CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   pimpleDyMFoam diverging (http://www.cfd-online.com/Forums/openfoam-solving/74432-pimpledymfoam-diverging.html)

gfilip March 31, 2010 12:51

pimpleDyMFoam diverging
 
Hello everyone,

I am using pimpleDyMFoam with a custom dynamicFvMesh to solve for the motion of a 2D circular cylinder with 1DOF (heave) with the standard SA model. I am having issues with the solver diverging after several time steps. The time step keeps decreasing to meet the maxCo criterion, while the actual Co oscillates and eventually blows up, resulting in the solver crashing. Here is a part of the log:

Code:

Courant Number mean: 0.181987 max: 57.4844
deltaT = 3.73109e-10
Time = 0.00065686

Pressure force = (-5.77062e+11 -1.75305e+13 1.484e-05)
Viscous force = (1.06804e+10 -3.28055e+09 4.6907e-05)
Total force = (-5.66381e+11 -1.75338e+13 6.1747e-05)
Pressure force = (-5.77062e+11 -1.75305e+13 1.484e-05)
Viscous force = (1.06804e+10 -3.28055e+09 4.6907e-05)
Total force = (-5.66381e+11 -1.75338e+13 6.1747e-05)
new force= (-5.66381e+11 -1.75338e+13 6.1747e-05)
damping force= (0 111.291 0)
spring force= (0 0.19882 0)
 displace component=                                0.0298225
DILUPBiCG:  Solving for Ux, Initial residual = 0.00118393, Final residual = 6.46833e-07, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.000226988, Final residual = 1.6964e-07, No Iterations 1
DICPCG:  Solving for p, Initial residual = 0.936208, Final residual = 9.29128e-07, No Iterations 303
time step continuity errors : sum local = 2.91692e-12, global = 3.30302e-14, cumulative = 2.10666e-12
DILUPBiCG:  Solving for Ux, Initial residual = 0.0011032, Final residual = 2.14598e-08, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.00026622, Final residual = 5.22804e-09, No Iterations 1
DICPCG:  Solving for p, Initial residual = 0.474501, Final residual = 9.38896e-07, No Iterations 298
time step continuity errors : sum local = 4.10823e-12, global = 4.30266e-14, cumulative = 2.14969e-12
DILUPBiCG:  Solving for nuTilda, Initial residual = 2.76369e-06, Final residual = 2.76369e-06, No Iterations 0
ExecutionTime = 24.02 s  ClockTime = 24 s

Courant Number mean: 0.0012636 max: 0.200559
deltaT = 4.47731e-10
Time = 0.00065686

Pressure force = (3.14683e+13 2.90887e+14 -0.000464347)
Viscous force = (6.73597e+09 -3.07824e+09 4.73848e-06)
Total force = (3.1475e+13 2.90884e+14 -0.000459609)
Pressure force = (3.14683e+13 2.90887e+14 -0.000464347)
Viscous force = (6.73597e+09 -3.07824e+09 4.73848e-06)
Total force = (3.1475e+13 2.90884e+14 -0.000459609)
new force= (3.1475e+13 2.90884e+14 -0.000459609)
damping force= (0 96.883 0)
spring force= (0 0.200467 0)
 displace component=                                0.0309868
DILUPBiCG:  Solving for Ux, Initial residual = 0.016213, Final residual = 8.38248e-08, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 0.0037189, Final residual = 6.18129e-07, No Iterations 1
DICPCG:  Solving for p, Initial residual = 0.614507, Final residual = 8.80742e-07, No Iterations 344
time step continuity errors : sum local = 2.19871e-12, global = 1.48693e-14, cumulative = 2.16456e-12
DILUPBiCG:  Solving for Ux, Initial residual = 0.0376498, Final residual = 4.48819e-09, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 0.00476686, Final residual = 1.9605e-06, No Iterations 1
DICPCG:  Solving for p, Initial residual = 0.494856, Final residual = 9.71665e-07, No Iterations 320
time step continuity errors : sum local = 8.84475e-12, global = 5.15065e-14, cumulative = 2.21606e-12
DILUPBiCG:  Solving for nuTilda, Initial residual = 1.94363e-05, Final residual = 1.35167e-08, No Iterations 1
bounding nuTilda, min: -1.48587e-17 max: 3.92394 average: 0.00253206
ExecutionTime = 26.15 s  ClockTime = 26 s

