Problem understanding nFaces / startFace

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 November 4, 2009, 18:22 Beginners Problem: patch is not divisible by the number of cells #1 Member   Florian Join Date: Nov 2009 Posts: 59 Rep Power: 10 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::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 Last edited by Horus; November 4, 2009 at 22:39.

 November 5, 2009, 03:28 #2 Senior Member   Hrvoje Jasak Join Date: Mar 2009 Location: London, England Posts: 1,810 Rep Power: 25 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 __________________ Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk

 November 5, 2009, 07:57 #3 Member   Florian Join Date: Nov 2009 Posts: 59 Rep Power: 10 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

 November 5, 2009, 08:15 #4 Senior Member   Anonymous Join Date: Mar 2009 Posts: 110 Rep Power: 10 Florian, run it through checkMesh for more information.

 November 5, 2009, 10:54 #5 Member   Florian Join Date: Nov 2009 Posts: 59 Rep Power: 10 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. <

 November 7, 2009, 13:01 #6 Member   Florian Join Date: Nov 2009 Posts: 59 Rep Power: 10 Dare to bump it up. Anybody any hint for me?

 November 20, 2009, 07:20 #7 New Member   Robin Koldeweij Join Date: Nov 2009 Posts: 19 Rep Power: 10 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 ( ) );``` 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

 November 21, 2009, 04:34 #8 Member   Florian Join Date: Nov 2009 Posts: 59 Rep Power: 10 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

 December 12, 2009, 17:36 #9 New Member   toupador Join Date: Oct 2009 Posts: 5 Rep Power: 10 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::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?

 December 13, 2009, 13:26 #10 New Member   Robin Koldeweij Join Date: Nov 2009 Posts: 19 Rep Power: 10 IS the amount of cells in z-direction equal to 1?

 December 13, 2009, 16:34 #11 Member   Florian Join Date: Nov 2009 Posts: 59 Rep Power: 10 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 ( ( ) );``` 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

 December 15, 2009, 15:33 #12 New Member   toupador Join Date: Oct 2009 Posts: 5 Rep Power: 10 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.

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