Example sheet 2

Question 1

Power, thrust, velocity equation

Answer 1

Power = T * V
T = Drag

Question 2

Thrust =

Answer 2

Drag = W / (L/D)

Question 3

Lift slope for aerofoil of infinite wing span

Answer 3

dCl/dα = a = a0/ ( 1 + a0/πAR * (1 + T))

Question 4

List four elementary solutions to laplace equations

Answer 4

1. uniform flow
2. source/sink
3. doublet
4. vortex

Question 5

How much reduction could be made if blunt body was streamlined

Answer 5

up to 20 times

Question 6

Describe 3 main parts of F1 car that can generate down force

Answer 6

1. Front wing
2. Diffuser
3. Rear wing

Question 7

What part of an f1 car generates most form drag

Answer 7

4 open wheels

Question 8

Explain how DRS (drag reduction system) works

Answer 8

Increased down force means increased induced-drag.

DRS slightly reduces incidence of rear wing during take over to reduce this drag

Question 9

For an elliptical planform, what is the difference in Cl for a 2D and 3D model

Answer 9

CL = Cl

Question 10

Derive expression for Cl as a function of geometrical angle of attack and AR

Answer 10

Cl = 2πα(eff)
Cl = 2π(α - αi)

αi = Cl / πAR = 2(α-αi) / AR

αi = 2α/ AR + 2

Cl = 2πα(eff) = 2πα( 1 - 2 / AR+2)

Question 11

List benefits of formation flying

Answer 11

1. Biggest benefit is drag reduction as wing tip vortices produce ‘free lift’ for planes flying behind - increased efficiency if larger plane at the front
2. streamline air traffic control by treating flock as 1 entity
3. passenger comfort
4. automation
5. passenger safety