Courant Number mean: 0.00577774 max: 0.207404
deltaT = 5.37277e-10
Time = 0.000656861

Pressure force = (2.07155e+09 -5.18228e+15 0.0122243)
Viscous force = (2.52242e+09 -1.35877e+11 5.65746e-05)
Total force = (4.59397e+09 -5.18242e+15 0.0122809)
Pressure force = (2.07155e+09 -5.18228e+15 0.0122243)
Viscous force = (2.52242e+09 -1.35877e+11 5.65746e-05)
Total force = (4.59397e+09 -5.18242e+15 0.0122809)
new force= (4.59397e+09 -5.18242e+15 0.0122809)
damping force= (0 383.723 0)
spring force= (0 0.208293 0)
 displace component=                                0.0100557
DILUPBiCG:  Solving for Ux, Initial residual = 0.207082, Final residual = 3.86788e-06, No Iterations 3
DILUPBiCG:  Solving for Uy, Initial residual = 0.139973, Final residual = 2.91468e-06, No Iterations 3
DICPCG:  Solving for p, Initial residual = 0.98152, Final residual = 9.09526e-07, No Iterations 333
time step continuity errors : sum local = 2.52805e-11, global = 4.02247e-14, cumulative = 2.25629e-12
DILUPBiCG:  Solving for Ux, Initial residual = 0.40134, Final residual = 6.16425e-06, No Iterations 4
DILUPBiCG:  Solving for Uy, Initial residual = 0.0181964, Final residual = 2.29782e-06, No Iterations 3
DICPCG:  Solving for p, Initial residual = 0.981988, Final residual = 8.49443e-07, No Iterations 293
time step continuity errors : sum local = 1.21941e-09, global = 2.49295e-12, cumulative = 4.74924e-12
DILUPBiCG:  Solving for nuTilda, Initial residual = 0.000310185, Final residual = 9.04832e-06, No Iterations 1
bounding nuTilda, min: -0.402278 max: 67.8727 average: 0.0384613
ExecutionTime = 28.24 s  ClockTime = 28 s

Courant Number mean: 0.11094 max: 21.5535
#0  Foam::error::printStack(Foam::Ostream&) in "/home/greg/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#1  Foam::sigFpe::sigFpeHandler(int) in "/home/greg/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#2  Uninterpreted:
#3  Foam::Time::adjustDeltaT() in "/home/greg/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#4  Foam::Time::setDeltaT(double) in "/home/greg/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#5  main in "/home/greg/OpenFOAM/OpenFOAM-1.6.x/applications/bin/linuxGccDPOpt/pimpleDyMFoam"
#6  __libc_start_main in "/lib/tls/i686/cmov/libc.so.6"
#7  _start at /build/buildd/eglibc-2.10.1/csu/../sysdeps/i386/elf/start.S:122
Floating point exception

I have experimented with PIMPLE settings, and under-relaxation. My current settings in fvSolution are:

Code:

PIMPLE
{
    nOuterCorrectors 2;
    nCorrectors    1;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue      0;
}


relaxationFactors
{
    U              0.7;
    p              0.2;
    nuTilda        0.7;
}


And my fvSchemes:

