Lecture 9 - Induced Drag

Question 1

Aspect ratio of wings?
Symbol meanings?

Answer 1

AR = b/c

AR - Aspect Ratio
b - span
c - chord

Question 2

Aspect ratio when chord varies?

Answer 2

AR = b^2/S

S - wing area

Question 3

Source of induced drag?

Answer 3

Vortex induced velocity and arising from the generation of lift.

Question 4

Effects of downwash velocity?

Answer 4

modifies the effective flow direction and
reduces α

Question 5

Induced drag coefficient equation?

Answer 5

C_Di = C_L^2/pi*AR

Question 6

Why do birds fly in a V-formation?

Answer 6

The up wash created by trailing vortices assists each bird in supporting its own weight in flight.

Question 7

Purpose of plane winglets?

Answer 7

The effective aspect ratio is increased without adding to the span
Energy in the vortex contributes to the thrust rather than drag

Question 8

How do winglets work?

Answer 8

Each wing generates a trailing vortex at its tip.
Winglets enable:
a lower induced drag and a decrease in fuel consumption 3% to 5%

Question 9

What is geometric twist?

Answer 9

angles of attack at wing root and at wing tip are different

Question 10

What is aerodynamic twist?

Answer 10

wing cross section shape varies from wing root to wing tip