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

Does realizable k-e model with enhanced wall treatment work for surface roughness?

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

Reply
 
LinkBack Thread Tools Display Modes
Old   May 4, 2012, 12:38
Default Does realizable k-e model with enhanced wall treatment work for surface roughness?
  #1
New Member
 
Yangyang
Join Date: Aug 2011
Posts: 9
Rep Power: 5
zyy95900 is on a distinguished road
Hi everyone,

I am trying to simulate in duct flow with surface roughness. I am using realizable k-e model with enhanced wall treatment now. I know k-e model not good for boundary simulation, but how about the realizable k-e model with enhanced wall treatment. Does realizable k-e model with enhanced wall treatment work well with surface roughness simulation? Is this correct model. If not, which turbulence model I should use? I have try SST K-W model but the result seems not good.

Thanks.
zyy95900 is offline   Reply With Quote

Old   May 4, 2012, 21:27
Default
  #2
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 591
Rep Power: 11
LuckyTran is on a distinguished road
Quote:
Originally Posted by zyy95900 View Post
Hi everyone,

I am trying to simulate in duct flow with surface roughness. I am using realizable k-e model with enhanced wall treatment now. I know k-e model not good for boundary simulation, but how about the realizable k-e model with enhanced wall treatment. Does realizable k-e model with enhanced wall treatment work well with surface roughness simulation? Is this correct model. If not, which turbulence model I should use? I have try SST K-W model but the result seems not good.

Thanks.
In Fluent, the rough wall treatment is not compatible with the enhanced wall function approach for the epsilon based models. You must use the standard wall functions or use an omega based model.

Wall/surface roughness is a wall modelling problem, not strictly a turbulence modeling problem. Also, recall that SST k-w is just a hybrid standard k-epsilon with omega treatment near walls.

I would imagine that neither model should have much difficulty simulation rough walls for simple duct flows.

Last edited by LuckyTran; May 4, 2012 at 21:45.
LuckyTran is offline   Reply With Quote

Old   May 4, 2012, 23:19
Default
  #3
New Member
 
Yangyang
Join Date: Aug 2011
Posts: 9
Rep Power: 5
zyy95900 is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
In Fluent, the rough wall treatment is not compatible with the enhanced wall function approach for the epsilon based models. You must use the standard wall functions or use an omega based model.

Wall/surface roughness is a wall modelling problem, not strictly a turbulence modeling problem. Also, recall that SST k-w is just a hybrid standard k-epsilon with omega treatment near walls.

I would imagine that neither model should have much difficulty simulation rough walls for simple duct flows.
Thanks for reply.
In my case, the intruduced roughness is for increasing the turbulence in duct, which increasing the reactant mass transfer to reaction surface (wall). So I think I should use a turbulence model. I have try the standard wall function (k-e model), but the turbulence intensity on duct wall go infinit. I think turbulence intensity on duct wall should be zero.
Can you tell me which model is best in my case? k-e with standard wall treatment or k-e with enhanced wall treatment or SST k-w?

Thanks.
zyy95900 is offline   Reply With Quote

Old   May 4, 2012, 23:54
Default
  #4
Senior Member
 
Lucky Tran
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 591
Rep Power: 11
LuckyTran is on a distinguished road
Quote:
Originally Posted by zyy95900 View Post
I have try the standard wall function (k-e model), but the turbulence intensity on duct wall go infinit. I think turbulence intensity on duct wall should be zero.
Turbulence intensity increases as you approach the wall and reaches a maximum value before being damped very close to the wall. That is a well known fact. It depends on your near wall grid resolution whether or not you will see the resulting decrease but what you stated is consistent with what is known about wall-bounded turbulence.

Quote:
Originally Posted by zyy95900 View Post
Can you tell me which model is best in my case? k-e with standard wall treatment or k-e with enhanced wall treatment or SST k-w?
You cannot use enhanced wall treatment, see my last post. Both models are good, you can use either. I wouldn't use the standard k-epsilon model though, I'd go for realizable k-epsilon or SST k-omega model as they are superior.
LuckyTran is offline   Reply With Quote

Old   May 5, 2012, 00:22
Default
  #5
New Member
 
Yangyang
Join Date: Aug 2011
Posts: 9
Rep Power: 5
zyy95900 is on a distinguished road
Thank you very much.
zyy95900 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
natural convection mehrdadeng CFX 10 February 25, 2011 06:25
Help: about the enhanced wall treatment maximus FLUENT 0 May 10, 2006 11:55
Y+ Values for Enhanced Wall Treatment Gerd FLUENT 5 November 21, 2005 09:23
Enhanced wall treatment? bylin FLUENT 3 November 21, 2003 13:33
Wall functions Abhijit Tilak Main CFD Forum 6 February 5, 1999 02:16


All times are GMT -4. The time now is 05:01.