C04 - Aerodynamic Force

Question 1

Define Aerodynamic Force?

Answer 1

A reactive force, resulting from the force exerted by a thin body to bend the airflow.

Question 2

The Static Pressure of the flow above a thin body is ‘____’ pressure?

Answer 2

Low.

Question 3

The Static Pressure of the flow below a thin body is ‘____’ pressure?

Answer 3

High.

Question 4

Air flow always ‘____’ above the upper surface?

Answer 4

Accelerates.

Question 5

Air flow always ‘____’ below the upper surface?

Answer 5

Slows.

Question 6

The flow field plots the ‘____’ energy and the pressure field plots the ‘____’ energy (2)?

Answer 6

• Kinetic.

- Pressure.

Question 7

True or False. Angle of Attack is absolutely critical to the production of low pressure and flow bending?

Answer 7

True.

Question 8

Where the flow is faster, the Static Pressure is ‘____’ and when the flow is slower the Static Pressure is ‘____’?

Answer 8

• Lower.

- Higher.

Question 9

A pressure acting on a surface provides a force. What is this formula?

Answer 9

F = P x A (Pressure x Area).

Question 10

The overall net force acting on an object in an airflow is called what?

Answer 10

Total Reaction.

Question 11

True or False. When a flow is faster, the Static Pressure must have reduced. Why (2)?

Answer 11

• True.

- Because the Dynamic Pressure has increased.

Question 12

True or False. When a low is slower, the Dynamic Pressure must decrease. Why (2)?

Answer 12

• True.

- Because Dynamic Pressure is proportional to the relative airflow.

Question 13

Define Stagnation Point?

Answer 13

A point on an object’s surface where the airflow comes to a complete stop.

Question 14

What happens to Dynamic Pressure at a Stagnation Point?

Answer 14

Turns to zero and is converted to Static Pressure.

Question 15

How many Stagnation Points are there on a surface? Where are they found? (2)?

Answer 15

• 2.

- Front of the object and where the airflow meets towards the rear object.

Question 16

Name two types of Drag the Viscosity of the air produces?

Answer 16

• Skin Friction Drag.

- Form Drag (Pressure Drag).

Question 17

Define Skin Friction?

Answer 17

The Drag is caused directly from friction within the Boundary Layer.

Question 18

Define Boundary Layer?

Answer 18

A volume of air around the surface which flows slower than the free stream velocity.

Question 19

Define Form Drag?

Answer 19

Rearwards acting force as a result from the shape of an Aerofoil.

Question 20

The more upwards the Total Reaction, the more ‘____’ can be produced?

Answer 20

Lift.

Question 21

Name five basic parts of the Aerofoil?

Answer 21

• Leading Edge.
• Trailing Edge.
• Chord Line.
• Upper Camber.
• Lower Camber.

Question 22

What type of Leading Edge Radius favours attachment and streamlining of relative airflow?

Answer 22

Large.

Question 23

What type of Leading Edge Radius favours detachment and streamlining of relative airflow?

Answer 23

Small.

Question 24

Define Chord Line?

Answer 24

An imaginary straight line between the centre of the leading and trailing edge.

Question 25

Define Chord?

Answer 25

The distance from the leading edge to the trailing edge measured along the Chord Line.

Question 26

Define Angle of Attack?

Answer 26

The angle between the Chord Line and the Relative Air Flow.

Question 27

What is the Angle of Attack stalling angle?

Answer 27

16°.

Question 28

Define Mean Camber Line?

Answer 28

An imaginary line equal distance between the upper and lower surfaces.

Question 29

Define Camber?

Answer 29

The distance between the Mean Camber Line and the Chord Line

Question 30

Name 4 aerofoil types?

Answer 30

• Positive Camber.
• Negative Camber.
• Symmetrical.
• Biconvex.

Question 31

Define the Thickness-Chord ratio?

Answer 31

The ratio of the aerofoil’s maximum thickness to the length of its chord.

Question 32

What Thickness-Chord ratio does a low-speed aerofoil have?

Answer 32

High T/C.

Question 33

What Thickness-Chord ratio does a high-speed aerofoil have?

Answer 33

Low T/C.

Question 34

The distinctive upward flow of air before the Leading Edge is known as ‘____’?

Answer 34

Upwash.

Question 35

The distinctive downward flow of air before the Trailing Edge is known as ‘____’?

Answer 35

Downwash.

Question 36

Define Centre of Pressure?

Answer 36

The point of origin of the Total Reaction is the average point from which the forces act.

Question 37

Name two components of Total Reaction?

Answer 37

• Lift.

- Drag.

Question 38

Drag is the component which is ‘____’ to the free stream flow?

Answer 38

Parallel.

Question 39

Lift is the component which is ‘____’ to the free stream flow?

Answer 39

Perpendicular.