[GrivalszkiP]

Hi,

I'm trying to simulate a simple heat transfer case (getting to know the software for further researches) with buoyantBoussinesqPimpleFoam. Unfortunately, I have some numeric error in the results (pictures attached).

Why is this weird field in the corner? How can I get rid of it?

Thank you in advance!

Griva

[ErenC]

As a novice myself, you need to share your files too. All I can assume is you have way too course mesh. I modified buoyantBoussinesqPimpleFoam and used many times and never had this kind of issue.

[GrivalszkiP]

Thank you, but I don't think so... Anyway, here are my files:

U

PHP Code:

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0.1 0 0);

boundaryField
{
    inlet1
    {
        type            fixedValue;
        value           uniform (0.1 0 0);
    }

    inlet2
    {
        type            fixedValue;
        value           uniform (0.141 -0.141 0);
    }

    outlet
    {
        type            zeroGradient;
    }
    
    walls
    {
        type            noSlip;
    }
} 


p

PHP Code:

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    inlet1
    {
        type            zeroGradient;
    }
    
    inlet2
    {
        type            zeroGradient;
    }
    
    outlet
    {
        type            fixedValue;
        value            uniform 0;
    }

    walls
    {
        type            zeroGradient;

    }
} 


alphat

PHP Code:

dimensions      [0 2 -1 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    inlet1
    {
        type            calculated;
        value            uniform 0;
    }
    
    inlet2
    {
        type            calculated;
        value            uniform 0;
    }
    
    outlet
    {
        type            calculated;
        value            uniform 0;
    }
    
    walls
    {
        type            alphatJayatillekeWallFunction;
        Prt             0.85;
        value           uniform 0;
    }

} 


T

PHP Code:

dimensions      [0 0 0 1 0 0 0];

internalField   uniform 293.15;

boundaryField
{
    inlet1
    {
        type            fixedValue;
        value           uniform 293.15;
    }
    
    inlet2
    {
        type            fixedValue;
        value           uniform 303.15;
    }

    outlet
    {
        type            zeroGradient;
    }

    walls
    {
        type            zeroGradient;
    }
} 


nut

PHP Code:

dimensions      [0 2 -1 0 0 0 0];

internalField   uniform 0;

boundaryField
{

    inlet1
    {
        type            calculated;
        value           uniform 0;
    }

    inlet2
    {
        type            calculated;
        value           uniform 0;
    }
    
    outlet
    {
        type            calculated;
        value           uniform 0;
    }

    walls
    {
        type            nutkWallFunction;
        value           uniform 0;
    }
} 


k

PHP Code:

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0.1;

boundaryField
{
    inlet1
    {
        type            fixedValue;
        value           $internalField;
    }
    
    inlet2
    {
        type            fixedValue;
        value           $internalField;
    }

    outlet
    {
        type            inletOutlet;
        inletValue      $internalField;
        value           $internalField;
    }
    
    walls
    {
        type            kqRWallFunction;
        value           uniform 0.1;
    }
} 


epsilon

PHP Code:

dimensions      [0 2 -3 0 0 0 0];

internalField   uniform 0.01;

boundaryField
{

    inlet1
    {
        type            fixedValue;
        value           uniform 0.01;
    }
    
    inlet2
    {
        type            fixedValue;
        value           uniform 0.01;
    }
    
    outlet
    {
        type            inletOutlet;
        inletValue      uniform 0.01;
        value           uniform 0.01;
    }

    walls
    {
        type            epsilonWallFunction;
        value           uniform 0.01;
    }
} 


p_rgh

PHP Code:

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    inlet1
    {
        type            zeroGradient;
    }

    inlet2
    {
        type            zeroGradient;
    }

    outlet
    {
        type            zeroGradient;
    }
    
    walls
    {
        type            fixedFluxPressure;
    }
} 


transportProperties

PHP Code:

transportModel Newtonian;

// Laminar viscosity
nu              1e-06;

// Thermal expansion coefficient
beta            2e-04;

// Reference temperature
TRef            293.15;

// Laminar Prandtl number
Pr              7.56;

// Turbulent Prandtl number
Prt             0.7; 


fvSchemes

PHP Code:

