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Converging then Diverging Residuals???

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Old   September 19, 2006, 07:24
Default Converging then Diverging Residuals???
  #1
Erika Johnson
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Hello,

I was wondering if anyone has ever had any experience with residuals that intially start to converge and then after several iterations (i.e. 25,000+), they start to diverege???

I am working with the Reynolds Stress Model and I have decent convergence (1e-05) on everything except continuity (1e-2). In trying to get continuity to converge I let the simulation run and now at 25,000+ iterations I'm noticing that my Reynolds stresses, y-velocity, k and epsilon are starting to diverge slowly...Is the simulation adjusting itself in order to get the continuity to converge???

If it helps at all I'm simulating a flat plate boundary layer with super super fine mesh and low freestream intensity (0.2%).

Any ideas???

Thanks so much, Erika
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Old   September 19, 2006, 10:20
Default Re: Converging then Diverging Residuals???
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sam
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It is normal dont worry
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Old   September 19, 2006, 10:24
Default Re: Converging then Diverging Residuals???
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Erika Johnson
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So then should I allow the solution to progress??? Will it eventually converge???
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Old   September 19, 2006, 10:27
Default Re: Converging then Diverging Residuals???
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sam
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yes. But not in absolute terms. It may start fluactuating between some value i.e diverging and converging. check the mass flow balance(it is ur gloval convergence)
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Old   September 19, 2006, 10:30
Default Re: Converging then Diverging Residuals???
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Erika Johnson
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Thanks for your help!
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Old   September 19, 2006, 10:32
Default Re: Converging then Diverging Residuals???
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sam
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wats ur msn or yahoo id?
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Old   September 19, 2006, 10:35
Default Re: Converging then Diverging Residuals???
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Erika Johnson
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I don't have one.
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Old   September 19, 2006, 10:37
Default Re: Converging then Diverging Residuals???
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sam
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which type of flow u r working on
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Old   September 19, 2006, 10:45
Default Re: Converging then Diverging Residuals???
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Erika Johnson
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I'm simulating a boundary layer experiment that was conducted in a wind tunnel with very low free stream turbulence intensity (0.02%). I'm actually trying to duplicate the turbulence intensity curves that Klebanoff published in his experiment from 1955 (Characteristics of Turbulence in a Boundary layer with Zero Pressure Gradient).
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