8.2 Aerodynamics Flashcards by Deleted Deleted

Where is air not compressible

The subsonic region

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What is the continuity equation

A1V1 =A2V2

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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

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What term is used when diameter increases and speed decreases?

Diffuser outlet

And vice versa is jet outlet

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What does the Bernoulli equation state

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

The total pressure remains constant

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What does IAS stand for

Indicated Air Speed

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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

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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

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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

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What is the profile of a wing

A cross sectional area of the wing

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What is the cord line

A straight line connecting the leading edge and the trailing edge

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What is the mean camber line

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

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What is the camber of the profile

The displacement of the mean camber line from the cord line

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What is the maximum camber of a low speed profile

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

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What is the fineness ratio

The maximum thickness as a fraction or percentage of the chord

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What is the maximum thickness of a typical low speed aerofoil

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

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What is the flight path velocity

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

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What is the relative wind

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

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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

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What is the angle of incidence

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

Denoted by gamma

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What is taper ratio

Tip chord to root chord

Lambda = ct/cr

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What is the average chord

The geometric average of all chords

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What is aspect ratio

Wing span divided with average chord

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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

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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

What are the two main aerodynamic forces

Lift | Drag

What is the centre of pressure

The point on which all pressures and forces act on

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

What is the formula for theoretical lift

1/2 rho x velocity squared x area

How is actual lift calculated

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

What is the coefficient of lift

The measured lift _____________________ Theoretical lift

What is the formula for coefficient of lift

CL = measured lift _______________ Theoretical lift

What is the coefficient of drag?

Measured drag ________________ Theoretical drag Same equation as coefficient of lift

What is CL max and Alpha max

Max angle of attack and max coefficient of lift before stall

What is the coefficient of lift affected by

Angle of attack and shape of profile

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

What happens to drag when you increase angle of attack

Drag increases

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

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

Always form in pairs - travel counter clockwise

How do you determine the area of a swept wing

Wingspan x Average chord

How do you determine aspect ratio on a swept wing

Wingspan ___________ Average chord

What are the 3 main categories of drag

- Induced - parasite - Compressible

What is induced drag formed by

The drag on the wing caused by lift

How is parasite drag produced

Not related to lift. Can be caused by distribution of pressure, friction or interference

What are the 3 forms of parasite drag

- Form - Friction - Interference

What is compressible drag caused by

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

Where would you find induced drag

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

What types of wing will produce more induced drag

Low aspect ratio

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

Less drag

What is the relationship between form drag and friction drag

High form drag = Low friction drag

What is the Boundary layer also called

Retarded air

What are the two basic types of boundary layer

- Turbulent boundary layer | - Laminar boundary layer

What is a boundary layer

Layer of air trapped of surface of wing due to friction

Where is the laminar boundary layer found

Immediately downstream of the leading edge

Where is the turbulent boundary layer found

Downstream of the laminar boundary layer

What boundary layer would produce more kinetic energy

Turbulent layer

How can interference drag be reduced

By the use of engine fairings

When does compressible drag occur

Transonic and supersonic flight

What is total drag

Induced drag and parasite drag combine to give total drag

What is the advantage of having a thicker wing

Raises coefficient of lift at higher angle of attack

What is the advantage of a cambered wing

Increases co-efficient of lift at low angles of attack

What are the two wing type designs

Geometrically twisted | Aerodynamically twisted