Fundamentals

Question 1

Define the Chord of an aerofoil

Answer 1

distance from leading edge to trailing edge

Question 2

Define the Camber of an aerofoil

Answer 2

maximum distance between the mean camber line and the chord line.

Question 3

Define the thickness of an aerofoil

Answer 3

the distribution of the aerofoil along the camber line

Question 4

Whats the equation for a wing aspect ratio AR with varying chord?

Answer 4

b^2/S

wing span squared over wing area

Question 5

Whats the equation for the standard mean chord in a varying chord wing?

Answer 5

S/b
or
b/AR

Question 6

What 3 aspects do Tensors cover?

Answer 6

Magnitude, Direction and Orientation

Question 7

Define vorticity

Answer 7

Vorticity is the microscopic measure of rotation at any point in a fluid. This relates to the average angular momentum of a fluid particle.

Question 8

If vorticity is zero everywhere, how is the flow described?

Answer 8

Irrotational

Question 9

What vector operation is used to find vorticity?

Answer 9

Curl of the Velocity vector

Question 10

Define Circulation

Answer 10

Circulation is 2D scaler vorticity that gives a macroscopic measure of rotation within a flow.

Question 11

What is a potential flow?

Answer 11

A simplified flow in which a scalar function can be used to represent a velocity vector field. V = grad fi (velocity potential)

Question 12

What are the constraints of a potential flow?

Answer 12

Flow must be irrotational and incompressible

Fi must meet continuity equation (laplace equation)

Question 13

Why is a potential flow always irrotational ?

Answer 13

Becasue a curl of a gradiant is always ZERO

Question 14

Why must potential flow be incompresssible?

Answer 14

Because in incompressible flow the divergence of the velocity field is ZERO, this then means the laplacian of the scalar is also ZERO.

Question 15

What makes the laplacian of potential flow significant?

Answer 15

potential flow solutions to the laplace equation can be superimposed and so problems can be broken down into smaller ones. eg source + sink = doublet

Question 16

What are the issues with using potential flow to solve problems?

Answer 16

They are not real flows
Cannot be used near solid bodies that have boundary conditions
Cannot be used where vorticity is expected

Question 17

What does it mean if the Coefficient of pressure is positive?

Answer 17

p > p(inf)

V < V(inf)

Question 18

What does it mean if the Coefficient of pressure is negative?

Answer 18

p < p(inf)

V > V(inf)

Question 19

What are the two aerodynamic forces and what are they casued by?

Answer 19

Pressure forces - caused by interactions (collisions) with a body surface
Shear forces - caused by viscocity in fluid

Question 20

The resultant aerodynamic force can be split into two pairs of components, what are these?

Answer 20

Lift and Drag (lift is perpeducular to motion)

Normal and Axial (normal is perpedicular to chord)

Question 21

Define the centre of pressure

Answer 21

The location of average pressure, moves with angle of attack and lift. Moment is always ZERO

Question 22

Define the aerodynamic centre

Answer 22

The location where the moment remains constant no matter the angle of attack

Question 23

What are the 3 aerodynamic moments and their corresponding axes?

Answer 23

Pitch - y
Roll - x
Yaw - z

Question 24

In this module what do upper and lower case letters stand for?

Answer 24

Upper case - 3D

Lower case - 2D

Question 25

Define the Reynolds numbers

Answer 25

Ratio between inertial forces and viscous forces.

The higher the number the more complex aerodynamic calculations

Question 26

Define Mach number

Answer 26

Ratio of velocity over characteristic speed of sound

Question 27

What is the local mach number and why can it be important

Answer 27

The local mach number (the one corresponding to air around wings) can be diffrerent to the free stream M number due to differing velocities. In the transonic region compressibiity effects may appear on the top surface of aerofoil.