[walakaka]

Hi there,

I am wanting my pressure residuals to converge once it drops below 1e-6. However, even after the residuals drop below 1e-6, PimpleFoam Continues to iterate its outerncorrectors up till 200 iterations.

Does anyone know why this is the case.

Here is my fvSolution file:

**************************************

solver PCG;
preconditioner DIC;
tolerance 1e-5;
relTol 0;
}

p_rgh
{
solver PCG;
preconditioner DIC;
tolerance 1e-07;
relTol 0.05;
}

p_rghFinal
{
$p_rgh;
relTol 0;
}

U
{
solver smoothSolver;
smoother symGaussSeidel;
tolerance 1e-06;
relTol 0;
}
}

PIMPLE
{
momentumPredictor no;
nOuterCorrectors 200;
nCorrectors 2;
nNonOrthogonalCorrectors 0;
residualControl
{
p
{
tolerance 1e-6;
relTol 0;
}
}
}

relaxationFactors
{
equations
{
".*" 1;
}
}

**********************************************

Here is a snippet of the log file (you can see Iteration 12 has definitely converged):

***********************************************

PIMPLE: iteration 11
smoothSolver: Solving for alpha.water, Initial residual = 0.000240257, Final residual = 4.2394e-10, No Iterations 3
Phase-1 volume fraction = 0.518487 Min(alpha.water) = -5.21399e-05 Max(alpha.water) = 1.09024
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.518487 Min(alpha.water) = -0.000149382 Max(alpha.water) = 1.08945
DICPCG: Solving for p_rgh, Initial residual = 4.67206e-07, Final residual = 8.61561e-08, No Iterations 3
time step continuity errors : sum local = 4.08652e-09, global = -3.18898e-10, cumulative = 0.000898511
DICPCG: Solving for p_rgh, Initial residual = 1.17071e-07, Final residual = 7.90011e-08, No Iterations 1
time step continuity errors : sum local = 3.74715e-09, global = -3.18966e-10, cumulative = 0.000898511
PIMPLE: iteration 12
smoothSolver: Solving for alpha.water, Initial residual = 0.000240257, Final residual = 4.23937e-10, No Iterations 3
Phase-1 volume fraction = 0.518487 Min(alpha.water) = -5.21399e-05 Max(alpha.water) = 1.09024
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.518487 Min(alpha.water) = -0.000149382 Max(alpha.water) = 1.08945
DICPCG: Solving for p_rgh, Initial residual = 4.51662e-07, Final residual = 8.37249e-08, No Iterations 3
time step continuity errors : sum local = 3.9712e-09, global = -3.19133e-10, cumulative = 0.00089851
DICPCG: Solving for p_rgh, Initial residual = 1.15396e-07, Final residual = 7.70865e-08, No Iterations 1
time step continuity errors : sum local = 3.65634e-09, global = -3.19198e-10, cumulative = 0.00089851

************************************************** ***********

Kind regards
Shafik

[walakaka]

Originally Posted by walakaka

PIMPLE: iteration 12
smoothSolver: Solving for alpha.water, Initial residual = 0.000240257, Final residual = 4.23937e-10, No Iterations 3
Phase-1 volume fraction = 0.518487 Min(alpha.water) = -5.21399e-05 Max(alpha.water) = 1.09024
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.518487 Min(alpha.water) = -0.000149382 Max(alpha.water) = 1.08945
DICPCG: Solving for p_rgh, Initial residual = 4.51662e-07, Final residual = 8.37249e-08, No Iterations 3
time step continuity errors : sum local = 3.9712e-09, global = -3.19133e-10, cumulative = 0.00089851
DICPCG: Solving for p_rgh, Initial residual = 1.15396e-07, Final residual = 7.70865e-08, No Iterations 1
time step continuity errors : sum local = 3.65634e-09, global = -3.19198e-10, cumulative = 0.00089851

Kind regards
Shafik

Also, can someone please explain the difference between No Iterations 1 and Pimple: iteration 12.
Can't seem to understand the explanation available!

Regards
Shafik

[kera]

Hallo Shafik,

instead of setting the residual control for p, set the residual control for p_rgh, as interFoam solves for p_rgh instead of p.

No Iterations 1 --> that you have pointed it out, is nothing but the number of iterations taken to solve p_rgh for the given/set tolerance in fvSolution.

Pimple: iteration 12 --> is the number of outer corrections (nOuterCorrectors) in your case max 200.

Have a look at this literature

hope this helps!

Regards,
Ricky

Originally Posted by walakaka

Also, can someone please explain the difference between No Iterations 1 and Pimple: iteration 12.
Can't seem to understand the explanation available!

Regards
Shafik

[walakaka]

Originally Posted by kera

Hallo Shafik,

instead of setting the residual control for p, set the residual control for p_rgh, as interFoam solves for p_rgh instead of p.

No Iterations 1 --> that you have pointed it out, is nothing but the number of iterations taken to solve p_rgh for the given/set tolerance in fvSolution.

Pimple: iteration 12 --> is the number of outer corrections (nOuterCorrectors) in your case max 200.

Have a look at this literature

hope this helps!

Regards,
Ricky

Hi Ricky!

Thanks alot for your help, and thanks for introducing the particular literature to me!

My simulation works now and I will explore the book to further understand the PIMPLE algorithm.

Regards
Shafik