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Which one to rely on, segregated or coupled?

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Old   March 11, 2009, 06:35
Default Which one to rely on, segregated or coupled?
  #1
Freeman
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Hi all users,

I have just make a simulation over a little 3D airfoil shape (at M=0.56, 0.5mill tetra cells with prisms at the boundary layer, k-e realizable, 2nd order QUICK). When I solve it with segregated solver I get Cd=0.09, but when I switch to coupled (density based) solver I get 0.064 (with a periodic oscillation between +/-.0006)

Which solution should I rely on?? Thenks to all

Freeman
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Old   March 11, 2009, 07:42
Default Re: Which one to rely on, segregated or coupled?
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Ben
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Since it's a Compressible Flow Simulation one need to go for Coupled Solver Option. I feel you should rely on Coupled solver result.
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Old   March 11, 2009, 07:59
Default Re: Which one to rely on, segregated or coupled?
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Freeman
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Thanx Ben... I have heard here in CFD that some users have successfully used segregated up to M=0.7 and even more. By the way, I am specifying fluent to use a constant flight air density of 0.23 (because of flight operations at 14.000m): may I use another kind of density because of this coupled solver enhabled (I mean, any sort of variable density)?

thanks in advance

Freeman
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Old   March 11, 2009, 08:12
Default Re: Which one to rely on, segregated or coupled?
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Freeman
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Hi again,

I am quite disturbed, because I simulate before this wing, another similar shape, with very similar simualtion parameters (same cell count and prism layer, k-e realizable, etc.) and both segregated and coupled threw me the same results!

I don't undersand now this difference...
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