Hey Martin
 

Hello Martin. Is it possible to mesh such a geometry as that prescribed in my blockMeshdict with facemerging? It is just a flat plate.

Cheers
Deji

Hi Deji,

does the attached blockMeshDict fit your intention? It uses mergePatchPairs to connect the two blocks with different numbers of elements.

Martin

Hi Martin. I will check it. Thanks.

Hello Martin. I was able to get it work, thanks much. Now the purpose that I asked if that was possible in OpenFOAM is because I would like to use snappyHexMesh utility on this mesh. Thus far, it isn't working and the code doesn't like it. How do you think one can refine the mesh with a tool such as snappyHexMesh?

Cheers,
Deji

Hi Deji,

here I must give up, I'm no regular snappy user ;-)

May be one of the others foamers can give advice here?

Martin

Hallo Deji,

could you figure out what kind of refinement zone do you need?
I mean, you need a box, a cylinder a sphere or something else, since with snappyHex you can also use an stl file to set a refinement zone.

Having these details maybe I can help,

Cheers,

Elia

Hello again. It is a box refinement zone that I actually need. Now, I do know how to use snappyHexmesh, the issue is that I used mergePatchPairs when I ran blockMesh. And the mesh is not fully hexes, a part of the mesh looked somewhat unstructured. The blockMeshDict that Martin posted has the file, please take a look at it and tell me if snappyHexMesh can be used for it.

Hello Deji,

I've made several tests.
I've seen that after using merging PatchPairs you can normally use snappyHexMesh but only for refining regions that not cross the merged patches.

I've attached a figure with paraFoam of what happens when one refines before and after the merged zone.

Attachment 10384

Attachment 10385

Of course when I use a cylinder refinement region that cross the merged patches it doesn't work.

I've also tried by not using mergePatchPairs and directly using snappyHexMesh after blockMesh. The result is, at least for me, that after using snappy it will left you only the region belonging to the master patch, whatever I try, it replies me always the same.
I've attached also a figure with this situation.

Attachment 10386

Hope it can helps you,

Cheers,

Elia

Thanks much Elia. I did try that and did see as well that snappyHexMesh doesn't allow one to refine the mesh if the region across the merged patch was prescribed. :confused: So there is no way around this? I wish this was possible in OpenFOAM, otherwise I will have to construct such a mesh with gmsh. Thanks again Elia.

Cheers,
Deji

Unfortunately I cannot do anymore, at least for now.
Anyway you could also try to build two refiniement zone just before and after the merged regions with some boxes, and see if it fullfills your requirements, since maybe the non hexahedral cells built within the merging process will disturb the solution more than this refined-not refined-refined again passing through the merged patch.

Good luck,

Elia

Insertion of a Cylinder
 

Dear Martin, as you may see in the included file, I'm trying to expand the geometry you should know, by making it cylindrical through the arc edge. No problem occurs until I insert a small pipe, because it generates an undesired mesh. How could I solve this problem? I thank you in advance for any consideration that you will give to this post.

Paolo

Hi Paolo,

blockMesh is definitely not the primary choice to create a 3D mesh for your geometry.

Is there any special reason that you don't use Salome or another free mesh generator?

Martin

No Martin, there's not a reason, I just thought I could do that directly on blockMesh.
I'll try this Salome you talk about, and I'll let you know. Thanks :)

3D mesh solved
 

Hi Martin, I succeed in generating a 3D mesh with blockMesh, I just redefined my strategy in the block construction and everything worked fine, even checkMesh didn't find any error in the mesh. Simulations run well too, if you are interested in it, I'll post the blockMeshDict file.

Paolo

Hi Paolo,

yes, I am interested... always eager to learn more about blockMesh strategies ;-)

Martin

Here is the file!

Congratulations ;-)

CU and thanks for posting...

