[klausb]

Hi,

I want to create a 2D mesh with cfMesh for airfoils analysis. The mesh has the following requirements:

1: O-mesh
2: y+ = 5 boundary layer
3: 300 cells at the airfoil surface
4: About 50.000 cells in total
5: Gradually coarser mesh starting at the airfoil boundary layer, ending at the farfield domain boundary

The airfoil contour with a blunt trailing edge and the farfield boundary are defined in airfoil_farfield.stl and are called inside the file airfoil and farfield respectively.

So far I am able to create a boundary layer mesh around the airfoil (still with too many cells) but at the same time there's always mesh refinement at the farfield boundary where the mesh should be very coarse.

How can I avoid the refinement at the farfield boundary?

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                |
| \\      /  F ield         | OpenFOAM GUI Project: creativeFields           |
|  \\    /   O peration     | Version:  0.8.9.0                              |
|   \\  /    A nd           | Web: www.c-fields.com                          |
|    \\/     M anipulation  |                                                |
\*---------------------------------------------------------------------------*/

FoamFile
{
version    2;
format    ascii;
class    dictionary;
location    "system";
object    meshDict;
}

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

maxCellSize         5;

minCellSize         0.002;

surfaceFile        "airfoil_farfield.stl";

localRefinement
{
  "farfield.*"
{
cellSize 5;
}
}


boundaryLayers
{
    patchBoundaryLayers
    {
        "airfoil.*"
        {
        nLayers                 20;
        boundaryCellSize                0.002;
        maxFirstLayerThickness             0.01;
        thicknessRatio          1.2;
        }
    }
}

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

attached a picture of the mesh

[dickcruz]

What does it look like when you turn the BL settings off?

[klausb]

the mesh looks the same just without a boundary layer mesh at the airfoil surface.

Any idea how to avoid the refinement at the farfield boundary and how to create a constantly coarser mesh towards the farfield boundary?

[peyman.davvalo.khongar]

Originally Posted by klausb

Hi,

I want to create a 2D mesh with cfMesh for airfoils analysis. The mesh has the following requirements:

1: O-mesh
2: y+ = 5 boundary layer
3: 300 cells at the airfoil surface
4: About 50.000 cells in total
5: Gradually coarser mesh starting at the airfoil boundary layer, ending at the farfield domain boundary

The airfoil contour with a blunt trailing edge and the farfield boundary are defined in airfoil_farfield.stl and are called inside the file airfoil and farfield respectively.

So far I am able to create a boundary layer mesh around the airfoil (still with too many cells) but at the same time there's always mesh refinement at the farfield boundary where the mesh should be very coarse.

How can I avoid the refinement at the farfield boundary?

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                |
| \\      /  F ield         | OpenFOAM GUI Project: creativeFields           |
|  \\    /   O peration     | Version:  0.8.9.0                              |
|   \\  /    A nd           | Web: www.c-fields.com                          |
|    \\/     M anipulation  |                                                |
\*---------------------------------------------------------------------------*/

FoamFile
{
version    2;
format    ascii;
class    dictionary;
location    "system";
object    meshDict;
}

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

maxCellSize         5;

minCellSize         0.002;

surfaceFile        "airfoil_farfield.stl";

localRefinement
{
  "farfield.*"
{
cellSize 5;
}
}


boundaryLayers
{
    patchBoundaryLayers
    {
        "airfoil.*"
        {
        nLayers                 20;
        boundaryCellSize                0.002;
        maxFirstLayerThickness             0.01;
        thicknessRatio          1.2;
        }
    }
}

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

attached a picture of the mesh

Moi!

If I understand it correctly, you want to have boundary layers around your airfoil face but you dont want any refinement at farfield face. isn't it?

If this is the case, why do you use localRefinement for farfield face? if you dont want that face to be refined, dont use it in localRefinement. Then it should be like this:

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

maxCellSize         5;

minCellSize         0.002;

surfaceFile        "airfoil_farfield.stl";

localRefinement
{
}


boundaryLayers
{
    patchBoundaryLayers
    {
        "airfoil.*"
        {
        nLayers                 20;
        boundaryCellSize                0.002;
        maxFirstLayerThickness             0.01;
        thicknessRatio          1.2;
        }
    }
}

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

If this is not your problem, please explain more.

Moikka,

Peyman