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[mesh manipulation] how should we remove the Concave cells from the mesh? |
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August 19, 2013, 09:32 |
how should we remove the Concave cells from the mesh?
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#1 |
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saeideh mohamadi
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hi
when i run the "checkMesh" utility, it doen't complain anything, but when i execute "checkMesh -allGeometry -allTopology" it complains from concave cells, and report 1 failed mesh, i put the report of checkMesh & checkMesh -allGeometry -allTopology and also some pics from my mesh in the following, my question is, how can i improve my mesh to remove these concave cells from my mesh to have a good mesh? Thanks in advance for any suggestion ""1. checkMesh"" Code:
Create time Create polyMesh for time = 0 Time = 0 Mesh stats points: 206578 internal points: 0 faces: 403232 internal faces: 199837 cells: 99981 faces per cell: 6.03184 boundary patches: 6 point zones: 0 face zones: 0 cell zones: 0 Overall number of cells of each type: hexahedra: 96539 prisms: 301 wedges: 0 pyramids: 0 tet wedges: 0 tetrahedra: 0 polyhedra: 3141 Breakdown of polyhedra by number of faces: faces number of cells 7 2798 8 343 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology topAndBottom 496 996 ok (non-closed singly connected) inlet 176 354 ok (non-closed singly connected) outlet 176 354 ok (non-closed singly connected) front 99981 103289 ok (non-closed singly connected) back 99981 103289 ok (non-closed singly connected) airfoil_solid 2585 5170 ok (non-closed singly connected) Checking geometry... Overall domain bounding box (-5.97801 -11.4978 0.15) (21.0301 9.38239 0.25) Mesh (non-empty, non-wedge) directions (1 1 0) Mesh (non-empty) directions (1 1 0) All edges aligned with or perpendicular to non-empty directions. Boundary openness (1.33896e-18 5.41191e-21 3.12079e-14) OK. Max cell openness = 2.16716e-16 OK. Max aspect ratio = 2.51791 OK. Minimum face area = 2.51612e-07. Maximum face area = 0.0100472. Face area magnitudes OK. Min volume = 2.51612e-08. Max volume = 0.00100472. Total volume = 43.6397. Cell volumes OK. Mesh non-orthogonality Max: 30.6861 average: 3.70862 Non-orthogonality check OK. Face pyramids OK. Max skewness = 1.17932 OK. Coupled point location match (average 0) OK. Mesh OK. End Code:
Create time Create polyMesh for time = 0 Enabling all (cell, face, edge, point) topology checks. Enabling all geometry checks. Time = 0 Mesh stats points: 206578 internal points: 0 edges: 509829 internal edges: 99856 internal edges using one boundary point: 0 internal edges using two boundary points: 99856 faces: 403232 internal faces: 199837 cells: 99981 faces per cell: 6.03184 boundary patches: 6 point zones: 0 face zones: 0 cell zones: 0 Overall number of cells of each type: hexahedra: 96539 prisms: 301 wedges: 0 pyramids: 0 tet wedges: 0 tetrahedra: 0 polyhedra: 3141 Breakdown of polyhedra by number of faces: faces number of cells 7 2798 8 343 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Topological cell zip-up check OK. Face-face connectivity OK. <<Writing 4 cells with two non-boundary faces to set twoInternalFacesCells Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology Bounding box topAndBottom 496 996 ok (non-closed singly connected) (-5.97801 -11.4978 0.15) (21.0301 9.38239 0.25) inlet 176 354 ok (non-closed singly connected) (-5.97801 -8.04633 0.15) (-3.52856 9.38239 0.25) outlet 176 354 ok (non-closed singly connected) (18.5806 -11.4978 0.15) (21.0301 5.9309 0.25) front 99981 103289 ok (non-closed singly connected) (-5.97801 -11.4978 0.25) (21.0301 9.38239 0.25) back 99981 103289 ok (non-closed singly connected) (-5.97801 -11.4978 0.15) (21.0301 9.38239 0.15) airfoil_solid 2585 5170 ok (non-closed singly connected) (-3.00658e-05 -0.14046 0.15) (0.990449 0.0593403 0.25) Checking geometry... Overall domain bounding box (-5.97801 -11.4978 0.15) (21.0301 9.38239 0.25) Mesh (non-empty, non-wedge) directions (1 1 0) Mesh (non-empty) directions (1 1 0) All edges aligned with or perpendicular to non-empty directions. Boundary openness (1.33896e-18 5.41191e-21 3.12079e-14) OK. Max cell openness = 2.16716e-16 OK. Max aspect ratio = 2.51791 OK. Minimum face area = 2.51612e-07. Maximum face area = 0.0100472. Face area magnitudes OK. Min volume = 2.51612e-08. Max volume = 0.00100472. Total volume = 43.6397. Cell volumes OK. Mesh non-orthogonality Max: 30.6861 average: 3.70862 Non-orthogonality check OK. Face pyramids OK. Max skewness = 1.17932 OK. Coupled point location match (average 0) OK. Face tets OK. Min/max edge length = 0.000483718 0.100434 OK. All angles in faces OK. Face flatness (1 = flat, 0 = butterfly) : average = 1 min = 1 All face flatness OK. Cell determinant (wellposedness) : minimum: 1 average: 4.04297 Cell determinant check OK. ***Concave cells (using face planes) found, number of cells: 1357 <<Writing 1357 concave cells to set concaveCells Failed 1 mesh checks. End Last edited by wyldckat; August 20, 2013 at 18:08. Reason: Added [CODE][/CODE] |
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August 20, 2013, 18:23 |
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#2 |
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Bruno Santos
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Greetings Saeideh,
Without seeing where the concave cells are, it's hard to diagnose anything. My suggestions are as follows:
Best regards, Bruno
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August 21, 2013, 06:39 |
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#3 | |
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saeideh mohamadi
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Quote:
Dear bruno Thank you very much, your explanation was very usefull and obvious i am using paraFoam and the file extension ".OpenFOAM", so i checked the
Thank you again for your nice attention i study the references now, thank for introducing them too. |
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August 21, 2013, 14:45 |
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#4 |
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saeideh mohamadi
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Dear Bruno, i don't understand anythig usefull from this pics, for solving my failed meshs, would you please guide me again?
