Basic aerodynamic theory Flashcards
When moving air is bought completely to rest, the additional pressure imposed is called _______ pressure.
Dynamic
The amount of dynamic pressure acting on an object mainly depends on:
a. The density of the air flow
b. The velocity of the air flow
c. The ambient pressure of the air flow
d. The temperature of the air flow
e. The humidity of the air flow
The density of the air flow, The velocity of the air flow
In a moving airflow, a resultant aerodynamic force will act on an object because:
The total pressure acting on one side is not cancelled out by the other.
Select the correct statements regarding dynamic pressure:
Select one:
a. It applies evenly on all surfaces of an object.
b. It is the ambient pressure at any point in the atmosphere.
c. At an altitude, it is equal in all directions.
d. None of the above.
None of the above.
select the correct statements regarding static pressure:
Select one:
a. It applies evenly on all surfaces of an object.
b. It is the ambient pressure at any point in the atmosphere.
c. At an altitude, it is equal in all directions.
d. All of the above.
All of the above.
The depth of the aerofoil.
Thickness
The curvature of a line drawn equidistant between the upper and lower surfaces of an aerofoil.
Camber,
The edge facing into the airstream.
Leading Edge
The straight line joining the leading and trailing edges, measured as a distance.
Chord
The maximum thickness of the aerofoil expressed as a percentage of the chord.
Thickness/Chord ratio
The edge facing away from the airstream.
Trailing-Edge
Select the correct statements that relate to air passing through a Venturi tube.
As the airflow passes into the Venturi tube, and out the other side:
Select one or more:
a. Velocity remains roughly the same.
b. Velocity increases, then decreases.
c. Velocity decreases, then increases.
d. Density decreases, then Increases.
e. Pressure remains roughly the same.
f. Density increases, then decreases.
g. Pressure decreases, then increases
h. Density remains roughly the same.
i. Pressure increases, then decreases
Pressure decreases, then increases, Velocity increases, then decreases., Density remains roughly the same.
Fill in the missing words:
Bernoulli’s Theorem states that in the __(a)__ flow of an ideal fluid,
__(b)__ energy + __(c)__ pressure = a constant.
The correct answer is: (a) = ? → streamlined, (b) = ? → Dynamic, (c) = ? → Static
As angle of attack increases:
Select one:
a. The pressure envelope moves forwards
b. Increased pressure under the aerofoil
c. The point of lowest pressure moves forwards
d. Streamlines move closer towards the front
e. All of the above
All of the above
The Definition of lift is:
Select one:
a. The vertical component of the total force acting on an aerofoil
b. The component of the total force acting on an aerosol that acts parallel to the RAF
c. The component of the total force acting on an aerofoil that acts perpendicular to the RAF
d. The component of the total force that opposes weight
e. The total force acting on an aerofoil
The component of the total force acting on an aerofoil that acts perpendicular to the RAF
At extreme angles of attack:
Select one or more:
a. The pressure envelope collapses
b. Airflow separates and becomes turbulent
c. Decreased pressure under the aerofoil section
d. Reduction in lifting ability
e. All of the above
The correct answers are: The pressure envelope collapses, Airflow separates and becomes turbulent, Reduction in lifting ability
What is the Centre of Pressure?
Select one:
a. The point from which the Total Reaction force is considered to act from
b. The point from which the pressure is least
c. The point from which the pressure is greatest
d. The trailing Edge
e. The leading edge
The correct answer is: The point from which the Total Reaction force is considered to act from
As angle of attack increases:
Select one or more:
a. The TR force increases until the stalling angle, then quickly reduces.
b. The CoP gradually moves forwards until the stalling angle, then quickly moves aft.
c. The TR force tilts rearwards until the stalling angle, then quickly tilts far back.
d. The pressure increases above the aerofoil until the stalling angle, then quickly reduces.
e. All of the above
The correct answers are: The TR force increases until the stalling angle, then quickly reduces., The CoP gradually moves forwards until the stalling angle, then quickly moves aft., The TR force tilts rearwards until the stalling angle, then quickly tilts far back.
The Definition of Total Reaction Force is:
Select one or more:
a. The force that propels the aircraft forwards
b. The force acting on an aerofoil that acts perpendicular to the RAF.
c. The resultant sum of all the pressure vectors acting over an aerofoil.
d. The resistance to motion
e. The resultant sum of all the velocity vectors acting over an aerofoil.
f. The force acting on an aerofoil that acts parallel to the RAF.
g. The force generated if an object is placed in a moving airstream.
The correct answers are: The resultant sum of all the pressure vectors acting over an aerofoil., The force generated if an object is placed in a moving airstream.
The energy of motion of an air mass is called:
Select one:
a. Potential Energy
b. Dynamic Energy
c. Constant Energy
d. Static Energy
The correct answer is: Dynamic Energy
The total pressure acting at a point on an object is the sum of static pressure, plus ambient pressure.
Select one:
True
False
The total pressure acting at a point on an object is the sum of static pressure, plus dynamic pressure.
