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element with negative volume - FSI analysis

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Old   May 19, 2005, 08:07
Default element with negative volume - FSI analysis
  #1
Seb
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Hi,

I am modeling a wind blade using Fluid Solid Interaction (FSI).

After the first Load Step I have all the time the same error message: "Hexahedral element has negative or zero volume. Nodes on element must be numbered according to the right hand rule." The elements that cause this error message are the ones up the blade, at the place where the deformation is the most important. The problem probably comes from the mesh, but I have tried to refine it at the maximum of the limit capacity of my computer and I still have the same problem. I have the same problem either with hexahedral either tetrahedral elements…

Have somebody already had this problem? Thank you for your help. Seb
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Old   May 19, 2005, 18:39
Default Re: element with negative volume - FSI analysis
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Glenn Horrocks
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Hi,

Does the model run OK as a pure fluids model? ie, no FSI?

Regards, Glenn Horrocks
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Old   May 20, 2005, 07:36
Default Re: element with negative volume - FSI analysis
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Seb
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Hello,

Indeed my FLOTRAN model (corresponding to my FSI model without the solid part) is working normally. The results of this fluid analysis seem corrects. Actually, the problem is due to the fluid mesh that moves (option ALE for FSI analysis). After some iteration, it is like if some elements were too deformed and so that their volumes turned negative…moreover, the turbulence residuals ENKE and ENDS don't converge in the FSI analysis(but converged in the FLOTRAN analysis), so perhaps it is also linked with my problem…

Thank you for your help. Seb
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Old   May 22, 2005, 19:04
Default Re: element with negative volume - FSI analysis
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Glenn Horrocks
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Hi,

I have no experience with FLOTRAN, but what you are saying sounds sensible. If the elements distort and become poor quality then convergence will be difficult.

Glenn Horrocks
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