[flowwwww]

hello everyone,
I am working in a convection oven, specifically in the duct that inyect the hot air.
I have been trying to mesh the geometry, but i have found some problems with the edges on a change section part and a curve part.
Captura de pantalla de 2019-10-11 23-58-38.png Vertical part. Upper -->change section/ Lower --> curve
Horizontal part. No problem


Captura de pantalla de 2019-10-11 23-57-45.png

Captura de pantalla de 2019-10-11 23-56-20.png
Here are some of the setted parameters.


*************

castellatedMesh true;
snap true;
addLayers false;

// Geometry.

geometry
{
walls.stl
{
type triSurfaceMesh;
name walls;
}

inlet.stl
{
type triSurfaceMesh;
name inlet;
}

refinementBox
{
type searchableBox;
min (0.0 0.0 0.0 );
max ( 0.9 3.5 0.35 );
}

refinementCylinder1
{
type searchableCylinder;
point1 (0.9 0 0);
point2 (0.9 3.5 0);
radius 0.9;
}
castellatedMeshControls
{
maxLocalCells 100000;
maxGlobalCells 2000000;
minRefinementCells 10;
maxLoadUnbalance 0.10;
nCellsBetweenLevels 3;
// Explicit feature edge refinement
features
(

{
file "walls.eMesh";
level 3;
}
{
file "inlet.eMesh";
level 0;
}
refinementSurfaces
{
walls
{

level (2 2);

patchInfo
{
type wall;
inGroups (walls);
}
}
inlet
{
level (0 0);

patchInfo
{
type patch;
inGroups (inlet);
}
}
resolveFeatureAngle 5;
refinementRegions
{

refinementBox
{
mode inside;
levels ((1E15 2));
}

refinementCylinder1
{
mode inside;
levels ((1E15 2));
}
locationInMesh (0.001 2.0 0.2);
allowFreeStandingZoneFaces true;


snapControls
{
nSmoothPatch 3;
tolerance 4.0;
nSolveIter 5;
nRelaxIter 5;

// Feature snapping

nFeatureSnapIter 0;
implicitFeatureSnap false;
explicitFeatureSnap true;
multiRegionFeatureSnap true;
}


meshQualityControls
{

maxNonOrtho 90;
maxBoundarySkewness 20;
maxInternalSkewness 4;
maxConcave 80;
minVol -1e30;
minTetQuality 1e-30;
minArea -1;
minTwist 0.02;
minDeterminant 0.001;
minFaceWeight 0.02;
minVolRatio 0.01;
minTriangleTwist -1;

// Advanced

nSmoothScale 4;
errorReduction 0.75;
}
**********

In the other hand, i would like to ask if some of you know how to obtain a mesh inside the geometry besides the mesh in the geometry itself.



Thanks everyone.

[piotr.mecht]

Your snapControls settings are very coarse:


nSolveIter of 5 might be waay to little. I often use 100-300 iterations in most cases (your shape is quite simple, so 100 could be more than enough).

You also use explicit feature snapping, but your nFeatureSnapIter value is 0, so it doesn't snap to any explicitly defined features (edges provided in walls.eMesh) at all.

Originally Posted by flowwwww

In the other hand, i would like to ask if some of you know how to obtain a mesh inside the geometry besides the mesh in the geometry itself.

What do you mean? Do you want to put an obstacle in your flow? You can provide another STL inside your channel, or you can provide STL with multiple solids defined

[virengos]

SnappyHexmesh is a really great mesher, but it comes with a steep learning curve though. For simple objects, like the duct, you could easily use the Salome software for meshing with a robust boundary layer and furthermore omit the blockmesh creation in OF. Let me know, if you need some further support on this.
best,
Damian

[flowwwww]

Thanks Virgengos for the advice. I am a begginer in OpenFOAM and sHM, but i would like to learn this helpful tools now. Starting with problem with simple geometry.

[flowwwww]

I adjusted some parameters according to the advices. My snap controls and meshqualitycontrols changed to the followings.


********

snapControls
{
nSmoothPatch 10;
tolerance 1.0;
nSolveIter 100;
nRelaxIter 5;

// Feature snapping

nFeatureSnapIter 35;
implicitFeatureSnap false;
explicitFeatureSnap true;
multiRegionFeatureSnap true;
}


meshQualityControls
{

maxNonOrtho 90;
maxBoundarySkewness 20;
maxInternalSkewness 4;
maxConcave 80;
minVol -1e30;
minTetQuality 1e-30;
minArea -1;
minTwist 0.02;
minDeterminant 0.001;
minFaceWeight 0.02;
minVolRatio 0.01;
minTriangleTwist -1;

// Advanced

nSmoothScale 4;
errorReduction 0.75;
}
**********


This changes give me a way better mesh. But i still having some little problems.

foto1.png

foto2.png
I dont know if you have some ideas of small changes to improve it or this one is enough.

Best regards.

[piotr.mecht]

It often requires some trial and error to make your best mesh..
I'd look at:

//- Relative distance for points to be attracted by surface feature point
    //  or edge. True distance is this factor times local
    //  maximum edge length.
    tolerance 1.0; //1.0;

or this duo:

//-    Existing cell edges are aligned with feature lines by default. 
    //    Unsuccessful alignment will result in concavity which consequently will lead to non-orthogonality 
    //    on the extruded mesh at the layer adding phase. 
    //    Where the mesh quality fails the extrusion is disabled. 
    //    Resulting in no prismatic layer coverage in the area. 
    //    The settings is typically followed by the layerTerminationAngle and detectExtrusionIsland 
    //    parameters in addLayerControls dictionary.
    //
    //    Sets the interval of iterations. Set to -1 to disable
    nFaceSplitInterval 2;
    
    //-    Angle at which the face is too concave and will be split. Default is 45 deg.
    concaveAngle 30;//40;

Sometimes, when you just change +1 or -1 cell in X, Y or Z in the background mesh the results are a bit different, so you can also play with this parameter.



There are some more keywords you can put into your snapControls:
https://www.openfoam.com/documentati...-snapping.html