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Old   November 5, 2006, 09:35
Default Unstructured-meshing for Unshrouded-Impeller
  #1
Turbomachinery
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Dear Friends,

I'd like to adopt the unstructured-mesh (using ICEM CFD tetra + prism) to unshrouded-impellers, i.e. there exists a gap between the blade-tip and the wall.

If the unstructured grid system based on tetra and prism, without hexahedral-meshing, should be applied, do the prism-layers have to be made on both the blade-tip and the shroud-wall to improve the boundary-layer resolution or on the shroud-wall only (and the tetra meshes on the blade-tip)....due to the narrow tip-clearance_^^.

I look forward to your constructive advice on it.

Thank you very much in advance...
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Old   November 5, 2006, 16:23
Default Re: Unstructured-meshing for Unshrouded-Impeller
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Glenn Horrocks
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Hi,

It is generally best to have full inflation/prism layers, but you may be able to use a tet mesh only right at the blade end. You will have to try it on your geometry and establish for yourself whether it is sufficient.

Glenn Horrocks
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Old   November 5, 2006, 18:28
Default Re: Unstructured-meshing for Unshrouded-Impeller
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Turbomachinery
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Thank you for relying to my query....

There is a tip-clearance (relatively small-gap comparing with other geometric dimension, e.g. diameter) and we are going to construct the 'tetra+prism' on the the stationary wall, the blade-tip and blade, and the hub surface.

Under the circumstances, if the total heights for the prism-layers be different due to the tip-clearance, the mesh structure could not be properly distributed for the computational domain, i.e. not uniformly distributed!

In case, the user's manual says that there are at least 2-3 tetrahedral meshes between the prism-layers.

How could I overcome this kind of problem...? (In this case, I wonder if the hexahedral-meshing should be adopted or not.)

Thanks a lot in advance.
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Old   November 6, 2006, 16:10
Default Re: Unstructured-meshing for Unshrouded-Impeller
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Glenn Horrocks
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Hi,

Sounds like you either need to use a smaller initial height in the tip region. You could also mesh this in a hexahedral mesher but with a little thought a tet/prism mesh should work.

Glenn Horrocks
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Old   November 7, 2006, 03:54
Default Re: Unstructured-meshing for Unshrouded-Impeller
  #5
Turbomachinery
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Dear Friend,

Could you make the prism-layers with good quality on both the blade-tip and the blade-around surfaces?

Due to the small gap between the blade-tip and the stationary wall, the total thickness of prism-layer on the blade-tip becomes very thin comparing with the prism-layer's thickness of the blade-around surface, which makes the whole structure of the prism-layers be irregular, i.e. the total thickness of each prism-layer may be different from the one designated by the user.

How could you handle this problem...?

With my best regards,
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