[emregungor]

Hello Everyone,

I have been trying a while compile my case with OF. My subject is cfd analysis of radome shape on fuselage (e.g A320 airplane). I researched a few similar studies. I found that they use motorBike case, they remove motorBike original surface data and put there their own data (.stl format). I tried this way but failed.

* 'surfaceFeatureExtract' command doesn't work on my terminal.

May be someone help me here about step by step for solution?

Thanks for your kindness,

[clapointe]

To help, we will need to see the error. Additionally, mentioning the OF version will help -- a quick scan of the current tutorial case does not appear to use surfaceFeatureExtract (now just surfaceFeatures, I think).

Caelan

[emregungor]

Hi,

Thanks for help. I shared my steps about commands. What am I supposed to do for proper case setup?

step-1.jpg

step-2.jpg

step-3.jpg

[clapointe]

It is difficult to follow/figure out what you did from images of your terminal -- it would be easier if you posted the series of commands you used and associated error with code tags. That said, it looks like the problem is the snappy step. Without seeing your dictionary I can only guess as to what the problem is. Can you post it?

Caelan

[emregungor]

1- $ run
2- $ cd Car (this file copy of motorBike Case. I copied and changed a few things;
a- changed directory name as Car
b- I put my car.stl file in place of the motorBike.obj file.
c- changed 'blockMeshDict' and their vertices values
d- changed 'snappyHexMeshDict' respectively
3- $ blockMesh (fine result)
4- $ snappyHexMesh (fine result with any error. But I didn't see my surface when I wrote $ paraFoam for visualize)
5- $ .//Allrun
6- $ paraFoam (again same thing happened, I saw 'CarGroup' section in the left frame (in paraview). But it's disappeared when I was click-on this section.)

I hope described clearly my trouble. Because my knowledge insufficient about this subject

[clapointe]

That all looks fine. Can you post the snappyHexMeshDict?

Caelan

[emregungor]

I attached the document.

[clapointe]

I meant can you post it here with code tags -- then we can see it directly.

Caelan

[emregungor]

Originally Posted by clapointe

I meant can you post it here with code tags -- then we can see it directly.

Caelan

Sorry,

/*--------------------------------*- C++ -*----------------------------------*\
========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Version: 6
\\/ M anipulation |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// Which of the steps to run
castellatedMesh true;
snap true;
addLayers true;


// Geometry. Definition of all surfaces. All surfaces are of class
// searchableSurface.
// Surfaces are used
// - to specify refinement for any mesh cell intersecting it
// - to specify refinement for any mesh cell inside/outside/near
// - to 'snap' the mesh boundary to the surface
geometry
{
Car
{
type triSurfaceMesh;
file "Car.stl";
}

refinementBox
{
type searchableBox;
min (-1.0 -0.7 0.0);
max ( 8.0 0.7 2.5);
}
};



// Settings for the castellatedMesh generation.
castellatedMeshControls
{

// Refinement parameters
// ~~~~~~~~~~~~~~~~~~~~~

// If local number of cells is >= maxLocalCells on any processor
// switches from from refinement followed by balancing
// (current method) to (weighted) balancing before refinement.
maxLocalCells 100000;

// Overall cell limit (approximately). Refinement will stop immediately
// upon reaching this number so a refinement level might not complete.
// Note that this is the number of cells before removing the part which
// is not 'visible' from the keepPoint. The final number of cells might
// actually be a lot less.
maxGlobalCells 2000000;

// The surface refinement loop might spend lots of iterations refining just a
// few cells. This setting will cause refinement to stop if <= minimumRefine
// are selected for refinement. Note: it will at least do one iteration
// (unless the number of cells to refine is 0)
minRefinementCells 10;

// Allow a certain level of imbalance during refining
// (since balancing is quite expensive)
// Expressed as fraction of perfect balance (= overall number of cells /
// nProcs). 0=balance always.
maxLoadUnbalance 0.10;


// Number of buffer layers between different levels.
// 1 means normal 2:1 refinement restriction, larger means slower
// refinement.
nCellsBetweenLevels 3;



// Explicit feature edge refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

// Specifies a level for any cell intersected by its edges.
// This is a featureEdgeMesh, read from constant/triSurface for now.
features
(
{
file "Car.eMesh";
level 6;
}
);



// Surface based refinement
// ~~~~~~~~~~~~~~~~~~~~~~~~

// Specifies two levels for every surface. The first is the minimum level,
// every cell intersecting a surface gets refined up to the minimum level.
// The second level is the maximum level. Cells that 'see' multiple
// intersections where the intersections make an
// angle > resolveFeatureAngle get refined up to the maximum level.

refinementSurfaces
{
Car
{
// Surface-wise min and max refinement level
level (5 6);

// Optional specification of patch type (default is wall). No
// constraint types (cyclic, symmetry) etc. are allowed.
patchInfo
{
type wall;
inGroups (CarGroup);
}
}
}

// Resolve sharp angles
resolveFeatureAngle 30;


// Region-wise refinement
// ~~~~~~~~~~~~~~~~~~~~~~

// Specifies refinement level for cells in relation to a surface. One of
// three modes
// - distance. 'levels' specifies per distance to the surface the
// wanted refinement level. The distances need to be specified in
// descending order.
// - inside. 'levels' is only one entry and only the level is used. All
// cells inside the surface get refined up to the level. The surface
// needs to be closed for this to be possible.
// - outside. Same but cells outside.

