Aerofoils

Question 1

What do you know about aerofoils?

Answer 1

-2D bodies with streamlined shape and high finesse
- LE, TE, chord, camber, mean camber line, thickness
- Design considerations: thickness distribution, mean camber line, camber, leading/trailing edge shape, coefficients as functions of Re, M, AoA
- NACA 4-digit series

Question 2

How does an aerofoil produce lift?

Answer 2

• Pressure (normal) and shear stress (tangential) distributions over aerofoil surface
• Integrate distributions over aerofoil surface to get lift, drag, moment
• curved profile of aerofoil results in high pressure on lower surface, low pressure on upper surface
• most lift produced by first 25% of aerofoil
• Normal, axial, lift, drag
• Can determine forces and moments at leading edge or aerodynamic centre

Question 3

How can aerofoil performance be documented?

Answer 3

• Lift curve: zero lift AoA, lift slope, Stall angle of attack, max cl
• drag curve: minimum cd
• Moment curve: aerodynamic centre, centre of pressure, negative = pitch downwards