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

Velocity Vectors in VLM Tornado Code

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 30, 2010, 17:39
Default Velocity Vectors in VLM Tornado Code
  #1
New Member
 
Join Date: Aug 2010
Posts: 7
Rep Power: 6
jd88 is on a distinguished road
Hello,

I would like to use the vortex lattice code Tornado to do an analysis over a swept wing. I was wondering if anyone knows if and how I can modify the source code so that instead of getting just the pressure distribution I can also get the velocity vectors.

Where should I start? What needs to be added?

Thank you
jd88 is offline   Reply With Quote

Old   September 3, 2010, 14:44
Default
  #2
New Member
 
César Vecchio
Join Date: Jul 2010
Location: Córdoba, Argentina
Posts: 21
Rep Power: 7
CAVT is on a distinguished road
It's impossible to do so not only in Tornado but also in any other VLM or doublet lattice method. That's because these methods calculate DeltaCp but not Cp on upper or lower surface (consequence of assuming a thin surface), in which case you would perfectly be able to calculate V from the formula:

Cp=1-(V/Vinf)^2

You might be able to do a trick by using a Weissinger method which uses actual airfoil data for chordwise load distribution, or examining section by section using airfoil softs like Xfoil, Javafoil or PABLO (this one's available for MatLab) and setting the section Cl you obtain in Tornado as an objective to reach and then you will have a guess. However, this is not going to estimate (IMHO) crossflow, which in swept wings is important.

My suggestion would be using a panel method, which still uses potential flow, needs low computer resources and accounts for airfoil thickness (you can even estimate some boundary layer properties). Try with these two, which are open source:

http://3dpanelmethod.com/index.php (there's a legacy version in MatLab/SciLab language).
http://xflr5.sourceforge.net/xflr5.htm

Hope it helps
CAVT is offline   Reply With Quote

Old   September 3, 2010, 16:11
Default
  #3
New Member
 
Join Date: Aug 2010
Posts: 7
Rep Power: 6
jd88 is on a distinguished road
Somewhere in Tornado or any VLM method has to calculate the circulation of each vortex segment. And once these circulation are known can't I just use the circulations and potential flow to determine the velocity induced at any point by all of the vortex segments. Then add this to the free stream velocity and obtain the velocity at that point.

That is what I am currently trying to do. I thought I was doing it correctly but the answer doesn't make any sense to me currently. Is there something wrong with this idea?
jd88 is offline   Reply With Quote

Old   September 3, 2010, 16:22
Default
  #4
New Member
 
César Vecchio
Join Date: Jul 2010
Location: Córdoba, Argentina
Posts: 21
Rep Power: 7
CAVT is on a distinguished road
Could be if you think it in that way, but honestly I never tried it and never seen anyone doing so. The variable you want to check then is, I think, results.gamma, which is solved in the solver9.m file.
You may want to look at the Treftz plane calculation file, the code there might be of interest for you.
Success with it
CAVT is offline   Reply With Quote

Old   September 3, 2010, 16:40
Default
  #5
New Member
 
César Vecchio
Join Date: Jul 2010
Location: Córdoba, Argentina
Posts: 21
Rep Power: 7
CAVT is on a distinguished road
TAke into account that even if you calculate the velocities on points which would correspond to the actual surface, you cannot guarantee they are good values, since there wasn't any tangency condition indicated. I reccomend you to validate the results at least for one or two cases with a panel method. But you made me realize of a new possibility, thank you for your doubt, sometimes we need to hit the wall to see it .
CAVT is offline   Reply With Quote

Old   September 3, 2010, 16:42
Default
  #6
New Member
 
Join Date: Aug 2010
Posts: 7
Rep Power: 6
jd88 is on a distinguished road
Thanks! I also thought there would be a problem when calculating the velocity on the surface. I was thinking of just sticking to points that are just above or below the surface. Hopefully that works a little better. I have been working on getting the code working for awhile. I will let you know how it goes.
jd88 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
plot field velocity vectors in fieldview gaurav FieldView 0 October 7, 2009 10:51
Inlet Velocity in CFX aeroman CFX 12 August 6, 2009 18:42
2 velocity vectors ashish CFX 3 June 19, 2007 18:32
State of the art in CFD technology Juan Carlos GARCIA SALAS Main CFD Forum 39 November 1, 1999 15:34
What kind of Cmmercial CFD code you feel well? Lans Main CFD Forum 13 October 27, 1998 11:20


All times are GMT -4. The time now is 23:07.