CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Help For Turbulence Modeling,please!

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree5Likes
  • 1 Post By nikhil
  • 2 Post By mrdumpa
  • 1 Post By mrji8011
  • 1 Post By shaoda169

Reply
 
LinkBack Thread Tools Display Modes
Old   August 12, 2011, 10:40
Default Help For Turbulence Modeling,please!
  #1
New Member
 
Pooya
Join Date: May 2010
Posts: 26
Rep Power: 7
Yapoo is on a distinguished road
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!
Yapoo is offline   Reply With Quote

Old   August 13, 2011, 21:24
Default
  #2
New Member
 
Nik
Join Date: Mar 2010
Location: Michigan
Posts: 25
Rep Power: 7
nikhil is on a distinguished road
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
Yapoo likes this.
nikhil is offline   Reply With Quote

Old   August 14, 2011, 13:58
Default
  #3
New Member
 
mahendra
Join Date: Aug 2011
Posts: 6
Rep Power: 5
mrdumpa is on a distinguished road
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
ramakant and Yapoo like this.
mrdumpa is offline   Reply With Quote

Old   August 14, 2011, 23:51
Default
  #4
New Member
 
mj
Join Date: Apr 2011
Posts: 24
Rep Power: 6
mrji8011 is on a distinguished road
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 likes this.
mrji8011 is offline   Reply With Quote

Old   August 15, 2011, 15:09
Smile Thnx
  #5
New Member
 
Pooya
Join Date: May 2010
Posts: 26
Rep Power: 7
Yapoo is on a distinguished road
Quote:
Originally Posted by mrji8011 View Post
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
Yapoo is offline   Reply With Quote

Old   August 17, 2011, 06:41
Default
  #6
New Member
 
Join Date: Nov 2009
Posts: 13
Rep Power: 7
shaoda169 is on a distinguished road
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!
Yapoo likes this.
shaoda169 is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 22:11.