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Old   June 6, 2007, 17:24
Default delta wing modelling in cfx
  #1
kaushik
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Hi i am trying to model delta wing in cfx for study of vortex breakdown. But i am not able to catch neither the leading edge vortex nor its breakdown. I am trying for mach no 0.3 and 0.8 with k-e turbulence model. Does anyone know how to model this stuff in cfx? Your advice will help me a lot.

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Old   June 6, 2007, 17:36
Default Re: delta wing modelling in cfx
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Joe
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Modelling highly separated flow from wings is not a trivial problem.

If you are trying to do that with the ke model. You first need to improve your understanding of turbulence and turbulence modelling before you proceed.

http://scholar.google.com/ has many papers on this subject.
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Old   June 6, 2007, 17:44
Default Re: delta wing modelling in cfx
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Joe
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Try this for size: http://www.fulton.asu.edu/~squires/p...ions/dles5.pdf
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Old   June 6, 2007, 17:56
Default Re: delta wing modelling in cfx
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Peter Attar
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while I wouldn't expect you to capture the breakdown location dynamics or any sort of secondary vortices correctly without the proper turbulence model, you should be able to get a leading edge vortex regardless of the turbulence model. Do you have a sharp edged delta wing? If so the primary separation location is fixed at the leading edge. What is the leading edge sweep? What angles of attack are you looking at? My guess is that you probably need to refine the mesh along the leading edge.

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Old   June 6, 2007, 18:11
Default Re: delta wing modelling in cfx
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kaushik
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thanks for your replies. angle sweep is 65. i am trying with 20 degree angle of attack. i think the leading edge is sharp. i created the geometry by lofting bicinvex section. I tried with laminar models. i got some vorticity but not at the begining of the leading edge. instead at half chord length. should refining of mesh work? can you give me any advice how fine mesh should be at leading edge.
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Old   June 6, 2007, 18:17
Default Re: delta wing modelling in cfx
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Peter Attar
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That I cannot tell you. If I were you I would start at a lower angle of attack maybe 12 to 15 degrees. For example mesh densities look for papers by Visbal and Gordnier. They have computed solutions for high sweep delta wings which should be of some use to you.

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Old   June 7, 2007, 04:09
Default Re: delta wing modelling in cfx
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Dr. FLow Squad
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Try the SST model. Th k-Epsilon is now to stick to the surfaces to much. Otherwise you should have a look at the SAS model, which is new in CFX 11. I have not tried it myself but it looks promising.

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