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Beginners Problem: patch is not divisible by the number of cells

Hello,

I've been playing around with openfoam for some time (actually freefoam which is based on openfoam 1.5) and after having worked through the tutorials I want to start my own little pet case.
So far I've successfully created the geometry. It is 2D, with an inlet on side and an outlet on the other. There is a rectangle (balken) in the middle, all other boundaries are empty (frontAndBack). This is my blockMeshDict file.

Code:

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    object      blockMeshDict;

}



convertToMeters 1;



vertices        

(

    (0 0 0)

    (10 0 0)

    (10 10 0)

    (0 10 0)

    (0 0 1)

    (10 0 1)

    (10 10 1)

    (0 10 1)



    (4 4 0)

    (6 4 0)

    (6 6 0)

    (4 6 0)



    (4 4 1)

    (6 4 1)

    (6 6 1)

    (4 6 1)



);



blocks          

(

    hex (0 1 2 3 4 5 6 7) (40 40 1) simpleGrading (1 1 1)  // global

    hex (8 9 10 11 12 13 14 15) (1 1 1) simpleGrading (1 1 1) // balken, the solid rectangle

);



edges           

(

);



patches         

(

    wall balken

    (

        (8 9 10 11)

        (12 13 14 15)

        (8 11 15 12)

        (11 10 14 15)

        (10 9 13 14)

        (8 9 13 12)

    )



    patch inlet

    (

        (0 3 7 4)

    )



    patch outlet

    (

        (2 6 5 1)

    )

    empty frontAndBack 

    (

        (0 3 2 1)

        (4 5 6 7)

        (1 5 4 0)

        (3 7 6 2)

    )



);



mergePatchPairs 

(

);

blockMesh gives no errors and the geometry in Paraview looks fine. However icoFoam complains:

Code:

This mesh contains patches of type empty but is not 1D or 2D

    by virtue of the fact that the number of faces of this

    empty patch is not divisible by the number of cells.



    From function emptyFvPatchField<Type>::updateCoeffs()

    in file /Users/florian/freeFoam/build/include/finiteVolume/../../../freefoam-0.1.0rc4/src/finiteVolume/fields/fvPatchFields/constraint/empty/emptyFvPatchField.C at line 148

What could be the problem here? Could it be that I put one block (balken) just over the the first one (which is my global domain)?

Thanks for any hints,

Florian

You did not define the empty patch correctly. This is meant for 2-D or 1-D, for the front and back plane: it means that the number of faces in the empty patch (for 2-D) should be twice the number of cells.

The code says this is not the case for you. Have a look at the mesh in paraview, switch on patch names and it should be obvious.

Enjoy,

Hrv

Hello,
for me the mesh looks fine in Paraview. frontAndBack is a mesh that covers the two sides and "ceiling" and "floor", forming a kind of rectangular tunnel.
How do I define the number faces? The file boundary which contains the nFaces entry is created from the blockMesh utility, so there is no use to edit something there.
Sorry, I still don't see what is the problem here. Could you be a bit more detailed?

Thanks,

Florian

Florian,

run it through checkMesh for more information.

Ok, the complete checkMesh output is:

Code:

Create time



Create polyMesh for time = constant



Time = constant



Mesh stats

    points:           3370

    internal points:  0

    faces:            6486

    internal faces:   3120

    cells:            1601

    boundary patches: 4

    point zones:      0

    face zones:       0

    cell zones:       0



Number of cells of each type: 

    hexahedra:     1601

    prisms:        0

    wedges:        0

    pyramids:      0

    tet wedges:    0

    tetrahedra:    0

    polyhedra:     0



Checking topology...

    Boundary definition OK.

    Point usage OK.

    Upper triangular ordering OK.

    Face vertices OK.

   *Number of regions: 2

    The mesh has multiple regions which are not connected by any face.

  <<Writing region information to "constant/cellToRegion"



Checking patch topology for multiply connected surfaces ...

    Patch               Faces    Points   Surface topology                  

    balken              6        8        ok (closed singly connected)      

    inlet               40       82       ok (non-closed singly connected)  

    outlet              40       82       ok (non-closed singly connected)  

    frontAndBack        3280     3362     ok (non-closed singly connected)  



Checking geometry...

    Overall domain bounding box (0 0 0) (10 10 1)

    Mesh (non-empty) directions (1 0 0)

    Mesh (non-empty, non-wedge) dimensions 1

    All edges aligned with or perpendicular to non-empty directions.

Trying to instantiate 'mpiPstreamImpl'

    Boundary openness (0 0 0) OK.

    Max cell openness = 0 OK.

    Max aspect ratio = 4 OK.

