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Old   August 22, 2022, 10:13
Default Need help to validate my simulation result
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Tintunoo
Join Date: Jul 2022
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problem description -
-free fall rocket like object drop from 500 meters.
-desired results are forces and moment coefficient for rigid body simulation.
-free stream velocity 60 m/s.
-angle of attack 5 deg.

simulation setup -
-box far field domain 10 times body length for 3D simulation.
-inlet, top and bottom patches are velocity inlet type.
-symmetry sides.
-pressure outlet.
-turbulent Model is kOmegaSST.
-simpleFoam solver.

Mesh
-snappyHexMesh with 3 boundary layers of thickness 0.7
-total number of cell 1 Million.

HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (59.771681 5.02293445 0);

boundaryField
{
    airdrop
    {
        type            noSlip;
    }
    inlet
    {
        type            fixedValue;
        value           uniform (59.771681 5.02293445 0);
    }
    outlet
    {
        type            zeroGradient;
    }
    sides
    {
        type            symmetry;
    }
}




// ************************************************************************* //
HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "1";
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -2 0 0 0 0];


internalField   uniform 0;

boundaryField
{
    airdrop
    {
        type            zeroGradient;
    }
    inlet
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }
    sides
    {
        type            symmetry;
    }
}


// ************************************************************************* //
HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "1";
    object      omega;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 0 -1 0 0 0 0];


internalField   uniform 864200;

boundaryField
{
    airdrop
    {
        type            omegaWallFunction;
        value           uniform 1;
    }
    inlet
    {
        type            turbulentMixingLengthDissipationRateInlet;
        mixingLength    0.014;
        value           uniform 0.014;
    }
    outlet
    {
        type            zeroGradient;
    }
    sides
    {
        type            symmetry;
    }
}


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

HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "1";
    object      nut;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -1 0 0 0 0];


internalField   uniform 0;

boundaryField
{
    airdrop
    {
        type            nutkWallFunction;
        value           uniform 0;
    }
    inlet
    {
        type            calculated;
        value           uniform 0.01934;
    }
    outlet
    {
        type            calculated;
        value           uniform 0;
    }
    sides
    {
        type            symmetry;
    }
}


// ************************************************************************* //
HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "1";
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -2 0 0 0 0];


internalField   uniform 0.1;

boundaryField
{
    airdrop
    {
        type            kqRWallFunction;
        value           uniform 1;
    }
    inlet
    {
        type            turbulentIntensityKineticEnergyInlet;
        intensity       0.01;
        value           uniform 0.01;
    }
    outlet
    {
        type            zeroGradient;
    }
    sides
    {
        type            symmetry;
    }
}


// ************************************************************************* //
HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      transportProperties;
}

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

transportModel  Newtonian;

nu              1.5e-05;

// ************************************************************************* //
HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      turbulenceProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

simulationType RAS;

RAS
{
    RASModel        kOmegaSST;

    turbulence      on;

    printCoeffs     on;
}

// ************************************************************************* //
HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     simpleFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         15000;

deltaT          1;

writeControl    timeStep;

writeInterval   10;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

functions
{
	forceCoeffs1
{
    type            forceCoeffs;
    libs            ("libforces.so");
    writeControl    writeTime;
    writeFields     true;

    patches         (fuckingbomb);
    p               p;
    U               U;
    rho             rhoInf;      // Indicates incompressible
    log             true;
    rhoInf          1;           // Required when rho = rhoInf
    liftDir         (0 1 0);
    dragDir         (1 0 0);
    CofR            (0 0 0);  // Axle midpoint on ground
    pitchAxis       (0 0 1);
    magUInf         60;
    lRef            2.41;          // Wheelbase length
    Aref            4.56;          // Estimated
    
}

yPlus1
{
    // Mandatory entries (unmodifiable)
    type            yPlus;
    libs            (fieldFunctionObjects);

    // Optional (inherited) entries
    writePrecision  8;
    writeToFile     true;
    useUserTime     true;
    region          region0;
    enabled         true;
    log             true;
    timeStart       0;
    timeEnd         1000;
    executeControl  timeStep;
    executeInterval 1;
    writeControl    timeStep;
    writeInterval   10;
}



