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Old   August 2, 2007, 21:20
Default transition model convergence problem
  #1
hammam
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Hello

i am simulating naca0012 airfoil using cfx sst turbulence model with Gamma-theta transition model .

the problem is the convergence rate at the start of solution is very good then when the lift and drag coefficients is close to the right solution the convergence become too slow then it become unstable ( zigzag curve) .

so what is the probelm?

n.b: i have an excamaination sign ! beside the aspect ratio at the cfx solver start screen with 7000 Maximum Aspect Ratio

thanks M.Hammam
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Old   August 6, 2007, 18:40
Default Re: transition model convergence problem
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Glenn Horrocks
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Hi,

Try running double precision, or improving mesh quality.

Glenn Horrocks
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Old   August 6, 2007, 19:04
Default Re: transition model convergence problem
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hammam
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hello

but when i run double precision it tells me an error message "out of memory'

and i think that my mesh quality is grater than 0.8 but the problem is the aspect ratio how to justify between it and low y+ value !!!

thanks
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Old   August 7, 2007, 18:33
Default Re: transition model convergence problem
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Glenn Horrocks
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Hi,

If you can't improve the mesh quality then you will just have to get access to a larger computer. Also consider running parallel. CFD is very computationally intensive and you can't expect to run every type of analysis on a desktop PC.

Glenn Horrocks
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