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

y+Factor: Help understanding?

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

Like Tree3Likes
  • 3 Post By kyle

Reply
 
LinkBack Thread Tools Display Modes
Old   January 26, 2012, 03:22
Default y+Factor: Help understanding?
  #1
Senior Member
 
Join Date: Dec 2010
Posts: 135
Rep Power: 6
eRzBeNgEl is on a distinguished road
Hi guys

I really have a problem understanding the wall y+ factor and its`range.
Am I right, that the y+ factor is a number which shows the code when to switch between far field and wall treatment functions?

In Star-CCM+ are three different types fo Wall-treatments I could choose implmented:

High-Reynolds wall treatment,
Low-Reynolds wall treatment and
All-Two-Layer Treatment (mix of High and Low-Re).

1st question: What is the range of high- and or low Reynolds models?
2nd question: What is the range of wall y+: In the User Guide I found for ke-Model realizabel a range for high Reynolds y+ > 30 and for low-Re y~1, 2Layer: y+ ~30-50.

-> This means if I have got an y+ value of 8 on a surface (ke_Modell RLZ:All-Layer Treatment), i need to optimize the mesh on surface so that the y+ factor is 30 in minumum?
eRzBeNgEl is offline   Reply With Quote

Old   January 26, 2012, 16:45
Default
  #2
Senior Member
 
Join Date: Mar 2009
Location: Austin, TX
Posts: 134
Rep Power: 9
kyle is on a distinguished road
The Star-CCM+ "All y+" model is useful because you do not have to go through your model and specify which walls use a low Reynolds approach and which use a high y+ wall function. The model does not promise any sort of accuracy in the range of 1<y+>30. You should have the bulk of your y+ values be either <1 or between something like 20 and 200.
kyle is offline   Reply With Quote

Old   January 26, 2012, 17:23
Default
  #3
Senior Member
 
Join Date: Dec 2010
Posts: 135
Rep Power: 6
eRzBeNgEl is on a distinguished road
Quote:
Originally Posted by kyle View Post
The Star-CCM+ "All y+" model is useful because you do not have to go through your model and specify which walls use a low Reynolds approach and which use a high y+ wall function. The model does not promise any sort of accuracy in the range of 1<y+>30. You should have the bulk of your y+ values be either <1 or between something like 20 and 200.
Thanks Kyle for your help again, and again, and again*g* :-)
eRzBeNgEl 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
Understanding Code behind BCs Linse OpenFOAM Programming & Development 8 January 9, 2012 09:58
Ambiguity in understanding interfaces in CFX saisanthoshm88 CFX 9 February 2, 2011 15:05
Is this understanding of turbulence models correct? 3kha Main CFD Forum 3 January 31, 2011 22:31
Problem understanding rhoPisoFoam MatP OpenFOAM Running, Solving & CFD 1 May 15, 2010 13:21
Understanding of channelOodles and oodles solver fs82 OpenFOAM 1 September 23, 2009 10:36


All times are GMT -4. The time now is 00:12.