Code:

ddtSchemes
{
    default Euler;
}

gradSchemes
{
    default        Gauss linear;
    grad(p)        Gauss linear;
    grad(U)        Gauss linear;
}

divSchemes
{
    default        Gauss QUICK phi;
//    div(phi,U)      Gauss limitedLinear 1;
    div(phi,U)      Gauss upwind;
    div(phi,k)      Gauss limitedLinear 1;
    div(phi,epsilon) Gauss limitedLinear 1;
    div(phi,R)      Gauss limitedLinear 1;
    div(R)          Gauss linear;
    div(phi,nuTilda) Gauss limitedLinear 1;
    div((nuEff*dev(grad(U).T()))) Gauss linear;
}

laplacianSchemes
{
    default        none;
    laplacian(nu,U) Gauss linear corrected;
    laplacian(nuEff,U) Gauss linear corrected;
    laplacian((1|A(U)),p) Gauss linear corrected;
    laplacian(DkEff,k) Gauss linear corrected;
    laplacian(DepsilonEff,epsilon) Gauss linear corrected;
    laplacian(DREff,R) Gauss linear corrected;
    laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;
    laplacian(rAU,pcorr) Gauss linear corrected;
    laplacian(rAU,p) Gauss linear corrected;
}

interpolationSchemes
{
    default        linear;
    interpolate(U)  linear;
}

snGradSchemes
{
    default        corrected;
}

fluxRequired
{
    default        no;
    p;
}


I'd appreciate any hints.


-Greg

TReviol March 28, 2012 16:21

Hi Greg,

try to run "unset FOAM_SIGFPE" in the commandline, before you run your job.

Regards

Thomas

jferrari April 2, 2012 14:24

Greg,

Were you able to get this working? Would you mind posting your dynamic mesh dictionary? I'm interested in seeing it.

Thanks,
Joe

gfilip April 2, 2012 15:20

Hi Thomas and Joe,

I was able to get the case working but it has been a while. Unfortunately I had a different workstation at that time and those case setups have not made the move, so I am unable to share the dynamic mesh dict with you. Sorry!


Greg

ebah6 April 2, 2012 22:51

Hey gfillip,

I understand you no longer have the data, but do you remember a bit of what you did to solve the problem. I am running into similar difficulties where the Courant number keeps increasing until the job crashes.
Here are my few lines of my log file:
--------------------------------

Courant Number mean: 0.0553216 max: 1.49585
deltaT = 1e-05
Time = 7e-05

solidBodyMotionFunctions::rotatingMotion::transfor mation(): Time = 7e-05 transformation: ((0 0 0) (1 (0 0 0.00071295)))
AMI: Creating addressing and weights between 152 source faces and 152 target faces
AMI: Patch source weights min/max/average = 1.00045, 1.00059, 1.00051
AMI: Patch target weights min/max/average = 1.00027, 1.00041, 1.00034
PIMPLE: iteration 1
smoothSolver: Solving for Ux, Initial residual = 0.821499, Final residual = 0.0529954, No Iterations 2
smoothSolver: Solving for Uy, Initial residual = 0.772528, Final residual = 0.0435714, No Iterations 2
smoothSolver: Solving for Uz, Initial residual = 0.889394, Final residual = 0.0573016, No Iterations 3
GAMG: Solving for p, Initial residual = 0.927555, Final residual = 0.00793319, No Iterations 3
time step continuity errors : sum local = 0.00232858, global = 1.09112e-05, cumulative = 4.39653e-05
PIMPLE: iteration 2
smoothSolver: Solving for Ux, Initial residual = 0.624835, Final residual = 0.0579445, No Iterations 8
smoothSolver: Solving for Uy, Initial residual = 0.528869, Final residual = 0.0500303, No Iterations 7
smoothSolver: Solving for Uz, Initial residual = 0.667562, Final residual = 0.0371676, No Iterations 4
GAMG: Solving for p, Initial residual = 0.921425, Final residual = 0.00829498, No Iterations 2
time step continuity errors : sum local = 0.0183302, global = 0.000417751, cumulative = 0.000461716
PIMPLE: iteration 3
DILUPBiCG: Solving for Ux, Initial residual = 0.469402, Final residual = 0.00155559, No Iterations 1001
DILUPBiCG: Solving for Uy, Initial residual = 0.456055, Final residual = 0.00192389, No Iterations 1001
DILUPBiCG: Solving for Uz, Initial residual = 0.657918, Final residual = 7.2394e-07, No Iterations 26
GAMG: Solving for p, Initial residual = 0.940662, Final residual = 9.79822e-07, No Iterations 23
time step continuity errors : sum local = 5.83896e-06, global = -5.30525e-07, cumulative = 0.000461185
DILUPBiCG: Solving for epsilon, Initial residual = 0.989478, Final residual = 10537.6, No Iterations 1001
bounding epsilon, min: -1.28949e+18 max: 9.22403e+17 average: -3.22331e+14
DILUPBiCG: Solving for k, Initial residual = 1.42853e-05, Final residual = 6.87541e-07, No Iterations 30
bounding k, min: -1.84393e+10 max: 2.85172e+12 average: 1.06974e+10
ExecutionTime = 12.17 s ClockTime = 13 s

