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Old   March 13, 2008, 07:40
Default mesh independancy?
  #1
amine
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Hi,

i've set a mesh which converged,but when refining the convergence was achieved ,is the problem a timescale kind or acually a mesh one.

thanks
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Old   March 13, 2008, 07:48
Default Re: mesh independancy?
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matej
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Dear amine, it is hard to understand what whould you like to know.

both cases converged, so what is the problem?

matej
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Old   March 13, 2008, 08:22
Default Re: mesh independancy ?
  #3
amine
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Hi,

my question was, i set a mesh that converged,when refining that mesh the solution didn't converge at least after a large timestep iterations & ocilated which wasn't the case previously.

thanks
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Old   March 13, 2008, 14:36
Default Re: mesh independancy ?
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Craig Hildreth
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You are probably resolving details in the flow the prior mesh could not and these disturbances are affecting convergence.
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Old   March 13, 2008, 17:42
Default Re: mesh independancy ?
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Glenn Horrocks
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Hi,

Craig is correct. Try using a larger physical timescale.

Glenn Horrocks
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Old   March 13, 2008, 18:05
Default Re: mesh independancy ?
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longbow
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I don't see the logic behind increasing timescale whenever you see oscillation. What if that oscillation is a real physical phenomenon? Using large timescale to get rid of oscillation just for sake of getting converged result is not always a good practice.
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Old   March 17, 2008, 17:41
Default Re: mesh independancy ?
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Glenn Horrocks
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Hi,

I agree with you longbow. The full answer is work through the points on this link, of which increasing timescale is one:

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

ps: I wrote this FAQ answer so I am well aware that there is more to it than just increasing the timestep!

But I am a lazy typer so couldn't be bothered writing the whole thing every time somebody asks it. This question has been asked dozens of times so it gets pretty boring.

Glenn Horrocks
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