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Hexa meshing or Tetra meshing???

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  • 1 Post By NITIN DEWANGAN
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Old   August 5, 2008, 01:23
Default Hexa meshing or Tetra meshing???
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NITIN DEWANGAN
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what would be the change in the solution when we make geometry thru hexa meshing or thru tetra meshing?

which one is most accurate and easy to make ?

thanks for help...

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Old   August 5, 2008, 06:46
Default Re: Hexa meshing or Tetra meshing???
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Rogerio Fernandes Brito
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Both have the same accuracy solution. But tetra mesh wastes more time of cpu and the most number of elements. with hexahedrical mesh, you can use a coarse mesh and you will have a good result. I made this type of comparison between tetraedron and hexahedrical meshes in solid simulations (without fluid air or water...).
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Old   August 5, 2008, 07:11
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MAB
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also the number of tetra is about 60,00000
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Old   August 5, 2008, 09:25
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John
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I wouldn't say tets and hexes give the same solution. I'm troubleshooting a combustion problem right now where I have one mesh which is 100% hex and the other is tet with an inflated prism layer.

The hex mesh runs just the way you'd expect with a clear flamefront all the way to the wall, but the tet mesh has a lot of numerical diffusion with the turbulence equations at the tet/prism boundary which is giving some non-physical results (such as preventing the flame from spreading into the inflated boundary).

If you have a copy of the CFX manual I'd recommend taking a looking at the section on discretization errors in the Theory manual and you'll see that tets and prisms are fundamentally treated differently by the solver.
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Old   August 5, 2008, 09:54
Default Re: Hexa meshing or Tetra meshing???
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Rogerio Fernandes Brito
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It depends on your problem, of course!
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Old   August 5, 2008, 09:59
Default Re: Hexa meshing or Tetra meshing???
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John
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I agree. For the most part the amount of numerical diffusion at the tet/prism boundary is neglible and does not have too great an impact on the solution; however, it seems that in flows with large gradients in shear stress or large differences is the rate of shear strain that these diffusion effects are more readily apparent.
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