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High nut values in random place and time

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Old   January 9, 2019, 08:42
Default High nut values in random place and time
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Join Date: Oct 2018
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Hi,


I'm working on a simple 2D flow. When I changed turbulence model from kEpsilon to kOmegaSST I noticed that simulation works fine for around 300-600 iterations but then in random cell nut value goes quite high (around~1-1000).

Depending on boundary conditions it happens on boundaries or somewhere on the internal field. From then whole simulation goes wrong and number of iterations for omega rises from 1-5 to 200-800 in a single time step. I already tried modifying boundary conditions and refining the mesh but it didn't solve my problem.

Does anybody got any idea what I've done wrong?
Enclosed pictures and boundary conditions.


Thanks a lot,
Krzysztof


p
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0;

boundaryField
{
    #includeEtc "caseDicts/setConstraintTypes"

    inlet-aa
    {
        type            zeroGradient;
    }
inlet-bb
    {
        type            zeroGradient;
    }
    outlet-close
    {
        type            fixedValue;
        value           uniform 0;
    }
outlet-cc
    {
        type            fixedValue;
        value           uniform 0;
    }
    upperwall-aa
    {
        type            symmetry;
    }
upperwall-cc
    {
        type            symmetry;
    }
axi-bb
    {
        type            symmetry;
    }
axi-close
    {
        type            symmetry;
    }
a
    {
    type         zeroGradient;
    }
b
    {
    type         zeroGradient;
    }

frontAndBackPlanes
    {
        type            empty;
    }

}
U
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (20 0 0);

boundaryField
{
    #includeEtc "caseDicts/setConstraintTypes"

    inlet-aa
    {
  
        type            freestream;
        freestreamValue      $internalField;
    }
inlet-bb
    {
        type            freestream;
        freestreamValue      $internalField;
    }
    outlet-cc
    {
        type            inletOutlet;
        inletValue      $internalField;
        value           $internalField;
    }
outlet-close
    {
        type            inletOutlet;
        inletValue      $internalField;
        value           $internalField;
    }
  a
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
b
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
upperwall-cc
    {
        type            symmetry;
    }
upperwall-aa
    {
        type            symmetry;
    }

axi-close
    {
        type            symmetry;
    }
axi-bb
    {
        type            symmetry;
    }
frontAndBackPlanes
    {
        type            empty;
    }
}
nut
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      nut;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0;

boundaryField
{
    #includeEtc "caseDicts/setConstraintTypes"

    inlet-aa
    {
        type         freestream;
    freestreamValue  1e-2;
        /*type            calculated;
        value           $internalField;*/
    }
inlet-bb
    {
        type         freestream;
    freestreamValue  1e-2;
        /*type            calculated;
        value           $internalField;*/
    }
    outlet-close
    {
        type        zeroGradient;
        /*type            calculated;
        value           $internalField;*/
    //type        fixedValue;
    //value        uniform 0;
    }
outlet-cc
    {
        type        zeroGradient;
        /*type            calculated;
        value           $internalField;*/
    //type        fixedValue;
    //value        uniform 0;
    }
    upperwall-cc
    {
        type            symmetry
    }
upperwall-aa
    {
        type            symmetry
    }
axi-close
    {
        type            symmetry;
    }
axi-bb
    {   
         type            symmetry;
        //value           uniform 0;
    }
    a
    {
        type            nutkWallFunction;
        value           uniform 0;
    }
    b
    {
        type            nutkWallFunction;
        value           uniform 0;
    }
frontAndBackPlanes
    {
        type            empty;
    }
}
k
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 1;

boundaryField
{
    #includeEtc "caseDicts/setConstraintTypes"

    inlet-aa
    {
        type            turbulentIntensityKineticEnergyInlet;
        intensity       0.05;       // 5% turbulent intensity
        value           $internalField;
    }

    inlet-bb
    {
        type            turbulentIntensityKineticEnergyInlet;
        intensity       0.05;       // 5% turbulent intensity
        value           $internalField;
    }
 outlet-close
    {
        type            inletOutlet;
        inletValue      $internalField;
    }
outlet-cc
    {
        type            inletOutlet;
        inletValue      $internalField;
    }
    upperwall-cc
{
        type            symmetry
    }
upperwall-aa
{
        type            symmetry
    }
axi-close
    {      
    type            symmetry;
    }
axi-bb
    { 
        type            symmetry;
    }
    a
    {
    type            kqRWallFunction;
        value           uniform 0;
}
    b
    {
    type            kqRWallFunction;
        value           uniform 0;
    }
frontAndBackPlanes
    {
        type            empty;
    }
}
omega
Code:
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      omega;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //


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

internalField   uniform 1e-10;//$turbulentOmega;

boundaryField
{
    #includeEtc "caseDicts/setConstraintTypes"
    inlet-aa
    {
        type            inletOutlet;
        inletValue      $internalField;
        value           $internalField;
    }
inlet-bb
    {
        type            inletOutlet;
        inletValue      $internalField;
        value           $internalField;
    }
outlet-cc
    {
        type            inletOutlet;
        inletValue      $internalField;
        value           $internalField;
    }

    outlet-close
    {
        type            inletOutlet;
        inletValue      $internalField;
        value           $internalField;
    }

    a
    {
        type            omegaWallFunction;
        value           $internalField;
    }
    b
    {
        type            omegaWallFunction;
        value           $internalField;
    }
axi-close
    {
        type            symmetry;
    }
axi-bb
    {
        type            symmetry;
    }
upperwall-aa
    {
        type            symmetry
    }
upperwall-cc
    {
        type            symmetry
    }
frontAndBackPlanes
    {
        type            empty;
    }
}
Attached Images
File Type: jpg nut.jpg (16.2 KB, 17 views)
File Type: png nut2.png (2.7 KB, 17 views)
File Type: png nut3.png (39.8 KB, 14 views)
File Type: png velocity.png (32.0 KB, 17 views)
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