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Wind Turbine blade in 120 wedge - boundary conditions

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Old   September 23, 2015, 12:02
Default Wind Turbine blade in 120 wedge - boundary conditions
  #1
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Fabrizio
Join Date: May 2015
Posts: 3
Rep Power: 7
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Hello,

I'm trying to simulate the flow around a wind turbine blade with the SRF approach, using the k-epsilon model.
The rotational speed of the wind turbine is 12 rpm, while the air velocity is set to 10 m/s.
My mesh seems to be acceptable.
However, I'm having trouble with the boundary conditions implementation on the farfieldPatch. The ones I currently have are the following:

Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    location    "0";
    object      Urel;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (0 10 0);

boundaryField
{

    inlet
    {
        type            SRFVelocity;
        inletValue      uniform (0 10 0);
        relative        no;
        value           uniform (0 0 0);
    }

    outlet
    {
        type            zeroGradient;
    }

   farfieldPatch
    {
/*        type            slip;*/
/*        type            SRFFreestreamVelocity;*/
/*        UInf            (0 10 0);*/
/*        type            zeroGradient;*/
        type            SRFVelocity;
        inletValue      uniform (0 10 0);
        relative        no;
        value           uniform (0 0 0);
    }

    plane1Patch
    {
        type            cyclicAMI;
    }

    plane2Patch
    {
        type            cyclicAMI;
    }

    bladePatch
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
}
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0;

boundaryField
{
    inlet
    {
        type            zeroGradient;
    }

    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }

    farfieldPatch
    {
        type            zeroGradient;
    }

    plane1Patch
    {
        type            cyclicAMI;
    }

    plane2Patch
    {
        type            cyclicAMI;
    }

    bladePatch
    {
        type            zeroGradient;
    }
}
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 200; // = (3/2)*(U*I)^2 //0.375

boundaryField
{

    inlet
    {
        type            fixedValue;
        value           $internalField;
/*        type            turbulentIntensityKineticEnergyInlet;*/
/*        intensity       0.05; */
/*        value           uniform 1; //placeholder*/
    }

    outlet
    {
        type            zeroGradient;
    }

    farfieldPatch
    {
        type            slip;
    }

    plane1Patch
    {
        type            cyclicAMI;
        value           $internalField;
    }

    plane2Patch
    {
        type            cyclicAMI;
        value           $internalField;
    }

    bladePatch
    {
        type            kqRWallFunction;
        value           $internalField;
    }
}
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      epsilon;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -3 0 0 0 0];

internalField   uniform 3500; // = Cmu^(3/4)*k^(3/2)/l //0.2695

boundaryField
{

    inlet
    {
        type            fixedValue;
        value           $internalField;
/*        type            turbulentMixingLengthDissipationRateInlet;*/
/*        mixingLength    0.14;*/
/*        value           uniform 1; //placeholder*/
    }

    outlet
    {
        type            zeroGradient;
    }

    farfieldPatch
    {
        type            slip;
    }

    plane1Patch
    {
        type            cyclicAMI;
    }

    plane2Patch
    {
        type            cyclicAMI;
    }

    bladePatch
    {
        type            epsilonWallFunction;
        U               Urel;
        value           $internalField;
    }
}
Regarding Urel, the boundary conditions on farfieldPatch slip, SRFVelocity and zeroGradient all give me the same weird discontinuity you can see in the picture.
SRFFreestreamVelocity (what does it do?) makes my solution diverge.

I also have doubts for the values of k and epsilon: using the suggested formulas ( http://www.cfd-online.com/Wiki/Turbu...ary_conditions ) I obtain the commented values. However, the solution diverges using those values, and after many trial and errors I got to very high final values. Is it possible that those are correct? Do I have to use the relative wind speed or the absolute wind speed to calculate them?

Thank you in advance for any suggestions!
Attached Images
File Type: jpg mesh.jpg (126.3 KB, 29 views)
File Type: jpg flow.jpg (35.6 KB, 37 views)
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Old   December 2, 2019, 06:47
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  #2
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mostafa kamal
Join Date: Jun 2019
Posts: 16
Rep Power: 3
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i think you should use simpleFoam with MRF option , i think the solver is more stable
mostafa kamal is offline   Reply With Quote

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