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

Boundary layer thickness in Xfoil

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

Reply
 
LinkBack Thread Tools Display Modes
Old   January 25, 2011, 10:50
Default Boundary layer thickness in Xfoil
  #1
New Member
 
Lukas
Join Date: Nov 2010
Posts: 11
Rep Power: 6
Nixmich is on a distinguished road
Hi,
does anybody know if it is possible to calculate the boundary layer thickness on an airfoil with Xfoil? I've managed to calculate delta* which is the displacement thickness but no success concerning the boundary layer thickness. Are there any alternatives if Xfoil doesn't work?
Nixmich is offline   Reply With Quote

Old   January 25, 2011, 12:32
Default
  #2
Senior Member
 
sail's Avatar
 
Vieri Abolaffio
Join Date: Jul 2010
Location: Always on the move.
Posts: 308
Rep Power: 8
sail is on a distinguished road
Quote:
Originally Posted by Nixmich View Post
Hi,
does anybody know if it is possible to calculate the boundary layer thickness on an airfoil with Xfoil? I've managed to calculate delta* which is the displacement thickness but no success concerning the boundary layer thickness. Are there any alternatives if Xfoil doesn't work?
use xflr5. it's open source, free, based on the "engine" of xfoil but it's more user friendly and can estimate the bl thickness.
sail is offline   Reply With Quote

Old   January 26, 2011, 04:00
Default
  #3
New Member
 
Lukas
Join Date: Nov 2010
Posts: 11
Rep Power: 6
Nixmich is on a distinguished road
Okay, I'll try that, thanks a lot!

Edit: ehm, like in Xfoil, I can plot the displacement thickness D*, but not the BL thickness...

Last edited by Nixmich; January 26, 2011 at 04:39.
Nixmich is offline   Reply With Quote

Old   January 26, 2011, 09:52
Default
  #4
Senior Member
 
sail's Avatar
 
Vieri Abolaffio
Join Date: Jul 2010
Location: Always on the move.
Posts: 308
Rep Power: 8
sail is on a distinguished road
i don't get it. the dotted red line on the foil should be the BL.
Attached Images
File Type: jpg test.jpg (88.0 KB, 61 views)
sail is offline   Reply With Quote

Old   January 26, 2011, 11:49
Default
  #5
New Member
 
Lukas
Join Date: Nov 2010
Posts: 11
Rep Power: 6
Nixmich is on a distinguished road
Thanks again for your help, but I think that's not the BL, although the box you have to check is labelled "show BL". The dotted line looks exactly like the D* line in xfoil (which does certainly not represent the BL thickness, as you can verify by some velocity profiles displayed on discrete points on the airfoil). Even if it was the BL, it wouldn't help me much because I can't read any values from that line.
The only thing I'm able to plot or export is D* vs x, again exactly the same values as in xfoil.
Nixmich is offline   Reply With Quote

Old   January 27, 2011, 04:59
Default
  #6
New Member
 
Chris Day
Join Date: Sep 2010
Posts: 8
Rep Power: 6
ChrisDanger is on a distinguished road
There are no general equations for boundary layer thickness. However, from the Xfoil 6.9 User Primer:

Quote:
The difference between the true viscous Cp distribution (solid line)
and the inviscid Cp distribution (dashed line) is due to the
modification of the effective airfoil shape by the boundary layers.
This effective airfoil shape is shown superimposed on the actual
current airfoil shape under the Cp vs x plot. The gap between
these effective and actual shapes is equal to the local displacement
thickness delta*, which can also be plotted in the VPAR menu.
This is only about 1/3 to 1/2 as large as the overall boundary
layer thickness
, which can be visualized via the BL or BLC commands
which display velocity profiles through the boundary layer.
That looks as accurate as it's going to get, unfortunately.
ChrisDanger 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
Boundary layer thickness ghazanfarzahedi Main CFD Forum 2 July 28, 2009 23:43
Boundary layer thickness calculation nat FLUENT 0 April 9, 2009 06:04
plotting boundary layer thickness graphs in a 3d Neelima FLUENT 1 March 29, 2006 18:04
Boundary Layer Thickness cfd-freak Main CFD Forum 3 March 27, 2003 13:18
boundary layer thickness 98.4F Main CFD Forum 1 December 29, 2000 08:23


All times are GMT -4. The time now is 19:35.