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problems k-epsilon for 3-D Fully turbulent Square-Pipe flow

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Old   February 16, 2017, 10:18
Default problems k-epsilon for 3-D Fully turbulent Square-Pipe flow
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Jorgen van Koppen
Join Date: Feb 2017
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Dear Openfoamers,

I have some problems with the solutions i get from my kepsilon model (also tried the other versions, RNG and realizable). The problem is that while according to the high Reynolds number ( v = 44 m/s, nu = 1.5e-4) the flow in the pipe should develop to a Turbulent flow it goes to a laminar profile (see pictures).

The Y+ is around 30-50 so that shouldnt be a problem
I have already tried changing solver settings and boundary condition values but that would not give a better solution. Same for making the mesh finer. I hope any of you might be able to help me with finding the problem since i'm stuck and haven't been able to find anything online so far.


Picture shows flow close to the end of the square pipe.

The settings i have are the flowing and are based on tutorials and research:
The pipe dimensions for the square pipe are:
y = 0.1016 meter
z = 0.1524 meter
x = 5.12 meter
Making it a square pipe with Inlet, 4 walls and an Outlet

So the blockMesh looks like this:

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;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 0.01;

vertices
(
// General form (just the inlet)
    (-512.70  1.27 0) // 0
    (      0  1.27 0) // 1

    (       0 11.43 0) // 2
     (-512.70 11.43 0) // 3
    


    (-512.70  1.27   15.24) // 4
    (       0  1.27 15.24) // 5


    (    0    11.43 15.24) // 6
    (-512.70 11.43  15.24) // 7
);

blocks
(
// normal blocks without yplus extra
    //block 1
    hex (0 1 2 3 4 5 6 7) (200 35 50) simpleGrading (0.1 
					    ((0.5 0.5 5)
						    (0.5 0.5 0.2)) 
                                                    ((0.5 0.5 5) 
						    (0.5 0.5 0.2)) 
                                                    )
);

edges
(
);

boundary
(
    inlet
    {
        type patch;
        faces
        (
             (0 3 7 4)
 
        );
    }
    outlet
    {
        type patch;
        faces
        (
              (1 2 6 5)
 
        );
    }
    upperWall
    {
        type wall;
        faces
        (
            (3 2 6 7)
	      	
        );
    }
    lowerWall
    {
        type wall;
        faces
        (
            (0 1 5 4) 
	    
        );
    }
    sideWallleft
    {
        type wall;
        faces
        (
            (0 1 2 3)
            	
        );
    }
    sideWallright
    {
        type wall;
        faces
        (
            (4 5 6 7)
           	
        );
    }
);

mergePatchPairs
(
);

// ************************************************************************* //
Epsilon:
inlet: fixed value 168,
outlet: zeroGradient
walls: epsilonWallFunction: uniform 168
K
inlet: turbulentIntensityKineticEnergyInlet: intensity 0.032 value 3.05
outlet: zeroGradient
walls: kqRWallFunction: uniform 3.05
U
inlet: timeVaryingMappedFixedValue with a Turbulent profile as input, average 44 (m/s)
outlet: zeroGradient
walls: noSlip
p
inlet: zeroGradient
outlet: fixedvalue uniform 0
walls: zeroGradient
nut
inlet: calculated uniform 0
outlet: calculated uniform 0
walls: nutkWallFunction uniform 0

and for the solver and solution settings:

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      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     simpleFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         2000;

deltaT          1;

writeControl    timeStep;

writeInterval   50;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;

functions
{
    #includeFunc streamlines
}

// ************************************************************************* //
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
{
    p
    {
        solver          GAMG;
        tolerance       1e-12;
        relTol          0.001;
        smoother        GaussSeidel;

        minIter		3;
        maxIter   	100;
        nPreSweeps      1;
        nPostSweeps     3;
        nFinestSweeps   3;
        scaleCorrection true;
        directSolverCoarsestLevel false;
        cacheAgglomeration on; 

        nCellsInCoarsestLevel   500;

        agglomerator          faceAreaPair;
        mergeLevels           1;
    }

    U
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-09;
        relTol          0.1;
    }

    k
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-09;
        relTol          0.1;
    }

    epsilon
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-09;
        relTol          0.1;
    }

    R
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-09;
        relTol          0.1;
    }
 
    nuTilda
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-09;
        relTol          0.1;
    }

    omega
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-09;
        relTol          0.1;
    }
 }

//    "(U|k|epsilon|omega|f|v2)"
//    {
//        solver          smoothSolver;
//        smoother        symGaussSeidel;
//        tolerance       1e-06;
//        relTol          0;
//        nSweep          1;
//        maxIter         100;
//   }


 SIMPLE
 {
    nNonOrthogonalCorrectors 0;
 }
//    consistent      yes;

//    residualControl
//    {
//        p               1e-5;
//        U               1e-5;
//        "(k|epsilon|omega|f|v2)" 1e-12;
//    }
//}


 relaxationFactors
 {
    p          0.3;
    U	       0.7;
    k	       0.7;
    epsilon    0.7;
    R          0.7;
    nuTilda    0.7;
 }


//relaxationFactors
//{
//    equations
//    {
//        U               0.95; // 0.9 is more stable but 0.95 more convergent
//        ".*"            0.95; // 0.9 is more stable but 0.95 more convergent
//    }
//}


// ************************************************************************* //
Thank you very much in advance!

And if you need more info let me know.

Greetings,

Jorgen
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