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[Sponsors] |
January 28, 2005, 05:21 |
Axisymmetrical mesh
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#1 |
Guest
Posts: n/a
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Hi,
I want to make a axi-symmetrical mesh for a cylinder. So I have constructed a 5 degree wedge as explained in the user guide, and defined the front and back as wedge-patches. Q1. However, I have a question regarding the points on the radius of the cylinder. Should there coordinates just be calculated as implied by fig. 6.3 in the userguide. So, if the x-axis goes in the radius-direction, the x-coordinate will be lower than the radius. Q2. Also, should the wedge be exactly 5 degrees or is this just a recommandation? Q3. And what about the curvature of the surface of the cylinder? Q4. I have made the outer edge of the cylinder a circle-arc, but it appears as a straight line in paraFoam. Is paraFoam just drawing straight lines between every points? And will openFOAM use/discover the bigger area due to the curvature? This is perhaps peanuts, but I like to be 100% certain. This is also why I use openFOAM! ;-) Kind regards, Rasmus |
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January 28, 2005, 05:25 |
Q1: Yes
Q2: Just a recommend
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#2 |
Guest
Posts: n/a
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Q1: Yes
Q2: Just a recommendation. Should be small enough that the difference between the arc and a straight line at the outer diameter does not matter, but large enough to avoid round-off problems with decimal precision. Q3: Neglected Q4: There are no arcs - it is a straight line. Remember, you are really using a 3-D solver to do axi-symmetric. Enjoy, Hrv |
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October 10, 2005, 12:06 |
Hi,
I want to test my new sol
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#3 |
Member
olivier Petit
Join Date: Mar 2009
Location: Göteborg, Sweden
Posts: 67
Rep Power: 17 |
Hi,
I want to test my new solver, In first time I tested my case with icoFoam in ordre to be sure that there is no probleme with my mesh created with blockMesh. when I run my case with icoFoam I had "Nan" in the 1st time step!! I think that I have no devision per zero! I will be happy If some one tel me what is the probleme with my goemetry or my mesh. how can I make my case in the forum? thanks a lot |
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October 10, 2005, 12:21 |
You've messed something up - t
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#4 |
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,907
Rep Power: 33 |
You've messed something up - try running checkMesh to see if the mesh is correct, check the wedge boundary conditions on the front and back, check the viscosity you've set (non-zero, but not really crucial), check that the differencing schemes are set up correctly and the boundary conditions are not stupid. Check the time step.
In short, check everything :-) Enjoy, Hrv
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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October 10, 2005, 13:15 |
Yup, the mesh is totally wrong
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#5 |
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,907
Rep Power: 33 |
Yup, the mesh is totally wrong:
- it's in 2 pieces - it is a 90 deg segment and not a wedge - it's got blocks that are inside out You will need to sort this out before moving on further. Try putting setenv FOAM_SIGFPE 1 into your dot-files and you'll get more messages, e.g.: coyote*138-> blockMesh . wedgeOliverBaily /*---------------------------------------------------------------------------*\ | ========= | | | \ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \ / O peration | Version: 1.2 | | \ / A nd | Web: http://www.openfoam.org | | \/ M anipulation | | \*---------------------------------------------------------------------------*/ Exec : blockMesh . wedgeOliverBaily Date : Oct 10 2005 Time : 17:15:39 Host : coyote PID : 6696 Root : /home/coyote/hjasak/OpenFOAM/hjasak-1.2/run/support Case : wedgeOliverBaily Nprocs : 1 Create time Reading block mesh description dictionary Creating block mesh Creating blockCorners Creating curved edges Creating blocks Creating patches Creating block mesh topology --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.35e-07 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.35e-07 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -8.5e-08 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.85e-07 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.35e-07 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.35e-07 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 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 136 zero or negative pyramid volume: -9.03125e-09 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -9.03125e-09 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -6.02083e-09 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.20417e-08 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -9.03125e-09 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -9.03125e-09 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 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 136 zero or negative pyramid volume: -2.70937e-08 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.70938e-08 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.80625e-08 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -3.6125e-08 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.70937e-08 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.70937e-08 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 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 136 zero or negative pyramid volume: -1.41563e-06 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.41563e-06 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -4.65583e-07 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.36567e-06 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.41562e-06 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.41562e-06 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 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 136 zero or negative pyramid volume: -4.24687e-06 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -4.24688e-06 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.39675e-06 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -7.097e-06 