Question

The aerodynamic center on the aerofoil is the point where

• A. pitching moment is equal to zero
• B. pitching moment is independent of the angle of attack
• C. the lift is independent of the angle of attack
• D. the pressure derivative becomes zero

Hint:

For subsonic aerofoils, the aerodynamic center is typically at the quarter chord.

Answer 1

The Correct Option is B

The aerodynamic center of an aerofoil is a critical point in aerodynamics, specifically in the study of aerofoils. It is defined as the point on the chord line of an aerofoil where the pitching moment is constant irrespective of the angle of attack. In other words, at this point, the aerodynamic forces acting on the aerofoil do not create a variable pitching moment as the angle of attack changes.

Considering the options provided:

• Pitching moment is equal to zero: This condition is typically found at the center of gravity but does not define the aerodynamic center.
• Pitching moment is independent of the angle of attack: This correctly defines the aerodynamic center, where changes in the angle of attack do not alter the pitching moment.
• The lift is independent of the angle of attack: The lift does vary with angle of attack, so this is not related to the aerodynamic center.
• The pressure derivative becomes zero: No standard definition of the aerodynamic center involves the pressure derivative being zero.

Therefore, the correct answer is:

pitching moment is independent of the angle of attack