residual = 0.999999, Final residual = 0.0180508, No Iterations 1
bounding k, min: -1.56134e+22 max: 6.46051e+40 average: 1.40592e+36
ExecutionTime = 72.457 s ClockTime = 73 s
Time = 9
DILUPBiCG: Solving for Ux, Initial residual = 0.258312, Final residual = 0.00394438, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.322752, Final residual = 0.00548298, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.134508, Final residual = 0.00229101, No Iterations 1
GAMG: Solving for p, Initial residual = 0.999988, Final residual = 0.00957924, No Iterations 10
time step continuity errors : sum local = 6.46819e+24, global = 6.00802e+18, cumulative = 2.72135e+19
DILUPBiCG: Solving for epsilon, Initial residual = 0.0935502, Final residual = 1.68919e-17, No Iterations 1
bounding epsilon, min: -5.66454e+59 max: 1.62366e+65 average: 4.84566e+60
DILUPBiCG: Solving for k, Initial residual = 0.271442, Final residual = 0.00498093, No Iterations 1
bounding k, min: -4.51792e+38 max: 2.46246e+56 average: 5.53053e+51
ExecutionTime = 83.2949 s ClockTime = 84 s
Time = 10
DILUPBiCG: Solving for Ux, Initial residual = 0.213457, Final residual = 0.000426911, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.194438, Final residual = 0.000360278, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.140209, Final residual = 0.000161624, No Iterations 1
GAMG: Solving for p, Initial residual = 0.00575245, Final residual = 5.53957e-05, No Iterations 1
time step continuity errors : sum local = 6.46819e+49, global = 8.29418e+43, cumulative = 8.29418e+43
DILUPBiCG: Solving for epsilon, Initial residual = 2.16312e-18, Final residual = 2.16312e-18, No Iterations 0
bounding epsilon, min: 1.59155e-21 max: 2.55066e+77 average: 2.55902e+72
DILUPBiCG: Solving for k, Initial residual = 0.00017126, Final residual = 6.14596e-07, No Iterations 1
bounding k, min: -9.10313e+53 max: 3.20352e+90 average: 3.67758e+85
ExecutionTime = 90.6045 s ClockTime = 91 s
Time = 11
DILUPBiCG: Solving for Ux, Initial residual = 0.0174846, Final residual = 0.000301742, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.00157757, Final residual = 2.24617e-05, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.0368666, Final residual = 0.000505577, No Iterations 1
#0 _ZN4Foam5error10printStackERNS_7OstreamE-0xb383f0
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libOpenFOAM.so"
#1 _ZN4Foam6sigFpe13sigFpeHandlerEi-0xb01820
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libOpenFOAM.so"
#2 Uninterpreted: [0xa0000000000107e0]
#3 _ZN4Foam17DICPreconditioner15calcReciprocalDERNS_5 FieldIdEERKNS_9lduMatrixE-0xef5f6e
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libOpenFOAM.so"
#4 _ZN4Foam11DICSmootherC1ERKNS_4wordERKNS_9lduMatrix ERKNS_10FieldFieldINS_5FieldEdEESB_RKNS_8UPtrListI KNS_17lduInterfaceFieldEEE-0xefe2d0
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libOpenFOAM.so"
#5 _ZN4Foam9lduMatrix8smoother30addsymMatrixConstruct orToTableINS_11DICSmootherEE3NewERKNS_4wordERKS0_R KNS_10FieldFieldINS_5FieldEdEESE_RKNS_8UPtrListIKN S_17lduInterfaceFieldEEE-0xeb2c00
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libOpenFOAM.so"
#6 _ZN4Foam9lduMatrix8smoother3NewERKNS_4wordERKS0_RK NS_10FieldFieldINS_5FieldEdEESB_RKNS_8UPtrListIKNS _17lduInterfaceFieldEEERNS_7IstreamE-0xf1a020
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libOpenFOAM.so"
#7 _ZNK4Foam10GAMGSolver10initVcycleERNS_7PtrListINS_ 5FieldIdEEEES5_RNS1_INS_9lduMatrix8smootherEEE-0xedc9e0
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libOpenFOAM.so"
#8 _ZNK4Foam10GAMGSolver5solveERNS_5FieldIdEERKS2_h-0xed4f70
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libOpenFOAM.so"
#9 _ZN4Foam8fvMatrixIdE5solveERNS_7IstreamE-0x1f46d20
in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/lib/linuxIA64GccDPOpt/libfiniteVolume.so"
#10 main in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/applications/bin/linuxIA64GccDPOpt/simpleFoam"
#11 __libc_start_main-0x739090
in "/lib/tls/libc.so.6.1"
#12 _start in "/home/g2/e090012/OpenFOAM/OpenFOAM-1.5/applications/bin/linuxIA64GccDPOpt/simpleFoam"

[kprzysowagmailcom]

Hi chiven,
there is obviously something causing time step continuity errors being sky high.
I recall that I had a similar problem when, by mistake, in boundary definition velocity direction was from outlet to inlet. Of course it should be other way around.
So, I would recommend to check your boundary conditions.
Cheers

[chiven]

Hello, Krzysztof, thanks a lot for your reply. You are right, and now the problems are over.

