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Numerical instabilities due to temperature at inlet

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Old   June 18, 2013, 08:31
Default Numerical instabilities due to temperature at inlet
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Hi Foamers,

I have a problem with my simulation case.
I want to simulate a flow through a cube with 1.5 m/s.
The temperature of the cube is 1373 K, the inflow should have 1573 K.

I use buoyantSimpleFoam and kEpsilon.

If I set the inlet-temp. to 1373 K everything works fine.

If i set the inlet.-temp. to 1573 K numerical instabilities at the inlet occure. The temperature in some areas rises quite high, respectively drops.

I have no idea why, I guess something in my BCs is wrong.

The BCs are:

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.2.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      epsilon;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
dimensions      [0 2 -3 0 0 0 0];
internalField   uniform 1.505e-4;
boundaryField
{
    baseleft
    {
        type            compressible::epsilonWallFunction;
        value           uniform 1.505e-4;
    }
    baseright
    {
        type            compressible::epsilonWallFunction;
        value           uniform 1.505e-4;
    }
    sides
    {
        type            compressible::epsilonWallFunction;
        value           uniform 1.505e-4;
    }
    back
    {
        type            fixedValue;
        value           uniform 1.505e-4;
    }
    outlet
    {
        type            zeroGradient;
    }
}

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //dimensions      [0 2 -2 0 0 0 0];
internalField   uniform 2.383e-3;
boundaryField
{
    baseleft
     {
        type            compressible::kqRWallFunction;
        value           uniform 2.383e-3;
    }   
    baseright
     {
        type            compressible::kqRWallFunction;
        value           uniform 2.383e-3;
    }   
    sides
     {
        type            compressible::kqRWallFunction;
        value           uniform 2.383e-3;
    } 
    back
    {
       type            fixedValue;
        value           uniform 2.383e-3;
    }
    outlet
    {
        type            zeroGradient;
    }
}

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //dimensions      [ 1 -1 -2 0 0 0 0 ];
internalField   uniform 101325;
boundaryField
{
    baseleft
     {
        type            zeroGradient;
    }   
    baseright
     {
        type            zeroGradient;
    }   
    sides
     {
        type            zeroGradient;
    } 
    back
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 101325;
    }
}
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      p_rgh;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //dimensions      [ 1 -1 -2 0 0 0 0 ];
internalField   uniform 101325;
boundaryField
{
    baseleft
     {
        type            zeroGradient;
    }   
    baseright
     {
        type            zeroGradient;
    }   
    sides
     {
        type            zeroGradient;
    } 
    back
    {
        type            zeroGradient;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 101325;
    }
}

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      T;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //dimensions      [0 0 0 1 0 0 0];
internalField   uniform 1373;
boundaryField
{
    ".*"
    {
        type            fixedValue;
        value           uniform 1373;
    }
    back
    {        
    type            fixedValue;
        value           uniform 1373;
    }
    outlet
    {
       type            zeroGradient;
    }
}

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    location    "0";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //dimensions      [0 1 -1 0 0 0 0];
internalField   uniform (0 0 0);
boundaryField
{
    ".*"
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    back
    {
        type            fixedValue;
        value           uniform (0 0 -1.5);
    }
    outlet
    {
        type            zeroGradient;
    }
}

Does anyone have an idea what is wrong??

Many thanks in advance,

regards
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