[gfilip]

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:

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:

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


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

And my fvSchemes:

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