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Old   July 14, 2004, 13:27
Default Meshing
  #1
Russ
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Hi all,

I'm trying to mesh up a aerofoil in 3d space, with an adaptive refined mesh, tetra.

The model is constructed as such, that the wing end meet the sidewalls, in order to analysis it flow characteristics with out the end tip vortices. The model needs to best analysed in 3d space to record the effect of boundary layer controls.

I obviously want the mesh close to the wing to be fine, and so i mesh the wing using the face mesh commands. Once meshed, I the mesh the fluid domain with volume mesh setting to a much courser value.

However, when i study the volume mesh, its seems that the fines mesh conditions applied to the faces of the wing are only taken in to account in the volume mesh at the side walls, and then the middle plane is of a course structure.

How can i force the mesh to be fine all along the wing???

Thanks in advance

Russ
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Old   July 15, 2004, 11:01
Default Re: Meshing
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Russ
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any ideas guys????
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Old   July 15, 2004, 11:28
Default Re: Meshing
  #3
Jörn Beilke
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http://www.gridpro.com/gridgallery/3elementairfoil.html
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Old   July 15, 2004, 13:33
Default Re: Meshing
  #4
George
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It's better for you to export your mesh into fluent and then save it as Boundary Grid. By doing this, only the surface mesh is kept and you can then use TGrid to create a refined boundary layer mesh in the vicinity of the wing, in order to capture the near wall viscous effects and a coarser tetrahedral grid occupying the rest of your domain. Also consider decomposing the domain near the wing into smaller volumes so that you can control the grid's density. If you can't use TGrid, then attach a boundary layer mesh on the wing with Gambit. It's not as straightforward as it may sounds but practice makes perfect.

Let me know if you have any further problems.

Regards,

George
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Old   July 15, 2004, 15:48
Default Re: Meshing
  #5
Russ
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Thanks george,

I dont know much about saving as Boundary grids, could you give me a brief insight.

Also, if I try and split the domain down into smaller volumes, is there a more efficient shape to create the smaller volumes as???

Thanks Russ
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Old   July 17, 2004, 15:07
Default Re: Meshing
  #6
George
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Hi Russ,

A brief guide on how to create a boundary grid is:

1) Mesh all the wall and interior faces in Gambit in a fashion that is suitable for your problem and by using those faces mesh the interior fluid volume. Don't worry about the quality of the volume mesh for the time being. Apply boundary conditions as usual. 2) Export the 3D volume mesh into Fluent, check it (grid -> check) and save it as boundary grid (file-> write... -> boundary grid...). This saves only the surface mesh and drops the volume cells. Notice that, in the imported grid from Gambit all the faces are "mixed" while, when writing the boundary grid these faces turn to "triangular". This is very important for creating your volume mesh in TGrid.

For further info about how to use TGrid, refer to the online manual and tutorial guides. In particular, look for the "hybrid mesh generation tutorial" for a more details.

About splitting your flow domain into smaller volumes... this is highly dependent on the cell type, the grid discretisation scheme etc. There are many examples that you can find on the internet, some of them really helpful. For an unstructured hybrid mesh you are basically limited by the software's discretisation algorithm and your own imagination.

Hope this helps.

Cheers,

George.
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Old   August 9, 2004, 03:43
Default Re: Meshing
  #7
ravi
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hai friend, i'm not well versed in FLUENT, indeed i'm a beginner, i need help frm u all, i need to know the basic mesh elements and types, pls help me, wat r the various mesh types? wat r the advantages of one over the other? pls help me
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