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

2d software for thick airfoils, Re=2-4M, Mach=.2-.3

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 12, 2011, 23:09
Default 2d software for thick airfoils, Re=2-4M, Mach=.2-.3
  #1
New Member
 
Frank
Join Date: Jul 2011
Posts: 2
Rep Power: 0
frank999 is on a distinguished road
What software would you recommend to get the most accurate drag estimation on a 20+% thick airfoil at 2 to 4 million Reynolds number and mach around .2? Let's say you don't want to exceed about 30 minutes run time on a descent 64 core cluster.

Would the same code be good for predicting maximum CL and the corresponding angle of attack, or would you recommend something else?
frank999 is offline   Reply With Quote

Old   July 13, 2011, 01:44
Default
  #2
Senior Member
 
Martin Hegedus
Join Date: Feb 2011
Posts: 497
Rep Power: 9
Martin Hegedus is on a distinguished road
I don't know the details of your problem, but given that your Reynolds number puts you in the transitional area, I think you may be looking for something with an appropriate turbulence model. Also, given your cpu requirements, I assume you are looking for a RANS model. Assuming a code like XFOIL doesn't work for you. I don't know the ins and outs of the various validation work for these models, but it seems that the ones used for transition are more "researchy" than production. In my opinion, you'll need to be careful with them. IMO, there seems to be a bit of hand waving about them and the wind tunnel data used for validation for these thick airfoils may be questionable too, especially at and past stall. Again, my opinion.
Martin Hegedus is offline   Reply With Quote

Old   July 24, 2011, 12:35
Default
  #3
New Member
 
Frank
Join Date: Jul 2011
Posts: 2
Rep Power: 0
frank999 is on a distinguished road
Yes, I think I need transition to be predicted well. I know Martin said the models may be more researchy, but any one in particular that would be recommended?

I've compared XFOIL and a RANS solver with wind tunnel data for a few cases. The w.t. data does seem sketchy and it's hard to determine which solver (XFOIL or RANS) is giving better predictions. Both solvers seem to over-predict CLmax significantly, XFOIL slightly more over-prediction. Minimum CD occurs at a significantly different CL between XFOIL, RANS, and wt data, and the curves are significantly different so it's hard to say which solver is better (again the wt data itself is questionable). Any comments / suggestions?

Any research out there addressing these problems, even on the experimental/testing side, to address these issues with thick airfoils?

Thanks
frank999 is offline   Reply With Quote

Old   July 24, 2011, 13:04
Default
  #4
Senior Member
 
Martin Hegedus
Join Date: Feb 2011
Posts: 497
Rep Power: 9
Martin Hegedus is on a distinguished road
Recently there was this conversation about CFX's gamma-theta transition model. Gamma Theta model and underpredicted lift

This is for a NACA 0020 but at a much lower Reynolds number (122,000) so the physics will probably be different. The difficulty was with predicting stall angle correctly. For that case, transition could happen on the bubble. However, for your case, the model may do better.
Martin Hegedus is offline   Reply With Quote

Reply

Tags
airfoil2d, stall, thick airfoil

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
multiple airfoils at once, are they affected? kdrbrk FLUENT 0 October 18, 2010 05:31
CAD integrated CFD Software kostikr Main CFD Forum 3 February 4, 2010 15:38
airfoils software test r. allup Main CFD Forum 0 July 5, 2000 12:30


All times are GMT -4. The time now is 11:23.