8.2 Flashcards
What is the continuity equation and what does it state?
V1 x A1 = V2 x A2
The speed of the airflow is inversely proportional to the area of the cross section of the tube
What is meant by Diffuser outlet?
When the diameter of the tube increases and the speed decreases
What is meant by Jet outlet?
When the diameter of the tube decreases and the speed increases
What does Bernoulli’s principle state?
The total pressure if the sum of the static and dynamic pressures
What is the point of stagnation?
The point at the leading edge where there is no speed of airflow and the static pressure is equal to the total pressure
What is up-wash?
Where some streamlines slope upwards in front of the wing and pass over the top
What is down-wash?
Where streamlines of the upper surface flow downwards when leaving the wing at the trailing edge
What is the Magnus effect?
Where a cylinder is spun and generates lift by increasing speed on the upper surface and decreasing speed on the lower surface
What is a profile?
A cross section of a wing (aerofoil)
What is the Chord?
A straight line connecting the leading edge and the trailing edge
What is the mean camber line?
The line drawn half way between the upper and the lower surfaces of the profile
What is the camber?
The displacement of the mean camber line from the chord line
What is the Fineness ratio?
The maximum thickness of the profile as a fraction
What is the flight path velocity?
The speed of the aircraft in a certain direction through the air
What is the relative wind?
The speed and direction of the air acting on the aircraft
What is the angle of attack?
The angle between the chord line of the profile and the relative wind
What is the equation of wing area?
Wing span x chord of the wing
What is the taper ratio equation?
Chord tip / chord root
What is the aspect ratio equation?
Wing span / average chord
What are the 2 aerodynamic forces?
Lift and drag
What is the centre of pressure?
The point where all pressures and all forces act
What variables can change the lift and drag?
Dynamic pressure
Surface area
Shape
Angle of attack
What is the equation for theoretical lift?
1/2 x p x V2 x A
How do you measure lift and drag?
Through a wind tunnel
Wha is the equation for the coefficient of lift?
Measured lift / theoretical lift
What does the polar (Lilienthal) diagram show?
The most efficient angle of attack
What are the 3 categories of drag?
Induced drag
Parasite drag
Compressible drag
What is induced drag?
Drag on the wing caused by the lift
What is parasite drag?
It can be form drag caused by the distribution of pressure, friction drag or interference drag
What is compressible drag?
Caused by the shockwaves on an aircraft approaching the speed of sound
What is form drag?
A parasite drag caused by the pressure distribution on a body
What is friction drag?
A type of parasite drag, the lower the friction drag, the higher the form drag
What are the 2 types of boundary layer?
Turbulent and laminar
What is the laminar boundary layer?
It’s immediately downstream of the leading edge
What is the turbulent boundary layer?
It’s downstream of the laminar boundary layer
What is interference drag?
The difference of the sum of the drags and the total drag on the wing strut and the engine
How can interference drag be reduced?
By fairings
When does compressible drag occur?
During transonic and supersonic flight
Why is compressible drag caused?
By shockwaves on an aircraft approaching the speed of sound
Why is compressible drag not present in subsonic flight?
The aircraft is travelling too slow
What is total drag?
A combination of induced drag and parasite drag
What are the 4 types of wing shape?
Elliptical
Rectangular
Tapered
Swept
Which part of an elliptical wing stalls first?
The whole wing stalls at the same time due to a constant down wash behind the wing
Which part of a rectangular wing stalls first?
The root stalls first followed by the tip due to a larger downwash at the tip than the root
Which part of a tapered wing stalls first?
The tip stalls first due to an increased downwash towards the root
Which part of a swept wing stalls first?
The tip stalls first
What makes a geometrically twisted wing?
When the camber of the profile is constant across the wingspan but the angle of incidence is greater at the root than the tip
What makes an aerodynamically twisted wing?
The camber of the profile is greater at the root than the tip and the angle of incidence is constant across the wing
What does MAC mean?
Mean aerodynamic chord
What happens in a wing root stall?
Aircraft goes to nose down position
Loses altitude
Speed increases
Aircraft recovers with no pilot input
What happens during a wing tip stall?
Aircraft goes to nose up
Angle of attack increases
Pilot input is needed to control aircraft
What do wing fences do?
Keep the air particles going in a straight line to control the boundary layer
What is a vortex generator used for?
To improve boundary layer control by producing lift
