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-   -   Help For Turbulence Modeling,please! (http://www.cfd-online.com/Forums/fluent/91498-help-turbulence-modeling-please.html)

Yapoo August 12, 2011 10:40

Help For Turbulence Modeling,please!
 
Hello Freinds!

I'm working on a problem of Catamaran hydrodynamic analysis in fluent.
i have a problem with a Turbulent intensity and turbulence viscosity ratio in k-e model. i try this values:

Turbulent intensity= 0.1%
Turbulence viscosity ratio= 1.01

but this erro was appear:
"turbulent viscosity limited to viscosity ratio of 1.000000e+005 in 10 cells "

what am i doing to solve this problem?
Thanks!

nikhil August 13, 2011 21:24

I think you are providing inappropriate boundary conditions as long as turbulence boundaries are considered.
May be should play around with the turbulence intensity and related parameters and ensure that these are close to actual flow conditions

mrdumpa August 14, 2011 13:58

1. In your problem you selected K-E model which is generally used for high
turbulent flows(Re).
2. Turbulent Intensity depend on Reynolds number ie.
Only for low turbulent Re that value will be less then 1% ( in this case)
So by varying that value check the solution once that may help you.
Ex: for Re of 5e4 the Turbulent intensity value is 4%
3. Similarly Turbulent Viscosity ratio ie
For High Turbulent(Re) flow that value range 100-1000.
For Low Turbulent flows generally that values lies 1 to 10.
So by varying that value check the solution once that may help you.

..As my understanding from fluent userguide...If it is not useful just ignore this

mrji8011 August 14, 2011 23:51

As I know it can be related to size of the cells close to wall. it means you need to decrease the dimention which is parallel to the walls

Yapoo August 15, 2011 15:09

Thnx
 
Quote:

Originally Posted by mrji8011 (Post 320064)
as i know it can be related to size of the cells close to wall. It means you need to decrease the dimention which is parallel to the walls


نه دوست عزیز با تغییر در پارامترهای توربولانس این مشکل حل شد ممنونم

shaoda169 August 17, 2011 06:41

if you are sure there exist low reynolds zone inside the domian, maybe the standard k-e model is not suitable for your problem, because it is developed for fully developed turbulent flows. But anyhow you can select other variations of k-e model for your problem, like RNG or Realized k-e.

Hope this can help u!


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