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3D wing + wind tunnel hexa structured meshing

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Old   October 20, 2010, 08:56
Default 3D wing + wind tunnel hexa structured meshing
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iswadi
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i have created a 3D half wing and enclosure the wing with cube to model a air/fluid domain of a wind tunnel. i suppressed the solid wing and then i am going to mesh the air/fluid domain with hexa structured mesh. i am using the ANSYS WORKBENCH 12.1. i know i should use blocking method before i meshed the air/fluid domain with structured hexa mesh. my questions are :

1) should i use ICEM CFD or the workbench meshing to do the blocking method? which one is easier to do the blocking method?

2) Can i use the Design Modeller to do the blocking? How?

3) where can i find the tutorial or any example on this topic? i have gone through the Design modeller tutorials but i cannot find any slicing technique to do the blocking.

Tanks in advance
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Old   October 20, 2010, 09:33
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Hi,

all the mesh processing you can do in ICEM. You can start it under Workbench, but still it is ICEM.
Unfortunately, I have never worked with Design modeler and hope I will not need this in future. As I know, it is made to work with some kinds of simple geometry models.

Concerning tutorial, you can check this one:
http://www.youtube.com/watch?v=tYrbScUH9RE
( thanks to Simon / PSYMN ).
That tutorial describes how to make a mesh around 2d profile, but the general approach should be the same or really close to shown there (depends on the ends of the wing: fuselage connection and free end, frontal and back).

You can (if allowed) also put here some pictures of your model with rough description of the simulation idea. Sometimes, it is really useful.

Best regards,
DST
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Old   October 26, 2010, 02:13
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sorry to take a long time to post my wing structure photo. it is only small and thin wing. it also have some mechanism below the wing.
first of all, i am going to build a hexa mesh on the wing if possible for static structural analysis. i know it is hard but it is worth
to try rather then never.

the second step is, i am going to proceed into external flow analysis on the wing to gain its aerodynamic performance.
in this case i must generate the hexa mesh around the wing.

can any body give me some suggestion to do the blocking for this kind of wing through ICEM CFD?
Attached Images
File Type: jpg deflected wing.jpg (52.6 KB, 182 views)
File Type: jpg gambar wing2.jpg (50.5 KB, 134 views)
File Type: jpg compliant structure2.jpg (47.3 KB, 121 views)
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Old   October 26, 2010, 09:05
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I would not recommend a hex mesh for this geometry. If you insist on one, you'll be forced to use ICEM, and good luck blocking it. If you haven't used ICEM in the past, it has a very steep learning curve.

Instead, I would recommend using the path conforming tetrahedral mesher in the meshing application.

And for the record, this:

"I have never worked with Design modeler and hope I will not need this in future. As I know, it is made to work with some kinds of simple geometry models."

Is very wrong. DM can work with very complex CAD models.
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Old   October 26, 2010, 10:08
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Hi,
michael_owen is correct concerning the complicity of the blocking process for this kind of structure. It will be much more effective to make this with some semi-automatic meshing process.
If you want to learn blocking, it is much faster and better to try and understand blocking on some other cases.

Concerning Design Modeler:

michael_owen, what do you consider as "can work with very complex CAD models"?

Means "can open, make some cuts, simplifications"? ICEM CFD can also make some cuts and simplifications. It hink, that ICEM can less then DM (as I mentioned, I did not work with DM).
Can it work as Pro_E with parametrical surfaces or Audodesk Alias with free-shape surfaces? These two programs as CATIA, UG/NX and some others can work with complex geometries.
As I know, DM is done mostly for preparation of CAD geometry for simulation - am I correct? Means, that complex geometry is done by some specific CAD programs and simplified with DM.

Best regards,
DST
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Old   October 26, 2010, 23:43
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it is very pleased to see someone had answer my question and right now i working to mesh the model with patch conforming tetrahedral method.

the next step is to test the model in external flow analysis (wind tunnel simulation).

the question is :
1) is it satisfy if i use the tetrahedral mesh for whole airflow region?
2) based on previous studies, most of airflow regions are build from structured hexa meshed (with o grid, c grid etc..). can anybody give me some idea how to do the blocking method around my model?

actually i have work with DM and it quite satisfy to my model. i think the best answer to use DM or not is depends on our model.
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Old   October 27, 2010, 11:47
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You should embed your geometry into a relatively small block, relatively close to the surface of the geometry, and tet mesh it. Embed this block in your far field domain, which will be easy to block out manually via slices in DM. Then you can sweep mesh the far field blocks to get hexes. You may have to apply quite a few edge sizings and edge and sweep biases to get the mesh you want. You should be able to Form New Part everything to get a conformal mesh.
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Old   October 27, 2010, 13:52
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This model is interesting enough that I would be willing to help with a quick Hex mesh...

I agree with my colleagues that tetra/prism would be an easier start for you, but Hexa really would give a better mesh in not much time (if you know what to do).

Essentially, you should imagine this model as a 2D circle. You would Ogrid that. Then in two of the quarters, there is a cut out... Ogrid in each of those, spit for the cutout and assign materials appropriately (solid/fluid). Then split for those little cuts. Finally extrude for 3D and associate to the actual shape and you are done. Sorry for the rough instructions, it shouldn't be a problem for me, but I am somewhat of an expert. Explaining the detailed steps to a newbie would be rough. You should start with the basics (tutorials) before tackling reality.

If you are not in a rush, I can probably work on this for a few minutes some time in the next few weeks.

I suspect that you plan to do some sort of FSI... And I suspect that the splits can open and close as the wing flexes? If so, you are entering into a world of added complexity.
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Old   October 27, 2010, 20:25
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Thank you PSYMN,
i agreed with you . it was a rough instruction for me as a newbie but i will try my best to follow your instructions. i am not in rush and i am really appreciate if you can help me in this meshing. Your suggestions, examples and advices will totally benefits me. can you tell me what kind of file format that you need? i will send you then.

Yes, this is a FSI study. the wing splits can open and close during flying. i am studying the aerodynamic complexity in this wing type.

mr micheal_owen,
correct me if i am wrong, did your instruction means that it will be a hybrid mesh?
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Old   October 28, 2010, 09:37
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Your design Modeler files (or ACIS or Parasolid or whatever) should be fine.
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