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Old   July 23, 2004, 11:50
Default Very important
  #1
Panos
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Hi I am modelling a 2d airfoil. When I use a finer mesh than 30000 I get the error that my mesh contains cracks. When I use a coarse mesh I don't ge it. What could be the case? Please help me because I have to present some results soon enough. I really appreciate it!
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Old   July 23, 2004, 19:41
Default Re: Very important
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Tom
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It is hard to give suggestions without more information. However, try runing vmerge and see if it helps. Use the check tool to run the crack check and put the failed cells into a cset. Then you can examine them to find the cause. You may have to maually move some vertices to remove the cracks. Tom
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Old   July 25, 2004, 06:29
Default Re: Very important
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PANOS
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Hi tom What I don't understand is that when I use a coarse mesh I don't get cracks. When I make a fine mesh cracks appear in my model. Again thanks a lot
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Old   July 26, 2004, 03:57
Default Re: Very important
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Anton Lyaskin
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This may be an old bug in check routine - if your cells are too thin (thinner then crack limit) then you can get this message. If there are no visual evidences of cracks jhst ignore it
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Old   July 26, 2004, 06:50
Default Re: Very important
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panos
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Thanks a lot Anton. One more thing..Could this bug affect my results also? Because for the case of the fine mesh I got unreasonable results. Again I really appreciate it
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Old   July 26, 2004, 15:09
Default Re: Very important
  #6
Anton Lyaskin
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You results can be affected not because of this bug, but because of the change of y+ value when you go from coarse mesh to fine one. I guess you're using High-Re turbulence model? It can be used only if y+>12. May be that's the problem. Becides fine mesh requires more time to converge and the whole convergence process is more difficult
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Old   July 27, 2004, 03:02
Default Re: Very important
  #7
matej
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Hi Panos,

well if you got a cracks in a mesh (think of them as of discontinuities) - then your results are rubish. First make a good mesh. Check the couples, if you refiend the mesh. chech the tolerances againsts the mesh size. do what Anton suggests.

matej
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Old   July 27, 2004, 06:46
Default Re: Very important
  #8
Panos
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Guys thank you very much for your help. Which one is the most adequate turbulence model I should use?
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