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Module 8 Richard > 8.2 Aerodynamics > Flashcards

8.2 Aerodynamics Flashcards

1
Q

Where is air not compressible

A

The subsonic region

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2
Q

What is the continuity equation

A

A1V1 =A2V2

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3
Q

What does the continuity equation state?

A

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

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4
Q

What term is used when diameter increases and speed decreases?

A

Diffuser outlet

And vice versa is jet outlet

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5
Q

What does the Bernoulli equation state

A

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

The total pressure remains constant

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6
Q

What does IAS stand for

A

Indicated Air Speed

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7
Q

What is the point of stagnation

A

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

There is no dynamic pressure if there is no flow

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8
Q

What is upwash and downwash

A

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

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9
Q

What is the Magnus effect

A

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

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10
Q

What is the profile of a wing

A

A cross sectional area of the wing

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11
Q

What is the cord line

A

A straight line connecting the leading edge and the trailing edge

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12
Q

What is the mean camber line

A

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

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13
Q

What is the camber of the profile

A

The displacement of the mean camber line from the cord line

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14
Q

What is the maximum camber of a low speed profile

A

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

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15
Q

What is the fineness ratio

A

The maximum thickness as a fraction or percentage of the chord

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16
Q

What is the maximum thickness of a typical low speed aerofoil

A

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

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17
Q

What is the flight path velocity

A

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

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18
Q

What is the relative wind

A

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

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19
Q

What is the angle of attack

A

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

Denoted by the Greek letter alpha

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20
Q

What is the angle of incidence

A

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

Denoted by gamma

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21
Q

What is taper ratio

A

Tip chord to root chord

Lambda = ct/cr

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22
Q

What is the average chord

A

The geometric average of all chords

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23
Q

What is aspect ratio

A

Wing span divided with average chord

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24
Q

What is the sweep angle

A

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

Positive sweep = backwards
Negative sweep = forwards

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25
Q

What is the dihedral angle

A

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

Swept up and swept down

26
Q

What are the two main aerodynamic forces

A

Lift

Drag

27
Q

What is the centre of pressure

A

The point on which all pressures and forces act on

28
Q

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

A
  • Dynamic Pressure
  • Surface area of the profile
  • The shape of the profile
  • The angle of attack
29
Q

What is the formula for theoretical lift

A

1/2 rho x velocity squared x area

30
Q

How is actual lift calculated

A

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

31
Q

What is the coefficient of lift

A

The measured lift
_____________________
Theoretical lift

32
Q

What is the formula for coefficient of lift

A

CL = measured lift
_______________
Theoretical lift

33
Q

What is the coefficient of drag?

A

Measured drag
________________
Theoretical drag

Same equation as coefficient of lift

34
Q

What is CL max and Alpha max

A

Max angle of attack and max coefficient of lift before stall

35
Q

What is the coefficient of lift affected by

A

Angle of attack and shape of profile

36
Q

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

A

Reduce the maximum coefficient of lift and max angle of attack

37
Q

What happens to drag when you increase angle of attack

A

Drag increases

38
Q

What is the Lilienthal (polar) diagram

A
  • To get the best angle of attack

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

39
Q

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

A

Always form in pairs - travel counter clockwise

40
Q

How do you determine the area of a swept wing

A

Wingspan x Average chord

41
Q

How do you determine aspect ratio on a swept wing

A

Wingspan
___________
Average chord

42
Q

What are the 3 main categories of drag

A
  • Induced
  • parasite
  • Compressible
43
Q

What is induced drag formed by

A

The drag on the wing caused by lift

44
Q

How is parasite drag produced

A

Not related to lift.

Can be caused by distribution of pressure, friction or interference

45
Q

What are the 3 forms of parasite drag

A
  • Form
  • Friction
  • Interference
46
Q

What is compressible drag caused by

A

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

47
Q

Where would you find induced drag

A

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

48
Q

What types of wing will produce more induced drag

A

Low aspect ratio

49
Q

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

A

Less drag

50
Q

What is the relationship between form drag and friction drag

A

High form drag = Low friction drag

51
Q

What is the Boundary layer also called

A

Retarded air

52
Q

What are the two basic types of boundary layer

A
  • Turbulent boundary layer

- Laminar boundary layer

53
Q

What is a boundary layer

A

Layer of air trapped of surface of wing due to friction

54
Q

Where is the laminar boundary layer found

A

Immediately downstream of the leading edge

55
Q

Where is the turbulent boundary layer found

A

Downstream of the laminar boundary layer

56
Q

What boundary layer would produce more kinetic energy

A

Turbulent layer

57
Q

How can interference drag be reduced

A

By the use of engine fairings

58
Q

When does compressible drag occur

A

Transonic and supersonic flight

59
Q

What is total drag

A

Induced drag and parasite drag combine to give total drag

60
Q

What is the advantage of having a thicker wing

A

Raises coefficient of lift at higher angle of attack

61
Q

What is the advantage of a cambered wing

A

Increases co-efficient of lift at low angles of attack

62
Q

What are the two wing type designs

A

Geometrically twisted

Aerodynamically twisted

Module 8 Richard (2 decks)

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