Best regards,
Chiven

[blacy]

Hey Guys!!

I have the same problemes changing my solvers to GAMG like mayol had.

FOAM FATAL IO ERROR : expected 'true' or 'false', found yes
file: /opt/OpenFOAM/caelinux-1.4.1/run/BLENDE/system/fvSolution:::scaleCorrection at line 41.
From function operator>>(Istream&, bool&)
in file primitives/bool/boolIO.C at line 72.
FOAM exiting

I just started working with OpenFoam and still be playing arround a bit. Here is my checkMesh log:

Create polyMesh for time = constant
Time = constant

Mesh stats
points: 27304
edges: 172646
faces: 283432
internal faces: 268924
cells: 138089
boundary patches: 3
point zones: 0
face zones: 0
cell zones: 0

Number of cells of each type:
hexahedra: 0
prisms: 0
wedges: 0
pyramids: 0
tet wedges: 0
tetrahedra: 138089
polyhedra: 0

Checking topology...
Boundary definition OK.
Point usage OK.
Upper triangular ordering OK.
Topological cell zip-up check OK.
Face vertices OK.
Face-face connectivity OK.
Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces ...
Patch Faces Points Surface
In 122 77 ok (not multiply connected)
Out 172 102 ok (not multiply connected)
Walls 14214 7137 ok (not multiply connected)

Checking geometry...
Domain bounding box: (-0.6 0 -0.6) (0.6 5 0.6)
Boundary openness (4.08264e-17 2.77916e-17 3.03938e-17) OK.
Max cell openness = 1.48446e-16 OK.
Max aspect ratio = 4.30296 OK.
Minumum face area = 1.32319e-05. Maximum face area = 0.028895. Face area magnitudes OK.
Min volume = 2.50715e-08. Max volume = 0.00159632. Total volume = 5.60409. Cell volumes OK.
Mesh non-orthogonality Max: 51.4236 average: 15.1122
Non-orthogonality check OK.
Face pyramids OK.
Max skewness = 0.791886 OK.
Min/max edge length = 0.00478093 0.295993 OK.
All angles in faces OK.
All face flatness OK.

Mesh OK.

To me, it seems that the mesh-scale is fine.

Any idea what causes the problems? Thanks for Help!

[gwierink]

Hi Michael,

FOAM FATAL IO ERROR : expected 'true' or 'false', found yes
file: /opt/OpenFOAM/caelinux-1.4.1/run/BLENDE/system/fvSolution:::scaleCorrection at line 41.

Have you had a look at system/fvSolution at line 41 and does it read there "yes" for "scaleCorrection"? Put "true" there instead of "yes" and see what happens.

[blacy]

Hi Gijs,

sorry for the late reply. Have been away for the weekend...

I tried to Put "true" there but the same errors occure. It is the same error for U,p,k and epsilon....

No idea what to do

[georgepehli]

Hello everyone!

I also get the time step continuity error and I am having a hard time solving the problem. My grid is built with gmsh and engrid (extrusion, boundary conditions, OpenFOAM export). It is unstructured, quasi 2D (i.e. sides are BL type = empty) and represents a multi element airfoil.

the grid works perfectly with simpleFoam and komegaSST until 16° AoA. When I try computations at 25° AoA I get the time step continuity errors. I have tried all the proposals from this thread (e.g. reduction of relaxation factors, high initial epsilon, smaller time step) it still crashes.

I am pretty sure that the problem has to do with the massive separation due to high AoA...but I have no idea what to do next.
Any proposals ??

Thanx a lot for you help!

cheers
George

[gwierink]

Hi George,

I'm not an aerodynamicist or anything, but could it be related to the pressure correction method? SimpleFoam uses the SIMPLE algorithm (of course ), which can be quite sensitive to relaxations factors and time step. The PISO algorithm may be less sensitive and contains an extra correction for skewness (do you have a more skewed mesh for higher angle of attack?). Have you tried e.g. pisoFoam (or turbFoam) to test this or do you need to use simpleFoam? Well, don't know if this is of any help, but it just comes to mind.

