[JTDN]

Hi everyone,

I'm new at OpenFoam, using OpenFoam V6 to run a 3D simulation on a modified Ahmed body (for those who don't know, it's a simplified car-like geometry used in automotive external aero).

My problem is that I can't get snappyhexmesh to actually snap the geometry. Basically it acts as if the geometry was not there. Since I'm new at openfoam and even newer at snappyhexmesh, I am sure there must be something obvious I am missing.

My geometry input is a closed stl (ASCII) with decent resolution. Basic patches (inlet, outlet etc) are defined directly in blockMesh.

For troubleshooting I've tried refining the initial blockMesh, changing parameters in surfaceFeaturesDict to get a very high number of feature edges, and finally I've tried a number of different locationInMesh parameters in snappyHexMeshDict, but no luck.

Please if you can let me know what I am missing it would be very helpful. i've included my blockMesh, features and snappy dicts as well as logs.

Thanks,

Jad

[snak]

Hi,


If you want to use OpenFOAM, you should read the log and messages.


Log from the snappyHexMesh tells the followings;

    Reading "/home/jtayoun/JT_run/run_openfoam/3_weeks/snappyDebugging/ahmedBody/system/snappyHexMeshDict.castellatedMeshControls.refinementSurfaces" from line 105 to line 106
      Not all entries in refinementSurfaces dictionary were used. The following entries were not used : 1(ahmed_body)

--> FOAM Warning :
    From function Foam::labelHashSet Foam::polyBoundaryMesh::patchSet(const Foam::UList<Foam::wordRe>&, bool, bool) const
    in file meshes/polyMesh/polyBoundaryMesh/polyBoundaryMesh.C at line 798
    Cannot find any patch or group names matching "ahmed_body.stl"
--> FOAM Warning :
    From function Foam::layerParameters::layerParameters(const Foam::dictionary&, const Foam::polyBoundaryMesh&)
    in file snappyHexMeshDriver/layerParameters/layerParameters.C at line 268
    Reading "/home/jtayoun/JT_run/run_openfoam/3_weeks/snappyDebugging/ahmedBody/system/snappyHexMeshDict.addLayersControls.layers"
    Layer specification for "ahmed_body.stl" does not match any patch.
Valid patches are
4
(
inlet
outlet
ground
frontAndBack
)

"ahmed_body.stl" does not match any patch.

Please read the snappyHexMeshDict in motorBike tutorial.
In geometry subdict, file name "motorBike.obj" is used and the patch is named as "motorBike".
In refinementSurfaces subsubdict in castellatedMeshControls subdict, patch name "motorBike" is used, not the file name "motorBike.obj".

You used patch name "car" in geometry subdict, and "ahmed_body" in castellatedMeshControls subdict. this is not consistent.

And, in AddLayersControls subdict, you used the geometry fle name "ahmed_body.stl" . This should be patch name (not geometry). There is an caution about this in the motorBike tutorial.

I'm not sure this fix your problem or not. but, at least, this will be a small improvement.

[JTDN]

Originally Posted by snak

Layer specification for "ahmed_body.stl" does not match any patch.
Valid patches are
4
(
inlet
outlet
ground
frontAndBack
)
[/CODE]
"ahmed_body.stl" does not match any patch.

Please read the snappyHexMeshDict in motorBike tutorial.
In geometry subdict, file name "motorBike.obj" is used and the patch is named as "motorBike".
In refinementSurfaces subsubdict in castellatedMeshControls subdict, patch name "motorBike" is used, not the file name "motorBike.obj".

You used patch name "car" in geometry subdict, and "ahmed_body" in castellatedMeshControls subdict. this is not consistent.

Thanks a lot for your reply! I had realised that and spent some time fiddling with the motorbike snappyhexmeshdict but couldn't really point to the problem. One question i have is how to define patches directly from an stl? As far as I know there is no way to define patches directly in an ASCII stl file.
Usually I compute the mesh on salome GUI (this is where i define all the patches), export it as .unv and convert it.
This time my only input is the .stl, and i've built the domain using blockMeshDict. Is there a dict in OF where i can define all the .stl surfaces as patches?

Thanks,

[JTDN]

I think this thread provides an answer: how to define patches with snappyHexMesh from a STL file ?

[snak]

Hi,


I just modified your snappyHexMeshDict as mentioned previous reply.
The name of patch is now consistent in the dict.