Am I correct to assume that for a low speed aircraft, the location of the camber in the MAC's airfoil will correspond with the aerodynamic center? Also, does that affect the moment coefficient? And what about a high speed aircraft (M>1)?
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2 Answers
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[Does] the location of the camber in the MAC's airfoil correspond with the aerodynamic center?
No.
The aerodynamic center is where the additional lift force from a change in angle of attack can be summed up. Since camber only determines the lift portion that is independent of angle of attack, changing the camber will not influence the aerodynamic center.
For a high aspect ratio wing in subsonic flow, the aerodynamic center is at the quarter chord position. With decreasing aspect ratio this point moves slowly forward until it arrives at the forward tip for a slender body.
Also, strictly speaking, there is no "location of camber" — camber is distributed over the whole chord. What you probably mean is the highest point of the camber line, but that point has little aerodynamic significance. The local curvature of that line is much more important.
Also, does that affect the moment coefficient?
Yes.
Generally, the more an airfoil is cambered towards its rear end, the higher its pitch moment coefficient will be. This is called "rear loading" and is used in order to combine decent thickness with good lift in transsonic airfoils. You can use the lengthwise location of the highest point of the camber line as a guide how high the moment coefficient will be.
And what about a high speed aircraft (M>1)?
That depends on wing sweep. Normally, aircraft designers try to keep the wing's leading edge subsonic over the full speed range. But I guess you wonder how the camber will influence a wing's performance once it moves at full supersonic speed. Well, the bad news is that camber will drive up wave drag without any influence on lift. Supersonic aircraft, therefore, use thin airfoils with very little camber, and the camber they have is only there because it helps in subsonic flight.
answered Mar 15, 2018 at 14:08
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No. Generally, for low speed aircrafts, the AC is located around 25%MAC(non-laminar airfoils) or 50%MAC(laminar airfoils) which, in both cases, represents the maximum thickness location not the camber(which is the maximum distance between the mean line and the chord line). AC is the place where de Cm is nearly constant, so you can say the Cm 'doesn't change'. The momemt, obvioulsly will change with the aircraft's attitude, but the coefficient doesn't. For supersonic flight it's, generally, AC is around 50%MAC.
