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What kind of turbulence modeling is applied for my problem in Fluent?

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Old   February 28, 2018, 15:10
Question What kind of turbulence modeling is applied for my problem in Fluent?
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Roh
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I'm trying to simulate a flow which is exiting from a nozzle. Just tried to know what kind of turbulence modeling is applied in Fluent for my problem. I found something in this page:

http://jullio.pe.kr/fluent6.1/help/html/ug/node404.htm

It looks like Fluent uses several kind of turbulence modeling such as Ensemble-average, Time-average, Favre-average. my setting is this:

Density-based
unsteady
using several turbulence modeling e.g. K-omega and K-omega SST and K-epsilon and RSM

What kind of RANS modeling is applied in Fluent for my problem? Ensemble-average, Time-average or Favre-average? Are all of these models called RANS?

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Old   February 28, 2018, 18:08
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Your turbulence models are the K-omega and K-omega SST and K-epsilon and RSM.

Quote:
Originally Posted by Roh View Post
It looks like Fluent uses several kind of turbulence modeling such as Ensemble-average, Time-average, Favre-average. my setting is this:
These are not turbulence models, these are different averages. All of them are a type of ensemble-average (all averages are formed from some kind of ensemble, but you need to define the ensemble).

Favre-average is a density-weighted time-average, which therefore makes it an arithmetic density-weighted time-average.

The 'RA' in RANS is Reynolds-average, which is typically what most people refer to as time-average. But this is the same as an arithmetic unity-weighted time-average which is simple case of of a Favre-average.

The governing equations whether you do RANS/FANS are equivalent once you express them in the Reynolds or Favre variables. What is different is the interpretation of the basic variables and results. Hence, it is not necessary to say whether K-omega is a RANS/FANS or whether it is a time-average of Favre-average because they're all equivalent as far as the solver (Fluent) is concerned.
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