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default         none;

    div(phi,U)      Gauss upwind;
    div(phi,T)      Gauss upwind;
    div(phi,k)      Gauss upwind;
    div(phi,epsilon) Gauss upwind;
    div(phi,R)      Gauss upwind;
    div(R)          Gauss linear;
    div((nuEff*dev2(T(grad(U))))) Gauss linear;
}

laplacianSchemes
{
    default         Gauss linear uncorrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         uncorrected;
} 


fvSolution

PHP Code:

solvers
{
    p_rgh
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance       1e-8;
        relTol          0.01;
    }

    p_rghFinal
    {
        $p_rgh;
        relTol          0;
    }

    "(U|T|k|epsilon|R)"
    {
        solver          PBiCGStab;
        preconditioner  DILU;
        tolerance       1e-6;
        relTol          0.1;
    }

    "(U|T|k|epsilon|R)Final"
    {
        $U;
        relTol          0;
    }
}

PIMPLE
{
    momentumPredictor no;
    nOuterCorrectors 1;
    nCorrectors     2;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue       0;
}

relaxationFactors
{
    equations
    {
        "(U|T|k|epsilon|R)" 1;
        "(U|T|k|epsilon|R)Final" 1;
    }
} 


controlDict

PHP Code:

application     buoyantBoussinesqPimpleFoam;

startFrom       latestTime;

startTime       0;

stopAt          endTime;

endTime         10;

deltaT          0.1;

writeControl    adjustableRunTime;

writeInterval   1;

purgeWrite      0;

writeFormat     ascii;

writePrecision  7;

writeCompression on;

timeFormat      general;

timePrecision   7;

runTimeModifiable yes;

adjustTimeStep  yes;

maxCo           1;
maxAlphaCo      1;
maxDeltaT       1; 


blockMeshDict

PHP Code:

scale   0.01;

vertices
(

    (-67 -15 -15)    //0
    (-34 -15 -15)    //1
    (0 -15 -15)        //2
    (83 -15 -15)    //3
    
    (-67 -15 15)    //4
    (-34 -15 15)    //5
    (0 -15 15)        //6
    (83 -15 15)        //7
    
    (-67 15 -15)    //8
    (-34 15 -15)    //9
    (0 15 -15)        //10
    (83 15 -15)        //11

    (-67 15 15)        //12
    (-34 15 15)        //13
    (0 15 15)        //14
    (83 15 15)        //15
    
    (-67 45 -15)    //16
    (-34 45 -15)    //17
    
    (-67 45 15)        //18
    (-34 45 15)        //19

);

blocks
(
    hex (0 1 9 8 4 5 13 12) (15 15 15) simpleGrading (1 1 1)        //A
    hex (1 2 10 9 5 6 14 13) (15 15 15) simpleGrading (1 1 1)        //B
    hex (2 3 11 10 6 7 15 14) (30 15 15) simpleGrading (1 1 1)        //C
    hex (9 10 17 16 13 14 19 18) (15 15 15) simpleGrading (1 1 1)    //D
    
);

edges
(
);

boundary
(
    inlet1
    {
        type patch;
        faces
        (
            (0 4 12 8)
        );
    }
    inlet2
    {
        type patch;
        faces
        (
            (16 18 19 17)
        );
    }
    outlet
    {
        type patch;
        faces
        (
            (11 15 7 3)

        );
    }
    
    walls
    {
        type wall;
        faces
        (
            (0 1 5 4)
            (1 2 6 5)
            (2 3 7 6)
            
            (4 5 13 12)
            (5 6 14 13)
            (6 7 15 14)
            
            (0 8 9 1)
            (1 9 10 2)
            (2 10 11 3)
            
            (8 12 13 9)
            (10 14 15 11)
            
            
            (9 13 18 16)
            (17 19 14 10)
            
            (13 14 19 18)
            (9 16 17 10)
        );
    }
);

mergePatchPairs
(
); 


[kcjarvis56]

The boundary conditions for the outlet appears to be a problem.

for p_rhg try something like:

outlet
{

type fixedValue;
value $internalField;
}

for U try something like:

outlet
{
type inletOutlet;
inletValue uniform (0 0 0);
value uniform (0 0 0);
}

for T try something like:
outlet
{
type inletOutlet;
inletValue $internalField;
value $internalField;
}

You should get good results with the above recommendations.

[GrivalszkiP]

Thank you, it's working!!