    Minumum face area = 0.0625. Maximum face area = 4.  Face area magnitudes OK.

    Min volume = 0.0625. Max volume = 4.  Total volume = 104.  Cell volumes OK.

    Mesh non-orthogonality Max: 0 average: 0

    Non-orthogonality check OK.

    Face pyramids OK.

    Max skewness = 0 OK.



Mesh OK.



End

At least there are a lot of OKs. ;-)
I guess:

Code:

   *Number of regions: 2

    The mesh has multiple regions which are not connected by any face.

  <<Writing region information to "constant/cellToRegion"

could indicate a problem. The cellToRegion file contains a dictionary with a lot 0, with a single 1 as the last entry.

But so far I'm still helpless...

Thanks your help,

Florian

Dare to bump it up. Anybody any hint for me?

Maybe a bit late, but if you look at your empty frontAndBack, there might be a problem with the part of "balken" there. A small portion of your front and back sides are formed by global AND balken. Maybe you should merge the balken patches of this side as slaves to global as master:

Code:

mergePatchPairs 

 



( 

<frontAndBack> <balken> ) 

);

or without the <> or with the vertices in places of the name. I don't really know, but I think it's something like this

My freeFoam (which is based on openFoam 1.5) says:

mergePatchPairs not currently supported.

Currently I'm running it on a Mac but since I'm about to migrate to Linux I'll try it again there with 1.6 in a couple of days.

Thanks,

Florian

Hallo
Maybe somebody can help. I've got the same Problem. I have created (in ICEM)a 2D geometrie and Mesh for airfoil in canal. in Parawien the mesh ist 2D (no split in z direction) but wenn i run the case (rhoSimpleFoam) i've got the following error :
This mesh contains patches of type empty but is not 1D or 2D
by virtue of the fact that the number of faces of this
empty patch is not divisible by the number of cells.

From function emptyFvPatchField<Type>::updateCoeffs()
in file /Users/florian/freeFoam/build/include/finiteVolume/../../../freefoam-0.1.0rc4/src/finiteVolume/fields/fvPatchFields/constraint/empty/emptyFvPatchField.C at line 148
please tell me what kann i do?

IS the amount of cells in z-direction equal to 1?

For my part: Yes (see my first posting). I have now upgraded from 1.5 to 1.6 on Linux but I get still the same error as Pat.

When I chang my blockMeshDict file to:

Code:

mergePatchPairs 

( 

 (<frontAndBack> <balken> ) 

);

as proposed by RBJ I get a segfault:

Code:

lorian@horus:~/OpenFOAM/run/canal> blockMesh 

/*---------------------------------------------------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  1.6                                   |

|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |

|    \\/     M anipulation  |                                                 |

\*---------------------------------------------------------------------------*/

Build  : 1.6-f802ff2d6c5a                                                      

Exec   : blockMesh                                                             

Date   : Dec 13 2009                                                           

Time   : 21:34:12                                                              

Host   : horus                                                                 

PID    : 5105                                                                  

Case   : /home/florian/OpenFOAM/run/canal                                      

nProcs : 1                                                                     

SigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).             



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

Create time                                                                    





Creating block mesh from

    "/home/florian/OpenFOAM/run/canal/constant/polyMesh/blockMeshDict"





Creating blockCorners



Creating curved edges



Creating blocks



Creating patches



Creating block mesh topology



Default patch type set to empty



Check block mesh topology



        Basic statistics

                Number of internal faces : 0

                Number of boundary faces : 12

                Number of defined boundary faces : 12

                Number of undefined boundary faces : 0



        Checking patch -> block consistency



Creating block offsets



Creating merge list .



Creating points with scale 1



Creating cells



Creating patches



Creating mesh from block mesh



Default patch type set to empty

Creating merge patch pairs



#0  Foam::error::printStack(Foam::Ostream&) in "/home/florian/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libOpenFOAM.so"

#1  Foam::sigSegv::sigSegvHandler(int) in "/home/florian/OpenFOAM/OpenFOAM-1.6/lib/linux64GccDPOpt/libOpenFOAM.so"

#2  ?? in "/lib64/libc.so.6"

#3  main in "/home/florian/OpenFOAM/OpenFOAM-1.6/applications/bin/linux64GccDPOpt/blockMesh"

#4  __libc_start_main in "/lib64/libc.so.6"

#5  _start at /usr/src/packages/BUILD/glibc-2.9/csu/../sysdeps/x86_64/elf/start.S:116

Segmentation fault

Thanks,

Florian

Thank you RBJ for your reply. i ve found my error now my mesh work fine.
I haved make mistake ICEM. I ve not correctly select the mesh for frontAndback someone was merged with internalMesh.