Martin

Error in executing blockMesh in axisymmetric case
 

Dear Martin,

I am trying to simulate an axisymmetric case. When I execute the blockMesh in OpenFOAM 2.1.1, I get this error:

Date : Feb 03 2014
Time : 18:46:49
Host : "mountaineer"
PID : 23677
Case : /auto/scratch/mdinc/drop_case3b_2D
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Disallowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Creating block mesh from
"/auto/scratch/mdinc/drop_case3b_2D/constant/polyMesh/blockMeshDict"
Creating curved edges
Creating topology blocks
Creating topology patches

Creating block mesh topology
#0 Foam::error::printStack(Foam::Ostream&) in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1 Foam::sigFpe::sigHandler(int) in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2
at sigaction.c:0
#3 Foam::wedgePolyPatch::initTransforms() in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#4 Foam::wedgePolyPatch::wedgePolyPatch(Foam::word const&, Foam::dictionary const&, int, Foam::polyBoundaryMesh const&) in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#5 Foam::polyPatch::adddictionaryConstructorToTable<F oam::wedgePolyPatch>::New(Foam::word const&, Foam::dictionary const&, int, Foam::polyBoundaryMesh const&) in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#6 Foam::polyPatch::New(Foam::word const&, Foam::dictionary const&, int, Foam::polyBoundaryMesh const&) in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#7 Foam::polyMesh::polyMesh(Foam::IOobject const&, Foam::Xfer<Foam::Field<Foam::Vector<double> > > const&, Foam::List<Foam::cellShape> const&, Foam::List<Foam::List<Foam::face> > const&, Foam::List<Foam::word> const&, Foam::PtrList<Foam::dictionary> const&, Foam::word const&, Foam::word const&, bool) in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#8 Foam::blockMesh::createTopology(Foam::IOdictionary const&, Foam::word const&) in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libblockMesh.so"
#9 Foam::blockMesh::blockMesh(Foam::IOdictionary const&, Foam::word const&) in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libblockMesh.so"
#10
in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/blockMesh"
#11 __libc_start_main in "/lib64/libc.so.6"
#12
in "/users/mdinc/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/bin/blockMesh"
Floating point exception (core dumped)

I cant understand what is the error but I could understand is that the error is due to wedgepolypatch. I am attaching my blockMeshDict for reference please find it.
Awaiting a reply sir. Thanks in advance.

Debuging errors blockMesh
 

Hello everybody...

I've got the following blockMesh file, I've followed the user guide indication about the right handed system but it doesnt work with my intend to create a suitable mesh, I'm going to post the error looking forward to something can catch the error, I'd appreciate it so much, thanks guys

Create time

Creating block mesh from
"/home/ecopetrol/OpenFOAM/OpenFOAM_simulations/coimbra_cluster_ext/constant/polyMesh/blockMeshDict"
Creating curved edges
Creating topology blocks
Creating topology patches

Reading patches section

Creating block mesh topology
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.85 for face 0
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.85 for face 1
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.7 for face 2
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -1 for face 3
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.85 for face 4
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.85 for face 5
--> FOAM Warning :
From function blockMesh::createTopology(IOdictionary&)
in file blockMesh/blockMeshTopology.C at line 255
negative volume block : 0, probably defined inside-out
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.825 for face 0
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.825 for face 1
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.75 for face 2
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.9 for face 3
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.825 for face 4
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.825 for face 5
--> FOAM Warning :
From function blockMesh::createTopology(IOdictionary&)
in file blockMesh/blockMeshTopology.C at line 255
negative volume block : 1, probably defined inside-out
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.666667 for face 0
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.666667 for face 1
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.666667 for face 2
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.666667 for face 3
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.666667 for face 4
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.666667 for face 5
--> FOAM Warning :
From function blockMesh::createTopology(IOdictionary&)
in file blockMesh/blockMeshTopology.C at line 255
negative volume block : 2, probably defined inside-out
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.0666667 for face 0
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.0666667 for face 1
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.0666667 for face 2
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.0666667 for face 3
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.0666667 for face 4
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.0666667 for face 5
--> FOAM Warning :
From function blockMesh::createTopology(IOdictionary&)
in file blockMesh/blockMeshTopology.C at line 255
negative volume block : 3, probably defined inside-out
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.6 for face 0
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.6 for face 1
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.6 for face 2
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.6 for face 3
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.6 for face 4
--> FOAM Warning :
From function cellModel::mag(const labelList&, const pointField&)
in file meshes/meshShapes/cellModel/cellModel.C at line 128
zero or negative pyramid volume: -0.6 for face 5
--> FOAM Warning :
From function blockMesh::createTopology(IOdictionary&)
in file blockMesh/blockMeshTopology.C at line 255
negative volume block : 4, probably defined inside-out