Regards |
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August 21, 2013, 14:49 |
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#5 |
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Bruno Santos
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OK, then can you please provide pictures where they only show the concave cells set on a few pictures, and the internal faces set on the other pictures?
Because I don't want to have to guess which ones are which ones
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August 21, 2013, 17:47 |
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#6 | |
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saeideh mohamadi
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Quote:
Thease are the pictures, here you are. The twoInternalFacesCells are the cells that exit in the 4 corner of the domain. |
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August 21, 2013, 17:54 |
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#7 |
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saeideh mohamadi
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When i unchecked the "use VTKpolyhedron " in object inspector, the pictures of concaveCell -cellSet change in this way, i attach them in the following.
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August 21, 2013, 18:30 |
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#8 |
Retired Super Moderator
Bruno Santos
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From what I can see, the "concave cells" are fine. I think checkMesh is in this case complaining about the fact that those cells have 2 faces on the same side, leading to 180 between those two faces, leading to the diagnose those cells as likely being concave.
As for "twoInternalFacesCells": there isn't a zoom picture to see them properly Without the VTK Polyhedron representation, what happens is that the cells are sliced (decomposed) into hexahedral or tetrahedral shaped cells, so that it's most likely to be properly represented on-screen. The polyhedral representation in ParaView is relatively more recent than the OpenFOAM/ParaView themselves, which is why the sliced cells is the standard representation.
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August 22, 2013, 04:44 |
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#9 | |
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saeideh mohamadi
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Quote:
Thease pictures are the zoom of "twoInternalFacesCells" that are in the corner of the domain. second without VTK Polyhedron checked third with VTK Polyhedron checked. The "twoInternalFacesCells" don't change when i checked the VTK Polyhedron. |
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August 22, 2013, 06:39 |
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#10 |
Retired Super Moderator
Bruno Santos
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Hi Saeideh,
It shows a single face Problem is that I have not idea where in space is that face You can open in that same ParaView, the same ".OpenFOAM" file, therefore having the same file opened twice. In the second one, you can choose to show the internal mesh, in wireframe mode. This should give us a better perception of where the faces. Either way, my guess is that everything is fine with the mesh. The indications given by checkMesh are simply situations that the user should confirm for him/herself. Best regards, Bruno
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August 22, 2013, 06:59 |
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#11 | |
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saeideh mohamadi
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Quote:
Thank you very much in the first picture, it can be seen 4 cells, that is located at 4 corner of the domain, in the second and third one i zoom to show one of this 4 cells better, because of it you see only one cell in those pics. why the cells that have 2 faces on the same side is created during meshing? |
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August 22, 2013, 07:57 |
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#12 |
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Bruno Santos
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Isn't there another face perpendicular to the one you're showing?
I don't remember if you indicated the mesher you've used, so it's hard to ascertain as to why the faces are not properly done.
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August 22, 2013, 09:54 |
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#13 | |
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saeideh mohamadi
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Quote:
yes it is, this cell that i zoom in, is in the front face, i extrude the front face 0.1, to have 3D mesh for analysis, but i set the front and back face to empty for 2D analysis. i use the snappyHexMesh utility for creating my mesh. |
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August 22, 2013, 09:58 |
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#14 |
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saeideh mohamadi
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some new pics from concaveCells
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August 22, 2013, 10:02 |
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#15 |
Retired Super Moderator
Bruno Santos
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When in doubt, compare with OpenFOAM's tutorials.
If you look at the tutorial "incompressible/icoFoam/cavity" and run the same complete checkMesh, it will also tell you that: Code:
<<Writing 4 cells with with two non-boundary faces to set twoInternalFacesCells edit: and like I wrote before, don't worry about these specific concave cells.
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Last edited by wyldckat; August 22, 2013 at 10:03. Reason: see "edit:" |
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August 22, 2013, 10:02 |
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#16 |
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saeideh mohamadi
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some new pics from concaveCell
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August 22, 2013, 10:10 |
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#17 | |
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saeideh mohamadi
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Quote:
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August 22, 2013, 10:19 |
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#18 |
Retired Super Moderator
Bruno Santos
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I think they are OK. Because the detection that is occurring is actually only because each one of those cells has 2 faces on the same side, which each one of those faces is connected to smaller cell, which is normal for these larger cells that are next to smaller cells.
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August 22, 2013, 11:39 |
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#19 | |
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saeideh mohamadi
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Quote:
i leave this 1 failed mesh that is reported from checkMesh -allGeometry because as i understand it doesn't effect on my analysis. Best Regards, Saeiseh. Last edited by s.m; August 23, 2013 at 03:58. |
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January 22, 2015, 06:47 |
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#20 |
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I noticed "two internalFacesCells" with "checkMesh -allTopology" in my 3D-case, too. I have an unstructured mesh generated with ICEM (export fluent_v6/nastran; import fluent3DMeshToFoam). These Cells are tetras and located along the border of two patches.
They have an effect on BCs, so it would be better to avoid this error. The error does not occur when I use a structured mesh or when I extrude a prism layer at the boundaries. Does someone know something about this problem? Kind regards Last edited by overdrive; January 22, 2015 at 10:19. |
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