[aliFauze]

Hello everyone,


I've been working with snappyHexMesh on a geometry that includes two regions: a solid region entirely within a fluid domain. I defined multiple patches for my geometry. The snappyHexMesh process retains the exterior patches, but after it finishes, I can't find the patches of the solid region which are supposed to be within the fluid. Instead, when I execute splitMeshRegions -cellZones, a new patch named "heater_to_room" is created that combines all the solid region's patches.
I tried to use the function surfaceToPatch but the patches are created just in the 0.001 file, and they are empty (nFaces 0 in the boundary file).


Can someone explain why the internal solid patches are not preserved as separate entities and how I might retain these internal solid patches within the fluid domain in the meshing process?
Any tips or suggestions would be greatly appreciated!


Thank you in advance!
Best Regards!

[wkernkamp]

There is not enough information here. You should look in your Dict files for the name heater_to_room.

[aliFauze]

Hello Will,
Thank you for your reply.
In my setup, the patch named "heater_to_room" is configured as follows in the mesh file:
heater_to_room
{
type mappedWall;
inGroups 1(wall);
nFaces 48002;
startFace 814235;
sampleMode nearestPatchFace;
sampleRegion room;
samplePatch room_to_heater;
}



My problem is that this patch combines all the faces, but in my original STL file and in my snappyHexMeshDict, I had separated the faces to apply different boundary conditions. How can I keep the original patch divisions?



PS: This is how I defined my patches in SHMDict

model.stl
{
type triSurfaceMesh;

regions
{
ceiling { name ceiling; }
floor { name floor; }
glass_doors { name glass_doors; }
insulated_walls { name insulated_walls; }
roof { name roof; }
back { name back; }
down { name down; }
front { name front; }
left { name left; }
right { name right; }
upper { name upper; }
}
}



and this are the patches in the output mesh file:
ceiling
{
type wall;
inGroups 1(wall);
nFaces 2668;
startFace 1578061;
}
floor
{
type wall;
inGroups 1(wall);
nFaces 5725;
startFace 1580729;
}
glass_doors
{
type wall;
inGroups 1(wall);
nFaces 828;
startFace 1586454;
}
insulated_walls
{
type wall;
inGroups 1(wall);
nFaces 26985;
startFace 1587282;
}
roof
{
type wall;
inGroups 1(wall);
nFaces 1768;
startFace 1614267;
}
room_to_heater
{
type mappedWall;
inGroups 1(wall);
nFaces 48002;
startFace 1616035;
sampleMode nearestPatchFace;
sampleRegion heater;
samplePatch heater_to_room;
}



Hopping it's clearer right now

[Yann]

Hello Ali,

splitMeshRegions automatically creates interface patches when splitting the mesh. So I think if you want to avoid it you should look into splitMeshRegions options.

The option -useFaceZones looks like it could be helpful:

-useFaceZones Use faceZones to patch inter-region faces instead of single patch

However I never used it so I'm not exactly sure how it works/behaves.

[aliFauze]

Hello Yann,


Thank you for you response, I tried running splitMeshRegions -cellZones -useFaces but it only duplicates the name, resulting in something like solid_to_fluid_solid_to_fluid instead of just solid_to_fluid. When I run splitMeshRegions -useFaces, it doesn't detect any regions.


Any advice on how to fix this?
Thanks!

[Yann]

It's very hypothetical since I never tried it myself, but I guess you need to define faceZones in snappy beforehand.

Could you post your snappyHexMeshDict?

[aliFauze]

Hello Yann,


Thank you for your response, and sorry for the late reply.


Here is my snappyHexMeshDict file.


/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v2312 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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


// 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
{
room.stl
{
type triSurfaceMesh;

regions
{
ceiling { name ceiling; }
floor { name floor; }
glass_doors { name glass_doors; }
insulated_walls { name insulated_walls; }
roof { name roof; }
}
}

heater.stl
{
type triSurfaceMesh;

regions
{
back { name back; }
down { name down; }
front { name front; }
left { name left; }
right { name right; }
upper { name upper; }
}
}

hot.stl
{
type triSurfaceMesh;

regions
{
a { name a; }
b { name b; }
c { name c; }
d { name d; }
e { name e; }
f { name f; }
}
}
}


// 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 1000000;

// 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 20000000;

// 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;
// Number of buffer layers between different levels.
// 1 means normal 2:1 refinement restriction, larger means slower
// refinement.
nCellsBetweenLevels 6;



// 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
(
);



// 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
{
room.stl
{
level (0 0);

regions
{
ceiling { level (0 0); patchInfo { type wall; }}
floor { level (0 0); patchInfo { type wall; }}
glass_doors { level (0 0); patchInfo { type wall; }}
insulated_walls { level (0 0); patchInfo { type wall; }}
roof { level (0 0); patchInfo { type wall; }}
}
}

heater.stl
{
level (0 0);

regions
{
back { level (3 3); patchInfo { type patch; }}
down { level (3 3); patchInfo { type patch; }}
front { level (3 3); patchInfo { type patch; }}
left { level (3 3); patchInfo { type patch; }}
right { level (3 3); patchInfo { type patch; }}
upper { level (3 3); patchInfo { type patch; }}
}
}

hot.stl
{
level (0 0);

regions
{
a { level (3 3); patchInfo { type patch; }}
b { level (3 3); patchInfo { type patch; }}
c { level (3 3); patchInfo { type patch; }}
d { level (3 3); patchInfo { type patch; }}
e { level (3 3); patchInfo { type patch; }}
f { level (3 3); patchInfo { type patch; }}
}
}

}

// Resolve sharp angles
resolveFeatureAngle 30;
locationsInMesh
(
(( 0.5647 0.12536 0.376) heater)
(( 1.4253 1.25635 1.243) room)
(( 0.5647 0.07645 0.113) hot)
);


// 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 1.0;

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

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

//- Highly experimental and wip: number of feature edge snapping
// iterations. Leave out altogether to disable.
// Of limited use in this case since faceZone faces not handled.
nFeatureSnapIter 10;

implicitFeatureSnap true;
multiRegionFeatureSnap true;
}