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Old   August 22, 2001, 07:18
Default Turbulent transition
  #1
Andrew Parker
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Can anybody tell me if it is ok to split my grid into laminar and turbulent regions? I am modeling a hydrofoil; does this violate any physical rules? It's just that I get better results if I split my grid.

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Andy
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Old   August 22, 2001, 11:24
Default Re: Turbulent transition
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Mary
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The turbulance equations are just models. Can I use toothpicks and popsicle sticks to model my bridge? Noone knows your system better than you and the more accurate the model, the closer the results are to reality.
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Old   August 23, 2001, 16:52
Default Re: Turbulent transition
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Dave
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if you are trying to model a wind tunnel experiment for example the transitional point (or line) is often forced by adding roughness to the aerofoil surface.

this is so simulate the transition in flight at a high reynolds number. therefore if the transition point is know you should force it by using a laminar region.

note .. some turbulence models may not let you split the grid like this i.e. spallart-allmaras
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Old   August 24, 2001, 07:55
Default Re: Turbulent transition
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Andrew Parker
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As far as I can see the Spalart-Allmaras model does allow this, in fact I have been told that if I enforce a laminar zone before the transition point then the turbulence model can not be k-epsilon, as there is no value of k at the beginning of the transition, and it will not be modeled probably. However, I am thinking that it may not be right to a have a laminar region as if my hydrofoil was in water at 10 m/s the water in front of it would be turbulent anyway.

Cheers

Andy
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Old   August 25, 2001, 15:00
Default Re: Turbulent transition
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Peter
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The mesh choice depends actually on the region you are interesting in. If you have strong interest in the turbulent regions, use then a mesh for turbulent cases, and study the areas you are interested in.
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