[Other] Structured mesh around airfoil

Flowkersma · March 4, 2021, 03:26

Hi,

Is the mesh fine after those steps? If you want to further split the wall boundary, you can use topoSet utility.

Best, Mikko

afa13 · March 4, 2021, 05:18

Hi Miikko,
I ran checkMesh and i got the following:

Code:

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create polyMesh for time = 0

Time = 0

Mesh stats
    points:           49800
    internal points:  0
    faces:            98853
    internal faces:   49053
    cells:            24651
    faces per cell:   6
    boundary patches: 3
    point zones:      0
    face zones:       0
    cell zones:       0

Overall number of cells of each type:
    hexahedra:     24651
    prisms:        0
    wedges:        0
    pyramids:      0
    tet wedges:    0
    tetrahedra:    0
    polyhedra:     0

Checking topology...
    Boundary definition OK.
    Cell to face addressing OK.
    Point usage OK.
    Upper triangular ordering OK.
    Face vertices OK.
    Number of regions: 1 (OK).

Checking patch topology for multiply connected surfaces...
    Patch               Faces    Points   Surface topology                  
    walls               249      498      ok (non-closed singly connected)  
    frontAndBack        49302    49800    ok (non-closed singly connected)  
    farfield            249      498      ok (non-closed singly connected)  

Checking geometry...
    Overall domain bounding box (-11.6194 -13.4897 0) (13.607 13.4897 1)
    Mesh has 2 geometric (non-empty/wedge) directions (1 1 0)
    Mesh has 2 solution (non-empty) directions (1 1 0)
    All edges aligned with or perpendicular to non-empty directions.
    Boundary openness (-4.78455e-20 -8.4208e-18 -7.00152e-15) OK.
    Max cell openness = 1.42909e-14 OK.
    Max aspect ratio = 536.007 OK.
    Minimum face area = 2.64583e-09. Maximum face area = 1.54076.  Face area magnitudes OK.
    Min volume = 2.64583e-09. Max volume = 0.585316.  Total volume = 537.939.  Cell volumes OK.
    Mesh non-orthogonality Max: 15.2625 average: 5.14365
    Non-orthogonality check OK.
    Face pyramids OK.
    Max skewness = 0.375565 OK.
    Coupled point location match (average 0) OK.

Mesh OK.

End

Then I checked the yPlus and I got the following:

Code:

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Create mesh for time = 0


SIMPLE: Convergence criteria found
        p: tolerance 0.1
        U: tolerance 0.001
        "(k|epsilon)": tolerance 0.01

Time = 0
Reading field p

Reading field U

Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian
Selecting turbulence model type RAS
Selecting RAS turbulence model kEpsilon
RAS
{
    RASModel        kEpsilon;
    turbulence      on;
    printCoeffs     on;
    Cmu             0.09;
    C1              1.44;
    C2              1.92;
    C3              0;
    sigmak          1;
    sigmaEps        1.3;
}

No MRF models present

No finite volume options present
yPlus yPlus write:
    writing object yPlus
    patch walls y+ : min = 0.0799493, max = 0.0808106, average = 0.0807724


Time = 57
Reading field p

Reading field U

Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian
Selecting turbulence model type RAS
Selecting RAS turbulence model kEpsilon
RAS
{
    RASModel        kEpsilon;
    turbulence      on;
    printCoeffs     on;
    Cmu             0.09;
    C1              1.44;
    C2              1.92;
    C3              0;
    sigmak          1;
    sigmaEps        1.3;
}

No MRF models present

No finite volume options present
yPlus yPlus write:
    writing object yPlus
    patch walls y+ : min = 0.214267, max = 11.3621, average = 1.23938


End

I am still new at openFoam. So i'm not familiar with all the commands. I followed your instructions to create a mesh from construct2D and generate it in openFoam. Can you please tell me how to split the farfield patch into an inlet and outlet patches step by step, because i used the help option of topoSet and I didnt know what to do next?