The correct answer is ‘False’.
A fluid like substance such as moving air has energy of motion in the form dynamic energy. That energy is converted into dynamic pressure when it is bought completely to rest.
Select one:
True
False
The correct answer is ‘True’.
Complete the statement below:
The prevailing pressure at any point in the atmosphere is called the _______ pressure.
Select one:
a. Relative
b. Unaffected
c. Static
d. Dynamic
e. Free stream
The correct answer is: Static
Relative airflow is airflow that is __(a)__ the aircraft and is __(b)__ by its passege through it. Although the airflow is actually stationary and the aircraft is moving, for simplicity we consider the aircraft as stationary and the airflow as moving.
Therefore if the aircraft is moving in one direction, then the relative airflow is considered to come from __(c)__ direction.
The correct answer is: (a) = ? → remote from, (b) = ? → unaffected, (c) = ? → the opposite
Select the correct statements that relate to air passing through a Venturi tube.
As the airflow passes into the Venturi tube, and out the other side:
Select one or more:
a. Velocity increases, then decreases.
b. Pressure decreases, then increases
c. Pressure remains roughly the same.
d. Density remains roughly the same.
e. Velocity remains roughly the same.
f. Density increases, then decreases.
g. Velocity decreases, then increases.
h. Density decreases, then Increases.
i. Pressure increases, then decreases
The correct answers are: Pressure decreases, then increases, Velocity increases, then decreases., Density remains roughly the same.
Select the correct statements that relate to streamlines through a Venturi tube.
Where the streamlines are closest:
Select one or more:
a. Is the highest pressure
b. Is the lowest pressure
c. Is the lowest density
d. Is the highest density
e. Is the lowest velocity
f. Is the highest velocity
The correct answers are: Is the highest velocity, Is the lowest pressure
Write down the missing word:
“The angle of attack where the airflow separates from most of the upper surface and the pressure envelope collapses is called ———– angle
The correct answer is: critical
Where is the stagnation point located?
Select one:
a. At the leading edge of the aerofoil
b. Where the airflow divides between the upper and lower surfaces of the aerofoil
c. Where the airflow is bought to rest.
d. All of the above.
The correct answer is: All of the above.
Over the normal operating ranges of angle of attack (0° - 5°), the Centre of Pressure (CoP) doesn’t really move that much at all.
Select one:
True
False
The correct answer is ‘True’.
The Definition of Drag is:
Select one:
a. The component of the total force that opposes weight
b. The total force acting on an aerofoil
c. The component of the total force acting on an aerosol that acts parallel and rearwards to the RAF
d. The component of the total force acting on an aerosol that acts perpendicular to the RAF
e. The vertical component of the total force acting on an aerofoil
The correct answer is: The component of the total force acting on an aerosol that acts parallel and rearwards to the RAF
As angle of attack increases:
Select one or more:
a. The TR force increases until the stalling angle, then quickly reduces.
b. The CoP gradually moves forwards until the stalling angle, then quickly moves aft.
c. The TR force tilts rearwards until the stalling angle, then quickly tilts far back.
d. The pressure increases above the aerofoil until the stalling angle, then quickly reduces.
e. All of the above
The correct answers are: The TR force increases until the stalling angle, then quickly reduces., The CoP gradually moves forwards until the stalling angle, then quickly moves aft., The TR force tilts rearwards until the stalling angle, then quickly tilts far back
Complete the statement below:
The prevailing pressure at any point in the atmosphere is called the _______ pressure.
Select one:
a. Dynamic
b. Unaffected
c. Relative
d. Free stream
e. Static
The correct answer is: Static
A fluid like substance such as moving air has energy of motion in the form dynamic energy. That energy is converted into dynamic pressure when it is bought completely to rest.
Select one:
True
False
The correct answer is ‘True’.
Where is the stagnation point located?
Select one:
a. At the leading edge of the aerofoil
b. Where the airflow divides between the upper and lower surfaces of the aerofoil
c. Where the airflow is bought to rest.
d. All of the above.
The correct answer is: All of the above.
At extreme angles of attack:
Select one or more:
a. The pressure envelope collapses
b. Airflow separates and becomes turbulent
c. Decreased pressure under the aerofoil section
d. Reduction in lifting ability
e. All of the above
The correct answers are: The pressure envelope collapses, Airflow separates and becomes turbulent, Reduction in lifting ability
The total pressure acting at a point on an object is the sum of static pressure, plus ambient pressure.
Select one:
True
False
The total pressure acting at a point on an object is the sum of static pressure, plus dynamic pressure.
The correct answer is ‘False’.
Angle of attack is the angle between the __(a)__ and the __(b)__ line.
The correct answer is: (a) = ? → Relative Airflow (RAF), (b) = ? → Chord
Over the normal operating ranges of angle of attack (0° - 5°), the Centre of Pressure (CoP) doesn’t really move that much at all.
Select one:
True
False
The correct answer is ‘True’.
The wings and tail sections designed to produce useful aerodynamic forces are called…..
aerofoils