forces output:
forces(pressure, viscous)((-2.16039e+11 -1.76242e+12 2.33002e+07) (-4.46086e+07 -2.83529e+08 5.60693e+07))
moment(pressure, viscous)((-7.72514e+11 9.4704e+10 4.1255e+10) (-9.58347e+07 1.70477e+07 1.15609e+07))

Courant Number mean: 4.69634 max: 8810.84
deltaT = 2.26963e-09
Time = 7.00023e-05

solidBodyMotionFunctions::rotatingMotion::transfor mation(): Time = 7.00023e-05 transformation: ((0 0 -8.67362e-19) (1 (0 0 0.000712973)))
AMI: Creating addressing and weights between 152 source faces and 152 target faces
AMI: Patch source weights min/max/average = 1.00045, 1.00059, 1.00051
AMI: Patch target weights min/max/average = 1.00027, 1.00041, 1.00034
PIMPLE: iteration 1
smoothSolver: Solving for Ux, Initial residual = 0.924264, Final residual = 0.0530127, No Iterations 2
smoothSolver: Solving for Uy, Initial residual = 0.641598, Final residual = 0.0386788, No Iterations 2
smoothSolver: Solving for Uz, Initial residual = 0.921792, Final residual = 0.0461483, No Iterations 2
GAMG: Solving for p, Initial residual = 1, Final residual = 5705.13, No Iterations 50
time step continuity errors : sum local = 9.40062e+08, global = 3.78949e+07, cumulative = 3.78949e+07
PIMPLE: iteration 2
smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 0.0224152, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 0.0293676, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 0.00299007, Final residual = 6.31039e-05, No Iterations 1
GAMG: Solving for p, Initial residual = 0.595319, Final residual = 9.86458e-05, No Iterations 1
time step continuity errors : sum local = 3.27194e+16, global = 4.33629e+15, cumulative = 4.33629e+15
PIMPLE: iteration 3
DILUPBiCG: Solving for Ux, Initial residual = 0.999996, Final residual = 5.86893e-07, No Iterations 28
DILUPBiCG: Solving for Uy, Initial residual = 0.999998, Final residual = 7.80082e-07, No Iterations 20
DILUPBiCG: Solving for Uz, Initial residual = 0.000201204, Final residual = 9.98882e-07, No Iterations 5
GAMG: Solving for p, Initial residual = 0.879029, Final residual = 7.05858e-07, No Iterations 47
time step continuity errors : sum local = 4.76118e+19, global = -8.01772e+18, cumulative = -8.01339e+18
DILUPBiCG: Solving for epsilon, Initial residual = 1, Final residual = 48876.6, No Iterations 1001
bounding epsilon, min: -1.7324e+51 max: 2.47572e+51 average: 5.46302e+48
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 6.79817e-07, No Iterations 96
bounding k, min: -1.36796e+48 max: 7.09554e+59 average: 6.62561e+56
ExecutionTime = 15.72 s ClockTime = 16 s

forces output:
forces(pressure, viscous)((5.96091e+57 4.44151e+57 3.98466e+52) (3.53788e+57 -2.92522e+58 1.66546e+57))
moment(pressure, viscous)((2.01323e+57 -2.60251e+57 -1.10323e+57) (-1.21739e+58 -1.87448e+57 -3.42054e+57))

