Flashcards in 8.2 Aerodynamics Deck (62):

1

## Where is air not compressible

### The subsonic region

2

## What is the continuity equation

### A1V1 =A2V2

3

## What does the continuity equation state?

### The speed of the airflow is inversely proportional to the area of the cross sectional area of the tube as long as density remains the same

4

## What term is used when diameter increases and speed decreases?

###
Diffuser outlet

And vice versa is jet outlet

5

## What does the Bernoulli equation state

###
Total pressure is always the sum of static pressure and dynamic pressure

The total pressure remains constant

6

## What does IAS stand for

### Indicated Air Speed

7

## What is the point of stagnation

###
The speed of the airflow falls to 0 and the static pressure = total pressure

There is no dynamic pressure if there is no flow

8

## What is upwash and downwash

###
Some of the streamlines move over the upper half of the aero foil - upwash

Downwash - when the air comes back and meets the air and comes down the back of the upper surface of the wing

9

## What is the Magnus effect

###
If a cylinder rotates, the circulatory flow causes an increase of speed on the upper surface of the cylinder and a lower speed on the lower surface.

The difference in pressure causes lift

10

## What is the profile of a wing

### A cross sectional area of the wing

11

## What is the cord line

### A straight line connecting the leading edge and the trailing edge

12

## What is the mean camber line

### A line drawn drawn half way between the upper and lower surfaces of the profile

13

## What is the camber of the profile

### The displacement of the mean camber line from the cord line

14

## What is the maximum camber of a low speed profile

### 5% of chord line located 45% aft of the leading edge

15

## What is the fineness ratio

### The maximum thickness as a fraction or percentage of the chord

16

## What is the maximum thickness of a typical low speed aerofoil

### Max thickness of 18% located 30% aft of the leading edge

17

## What is the flight path velocity

### The speed of the aircraft in a certain direction through the air

18

## What is the relative wind

### The speed and direction of the wind acting on the aircraft which is passing through it

19

## What is the angle of attack

###
The angle between the chord line of the profile and the relative wind

Denoted by the Greek letter alpha

20

## What is the angle of incidence

###
Between the chord line of the profile and the longitudinal axis of the aircraft

Denoted by gamma

21

## What is taper ratio

###
Tip chord to root chord

Lambda = ct/cr

22

## What is the average chord

### The geometric average of all chords

23

## What is aspect ratio

### Wing span divided with average chord

24

## What is the sweep angle

###
Angle between the Line of 25% chord and line perpendicular to the root chord

Positive sweep = backwards

Negative sweep = forwards

25

## What is the dihedral angle

###
The angle between the wing and the horizontal plane passing through the root of the wing.

Swept up and swept down

26

## What are the two main aerodynamic forces

###
Lift

Drag

27

## What is the centre of pressure

### The point on which all pressures and forces act on

28

## Aerodynamic forces of lift and drag depend on the combined effect of many variables, what are they?

###
- Dynamic Pressure

- Surface area of the profile

- The shape of the profile

- The angle of attack

29

## What is the formula for theoretical lift

### 1/2 rho x velocity squared x area

30

## How is actual lift calculated

### It is not possible to measure lift, it has to be measured in a wind tunnel

31

## What is the coefficient of lift

###
The measured lift

_____________________

Theoretical lift

32

## What is the formula for coefficient of lift

###
CL = measured lift

_______________

Theoretical lift

33

## What is the coefficient of drag?

###
Measured drag

________________

Theoretical drag

Same equation as coefficient of lift

34

## What is CL max and Alpha max

### Max angle of attack and max coefficient of lift before stall

35

## What is the coefficient of lift affected by

### Angle of attack and shape of profile

36

## How is the coefficient of lift affected on the wing if ice has formed on the leading edge

### Reduce the maximum coefficient of lift and max angle of attack

37

## What happens to drag when you increase angle of attack

### Drag increases

38

## What is the Lilienthal (polar) diagram

###
- To get the best angle of attack

- it will show most efficient angle of attack for the drag it is subject to

39

## What is the rule concerning the formation of vortexes on a wing

### Always form in pairs - travel counter clockwise

40

## How do you determine the area of a swept wing

### Wingspan x Average chord

41

## How do you determine aspect ratio on a swept wing

###
Wingspan

___________

Average chord

42

## What are the 3 main categories of drag

###
- Induced

- parasite

- Compressible

43

## What is induced drag formed by

### The drag on the wing caused by lift

44

## How is parasite drag produced

###
Not related to lift.

Can be caused by distribution of pressure, friction or interference

45

## What are the 3 forms of parasite drag

###
- Form

- Friction

- Interference

46

## What is compressible drag caused by

### Caused by the shock waves on an aircraft approaching the speed of sound

47

## Where would you find induced drag

### Turbulence at wing tips causes the streamlines to form from wing tip to vortices

48

## What types of wing will produce more induced drag

### Low aspect ratio

49

## If a wing has a high aspect ratio will it experience more or less induced drag

### Less drag

50

## What is the relationship between form drag and friction drag

### High form drag = Low friction drag

51

## What is the Boundary layer also called

### Retarded air

52

## What are the two basic types of boundary layer

###
- Turbulent boundary layer

- Laminar boundary layer

53

## What is a boundary layer

### Layer of air trapped of surface of wing due to friction

54

## Where is the laminar boundary layer found

### Immediately downstream of the leading edge

55

## Where is the turbulent boundary layer found

### Downstream of the laminar boundary layer

56

## What boundary layer would produce more kinetic energy

### Turbulent layer

57

## How can interference drag be reduced

### By the use of engine fairings

58

## When does compressible drag occur

### Transonic and supersonic flight

59

## What is total drag

### Induced drag and parasite drag combine to give total drag

60

## What is the advantage of having a thicker wing

### Raises coefficient of lift at higher angle of attack

61

## What is the advantage of a cambered wing

### Increases co-efficient of lift at low angles of attack

62