[jose_rodrig]

hi forum,

I am experiencing lots of instability with the solver reactionFoam with parallelization and they are not the janafthermo sort

My domain has around 260 000 elements and was divided in 32 domains for parallelization - divided as (16 2 1) to minimize proc borders. Im using the chemkin reader to read a single step combustion of CH4 oxidation in a GT combustor (diffusion flames). Inlet velocities are between 20 and 50 m/s.

I started fixing Courant No to 0.1. Everything looks good for about thousands of iterations but suddenly it crashes with a floating point exception. I say suddendly because I dont see a change in timestep or even the problematic janafThermo error message.

Also, it never crashes at the same timestep: if I simply restart the solver with the same parameters (no CourantNo change or any other) it will crash in a different timeStep.

It just goes!... as you can see in the following output after decreasing CourantNo to 0.035 (it still crashes!). I also attached a txt with the complete error message. Bellow the output i also posted the fvSolution and fvSchemes so you can take and criticize.

Thank you

José

[...]
DILUPBiCG: Solving for epsilon, Initial residual = 4.32044e-06, Final residual = 9.94436e-09, No Iterations 1
DILUPBiCG: Solving for k, Initial residual = 1.74131e-06, Final residual = 3.09184e-09, No Iterations 1
ExecutionTime = 161537 s ClockTime = 164174 s

Courant Number mean: 0.00125684 max: 0.0349221
deltaT = 3.80307e-07
Time = 0.3549768

Solving chemistry
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
DILUPBiCG: Solving for Ux, Initial residual = 1.19096e-05, Final residual = 6.46123e-09, No Iterations 1
[24] #0 Foam::error:rintStack(Foam::Ostream&)[25] #0 Foam::error:rintStack(Foam::Ostream&)[26] #0 Foam::error:rintStack(Foam::Ostream&)[27] #0
[...]

fvSolution

solvers
{
rho
{
solver PCG;
preconditioner DIC;
tolerance 1e-06;
relTol 0;
}
p
{
solver PCG;
preconditioner DIC;
tolerance 1e-6;
relTol 0.0;
}
pFinal
{
solver PCG;
preconditioner DIC;
tolerance 1e-6;
relTol 0.0;
}

"(U|Yi|hs|k|epsilon)"
{
solver PBiCG;
preconditioner DILU;
tolerance 1e-06;
relTol 0;
}
}

PISO
{
nCorrectors 3;
nNonOrthogonalCorrectors 6;
}
relaxationFactors
{
rho 0.6;
U 0.6;
pFinal 0.4;
p 0.4;
k 0.6;
epsilon 0.6;
hs 0.6;
T 0.6;
}

fvSchemes

ddtSchemes
{
default Euler; //CrankNicholson 1; //Euler;
}

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

divSchemes
{
default none;

div(phi,U) Gauss limitedLinearV 1;
div(phi,Yi_h) Gauss limitedLinear01 1;
div(phi,hs) Gauss limitedLinear 1;
div(phiU,p) Gauss limitedLinear 1;
div(phid,p) Gauss limitedLinear 1;
div(phi,epsilon) Gauss limitedLinear 1;
div(phi,k) Gauss limitedLinear 1;
div((muEff*dev2(grad(U).T()))) Gauss linear;
}

laplacianSchemes
{
default Gauss linear uncorrected;
laplacian(muEff,U) Gauss linear uncorrected;
laplacian(mut,U) Gauss linear uncorrected;
laplacian(DkEff,k) Gauss linear uncorrected;
laplacian(DepsilonEff,epsilon) Gauss linear uncorrected;
laplacian((rho*(1|A(U))),p) Gauss linear uncorrected;
laplacian(alphaEff,hs) Gauss linear uncorrected;
}

interpolationSchemes
{
default linear;
}

snGradSchemes
{
default uncorrected;
}

fluxRequired
{
default no;
p;
}