Courant Number mean: 2.99449e+25 max: 3.21959e+28
deltaT = 1.40989e-37
--> FOAM Warning :
From function Time::operator++()
in file db/Time/Time.C at line 1010
Increased the timePrecision from 6 to 7 to distinguish between timeNames at time 7.00023e-05
Time = 7.000227e-05

solidBodyMotionFunctions::rotatingMotion::transfor mation(): Time = 7.00023e-05 transformation: ((0 0 -8.67362e-19) (1 (0 0 0.000712973)))
AMI: Creating addressing and weights between 152 source faces and 152 target faces
AMI: Patch source weights min/max/average = 1.00045, 1.00059, 1.00051
AMI: Patch target weights min/max/average = 1.00027, 1.00041, 1.00034
PIMPLE: iteration 1
smoothSolver: Solving for Ux, Initial residual = 0.904795, Final residual = 0.0198399, No Iterations 2
smoothSolver: Solving for Uy, Initial residual = 0.920089, Final residual = 0.00357272, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 0.770617, Final residual = 0.0112283, No Iterations 1
GAMG: Solving for p, Initial residual = 1, Final residual = 3.34459e+74, No Iterations 50
time step continuity errors : sum local = 2.15853e+83, global = 2.27242e+82, cumulative = 2.27242e+82
PIMPLE: iteration 2
smoothSolver: Solving for Ux, Initial residual = 0.998805, Final residual = 1.80506, No Iterations 1000
smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 1.93583e-05, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 0.000531627, Final residual = 1.42642e-07, No Iterations 1
#0 Foam::error::printStack(Foam::Ostream&) in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2 in "/lib/x86_64-linux-gnu/libc.so.6"
#3 Foam::DICPreconditioner::calcReciprocalD(Foam::Fie ld<double>&, Foam::lduMatrix const&) in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#4 Foam::DICSmoother::DICSmoother(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&) in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#5 Foam::DICGaussSeidelSmoother::DICGaussSeidelSmooth er(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&) in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#6 Foam::lduMatrix::smoother::addsymMatrixConstructor ToTable<Foam::DICGaussSeidelSmoother>::New(Foam::w ord const&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&) in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#7 Foam::lduMatrix::smoother::New(Foam::word const&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::dictionary const&) in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#8 Foam::GAMGSolver::initVcycle(Foam::PtrList<Foam::F ield<double> >&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::lduMatrix::smoother>&) const in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#9 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#10 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libfiniteVolume.so"
#11
in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/bin/pimpleDyMFoam"
#12 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#13
in "/home/alpha/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/bin/pimpleDyMFoam"
Floating point exception

------------------------------------

If any one has a hint, please it welcome.

I checked the boundary conditions but it doesn't seem to come from there for they are very similar to those of the propeller example.

Thank all and best regards.

Attesz April 17, 2012 11:23

Your k and omega is blowing up, i would have a look on them first. Try underrelaxation, especially for omega, and decrease the absolute tolerance to 1e-12 by setting the relTol to 0. Also have a look on the yplus and your wall modelling approach (if yplus is too small, forcing wallFunctions can cause blowing up the k and omega)

dogan May 13, 2013 09:02

Hi all,

i am working on a transient pump simulation, and i am getting a floating point exception. My geometry has a rotating part and a stationary part and between them, i have two cyclicGgi interfaces. I am using OF1.6 ext, and pimpleDyMFoam as the solver. My simulation starts to run, it runs until for a while, then it crashes with the floating point exception error message. I have tried almost everything, but i couldn't solve the problem. Now i am worried about that if i am doing something wrong about the mesh manipulating steps. or in general, can someone summarize me which steps do i have to follow before i start with the transient simulation?

thanks in advance

Dogan

mali August 28, 2013 23:27

Hi All,

Sorry if the issue on this thread has been solved, but I've tried many things to get the pimpledymfoam run properly to my case: Flow Over A Square Cylinder with both ends are imposed with cyclic B.C. The Re is 22K and run with LES. Here is the chronology of my simulations,

1.0 Run with pisoFoam: Ok
2.0 Run with pimpleDymFoam: Not ok
2.1 Change cyclic to cyclicAMI: initially Ok, but blow up after fews time steps.
2.1.1 Change variables in the fvSolution: Ok
3.0 Increase the velocity from 1m/s to 2 m/s and run using the setting on 2.1.1: not ok, blow up after fews time steps.

