Exercise 3

Question 1

Airflow past an aerofoil such as the wing of an aeroplane can produce a _____ force.

Answer 1

Lift

Question 2

The most important airflow is the nearest the surface of the aerofoil and which is called the ___________.

Answer 2

Boundary layer

Question 3

A steady flow of molecules around the aerofoil where succeeding molecules follow each other is called _____ flow.

Answer 3

streamline

Question 4

A disturbed flow with eddying is called _____ flow

Answer 4

Turbulent

Question 5

Daniel _____ showed that in a streamline flow the total energy remains constant.

Answer 5

Bernoulli

Question 6

Static pressure in the air is exerted (in all directions/down/up)

Answer 6

In all direction

Question 7

Dynamic pressure is the pressure (due to motion/due to no motion)

Answer 7

Due to motion

Question 8

Bernoulli’s principle describes the natural effect that ‘in a streamline flow, the total pressure energy remains _____’

Answer 8

Constant

Question 9

Total pressure energy = ________________

Answer 9

Static pressure + dynamic pressure

Question 10

In streamline flow, if dynamic pressure increases then, for the total pressure energy to remain constant, the static pressure will ________.

Answer 10

Decrease

Question 11

If velocity increases, then dynamic pressure increases. For the total pressure to remain the same, the static pressure will ________.

Answer 11

Decrease

Question 12

If velocity increase, static pressure _______.

Answer 12

Decrease

Question 13

Increasing the curvature of the upper surface of the wing causes the airflow over it to(speed up/slow down).

Answer 13

Speed up

Question 14

If the velocity over the upper surface of the wing increases, then the static pressure will _______.

Answer 14

Decrease

Question 15

Curvature of the wing surfaces is called _______.

Answer 15

Camber

Question 16

The line drawn half-way between the upper and lower surfaces of the wing, which gives an indication of its curvature is called the __________.

Answer 16

Mean Camber Line

Question 17

The straight line joining the leading edge and the trailing edge of an aerofoil section is called the _____.

Answer 17

Chord line

Question 18

The length of the straight line joining the leading edge and the trailing edge is _____.

Answer 18

Chord

Question 19

The greatest distance between the upper

and lower surfaces of the wing is called _____.

Answer 19

Thickness

Question 20

As the airflow accelerates across the

upper surface of a well-cambered wing, the static pressure (increases/decreases).

Answer 20

Decrease

Question 21

In normal flight, the static pressure over the top surface of a well-cambered wing is (less than/greater than/the same as) the static pressure beneath the wing.

Answer 21

Less than

Question 22

The difference between the static pressure above and below the wing generates a ______ Force.

Answer 22

Lift

Question 23

As well as the lift force being generated by the aerofoil, it also generates a force opposing the relative motion of the aerofoil through the air – and this force opposing motion is called _____.

Answer 23

Drag

Question 24

The total force produced by an aerofoil is called the ______ ______, which can be resolved into two components: ____ and _____.

Answer 24

Total reaction
Lift
Drag

Question 25

The angle between the chord line of an aerofoil and the direction of the relative airflow well ahead of the aerofoil is ______ .

Answer 25

Angle of Attack (AoA)

Question 26

Even at zero degrees angle of attack, a wing with a well-cambered upper surface will cause the airflow to accelerate across it. The increase in velocity will cause a (decrease/increase) in static pressure over the upper surface, resulting in the generation of a ____ Force.

Answer 26

Decrease, lift

Question 27

If the angle of attack is increased gradually, the lifting ability of the wing (increases/decreases).

Answer 27

Increases

Question 28

At a critical angle of attack known as the stalling angle, the streamline airflow breaks down and becomes turbulent and the lifting ability of the wing (increases/remains good/decreases).

Answer 28

Decreases

Question 29

The forces acting on an aerofoil in-flight as a result of the changes in static pressure around it, may be considered to
act through a point known as the ____ __ ____

Answer 29

Centre of Lift

Question 30

As the angle of attack is gradually increased in the normal flight range the lifting ability of the wing increases and
the centre of pressure (moves forwards/stays in the same place/moves rearwards) on the wing.

Answer 30

Moves forwards

Question 31

Beyond the stalling angle of attack (the critical angle when the streamline airflow breaks down and becomes turbulent), the lifting ability of the wing decreases markedly and the CP (moves forwards/moves rearwards/remains stationary) on the wing.

Answer 31

Moves rearwards

Question 32

Name five items that the lift force generated by an aerofoil depends on: ____ shape, ____ of ____, air ______, _____ area, ______ of the air flow.

Answer 32

Lift = C(lift) x 1/2 x rho x V-square x S

Question 33

The wing shape and the angle of attack determine the profile that the aerofoil presents to the airflow and determines the lifting _____ of the wing.

Answer 33

Ability

Question 34

The ‘lifting ability’ of the wing is given the technical name ‘________ of ______’

Answer 34

Coefficient of lift

Question 35

The velocity of the airflow and the air density (rho) are combined in the one expression ‘1/2 x rho x V-squared’ which is called the _______ _______.

Answer 35

Dynamic pressure.

Question 36

Write down the formula that nearly describe the lift force that a wing can produce

Answer 36

Lift = C(lift) x 1/2 x rho x V-squared x S (wing area)