C04 - Aerodynamic Force Flashcards
Define Aerodynamic Force?
A reactive force, resulting from the force exerted by a thin body to bend the airflow.
The Static Pressure of the flow above a thin body is ‘____’ pressure?
Low.
The Static Pressure of the flow below a thin body is ‘____’ pressure?
High.
Air flow always ‘____’ above the upper surface?
Accelerates.
Air flow always ‘____’ below the upper surface?
Slows.
The flow field plots the ‘____’ energy and the pressure field plots the ‘____’ energy (2)?
- Kinetic.
- Pressure.
True or False. Angle of Attack is absolutely critical to the production of low pressure and flow bending?
True.
Where the flow is faster, the Static Pressure is ‘____’ and when the flow is slower the Static Pressure is ‘____’?
- Lower.
- Higher.
A pressure acting on a surface provides a force. What is this formula?
F = P x A (Pressure x Area).
The overall net force acting on an object in an airflow is called what?
Total Reaction.
True or False. When a flow is faster, the Static Pressure must have reduced. Why (2)?
- True.
- Because the Dynamic Pressure has increased.
True or False. When a low is slower, the Dynamic Pressure must decrease. Why (2)?
- True.
- Because Dynamic Pressure is proportional to the relative airflow.
Define Stagnation Point?
A point on an object’s surface where the airflow comes to a complete stop.
What happens to Dynamic Pressure at a Stagnation Point?
Turns to zero and is converted to Static Pressure.
How many Stagnation Points are there on a surface? Where are they found? (2)?
- 2.
- Front of the object and where the airflow meets towards the rear object.
Name two types of Drag the Viscosity of the air produces?
- Skin Friction Drag.
- Form Drag (Pressure Drag).
Define Skin Friction?
The Drag is caused directly from friction within the Boundary Layer.
Define Boundary Layer?
A volume of air around the surface which flows slower than the free stream velocity.
Define Form Drag?
Rearwards acting force as a result from the shape of an Aerofoil.
The more upwards the Total Reaction, the more ‘____’ can be produced?
Lift.
Name five basic parts of the Aerofoil?
- Leading Edge.
- Trailing Edge.
- Chord Line.
- Upper Camber.
- Lower Camber.
What type of Leading Edge Radius favours attachment and streamlining of relative airflow?
Large.
What type of Leading Edge Radius favours detachment and streamlining of relative airflow?
Small.
Define Chord Line?
An imaginary straight line between the centre of the leading and trailing edge.
Define Chord?
The distance from the leading edge to the trailing edge measured along the Chord Line.
Define Angle of Attack?
The angle between the Chord Line and the Relative Air Flow.
What is the Angle of Attack stalling angle?
16°.
Define Mean Camber Line?
An imaginary line equal distance between the upper and lower surfaces.
Define Camber?
The distance between the Mean Camber Line and the Chord Line
Name 4 aerofoil types?
- Positive Camber.
- Negative Camber.
- Symmetrical.
- Biconvex.
Define the Thickness-Chord ratio?
The ratio of the aerofoil’s maximum thickness to the length of its chord.
What Thickness-Chord ratio does a low-speed aerofoil have?
High T/C.
What Thickness-Chord ratio does a high-speed aerofoil have?
Low T/C.
The distinctive upward flow of air before the Leading Edge is known as ‘____’?
Upwash.
The distinctive downward flow of air before the Trailing Edge is known as ‘____’?
Downwash.
Define Centre of Pressure?
The point of origin of the Total Reaction is the average point from which the forces act.
Name two components of Total Reaction?
- Lift.
- Drag.
Drag is the component which is ‘____’ to the free stream flow?
Parallel.
Lift is the component which is ‘____’ to the free stream flow?
Perpendicular.
