Theory of Wing Sections

[a6zz]

Hey All,

Does anyone know what reference area is used to determine the cd and cl of airfoil characteristics in the book "Theory of Wing Sections" by Albert Von Doenhoff and IRA Abbott.

Cheers

[kilcoo316]

Hey All,

Does anyone know what reference area is used to determine the cd and cl of airfoil characteristics in the book "Theory of Wing Sections" by Albert Von Doenhoff and IRA Abbott.

Cheers

For aerofoil sections, the 'area' used will be the chord length.

[TauToadmiester]

IIRC, a section (NACA or others) is just simply the cross section and can give some insight to sub sonic lift characteristics, probable drag and stall, etc, whereas the chord and wing shape (straight, tapered, twisted to reduce angle of attack) is what 'carries forth' the cross section into the physical world and produces the actual drag and lift, both simultaneously of course.

Drag/lift will be reduced via the wing chord shape, taper, sweep, twist, etc and if there are augmenting parts such as a wing or tip fences or vortex generators and of course slats and flaps (augmenting the original wing section) and of course adjacent wings above or below (staggered).

The 2009 cars front wings have only angle of attack at the drivers control, 1 up 1 down per lap up to 6 degrees, the wing sections seem to be, but I am not sure at all, asymmetrical turbulent flow sections, but likely there are laminar flow and symmetrical sections used as well (the neutral center front wing seems to be a symmetrical low drag std shape but...).

Very little has been discussed about the front wing use (in race) so far this year by drivers or team members, hope to hear more!!

[a6zz]

Hey All,

Does anyone know what reference area is used to determine the cd and cl of airfoil characteristics in the book "Theory of Wing Sections" by Albert Von Doenhoff and IRA Abbott.

Cheers

For aerofoil sections, the 'area' used will be the chord length.

That is just the planform area isnt it...

IS that also for drag coefficient calculation?

the book has worked it out for a 2d airfoil and i have made a 2d model in CFD to compare the cd and cl...and CFD gives me force outputs hence using the lift and drag equation would give me the cd and cl values, thats why i was asking what area to use. And i could not find what area they used in the book.

Abzz

[kilcoo316]

That is just the planform area isnt it...

Correct.

For aerofoil sections, the calculations are based on a unit width (i.e. 1m) - so the chord is effectively the area.

IS that also for drag coefficient calculation?

Yes.

the book has worked it out for a 2d airfoil and i have made a 2d model in CFD to compare the cd and cl...and CFD gives me force outputs hence using the lift and drag equation would give me the cd and cl values, thats why i was asking what area to use. And i could not find what area they used in the book.

Yes. Use the wing chord. If this is for university you might also want to compare to XFOIL to examine viscous effects (or rather, the lack of). As you get nearer stall condition, be aware that the CFD results are almost certainly incorrect.


Note, that this applies to aircraft - where the reference area is taken as the wing area.


For ground vehicles - the typically reference area is the total frontal area of the vehicle.