Sudden jumps in Courant in the middle of the simulation
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Hi everybody
I'm running a case with PIMPLE foam with the LES turbulence model.
The problem is that in the middle of the simulation, sudden jumps of several order of magnitude in Courant number appears. Then, strange fact number 2, the simulation converges again :confused:
This is the log from pimple foam with the iteration before and after the jump
Code:
Courant Number mean: 0.186631 max: 1.8437
Time = 5.575
PIMPLE: iteration 1
DILUPBiCG: Solving for Ux, Initial residual = 0.00145738, Final residual = 6.64777e-09, No Iterations 6
DILUPBiCG: Solving for Uy, Initial residual = 0.0604873, Final residual = 7.45712e-09, No Iterations 9
DILUPBiCG: Solving for Uz, Initial residual = 0.0274295, Final residual = 8.88052e-09, No Iterations 8
DICPCG: Solving for p, Initial residual = 0.141566, Final residual = 0.00692174, No Iterations 4
DICPCG: Solving for p, Initial residual = 0.00791436, Final residual = 0.00037769, No Iterations 16
time step continuity errors : sum local = 7.22241e-08, global = -4.52688e-11, cumulative = -1.72326e-07
DICPCG: Solving for p, Initial residual = 0.0161718, Final residual = 0.000756972, No Iterations 5
DICPCG: Solving for p, Initial residual = 0.000876374, Final residual = 4.36954e-05, No Iterations 33
time step continuity errors : sum local = 8.49073e-09, global = -5.75816e-11, cumulative = -1.72383e-07
PIMPLE: iteration 2
DILUPBiCG: Solving for Ux, Initial residual = 3.12497e-05, Final residual = 8.99954e-09, No Iterations 4
DILUPBiCG: Solving for Uy, Initial residual = 0.000795909, Final residual = 1.19494e-09, No Iterations 8
DILUPBiCG: Solving for Uz, Initial residual = 0.00029896, Final residual = 314.057, No Iterations 1001
DICPCG: Solving for p, Initial residual = 0.999977, Final residual = 0.0263806, No Iterations 3
DICPCG: Solving for p, Initial residual = 0.0144061, Final residual = 0.000528999, No Iterations 8
time step continuity errors : sum local = 0.00441509, global = 9.945e-09, cumulative = -1.62438e-07
DICPCG: Solving for p, Initial residual = 0.755181, Final residual = 0.0195148, No Iterations 3
DICPCG: Solving for p, Initial residual = 0.0397071, Final residual = 9.8571e-07, No Iterations 250
time step continuity errors : sum local = 3.04181e-06, global = 1.62246e-07, cumulative = -1.91817e-10
ExecutionTime = 37649.6 s ClockTime = 37697 s
Courant Number mean: 2.76008 max: 43683.4
Time = 5.576
PIMPLE: iteration 1
DILUPBiCG: Solving for Ux, Initial residual = 0.289494, Final residual = 6.77395e-09, No Iterations 14
DILUPBiCG: Solving for Uy, Initial residual = 0.305659, Final residual = 7.22824e-09, No Iterations 14
DILUPBiCG: Solving for Uz, Initial residual = 0.316415, Final residual = 9.94743e-09, No Iterations 14
DICPCG: Solving for p, Initial residual = 0.960833, Final residual = 0.0456337, No Iterations 8
DICPCG: Solving for p, Initial residual = 0.0100212, Final residual = 0.000488464, No Iterations 49
time step continuity errors : sum local = 0.00244363, global = 1.20192e-05, cumulative = 1.2019e-05
DICPCG: Solving for p, Initial residual = 0.0416985, Final residual = 0.00189429, No Iterations 10
DICPCG: Solving for p, Initial residual = 0.00261552, Final residual = 0.000127246, No Iterations 92
time step continuity errors : sum local = 0.000612151, global = 5.09733e-05, cumulative = 6.29923e-05
PIMPLE: iteration 2
DILUPBiCG: Solving for Ux, Initial residual = 0.242781, Final residual = 2.21545e-09, No Iterations 14
DILUPBiCG: Solving for Uy, Initial residual = 0.247553, Final residual = 2.30642e-09, No Iterations 14
DILUPBiCG: Solving for Uz, Initial residual = 0.276608, Final residual = 2.33162e-09, No Iterations 15
DICPCG: Solving for p, Initial residual = 0.141775, Final residual = 0.0065789, No Iterations 5
DICPCG: Solving for p, Initial residual = 0.00722017, Final residual = 0.000357133, No Iterations 66
time step continuity errors : sum local = 0.00165265, global = 0.000112039, cumulative = 0.000175032
DICPCG: Solving for p, Initial residual = 0.0266265, Final residual = 0.00117149, No Iterations 6
DICPCG: Solving for p, Initial residual = 0.00134573, Final residual = 9.69224e-07, No Iterations 505
time step continuity errors : sum local = 4.90204e-06, global = -6.92753e-09, cumulative = 0.000175025
ExecutionTime = 37659.3 s ClockTime = 37707 s
as you can see the Uz could not be solved and the solver stopped after 1001 iterations.
I attached a plot of the MaxCo at each iteration on a semi logaritmic scale. As you can see, after the "jump" the Courant decrease and goes back to value around 1.7-2 as I want it. Then after a while a second jump happens.
This is the fvScheme
Code:
ddtSchemes
{
default backward;
}
gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
grad(U) Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss linear;
div(phi,k) Gauss limitedLinear 1;
div(phi,B) Gauss limitedLinear 1;
div(phi,nuTilda) Gauss limitedLinear 1;
div(B) Gauss linear;
div((nuEff*dev(T(grad(U))))) Gauss linear;
}
laplacianSchemes
{
default Gauss linear corrected;
laplacian(nuEff,U) Gauss linear corrected;
laplacian((1|A(U)),p) Gauss linear corrected;
laplacian(DkEff,k) Gauss linear corrected;
laplacian(DBEff,B) Gauss linear corrected;
laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;
}
interpolationSchemes
{
default linear;
interpolate(U) linear;
}
snGradSchemes
{
default corrected;
}
fluxRequired
{
default no;
p ;
}
and this the fvSolution
Code:
solvers
{
p
{
solver PCG;
preconditioner DIC;
tolerance 1e-06;
relTol 0.05;
};
pFinal
{
solver PCG;
preconditioner DIC;
tolerance 1e-06;
relTol 0;
};
U
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-08;
relTol 0;
};
UFinal
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-08;
relTol 0;
};
nuTilda
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-07;
relTol 0;
};
}
PIMPLE
{
nCorrectors 2;
nNonOrthogonalCorrectors 1;
nOuterCorrectors 2;
}
relaxationFactors
{
"U.*" 1;
"nuTilda.*" 1;
}
What should i do? Thank you very much |
