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How does Fluent RANS model work?

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Old   February 18, 2009, 21:50
Default How does Fluent RANS model work?
  #1
Tang Jingwei
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I have a very basic question here.

Am i right that Fluent only run on RANS and LES models?

Why is it that the user does not need to input any temporal discretization when he uses a RANS viscous model, say K-epsilon?

Is it because RANS model take the average of the different flow components at steady state?

If so, am i right that one can only use LES to visualise unsteady flows?
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Old   February 18, 2009, 21:57
Default Re: How does Fluent RANS model work?
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Carlos
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Hi,

You are right, RANS is time averaged so not really suitable for time-dependent problems. LES is the best in Fluent for this but you need ultra fine grids for complex 3D problems.

A compromise is to use DES or you can use URANS which is unsteady-RANS. This somehow uses RANS as unsteady and I think you can do this in the unsteady solver but I have only used RANS to date so not sure how it works.

Carlos.
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Old   February 18, 2009, 22:00
Default Re: How does Fluent RANS model work?
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Tang Jingwei
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Thanks for the reply!

How do i use URANS?
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Old   February 18, 2009, 22:09
Default Re: How does Fluent RANS model work?
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Carlos
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Not sure, think you select RANS model as normal then switch the solver from steady to unsteady. Thats all I know.

Carlos.
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Old   February 18, 2009, 22:10
Default Re: How does Fluent RANS model work?
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Tang Jingwei
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I get it! Thanks dude
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Old   February 18, 2009, 22:21
Default Re: How does Fluent RANS model work?
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Carlos
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No problem, good luck....
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Old   August 22, 2009, 15:08
Default RNG k-epsilon model
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Ganesan
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Ganesan Sethu is on a distinguished road
hai,
is this possible the molar concentration value is similar to laminar flow in unsteady flow? and is this needed to run turbulent model before to run LES model?
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