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Old   August 11, 2005, 11:02
Default Coupled meshes
  #1
Vyatscheslav
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Is it possible to mesh each part of an aircraft (eg:wings,fuselage,...: decomposition into 6 or 7 parts) and to couple these objects to compute the whole airflow pattern. Any idea, advice, or reference (paper) is welcome.

Thank you in advance. Vyatsheslav
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Old   August 11, 2005, 14:36
Default Re: Coupled meshes
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steve
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Yes it possible. The "CPMATCH" tools exist specifically to join up disimilar meshes.
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Old   August 11, 2005, 15:07
Default Re: Coupled meshes
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William Blake
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It is possible but not at all a good way to do it.

The following link shows a good way to solve your problem: :

http://www.gridpro.com/gridgallery/airplane.html

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Old   August 12, 2005, 05:14
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Hubert Janocha
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Yes, cpmatch works, but be carefull with high speed / high compressible flows. For this flows you need a very high quality mesh because of the sensitive physics / nature of the flow.

The way William Blake told is the best one (merged vertices between to meshes / blocks), but it is not really suitable in very complex geometries, and it is not a rapid way, but sometimes necessary. The keyword is block structured meshing.

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Old   August 12, 2005, 07:08
Default Re: Coupled meshes
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William Blake
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Gridpro is multiblock structured and the topologies and meshes for the examples in the grid gallery can be downloaded (you have to write an email and ask for the login data).

So this might be a fast start.
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Old   August 12, 2005, 07:28
Default Re: Coupled meshes
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Vyatscheslav
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Thanks for these elements of answer.

But let me precise what Iīm looking for. My work consists roughly of analysing the airflow pattern around the whole aircraft comparing different wings models. Iīd like to mesh fuselage and wings independently, and to couple both grids. That would allow me to mesh only my different wings models and not to have to remesh the fuselage each time.

Do you confirm what you said? Is it a way to do it with StarCD? Is GridPro (free) available on the internet?

Once again, thanks for your help. Vyatscheslav
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Old   August 12, 2005, 08:15
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William Blake
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It is possible to do it in your way but based on my 10 years of experience with starcd I would not advise you to do it.

GridPro is not free but the most suitable tool to do this kind of work. As long as you only change some values of the geometry like the thickness or the shape of the wing, the diameter of the engine, position of the fuselage ... , remeshing is fully automatic and takes you only some minutes.
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Old   August 17, 2005, 02:13
Default Re: Coupled meshes
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Vyatscheslav
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OK, thank you. And how does it works for the connections of the blocks? For example, if the mesh of the fuselage is done, and if I want to test a new wing: I will import the new CAD file, mesh it, and what about the connection? On the linking plane, how to do to make the points correspond (in fact to avoid to do like on starCD: couples,which implie loss of precision for the code). Also: where can I find some valuable documentation of GridPro, and how much is a license?

Vyatscheslav
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Old   August 17, 2005, 06:12
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William Blake
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If you mesh in gridpro, you mesh the complete geometry and not parts of it. After changing some part of the geometry you simply run the grid generation for some iterations.

It is also possible to mesh parts and use the "weld" utility to get a 1 by 1 connectivity but I never used that feature. http://www.gridpro.com/products/weld.html

For the licensing costs you should contact them directly. But it is usually not the cheapest code (mainly used by the NASA).

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Old   August 17, 2005, 09:42
Default Re: Coupled meshes
  #10
William Blake
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I tried to send you some tutorials via email but your email doesn't work.

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Old   August 17, 2005, 10:31
Default Re: Coupled meshes
  #11
Vyatscheslav
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Thanks a lot. In fact, itīs .fr and not .com ...

Yes, the weld seems to be a possible solution. When you say connection 1 by 1, do mean itīs possible to mesh a part (eg fuselage), to keep in memory the nodes on the connecting plane, and to use these datas to mesh the other part (eg wing)? I think itīs an important feature, allowing to use higher order of discretisation for the solver.

Other question: itīs not clearly stated on their site, but: when the mesh is done, is there an output file format to solve with starCD.

Vyatscheslav
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Old   August 17, 2005, 11:31
Default Re: Coupled meshes
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William Blake
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I never used weld myself. It should be much easier and faster do create the whole mesh at once again every time you change someting.

Export to StarCD is no problem. You can use Nastran or SrarCD format.

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