}


// ************************************************************************* //
HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
    default steadyState;
}

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

divSchemes
{
    default         none;
    div(phi,U)      bounded Gauss linearUpwind grad(U);
    div(phi,k)      bounded Gauss upwind;
    div(phi,omega)  bounded Gauss upwind;
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

wallDist
{
    method meshWave;
}


// ************************************************************************* //
HTML Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2012                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    p
    {
        solver           GAMG;
        tolerance        1e-7;
        relTol           0.1;
        smoother         GaussSeidel;
    }

    Phi
    {
        $p;
    }

    U
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-8;
        relTol           0.1;
        nSweeps          1;
    }

    k
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-8;
        relTol           0.1;
        nSweeps          1;
    }

    omega
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-8;
        relTol           0.1;
        nSweeps          1;
    }
}

SIMPLE
{
    nNonOrthogonalCorrectors 3;
}

potentialFlow
{
	nNonOrthogonalCorrectors 10;
}

relaxationFactors
{
    fields
    {
        p               0.3;
    }
    equations
    {
        "(U|k|omega)"   0.7;
        "(U|k|omega)Final" 1.0;
    }
}

cache
{
    grad(U);
}

// ************************************************************************* //
Result -
only Ux and omega resudual went below 1e-5.
other residual doesn't goes below 1e-3.
-yplus value are y+ : min = 81.6281, max = 13216.4, average = 1185.81

HTML Code:
Time = 639

smoothSolver:  Solving for Ux, Initial residual = 9.52204e-05, Final residual = 6.89428e-06, No Iterations 3
smoothSolver:  Solving for Uy, Initial residual = 0.000402492, Final residual = 2.90737e-05, No Iterations 3
smoothSolver:  Solving for Uz, Initial residual = 0.00496712, Final residual = 0.000361654, No Iterations 3
GAMG:  Solving for p, Initial residual = 0.00923487, Final residual = 0.000304668, No Iterations 2
GAMG:  Solving for p, Initial residual = 0.0010415, Final residual = 5.96551e-05, No Iterations 2
GAMG:  Solving for p, Initial residual = 0.000171178, Final residual = 1.68851e-05, No Iterations 2
GAMG:  Solving for p, Initial residual = 4.20648e-05, Final residual = 2.52407e-06, No Iterations 3
time step continuity errors : sum local = 6.28704e-08, global = 1.01751e-09, cumulative = 0.00119196
smoothSolver:  Solving for omega, Initial residual = 2.4579e-05, Final residual = 1.75449e-06, No Iterations 3
smoothSolver:  Solving for k, Initial residual = 0.000100212, Final residual = 7.69947e-06, No Iterations 3
ExecutionTime = 3194.77 s  ClockTime = 3379 s

forceCoeffs forceCoeffs1 execute:
    Coefficients
        Cd       : 0.267388	(pressure: 0.251521	viscous: 0.0158662)
        Cs       : -0.0281329	(pressure: -0.0283496	viscous: 0.000216715)
        Cl       : 0.337512	(pressure: 0.336583	viscous: 0.000929208)
        CmRoll       : 0.206183	(pressure: 0.205689	viscous: 0.000494358)
        CmPitch       : 0.669585	(pressure: 0.657872	viscous: 0.011713)
        CmYaw       : -0.125541	(pressure: -0.116004	viscous: -0.00953733)
        Cd(f)    : 0.339877
        Cd(r)    : -0.0724894
        Cs(f)    : -0.139607
        Cs(r)    : 0.111475
        Cl(f)    : 0.838341
        Cl(r)    : -0.500829
Question -
-is my result acceptable and how can i improve to have convergance. Thank in advances.
Attached Images
File Type: png residual.png (41.5 KB, 7 views)
File Type: png Cl.png (17.9 KB, 6 views)
File Type: png Cd.png (17.2 KB, 5 views)
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convergence issue, free fall analysis, incompressible fluid, simple algorithm

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