Module 2 - Wings

Question 1

What happens to flow over the upper surface of a finite ring?

Answer 1

It is deflected towards the root, due to air flowing over the wing tips (from lower surface to upper)

Question 2

What are 2 ways to alter a wing’s lift distribution?

Answer 2

1. Alter platform shape
2. Add geometric or aerodynamic twist

Question 3

Why is an elliptical lift distribution ideal?

Answer 3

Lowest induced drag

Question 4

What is the geometric angle of attack?

Answer 4

Angle between chord and relative wind

Question 5

What is the effective angle of attack?

Answer 5

Angle experienced by the aerofoil in a finite wing, angle between the chord line and the local relative wind

Question 6

What is the induced angle of attack?

Answer 6

Angle at which the local relative wind is deflected downwards from the relative wind due to downwash

Question 7

What is downwash?

Answer 7

Downwards velocity in wake of wing due to tip vortices

Question 8

What is the local relative wind?

Answer 8

Relative wind experienced by the aerofoil when effects of downwash are considered

Question 9

What is upwash? How is it used?

Answer 9

Upwards velocity induced outside wake due to tip vortices

Question 10

What types of drag are experienced by a wing?

Answer 10

1. Pressure
2. Skin-friction
3. Induced

Question 11

What flow structures form on a delta wing? What happens at very high angles of attack?

Answer 11

Leading edge vortices which produce a low pressure zone increasing lift towards leading edge, but at a high enough angle of attack these vortices breakdown and become unstable leading to unsteady flow and buffeting of the wing

Question 12

What changes could be made to the wing to lower induced drag?

Answer 12

Increase aspect ratio, make the lift distribution more elliptical (increase span efficiency factor)