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

Y-Plus values at aerofoil leading edge and trailing edge at high incidence

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

Like Tree2Likes
  • 1 Post By Far
  • 1 Post By Martin Hegedus

Reply
 
LinkBack Thread Tools Display Modes
Old   July 27, 2011, 13:36
Default Y-Plus values at aerofoil leading edge and trailing edge at high incidence
  #1
New Member
 
Join Date: May 2011
Posts: 1
Rep Power: 0
Engr07 is on a distinguished road
Hi all,

I simulated flow over an aerofoil to get the forces and moment using Spalart-Allmaras turbulence model. The grid was done so as to achieve the y-plus values less than 1.0.

At zero degree I was able to keep the y plus less than 1.0 over the complete aerofoil but not the trailing edge-The aerofoil has a blunt trailing edge.

At 10 degree y-plus values at the leading edge were about 3.0 and were also larger than 1.0 at the trailing edge.

Since it is "good practice" to keep the number less than 1.0, I need to know how significant is the issue of not achieving this at the leading and the trailing edges.

Any help is greatly appreciated.

AMal
Engr07 is offline   Reply With Quote

Old   June 28, 2012, 18:49
Default
  #2
New Member
 
Lee
Join Date: Jun 2012
Posts: 4
Rep Power: 5
rlc113 is on a distinguished road
Hey AMal, it has been my experience that the y+ values are crucial to drag prediction. I am currently working on a similar case in which my y+ values are << 1 everywhere except the Leading edge. When comparing my case with a case ran with someone with a bit more experience I noticed a significant underprediction on my solution. I have added more fidelity and decreased the delta1 value in that area and I am rerunning the case. I will report back with the difference.

Let me know if you find anything yourself.
rlc113 is offline   Reply With Quote

Old   June 29, 2012, 03:41
Default
  #3
Far
Super Moderator
 
Far's Avatar
 
Sijal Ahmed Memon (turboenginner@gmail.com)
Join Date: Mar 2009
Location: Islamabad Pakistan
Posts: 3,909
Blog Entries: 6
Rep Power: 38
Far will become famous soon enoughFar will become famous soon enough
Send a message via Skype™ to Far
with the hybrid wall functions (currently implemented in major CFD codes), the yplus values needed are Y+<10. See this reference :

http://num.math.uni-goettingen.de/ba...ings/knopp.pdf


http://num.math.uni-goettingen.de/ba...ngs/alrutz.pdf

http://tau.dlr.de/fileadmin/document...8_englisch.pdf

http://proceedings.fyper.com/eccomas...cuments/64.pdf
atg likes this.
Far is offline   Reply With Quote

Old   June 29, 2012, 04:22
Default
  #4
New Member
 
Lee
Join Date: Jun 2012
Posts: 4
Rep Power: 5
rlc113 is on a distinguished road
Hey Far, thanks for the info, I haven't checked it all out yet. Just wanted to say that the only solver I use is NASA's FUN3D, which to my opinion doesn't have a wall function. Any insight to that would be interesting.

I have the refined BL case running now. I also have the results of a case in which the inviscid spacing was refined by 40% or so, I will post up all my results when the the results are apparent.
rlc113 is offline   Reply With Quote

Old   June 29, 2012, 10:42
Default
  #5
Senior Member
 
Martin Hegedus
Join Date: Feb 2011
Posts: 497
Rep Power: 9
Martin Hegedus is on a distinguished road
For the SA model I usually try to get the y+<1 at about 5% to 10% of the chord. I doubt it matters for less than 5%, if the majority of the airfoil y+ is less than 1. The eddy viscosity at the leading edge is usually very small. It builds up along the chord. Thus, the leading edge flow is laminar, even when using the turbulence model. However, that is dependent on angle of attack. So, look at your eddy viscosity. As for the trailing edge, usually the boundary layer is thick, so I'm not sure why you are having an issue there. Unless you have a recirculation bubble at 10 deg. But, if you are at the very trailing edge tip, I doubt it matters. Again if the majority of the airfoil is y+<1.

If you are concerned, the best thing to do is reduce the off wall grid spacing by 1/2, run the code, and see if you get a difference in the skin friction.
atg likes this.
Martin Hegedus 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
[ICEM] Hole near sharp trailing edge of airplane/wing geometry jlichtwa ANSYS Meshing & Geometry 2 September 21, 2010 15:19
Which trailing edge is correct for meshing of aerofoils for CFX LSC CFX 0 May 10, 2009 12:45
Meshing trailing edge of aerofoil CC Main CFD Forum 7 December 10, 2008 21:22
Meshing trailing edge of aerofoil CC FLUENT 1 December 10, 2008 04:49
trailing edge problem Kuo Wei-Jen Main CFD Forum 2 April 14, 1999 10:09


All times are GMT -4. The time now is 11:58.