Wings Flashcards
1
Q
What are the main features of a wing?t
A
- 3D body made from 2D aerofoil profiles
- flow component in spanwise direction
- has a wing root and wingtips (free ends)
- Pressure differential leads to airflow from lower surface to upper surface at wingtips
- Flow over and under wing deflected
- Tip vortices at wingtips tips trail into wake and diffuse
- Upwasv outside of wake
- Downwash within wake
2
Q
Where does induced drag come from?
A
- Tip vortices result in downwash
- Downwash deflects relative wind downwards by a small angle
- resulting lift vector is tilted in direction of drag
- induced drag
3
Q
Why is an elliptical lift distribution desired? How can it be obtained?
A
Lowest induced drag - constant downwash as shown by lifting line theory
Can be obtained using an elliptical planform, or by adding geometric and/or aerodynamic twist to the wing
4
Q
What are the effects of a finite wing? How can these be mitigated? Why might this not be done?
A
- Induced drag
- reduction in lift at a given angle of attack
- lower lift curve
- no lift production at wing tips
- Can be reduced by increasing aspect ratio
- Space requirements or bending moments limit aspect ratio
