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Fluent equation error?!?

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Old   July 11, 2002, 08:19
Default Fluent equation error?!?
  #1
TOM
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For the same models, same results after iterations and convergence of the solution ( same .cas and .dat) , Fluent 5.3 does not give the same results than fluent 5.4 and fluent 5.4 different from fluent 5.5 for average, mass weighted average and facet average values.

Fluent 5.3 gives good results but not fluent 5.4 and 5.5

For example, an inlet set up at 75 m/s, fluent 5.3 gives around 74.9997 m/s for minimum, 74.9999 maximum and 74.9998 average facet values.

And Fluent 5.4 and 5.5 gives an average of 64, less than the minimum!!!!!

It has the same problem with different models.

Am I wrong or is there a problem.

Try with your model.

Looking for any answer, thanks.
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Old   July 12, 2002, 04:00
Default Re: Fluent equation error?!?
  #2
Boris
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I also encountered similar problems with Fluent 5.5.
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Old   July 12, 2002, 04:42
Default Re: Fluent equation error?!?
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TOM
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Therefore, where does this error come from? Is there an error in one equation or am I not doing it right?
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Old   July 12, 2002, 18:43
Default Re: Fluent equation error?!?
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Eric
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hi, tom and boris.

there were a number of updates made related to postprocessing functionality with the FLUENT 5.3, 5.4, and 5.5 releases. my suspicion is that the differences you are observing in the postprocessed results are not due to problems with the FLUENT models, but to whether FLUENT is using cell-center or face values when performing the numerical integration in the different versions. without knowing the specifics of your models, it would be difficult to determine the exact cause of the differences you are observing.

if you would be willing to share your models and observations with your local technical support representative, we would be happy to review these issues with you to find the cause.

thanks,

eric.
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Old   July 14, 2002, 16:58
Default Re: Fluent equation error?!?
  #5
Sohail
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hi Tom

R u sure that the convergence Criterion you r choosing are same for all the Fluent version you r using If you use different convergence Criterion then you may get difference in result. Even if you use same version of fluent with different convergence criterion result may differ. so I ask you set same convergence criterian. Inform me if it works.
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Old   July 15, 2002, 03:21
Default Re: Fluent equation error?!?
  #6
TOM
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Convergence criterion were exactly the same, because I read exactly the same file (one and only one) .cas and .dat on different version of Fluent.

Moreover, Fluent 6.0 give different results too.

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Old   July 15, 2002, 03:24
Default Re: Fluent equation error?!?
  #7
TOM
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Your explaination looks like to be coorect, but a difference of 15% is huge for those two diffent ways of analysing the results.
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