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Old   July 16, 2004, 16:49
Default transient
  #1
Jennifer Haque
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Dear All,

I am running a transient simulation and the convergence after the first 14 timesteps, seems to be fluctuating quite a lot. Is is normal to see quite a lot of fluctuations at the beginning of a transient run? Any comments or advice on how to improve this would be much appreciated.

Kind Regards Jennifer
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Old   July 17, 2004, 06:12
Default Re: transient
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Anne
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Hi Jennipher,

What are your time steps and coefficient loops? Have you tried reducing them?

In principle, such oscilation can be resolved by either increasing the coefficient loops or reducing the time step. CFX people recommend the latter, and from experience, I agree.

regards, Anne
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Old   July 18, 2004, 18:41
Default Re: transient
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Glenn Horrocks
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Hi Anne, Jennifer,

Often the initial conditions mean that there is some rapid transients occuring in the first few timesteps until it all settles down and the flow properly establishes itself. This means yes, it is common to have the solution fluctuate rapidly in the early part of the simulation until it settles down.

Glenn
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