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CFX-Mesh, guide vanes (baffles) and problems.

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Old   December 30, 2008, 19:16
Default CFX-Mesh, guide vanes (baffles) and problems.
R. Janny
Posts: n/a

I've been trying to mesh using CFX-Mesh (CFX 11 SP1) the following geometry:

geometry image 1 geometry image 2 geometry image 3 geometry image 4 meshing warning 1 meshing warning 2

It has a main body which was created using a external CAD software, exported as parasolid and then imported into DesignModeler as "frozen" geometry.

In DesignModeler I created all internal (guide vanes/baffles), using sketches extruded as "slice material" (the thickness is about 10 mm)

The problem is that CFX-Mesh is ether failing to mesh or generating very huge meshes. For example, if I mesh only the main body (without any internals) the total number of elements is around 1.600.000 (300.000 nodes). I then include just one set of guide vanes (extreme right when looking on those images above) and the generated mesh goes up to 3.100.000! (570.000 nodes). If I try to mesh the complete set, if the meshing process does not fail, I could end up with more than 13.000.000 elements.

The times that CFX-Mesh fails seems to be related to "infinite loops", because it either freezes on the task "Create Tetrahedra (Advancing Front): Elements - ....." or rises a error saying that a particular region (near a random guide vane edge) was not possible to be volume-meshed due to spacing issues.

The mesh parameters are the following:

Main body (default face spacing): angular resolution 18 degrees, minimum edge length 30 mm, maximum edge length 80 mm.

All vanes (internals): angular resolution 18 degrees, minimum edge length 10 mm, maximum edge length 45 mm.

I know that the problem is related to the guide vanes defining (geometry and/or mesh spacing?) or with the meshing strategy as a hole. I'll appreciate very much our insight in this matter and help me not to go mad!

Extra question: is there a way to create those vanes with zero thickness in DesignModeler? This is because when you create them using a given thickness, more surfaces are created and keep flying around until I define the ones that are really wall in CFX-Pre). I bet that these extra surfaces may trouble the meshing process, even though they will not be used (will be "fluid domain" in CFX-Pre).

Thank you.

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Old   December 31, 2008, 08:49
Default Re: CFX-Mesh, guide vanes (baffles) and problems.
R. Janny
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I've sorta of solved the problem by not using "thin surfaces". See image bellow:

geometry rebuild

This was not the solution I was looking for (I don't have ICEM to use surfaces directly, I must use CFX-Mesh), but did the trick. "My solution" will not work very good if the number of vanes/baffles is odd (not in "pairs") in a given cross-section area.

If anyone has a better (less complicated) idea, please feel free to share it!

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Old   October 1, 2012, 04:57
Default how to create guide vane
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Mausam Shresha
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i have created the turbine runner using the turbo grid. how to develop guide vane and stay vane along with it?
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