High Lift non flapped airfoil wanted 4

[laminarflow]

I have an application for a high lift airfoil without a flap. Stall issues not important. Thick is good, highly cambered OK. This airfoil will operate at high C/L only and will be used to generate downforce on a race car. What kind of max C/L can be reached without a flap on a highly cambered section? Is 2+ possible? Aspect ratio will be about 5. Thanks!

 

[235zzzo]

Hello Laminarflow!

I can not resist to suggest you, some research by yourself as deep as you need, following the famous book for all of us, since faculty in those good old days, which is "The Theory of Wing Sections" by Ira H. Abbott & Albert E. von Doenhoff, Dover Publications, Inc. New York, standar book number: 486-60586-8. I think you will find the most suitable airfoil.
Good luck, and best regards
zzzo

 

[aeropc]

Hello Laminarflow!

I am also looking for a rear wing high lift airfoil for a race vehicle. Would appreciate some info if you find the correct airfoil, and angle of attack.

Regards

 

[WhiteRabbit]

You may also try an Eppler 423. It is highly cambered. If you want to increase the CLmax you may also try to use a fixed deflected control surface or fixed flap or fixed slotted flap (depending on the complexity of your manufacturing resources) to increase the effective camber and help avoid trailing edge separation.

There is a considerable pitching moment associated with this airfoil but I do not believe this is much of a concern with this application. The drag bucket is also quite wide.

Good luck.

 

[lorenzo73]

Hi!
have you tried to add a Gurney flap on upper part of the wing?

with this device you will be able to increase a lot the Cl (but at a some drag cost...)

(if you will have questions about that, ask...).

Lorenzo

 

[laminarflow]

Gurney Flaps!!! I've always wondered what is the big deal about Gurney Flaps. It seems that the increase in C/L that it would provide could easily be achieved by just increasing the AOA a bit, which would produce less drag than the Gurney Flap. Has any one seen any REAL data on Gurney Flaps?

 

[lorenzo73]

Dear laminarflow,
in theory, the use of g-flaps has a very effective role.
you says that increasing alpha, you would obtain same results...not properly.
here there is the explanation:
the use of gurney simply increase downforce coeff, improving the extent of laminar flow on upper part of the wing. This is possible, because (as you probably know, the most critical part of a downf wing is the upper side), having great alphas (AOA), you will have a separated flow more extended (in a previous part of the wing) than a lower inclined wing (more inclined is the wing, more turbolence it will create and and stall max value <). This turbolence not allow the flow to remain attached on the upper surface of wing, modifying the shape, and creating a great amount of drag.
so, the primary function of g-flaps is to accelerate flow toward the upper part of wing on the aft portion.
as you probably know, the flow goes always in the region with lower P (in our case, the lower). It's proper on the upper side that the more P coeffs create the downforce.
Here, but, the flow, in the rear part of the wing (on a configuration of std wing), has not sufficient force to overcome the great P force exisisting in that region, < the velocity (in some cases to 0!!) and creating the separated region of laminar flow with vortices (the flow, near to surface goes in inverse direction of main flow). So, with the G-flap, the flow is more forced to accelerate to equalize P differences than in a no-G-flap configuration (this, because the &quot;bump&quot; created with the strip of G-flap, make the flow accelerate itself over this &quot;new obstacle&quot;...)
I've seen real data...the drag increases, it's obvious, but total Cl is very increased!
hope this can be useful..
Lo

 

[SmithSMC]

I did my senior thesis on this topic while I was an undergrad. The application was an inverted wing located at the front of the vehicle. What I found using CFD software was that a high camber wing (NACA 7220,etc) would be the most efficient, which was pretty much expected. Also, ground effect had a large influence on downforce. If you can, keep it as low as possible and you should be happy with the results. Unfortunately, I graduated before we had a chance to try it, but the numbers matched the book listed above very closely.

 

[sprintcar]

Question - what types of cars are we all working on?? I'm doing this for Outlaw Sprint Cars... with a LOT of Help from Lorenzo 73 (right Lo? )
Racing on dirt tracks adds another challenge to wing design - all the nice smooth wing surfaces get covered with clay when the track is wet. I've had 2&quot; build up on the gurney lip and almost that much stuck to the underside of the wing over the tires. We've tried release coatings, but when the mud comes out of the grooves of a 105&quot; diameter tire spinning over 1400 rpm, it tends to stay put!
I bet that would be some wind tunnel test...

 

[butelja]

I believe that wings on the front of champ cars sometimes have vortex generators on the bottom side to help prevent flow separation.

 

[lorenzo73]

in this last 2 years, in formulas cars i have seen a new development...instead of vortex generators (especially with high g-flaps inserted), 2 perpendicular &quot;devices&quot; in the front bottom part of the wing (with a L configuration, where the &quot;stick&quot; of the letter is attached on the wing).
this to improve flow on underside and separate well the flow that will go inward the wheels and flow going outward wheels.
but this &quot;trick&quot; it's only available for cars that have a front wing very lower and tunnels underside for the ground effect.
some similar things are already been proved to be effective in airplanes, where some wings have these devices (not at L configuration, but straight)in the lower part of the wing (in this case for another reason).

you can also test the double configuration vortex generator + g flap, but only if your wing is at a very critical alpha with prevalent flow separating (especially on the first part of the wing 0-50%).

in the end, but important....thanks to sprintcar....too gentle....

Hi to all!
Lo

 

[lmarchesini]

Hello,

have a look at &quot;Wings&quot; by Benzing. He brings some airfoils. Differently from the Abbot, it derives from experience on racecars.
btw: do you want to use it for a front wing or for a rear wing (i.e. will the wing work in strong ground effect ) ?
Ciao

 

[laro]

hello,
in any case the actual Renolds number is very important. why? because for Re > 200'000 conventional turbulant B.L. tricks work, below we ave to use tricks curing laminar separation or recirculations. for the latter case refer to the classic book Peter Chang &quot;Flow Separation&quot;. a very unconventional arrangements of such tricks was used successfully for a profile for Cl=2.5 without flaps chord 1m speed 80 kmh. at about chord 20% we used &quot;oblique grooves&quot; to trigger the B.L. to thin turbulent state. beyond chord 50% we applied perpendicular very deep recesses to reenergize the B.L. over the free jet turbulent B.L. crossing the recesses. (for the &quot;oblique grooves&quot; source see FAQ laro)

 

you may try S1223 (S for selig)
it is probably not the higher lift you can find but without flap, it could be interesting you try it
its Cl max is about 2.2 and its realy cambered
you cant find it at

http://amber.aae.uiuc.edu/~m-selig/ads/coord_database.html