Thanks!

Flowkersma · March 6, 2021, 06:59

The mesh has a high (geometric) quality. Why do you want to split the farfield boundary (see inletOutlet boundary condition that I mentioned in one of the previous messages)? Where exactly would you split the farfield patch?

afa13 · March 6, 2021, 10:33

Quote:

Originally Posted by Flowkersma

The mesh has a high (geometric) quality. Why do you want to split the farfield boundary (see inletOutlet boundary condition that I mentioned in one of the previous messages)? Where exactly would you split the farfield patch?

Hi Mikko,

I was just trying to understand how to split the faces and how to identify them in the code and assigning them to patches by playing around. It has nothing to do with my goal that is to simulate the flow around the airfoil and determine the lift and drag coefficients.
Can you check if my boundary conditions are ok?

Code:

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  8
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      epsilon;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

epsilonInlet  3.61; // Cmu^0.75 * k^1.5 / L ; L =10

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

internalField   uniform $epsilonInlet;

boundaryField
{

 farfield
    {
        type            freestreamPressure;
        freestreamValue $internalField;
        value           $internalField;
    }
    walls
    {
        type            epsilonWallFunction;
        value           $internalField;
    }
    frontAndBack
    {
        type            empty;
    }
}
    
}

// ************************************************************************* //

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0.2;

boundaryField
{
 farfield
    {
        type            freestreamPressure;
        freestreamValue $internalField;
        value           $internalField;
    }
   
    walls
    {
        type            kqRWallFunction;
        value           $internalField;
    }
    
    frontAndBack
    {
        type            empty;
    }
}


// ************************************************************************* //

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5.x                                   |
|   \\  /    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 (51.7844 5.52501 0);

boundaryField
{
    walls
    {
        type            noSlip;
    }
     farfield
    {
        type            freestreamVelocity;
        freestreamValue $internalField;
        value           $internalField;
    }

    frontAndback
    {
        type            empty;
    }
}


// ************************************************************************* //

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5.x                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0;

boundaryField
{
    walls
    {
        type            zeroGradient;
    }
     farfield
    {
        type            freestreamPressure;
        freestreamValue $internalField;
        value           $internalField;
    }
 
    frontAndback
    {
        type            empty;
    }
    
}


// ************************************************************************* //

Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5.x                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      nut;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 1.94e-05;

boundaryField
{
    walls
    {
        type            nutkWallFunction;
        value           $internalField;
    }
     farfield
    {
        type            freestreamPressure;
        freestreamValue $internalField;
        value           $internalField;
    }

    frontAndback
    {
        type            empty;
    }
}


// ************************************************************************* //

hoyos98 · March 7, 2022, 18:14

I suggest you visit https://aeroptimal.com/mesh (you must create an account to use this module), where you can create a full structured airfoil mesh - https://youtu.be/4Opu0zk7gFk . You can export .su2 .msh .foam .vtk

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March 4, 2021, 03:26		#21
Flowkersma Senior Member Mikko Join Date: Jul 2014 Location: The Hague, The Netherlands Posts: 243 Rep Power: 13	Hi, Is the mesh fine after those steps? If you want to further split the wall boundary, you can use topoSet utility. Best, Mikko

March 6, 2021, 06:59		#23
Flowkersma Senior Member Mikko Join Date: Jul 2014 Location: The Hague, The Netherlands Posts: 243 Rep Power: 13	The mesh has a high (geometric) quality. Why do you want to split the farfield boundary (see inletOutlet boundary condition that I mentioned in one of the previous messages)? Where exactly would you split the farfield patch?

March 7, 2022, 18:14		#25
hoyos98 New Member jose daniel Join Date: Apr 2020 Posts: 26 Rep Power: 6	I suggest you visit https://aeroptimal.com/mesh (you must create an account to use this module), where you can create a full structured airfoil mesh - https://youtu.be/4Opu0zk7gFk . You can export .su2 .msh .foam .vtk