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -4.24688e-06 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -4.24688e-06 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 negative volume block : 4, probably defined inside-out --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -7.66667e-07 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -7.66667e-07 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -7e-07 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -8.33333e-07 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -7.66667e-07 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -7.66667e-07 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 negative volume block : 5, probably defined inside-out --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.3e-06 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.3e-06 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.1e-06 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.5e-06 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.3e-06 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -2.3e-06 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 negative volume block : 6, probably defined inside-out --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.0945e-06 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.0945e-06 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.034e-06 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.155e-06 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.0945e-06 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.0945e-06 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 negative volume block : 7, probably defined inside-out --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -0.000246879 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -0.000246879 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -9.1675e-05 for face 2 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -0.000402083 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -0.000246879 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -0.000246879 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 negative volume block : 8, probably defined inside-out --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -9.03125e-09 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -9.03125e-09 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -1.80625e-08 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -9.03125e-09 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -9.03125e-09 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 negative volume block : 9, probably defined inside-out --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -3.01042e-09 for face 0 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -3.01042e-09 for face 1 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -6.02083e-09 for face 3 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -3.01042e-09 for face 4 --> FOAM Warning : From function cellModel::mag(const labelList&, const pointField&) in file meshes/meshShapes/cellModel/cellModel.C at line 136 zero or negative pyramid volume: -3.01042e-09 for face 5 --> FOAM Warning : From function blockMesh::createTopology(IOdictionary& meshDescription) in file createTopology.C at line 372 negative volume block : 10, probably defined inside-out Default patch type set to empty Caught arithmetic exception Abort Hrv
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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October 10, 2005, 13:36 |
1.what is wrong with two pices
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#6 |
Member
olivier Petit
Join Date: Mar 2009
Location: Göteborg, Sweden
Posts: 67
Rep Power: 17 |
1.what is wrong with two pices?
2.when I use 5deg in a wedge I have a problem with bad elements near to axis. 3. I dont understand what do you mean by: "it's got blocks that are inside out " best ragards |
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October 10, 2005, 13:43 |
1. Formally nothing, depending
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#7 |
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,907
Rep Power: 33 |
1. Formally nothing, depending on exactly what you're trying to do
2. Probably the same reason as here: your block definition is wrong 3. Read the manual (RTFM): http://www.opencfd.co.uk/openfoam/do...tml#x5-40002.1 Figure 2.3 specifies how a hex block needs to be defined in terms of vertices. If vertices 4, 5, 6, 7 are behind the vertices 0, 1, 2, 3, the block volume according the the figure will be negative. This is what you have done.
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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October 10, 2005, 14:03 |
thanks for your time and your
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#8 |
Member
olivier Petit
Join Date: Mar 2009
Location: Göteborg, Sweden
Posts: 67
Rep Power: 17 |
thanks for your time and your help
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December 23, 2005, 12:16 |
Could anybody let me know wher
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#9 |
Member
Ali Heidari
Join Date: Mar 2009
Location: Surrey, London, United Kingdom
Posts: 39
Rep Power: 17 |
Could anybody let me know where (in which dot file) to put 'setenv FOAM_SIGFPE 1'? Is this syntax correct or I have to add something to it.
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December 23, 2005, 13:03 |
Into your ~/.cshrc put
sete
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#10 |
Senior Member
Hrvoje Jasak
Join Date: Mar 2009
Location: London, England
Posts: 1,907
Rep Power: 33 |
Into your ~/.cshrc put
setenv FOAM_SIGFPE true Enjoy, Hrv
__________________
Hrvoje Jasak Providing commercial FOAM/OpenFOAM and CFD Consulting: http://wikki.co.uk |
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April 2, 2007, 15:00 |
round-off errors:
January 2
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#11 | |
Senior Member
Maka Mohu
Join Date: Mar 2009
Posts: 305
Rep Power: 18 |
round-off errors:
January 28, 2005: Quote:
How can we check for the later effect? This may come to be critical at high Re turbulent flows. I thought that one way, may be to do the a test computation on the same mesh with single and double precision (new option in V1.3) to check the sensitivity to round-off errors but it seems to be expensive option. Any body knows a better way or recommendation? Thanks. Best regards, Maka Thanks. |
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