refinementRegions
{
refinementBox
{
mode inside;
levels ((1E15 4));
}
}


// Mesh selection
// ~~~~~~~~~~~~~~

// After refinement patches get added for all refinementSurfaces and
// all cells intersecting the surfaces get put into these patches. The
// section reachable from the locationInMesh is kept.
// NOTE: This point should never be on a face, always inside a cell, even
// after refinement.
locationInMesh (3.0001 3.0001 0.43);


// Whether any faceZones (as specified in the refinementSurfaces)
// are only on the boundary of corresponding cellZones or also allow
// free-standing zone faces. Not used if there are no faceZones.
allowFreeStandingZoneFaces true;
}



// Settings for the snapping.
snapControls
{
//- Number of patch smoothing iterations before finding correspondence
// to surface
nSmoothPatch 3;

//- Relative distance for points to be attracted by surface feature point
// or edge. True distance is this factor times local
// maximum edge length.
tolerance 2.0;

//- Number of mesh displacement relaxation iterations.
nSolveIter 30;

//- Maximum number of snapping relaxation iterations. Should stop
// before upon reaching a correct mesh.
nRelaxIter 5;

// Feature snapping

//- Number of feature edge snapping iterations.
// Leave out altogether to disable.
nFeatureSnapIter 10;

//- Detect (geometric only) features by sampling the surface
// (default=false).
implicitFeatureSnap false;

//- Use castellatedMeshControls::features (default = true)
explicitFeatureSnap true;

//- Detect points on multiple surfaces (only for explicitFeatureSnap)
multiRegionFeatureSnap false;
}



// Settings for the layer addition.
addLayersControls
{
// Are the thickness parameters below relative to the undistorted
// size of the refined cell outside layer (true) or absolute sizes (false).
relativeSizes true;

// Per final patch (so not geometry!) the layer information
layers
{
"(lowerWall|Car).*"
{
nSurfaceLayers 1;
}
}

// Expansion factor for layer mesh
expansionRatio 1.0;

// Wanted thickness of final added cell layer. If multiple layers
// is the thickness of the layer furthest away from the wall.
// Relative to undistorted size of cell outside layer.
// See relativeSizes parameter.
finalLayerThickness 0.3;

// Minimum thickness of cell layer. If for any reason layer
// cannot be above minThickness do not add layer.
// Relative to undistorted size of cell outside layer.
minThickness 0.1;

// If points get not extruded do nGrow layers of connected faces that are
// also not grown. This helps convergence of the layer addition process
// close to features.
// Note: changed(corrected) w.r.t 17x! (didn't do anything in 17x)
nGrow 0;

// Advanced settings

// When not to extrude surface. 0 is flat surface, 90 is when two faces
// are perpendicular
featureAngle 60;

// At non-patched sides allow mesh to slip if extrusion direction makes
// angle larger than slipFeatureAngle.
slipFeatureAngle 30;

// Maximum number of snapping relaxation iterations. Should stop
// before upon reaching a correct mesh.
nRelaxIter 3;

// Number of smoothing iterations of surface normals
nSmoothSurfaceNormals 1;

// Number of smoothing iterations of interior mesh movement direction
nSmoothNormals 3;

// Smooth layer thickness over surface patches
nSmoothThickness 10;

// Stop layer growth on highly warped cells
maxFaceThicknessRatio 0.5;

// Reduce layer growth where ratio thickness to medial
// distance is large
maxThicknessToMedialRatio 0.3;

// Angle used to pick up medial axis points
// Note: changed(corrected) w.r.t 17x! 90 degrees corresponds to 130 in 17x.
minMedianAxisAngle 90;


// Create buffer region for new layer terminations
nBufferCellsNoExtrude 0;


// Overall max number of layer addition iterations. The mesher will exit
// if it reaches this number of iterations; possibly with an illegal
// mesh.
nLayerIter 50;
}



// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
#include "meshQualityDict"
}


// Advanced

// Write flags
writeFlags
(
scalarLevels
layerSets
layerFields // write volScalarField for layer coverage
);


// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1e-6;


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

[clapointe]

That all looks fine. However I am beginning to suspect something else. When you run snappy, you should notice multiple time directories are created. I expect that the car patch/group you want will exist in the final one of these directories. This happens if the -overwrite flag is not used.

Caelan

[emregungor]

Originally Posted by clapointe

I meant can you post it here with code tags -- then we can see it directly.

Caelan

Originally Posted by clapointe

That all looks fine. However I am beginning to suspect something else. When you run snappy, you should notice multiple time directories are created. I expect that the car patch/group you want will exist in the final one of these directories. This happens if the -overwrite flag is not used.

Caelan

I think, I don't understand. Because 'overwrite flag' didn't make any sense to me. I guess, I don't know what is this.

[clapointe]

It tells snappy to overwrite the mesh instead of creating new time directories. Use "snappyHexMesh -overwrite". There are a variety of tutorials that use the flag.

Caelan

[emregungor]

Would you share the tutorial you mentioned to me about that use the flag? Maybe I'll find the wrong tutorial when I'm looking for this. I don't want to do anything wrong. I'm confused enough.

[clapointe]

You can find a variety by searching the code for "snappyHexMesh -overwrite". That said, here is one (it is even the motorBike tutorial): https://github.com/OpenFOAM/OpenFOAM...torBike/Allrun.

Caelan

[emregungor]

Thanks Caelan, I wıll write again here after working all day.