Monitoring Question about p_rgh and U

Kahnbein.Kai · January 17, 2020, 08:27

Hello,
i have a question about monitoring the solver. The solver is interFoam on OFv7, i do a multiphase simulation.

Here is a extract from the log:

Code:

Courant Number mean: 3.19876e-05 max: 0.495667
Interface Courant Number mean: 1.25627e-06 max: 0.0671976
deltaT = 0.000229651
Time = 0.00630312

smoothSolver:  Solving for alpha.water, Initial residual = 1.26653e-06, Final residual = 1.7656e-11, No Iterations 1
Phase-1 volume fraction = 0.580631  Min(alpha.water) = -1.68629e-12  Max(alpha.water) = 1
MULES: Correcting alpha.water
MULES: Correcting alpha.water
Phase-1 volume fraction = 0.580631  Min(alpha.water) = -1.28064e-05  Max(alpha.water) = 1
DICPCG:  Solving for p_rgh, Initial residual = 4.84617e-05, Final residual = 2.30721e-06, No Iterations 2
time step continuity errors : sum local = 6.53424e-08, global = 1.90467e-11, cumulative = -5.15105e-08
DICPCG:  Solving for p_rgh, Initial residual = 6.84474e-06, Final residual = 3.23296e-07, No Iterations 7
time step continuity errors : sum local = 9.15619e-09, global = -6.09607e-11, cumulative = -5.15715e-08
DICPCG:  Solving for p_rgh, Initial residual = 1.88869e-06, Final residual = 9.77306e-08, No Iterations 17
time step continuity errors : sum local = 2.76788e-09, global = -4.499e-10, cumulative = -5.20214e-08
smoothSolver:  Solving for omega, Initial residual = 2.03198e-05, Final residual = 3.7555e-11, No Iterations 1
smoothSolver:  Solving for k, Initial residual = 0.00470494, Final residual = 2.12755e-09, No Iterations 1
 ExecutionTime = 434.44 s  ClockTime = 455 s

Here the related fvsolution:

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  4.1                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    "alpha.water.*"
    {
        nAlphaCorr      2;
        nAlphaSubCycles 1;
        cAlpha          1;

        MULESCorr       yes;
        nLimiterIter    3;

        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-8;
        relTol          0;
    }

    pcorr
    {
        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|k|omega).*"
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-06;
        relTol          0;
        minIter         1;
    }
}

PIMPLE
{
    momentumPredictor   no;
    nOuterCorrectors    1;
    nCorrectors         3;
    nNonOrthogonalCorrectors 0;
}

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

// ************************************************************************* //

Here now my questions:

Why is p_rgh three times solved ?

and
Why there are no velocity resiuals ? Shouldn't be there Ux, Uy and Uz ?

Best regards
Kai

ssa_cfd · January 17, 2020, 10:25

you set

Code:

nCorrectors 3;

this is the pressure correction step. so it solves the pressure 3 times.

To solve the velocity you should set

Code:

momentumPredictor yes;

Kahnbein.Kai · January 17, 2020, 10:47

Thank you very much ssa_cfd ! I will try it and report back. Best regards Kai

January 17, 2020, 10:25		#2
ssa_cfd Member ssa Join Date: Sep 2018 Posts: 93 Rep Power: 7	you set Code: nCorrectors 3; this is the pressure correction step. so it solves the pressure 3 times. To solve the velocity you should set Code: momentumPredictor yes;

January 17, 2020, 10:47		#3
Kahnbein.Kai Member Join Date: Feb 2018 Posts: 58 Rep Power: 8	Thank you very much ssa_cfd ! I will try it and report back. Best regards Kai