CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   How does Fluent RANS model work? (http://www.cfd-online.com/Forums/fluent/50604-how-does-fluent-rans-model-work.html)

Tang Jingwei February 18, 2009 21:50

How does Fluent RANS model work?
 
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?

Carlos February 18, 2009 21:57

Re: How does Fluent RANS model work?
 
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.

Tang Jingwei February 18, 2009 22:00

Re: How does Fluent RANS model work?
 
Thanks for the reply!

How do i use URANS?

Carlos February 18, 2009 22:09

Re: How does Fluent RANS model work?
 
Not sure, think you select RANS model as normal then switch the solver from steady to unsteady. Thats all I know.

Carlos.

Tang Jingwei February 18, 2009 22:10

Re: How does Fluent RANS model work?
 
I get it! Thanks dude

Carlos February 18, 2009 22:21

Re: How does Fluent RANS model work?
 
No problem, good luck....

Ganesan Sethu August 22, 2009 15:08

RNG k-epsilon model
 
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?


All times are GMT -4. The time now is 08:58.