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April 12, 2012, 22:01 |
Problem with mesh grading/refining
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#1 |
New Member
paul
Join Date: Apr 2012
Posts: 2
Rep Power: 0 |
Hi guys, I am a new user to openfoam and lately i have been experiencing some difficulties.
I have written a mesh for a naca0012 aerofoil. I was able to generate the mesh in openFoam with no mesh refinements however if i tried to refine the mesh around the aerofoil in the Y axis by using simple grading I get the following error : --> FOAM FATAL ERROR: Inconsistent point locations between block pair 0 and 4 probably due to inconsistent grading. From function blockMesh::calcMergeInfo() in file blockMesh/blockMeshMerge.C at line 294. I have attatched an image which describes the blocks used in the mesh and the blockMeshDict file. vertices ( (0.5 -5 0)//0 (1 -5 0)//1 (6 -5 0)//2 (0.5 0.052940 0)//3 (0.5 -0.052940 0)//4 (1 0 0)//5 (6 0 0)//6 (0.5 5 0)//7 (1 5 0)//8 (6 5 0)//9 (0.5 -5 0.1)//10 (1 -5 0.1)//11 (6 -5 0.1)//12 (0.5 0.052940 0.1)//13 (0.5 -0.052940 0.1)//14 (1 0 0.1)//15 (6 0 0.1)//16 (0.5 5 0.1)//17 (1 5 0.1)//18 (6 5 0.1)//19 ); blocks ( hex (0 1 5 4 10 11 15 14) (16 80 1) simpleGrading (1 1 1)//0 hex (1 2 6 5 11 12 16 15) (80 80 1) simpleGrading (1 1 1)//1 hex (3 5 8 7 13 15 18 17) (16 80 1) simpleGrading (1 1 1)//2 hex (5 6 9 8 15 16 19 18) (80 80 1) simpleGrading (1 1 1)//3 hex (3 4 0 7 13 14 10 17) (80 80 1) simpleGrading (1 1 1)//4 If i were to change the simpleGrading from (1 1 1) to (1 20 1) I get the error. any help is appreciated thanks |
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April 13, 2012, 02:58 |
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#2 |
Senior Member
Anton Kidess
Join Date: May 2009
Location: Germany
Posts: 1,377
Rep Power: 30 |
Your ungraded mesh is already broken, see output of 'checkMesh'. As for the grading, every block gets a local coordinate system, and you have to pay attention how they are aligned. With your current alignment the proper grading would be:
Code:
hex (0 1 5 4 10 11 15 14) (16 80 1) simpleGrading (1 2 1)//0 hex (1 2 6 5 11 12 16 15) (80 80 1) simpleGrading (1 2 1)//1 hex (3 5 8 7 13 15 18 17) (16 80 1) simpleGrading (1 0.5 1)//2 hex (5 6 9 8 15 16 19 18) (80 80 1) simpleGrading (1 0.5 1)//3 hex (3 4 0 7 13 14 10 17) (80 80 1) simpleGrading (2 0.5 1)//4 - Anton
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April 13, 2012, 03:12 |
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#3 |
New Member
paul
Join Date: Apr 2012
Posts: 2
Rep Power: 0 |
thanks for the reply, I believe I have fixed the broken mesh which was caused by the z-coordinates of the vertices (0.1) not matching the z-coordinates of the spline code (0.01).
I changed the way i defined block 4 from: hex(3 4 0 7 13 14 10 17) (10 80 1) simpleGrading(1 1 1)//4 to: hex (4 3 7 0 14 13 17 10) (10 80 1) simpleGrading (1 1 1)//4 When i ran blockMesh I get a new error regarding block 4 which is: Creating block mesh topology --> FOAM Warning : From function blockMesh::createTopology(IOdictionary&) in file blockMesh/blockMeshTopology.C at line 255 negative volume block : 4, probably defined inside-out Edit: After paying attention to the allignment of the blocks I am able to refine the mesh thanks, however would like to know how to resolve the warning message |
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April 13, 2012, 04:53 |
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#4 |
Senior Member
Anton Kidess
Join Date: May 2009
Location: Germany
Posts: 1,377
Rep Power: 30 |
Negative volume blocks are no problem for paraview, but will impact simulations. Your face normals are now defined inside-out.
Have a look at figure 5.5. Compare the ordering of the vertices with your own ordering, and pay attention to the direction of x1, x2 for your blocks (it will help you to add the local coordinate system for each block to your schematic figure). You don't have to reorder your vertices - see my example in the post earlier how to get the grading right for the current order.
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