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Getting convergence with unsteady problems

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Old   November 29, 2005, 11:40
Default Getting convergence with unsteady problems
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Freeman
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As a rule of a thumb, can I say that when running an unsteady simulation in any turbulence model, when I achieve a periodic oscillation in my residuals and in mass-weighted average plots, etc. solution has converged?

If not, this means that mass-weighted average quantities must flatten like in steady simulations?

Thanks!
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Old   November 29, 2005, 17:56
Default Re: Getting convergence with unsteady problems
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Matt
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Monitor a parameter like Lift or Drag, when they converge then it means your solution has converged.

Matt
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Old   November 29, 2005, 18:12
Default Re: Getting convergence with unsteady problems
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Freeman
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But in unsteady these parameters I don't think they keep constant: won't they be fluctuating according to also fluctuating velocity and pressure fields?
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Old   November 30, 2005, 11:57
Default Re: Getting convergence with unsteady problems
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Matt
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You reach a point where they do not oscillate much hence you can assume that the solution has converged. However, you can still write a PERL script to average out the final results.

Matt
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Old   December 1, 2005, 14:13
Default Re: Getting convergence with unsteady problems
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Freeman
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OK Matt, many thanks!

Then If I've understood well, when I am in unsteady problems I will get the convergence when my parameters of the flow (mass-weighted average and/or drag-coeff, etc.) have a (little) periodic oscillation, doesn't it?

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