Reading physicalType from existing boundary file

Default patch type set to empty

Check topology

Basic statistics
Number of internal faces : 4
Number of boundary faces : 22
Number of defined boundary faces : 22
Number of undefined boundary faces : 0
Checking patch -> block consistency

Creating block offsets
Creating merge list .

Creating polyMesh from blockMesh
Creating patches
Creating cells
Creating points with scale 1

Writing polyMesh
----------------
Mesh Information
----------------
boundingBox: (-8 0 0) (32 0.5 1)
nPoints: 619842
nCells: 308000
nFaces: 1233920
nInternalFaces: 614080
----------------
Patches
----------------
patch 0 (start: 614080 size: 200) name: inlet
patch 1 (start: 614280 size: 1840) name: bottom
patch 2 (start: 616120 size: 200) name: outlet
patch 3 (start: 616320 size: 1600) name: atmosphere
patch 4 (start: 617920 size: 616000) name: frontBack

and this is the blockMesh file

convertToMeters 1;

vertices
(
( -8 0 1 ) //0
( 6 0 1 ) //1
( 17 0 1 ) //2
( 32 0 1 ) //3
( -8 0.3 1 ) //4
( 12 0.3 1 ) //5
( 14 0.3 1 ) //6
( 32 0.3 1 ) //7
( -8 0.5 1 ) //8
( 12 0.5 1 ) //9
( 14 0.5 1 ) //10
( 32 0.5 1 ) //11
( -8 0 0 ) //12
( 6 0 0 ) //13
( 17 0 0 ) //14
( 32 0 0 ) //15
( -8 0.3 0 ) //16
( 12 0.3 0 ) //17
( 14 0.3 0 ) //18
( 32 0.3 0 ) //19
( -8 0.5 0 ) //20
( 12 0.5 0 ) //21
( 14 0.5 0 ) //22
( 32 0.5 0 ) //23
);

blocks
(
hex (0 1 5 4 12 13 17 16) ( 600 120 1 ) simpleGrading (1 1 1) //block0
hex (2 3 7 6 14 15 19 18) ( 900 120 1 ) simpleGrading (1 1 1) //block1
hex (4 5 9 8 16 17 21 20) ( 600 80 1 ) simpleGrading (1 1 1) //block2
hex (5 6 10 9 17 18 22 21) ( 100 80 1 ) simpleGrading (1 1 1) //block3
hex (6 7 11 10 18 19 23 22) ( 900 80 1 ) simpleGrading (1 1 1) //block4
);

edges
(
);

patches
(
patch inlet
(
(0 12 16 4)
(4 16 20 8)
)
wall bottom
(
(0 1 13 12)
(1 5 17 13)
(5 6 18 17)
(6 2 14 18)
(2 3 15 14)
)
patch outlet
(
(7 19 15 3)
(11 23 19 7)
)

patch atmosphere
(
(8 20 21 9)
(9 21 22 10)
(10 22 23 11)
)

empty frontBack
(
(0 4 5 1)
(2 6 7 3)
(4 8 9 5)
(5 9 10 6)
(6 10 11 7)
(12 13 17 16)
(14 15 19 18)
(16 17 21 20)
(17 18 22 21)
(18 19 23 22)
)
);

mergePatchPairs
(
);

Hallo Luigi,

try to change the way you define the blocks in your blockMeshDict. This negative volume warning is due to an incorrect definition for block number 0, 1, 2, 3 ,4 and 5.
Look at the orderering of the vertices that define each of these blocks.

Hope it helps,


Elia