1

Lift curves for airfoils with different camber

I have a rough idea about why $C_{{l}_{max}}$ increases with increase in camber. But I can't explain why the stall angle decreases simultaneously.

AEhere supports Monica
  • 8,581
  • 1
  • 35
  • 67
Nirmal
  • 319
  • 1
  • 3
  • 10

1 Answers1

4

At the same angle of attack, a cambered airfoil has a larger suction peak on the upper side (toward the leading edge), and a larger associated pressure recovery (toward the trailing edge).

Larger pressure recovery is equivalent to larger adverse pressure gradient, which leads to easier onset of boundary layer separation and stall.

JZYL
  • 11,066
  • 2
  • 15
  • 49
  • Now, decrease aspect ratio and check the AOA curve again. This is why the thick Gottingen airfoils of a century ago were so revolutionary, giving the slow flying, maneuvering dogfighters of that day many advantages over the thinner undercambered wing design. Ironicly, the thinner airfoils proved superior years later as Mach numbers increased towards one. – Robert DiGiovanni Oct 07 '19 at 06:20
  • @Robert DiGiovanni aspect ratio? I think you meant something else, there is no aspect ratio in 2D analysis. – AEhere supports Monica Oct 07 '19 at 10:41
  • @AEhere That's why we add the 3rd one. Thick Hershey wings make excellent recreational airfoils, and present the other side of the spectrum from thin supercritical wings (for some strange reason I keep writing about this). – Robert DiGiovanni Oct 07 '19 at 12:02
  • 1
    @RobertDiGiovanni the question is about airfoils, not wings, though, so bringing in the complexity of 3D flow doesn't seem like a good idea for something that can be explained in 2D. – AEhere supports Monica Oct 07 '19 at 13:12