I'll appreciate if anyone can give me the advice on resolving this problem (It already took me 3months to find out the right solution)

Thank YOU.

louisgag December 6, 2013 09:39

I'm affraid I can't be of any help here but I too have issues running pimpleDyMFoam. I've tried turbulent and laminar flow, various BC, various numerical schemes, various solution algorithms, etc. It seems the only solution which could work, and yet I have not tested it for long enough, is to use an extremely small Courant number (such as 0.05-0.2). And such a small Courant number sort of makes the use of the PIMPLE algorithm useless...

mali December 7, 2013 08:57

Hi Louisgag,

What dynamicFvMesh solver u use for your pimpleDyMFoam simulations? I used displacementLaplacian with no errors. But the results a bit different from experiment, especially for the upper branch.

louisgag December 9, 2013 08:12

Hi mali,

I use multiSolidBodyMotionFvMesh.

Another strange thing I noticed is that when the simulation diverges, I can restart it from an earlier save and it will not diverge again until later. In this mode I end up with a simulation that never really diverges since it can always be restarted. As anyone experienced this behavior ?

sivakumar December 12, 2013 12:32

Hi There,
I want to use pimpleDyMFoam, I have a small question.
I want use 1/8 th of my fan geometry with cyclic faces, is it possible can I use pimpleDyMFoam for this case? or do I need to use full 8 bladed geometry?

Please clear my doubt.

Thanks,
Siva

Kaskade December 13, 2013 04:32

Could maybe send of what you want to achieve?

But I am afraid with the regular OpenFOAM it's not possible. Instead have a look at the extend-Version and overlapGGI.

sivakumar December 13, 2013 04:43

Dear Onno,
Thanks for your reply, so far I am using MRFSimpleFoam, the results are fine for high volume flow rate, but for low volume flow rate, I am not able to attain the convergence and its oscillating badly, so I decided to go for transient simulation with pimpleDyMFoam.

My ultimate aim is to do low volume flow rate simulation.

simulating full geometry is not a good option, because the mesh size will be really too much.

suggest me something,


Thanks,
Siva

Kaskade December 13, 2013 04:51

Like I said, please post a drawing of your geometry. I

What is your goal? What type of mesh are you using? Which turbulence models, which solvers, which schemes?

sivakumar December 13, 2013 05:02

1 Attachment(s)
Hi, here is some answer for your questions

What is your goal?

As I said in the previous post, aim is to simulate low volume flow rate.

What type of mesh are you using?

Fully hex mesh (non conformal)

Which turbulence models, which solvers, which schemes?

KEpsilon turbulence model, pimpleDyMFoam, mostly Upwind ( I am not concerning about the accuracy)


As you requested, I have attached the fig. please have a look.

Thanks,
Siva

Kaskade December 13, 2013 05:11

Could you maybe send your fvSchemes and fvSolution as well? What timeStep/maxCo are you using?

sivakumar December 13, 2013 05:30

Hi,
my question is bit away from our discussion,
just I want to check, is it possible to do simulation with cyclic faces (1/8th of Geometry using pimpleDyMFoam).

After getting clear idea, I will go forward with settings.
right now I tried fvSchemes and fvSolutions from propeller case.

I have edited the mxCo number thats it.
I know I need to do more refinement according to my case, but I didnt do anything so far.

Thanks,
Siva

Kaskade December 13, 2013 05:50

If the mesh motion causes the interfaces to stop matching, then AMI can't handle it, but overlapGGI can.


See here: http://web.student.chalmers.se/group...SlidesOFW5.pdf

sivakumar December 13, 2013 05:58

Thanks Onno, I will have a look.

Siva


All times are GMT -4. The time now is 01:52.