[georgepehli]

gwierink thanks for the tips

I am actually building my unstructured grids with Gmsh and then extrude them with EnGrid...meaning that the whole process is more or less standard for any airfoil I use. I therefore think that the grid itself is not really problematic. My checkMesh does not give me any errors...and the aspect ratios and expansion ratios are good. It might be the sensitivity of simpleFoam to relaxation and time step....but maybe I try to find some other possible solutions as well before I change the model.

The problem is that I am running the computations via script which goes from one AoA to the other in order to get the airfoil polar at the end. I suspect that is I change solver between AoA then my polar will have sort of..random errors.

Anyway, thanx again for the tips!!

cheers
George

[jonmec]

Originally Posted by tian

Hi Eduarda,

can you compile the original simpleFoam solver without trouble? If yes, you can replace four files from the simpleConvergenceFoam to the original folder (make a copy before):

initConvergenceCheck.H
convergenceCheck.H
pEqn.H
UEqn.H

Bye
Thomas

Hello Thomas,

Could you send to me the following files, please?

initConvergenceCheck.H
convergenceCheck.H
pEqn.H
UEqn.H

Tnahks

[jishnusoni]

Hello All,

I am trying to simulate an impingingjet using the simpleFoam in OF1.6.x. I am trying to follow the threads and tried different things. But I am still getting the same error. I am posting my error and attaching my initial bc. Your support will be greatly appreciated.

Time = 759

DILUPBiCG: Solving for Ux, Initial residual = 0.364807, Final residual = 0.0331038, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.401396, Final residual = 0.0185339, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.439448, Final residual = 0.0046591, No Iterations 1
GAMG: Solving for p, Initial residual = 0.569614, Final residual = 0.00428777, No Iterations 66
time step continuity errors : sum local = 3.14096e+42, global = 3.09629e+39, cumulative = 6.80133e+40
DILUPBiCG: Solving for epsilon, Initial residual = 1.08298e-09, Final residual = 1.08298e-09, No Iterations 0
DILUPBiCG: Solving for k, Initial residual = 0.000115294, Final residual = 2.84805e-06, No Iterations 2
ExecutionTime = 47327.3 s ClockTime = 48069 s

Time = 760

DILUPBiCG: Solving for Ux, Initial residual = 0.506818, Final residual = 0.00973123, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 0.603294, Final residual = 0.0122224, No Iterations 2
DILUPBiCG: Solving for Uz, Initial residual = 0.280386, Final residual = 0.00518198, No Iterations 2
GAMG: Solving for p, Initial residual = 0.0695246, Final residual = 0.000686704, No Iterations 30
time step continuity errors : sum local = 1.41992e+43, global = 4.71133e+41, cumulative = 5.39147e+41
DILUPBiCG: Solving for epsilon, Initial residual = 3.87187e-11, Final residual = 3.87187e-11, No Iterations 0
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 0.0894909, No Iterations 1
bounding k, min: -7.27376e+51 max: 5.05817e+89 average: 5.17561e+84
ExecutionTime = 47386.5 s ClockTime = 48159 s

Time = 761

DILUPBiCG: Solving for Ux, Initial residual = 0.417362, Final residual = 0.0145424, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.51114, Final residual = 0.0224704, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.376437, Final residual = 0.0288099, No Iterations 1
GAMG: Solving for p, Initial residual = 0.629327, Final residual = 0.00528483, No Iterations 8
time step continuity errors : sum local = 1.11456e+78, global = 4.87405e+75, cumulative = 4.87405e+75
DILUPBiCG: Solving for epsilon, Initial residual = 4.23728e-09, Final residual = 4.23728e-09, No Iterations 0
#0 Foam::error:rintStack(Foam::Ostream&) in "/home/jish/OpenFOAM/OpenFOAM-1.6.x/lib/linux64GccDPOpt/libOpenFOAM.so"
#1 Foam::sigFpe::sigFpeHandler(int) in "/home/jish/OpenFOAM/OpenFOAM-1.6.x/lib/linux64GccDPOpt/libOpenFOAM.so"
#2 ?? in "/lib/libc.so.6"
#3 Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/home/jish/OpenFOAM/OpenFOAM-1.6.x/lib/linux64GccDPOpt/libOpenFOAM.so"
#4 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/jish/OpenFOAM/OpenFOAM-1.6.x/lib/linux64GccDPOpt/libfiniteVolume.so"
#5 Foam::lduMatrix::solverPerformance Foam::solve<double>(Foam::tmp<Foam::fvMatrix<doubl e> > const&) in "/home/jish/OpenFOAM/OpenFOAM-1.6.x/lib/linux64GccDPOpt/libincompressibleRASModels.so"
#6 Foam::incompressible::RASModels::kEpsilon::correct () in "/home/jish/OpenFOAM/OpenFOAM-1.6.x/lib/linux64GccDPOpt/libincompressibleRASModels.so"
#7 main in "/home/jish/OpenFOAM/OpenFOAM-1.6.x/applications/bin/linux64GccDPOpt/simpleFoam"
#8 __libc_start_main in "/lib/libc.so.6"
#9 _start at /build/buildd/eglibc-2.10.1/csu/../sysdeps/x86_64/elf/start.S:116
Floating point exception




thanks

regards
jish

[swaps]

