8.2 Airflow Around A Body

Question 1

What is static pressure

Answer 1

Stationary

Question 2

What is dynamic pressure

Answer 2

1/2 p x v2

Question 3

What is Bernoulli’s theorem

Answer 3

Total pressure = Static + dynamic

Question 4

What is a jet outlet

Answer 4

When diameter decreases and speed increases

Question 5

What is a diffuser outlet

Answer 5

When diameter increases and speed decreases

Question 6

What is a Venturi tube

Answer 6

Airflow increases when it narrows

Question 7

What is the boundary layer

Answer 7

Is the layer of fluid density above the surface of the skin
It is retarded air

Question 8

What is laminar flow

Answer 8

When particles in fluid all flow parallel to one another
This is desirable as less drag so more fuel efficient and high lift
Flow over the leading edge

Question 9

What is turbulent flow

Answer 9

High pressure in turbulent air
There is more friction drag
High aot cause greater amounts of turbulent flow

Question 10

What is free stream airflow

Answer 10

Air above boundary layer that is unaffected by friction

Question 11

What is relative airflow

Answer 11

Direction of airflow with respect to moving body

Question 12

Where is transition point of laminar flow

Answer 12

Max thickness and lowest pressure where flow separates

Question 13

What is upwash

Answer 13

Air flowing towards the wing will flow upwards to the low pressure upper surface of the wing

Question 14

What is downwash

Answer 14

The fluid flow returns to its original state

Question 15

What do door gutters help with

Answer 15

Reflect upwash and downwash

Question 16

What are vortices

Answer 16

Are circular patterns of rotating air behind a wing
Goes clockwise at left wing tip
Anti-clockwise at right

Question 17

What is the camber line

Answer 17

Line that is equidistant from the upper and lower surface
Mid line between top and bottom surface

Question 18

What is chord line

Answer 18

Line between the leading and trailing edge
Low speed profile has max camber 5% 45% aft leading egdge

Question 19

What is finess ratio

Answer 19

Max thickness of a section expressed as a percentage

Question 20

What is aspect ratio

Answer 20

Ratio of wing length to width
High ar = low drag
Low ar = high drag

Question 21

What is washin wings

Answer 21

Angle of incedence is greater at wing tip than wing root
Aerodynamically twisted wings are washin

Question 22

What is wash out wings

Answer 22

Angle of incedence is greater at the root than the wing tip
These are geometrically twisted

Question 23

What is the mean aerodynamic chord

Answer 23

Average chord length of a tapered or swept wing
Centre or lift and centre of pressure act here

Question 24

What is the angle of attack

Answer 24

Angle between relative wind and relative chord line

Question 25

What is angle of incedence

Answer 25

Angle between the chord line and aircraft centre line

Question 26

What are the wing shapes

Answer 26

Elliptical entire wing stalls
Rectangular root stall first nose down
Swept back tip stall first nose up

Question 27

Why are wings swept back

Answer 27

To reduce critical Mach number

Question 28

What is induced drag

Answer 28

Downwards flow of the wing tip vortice inside the span

Question 29

What is form drag

Answer 29

Caused by differences in pressure between leading and trailing edge

Question 30

What is friction drag

Answer 30

Inversely proportional to form drag

Question 31

What is interference drag

Answer 31

Turbulence in airflow caused by sharp corners
Fairings used to counteract

Question 32

How is lift generated

Answer 32

Air circulating around the aerofoil by the Magnus effect

Question 33

What is glide ratio

Answer 33

Highest lift to lowest drag at a certain aoa 4 degreees