Originally Posted by paulo

Hello Mayol and all,

As simpleFoam will look for the steady state solution, I usually apply a big epsilon starting value in the domain (about 100 times the value of a boundary) and wait for the solver to "change" it. You'll see that the values go down quickly, and the solution almost always gets stabilized.

Give a feedback if it worked for you.

Any comments are appreciated.

Regards,

Paulo Rocha.

I am trying to simulate MRF case. with OF 2.4.0. So i had considered "mixervessel2D" as a base case and modified the boundary conditions for my case. Mesh file for the geometry is available from https://openfoamwiki.net/index.php/MRFSimpleFoam. I had specified the same BCs as provided in above link and tried to simulate the case. But i am getting Time Step Cont. Error. I had tried what you suggested for epsilon but still getting the same error. I had also tried with epsilon values 1000 times greater than its value at boundary. Also if we "OFF" the turbulence model than code run for all the iterations(num of iteratoin = 1500 in my case) that we specify in the controlDict, still Time Step Cont. Error is too high. when turbulence model is "ON" the code gives Time Step Continuity Error after few iterations only. Why it is so?

[ab2484]

Originally Posted by paulo

Hello Mayol and all,

As simpleFoam will look for the steady state solution, I usually apply a big epsilon starting value in the domain (about 100 times the value of a boundary) and wait for the solver to "change" it. You'll see that the values go down quickly, and the solution almost always gets stabilized.

Give a feedback if it worked for you.

Any comments are appreciated.

Regards,

Paulo Rocha.

Hi Paulo,

I found that this solution helped keep the run stable. Thanks!

[crizpi21]

Hi,

I am running an incompressible case of a flow past a cube with rounded edges in order to calculate the drag coefficient (I use komegasstsas as turbulence model). So far, I have used pimpleFoam but the simulations take too long so I want to use a steady-state solver such as simpleFoam to speed up the process.

However, my simulation is not converging. I am getting incredibly high values for the forces and also getting high time step continuity errors before the simulation stops:
time step continuity errors : sum local = 9.01619e+17, global = 7.91561e+15, cumulative = 8.6525e+15

I have tried with different relaxationFactors for p (starting with 0.3 and down to 0.05) but nothing changes. I have checked my mesh and everything is OK. Does anyone know what I may be doing wrong?

This are my fvSolution file

solvers
{
    p
    {
        solver          GAMG;
        tolerance       1e-06;
        relTol          0.1;
        smoother        GaussSeidel;
    }

    pFinal
    {
        $p;
        tolerance       1e-06;
        relTol          0;
    }

    "(U|k|omega)"
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        tolerance       1e-05;
        relTol          0;
    }
    "(U|k|omega)Final"
    {
      $U;
      relTol          0;
    }

}

SIMPLE //PIMPLE*
{
    nCorrectors     4;
    nNonOrthogonalCorrectors 1;
    pRefCell        0;
    pRefValue       0;
}

relaxationFactors
{
  p     0.05;
  U     0.7;
  k     0.7;
  omega 0.7;

}

and my fvSchemes file

ddtSchemes
{
    default         steadyState; //antes Euler, específico de simpleFoam
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default         none;
    div(phi,U)      bounded Gauss upwind;
    div(phi,k)      bounded Gauss upwind;
    div(phi,omega)  bounded Gauss upwind; //añadido en base a div(phi,k) y a tutorial de internet FLow_past_a_cylinder
    div(phi,nuTilda) bounded Gauss upwind;
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

wallDist
{
    method meshWave;
}

Any help or suggestion would be welcome. Please let me know if you need any other files.

Thanks in advance,

Cristina

[Cagatayemre]

Hello Cristina. Can I see your mesh quality. Do you have 0 area faces. You can set minimum face area to some reasonable value. You should get rid of skew and nonorthogonal faces. You can play with included angle setting in surfaceFeatureExtractDict. Resolve feature angle in SnappyHexMeshDict works with includedAngle setting in terms of curvature (edge) refinement. You can use cell limited schemes. You can use bounded Gauss upwind schemes. you can increase snapping iterations. How is your stl geometry quality ?