Aerodynamics Flashcards
What is the kinetic energy equation?
KE = 1/2 x p x V^2
Kinetic Energy = 1/2 x density x velocity squared
What is laminar flow?
Smooth regular airflow patterns around an object
What is turbulent flow?
When airflow is disturbed and separates from the surface of the body
What is the continuity equation?
V1 x A1 = V2 x A2
Speed of airflow is inversely proportional to the cross sectional area if density remains constant.
What is Bernoullis Principle?
P tot = p + q
Total pressure = static pressure + dynamic pressure
Total pressure remains constant
Which regards to bodies in motion what is the dynamic pressure equation?
q = 1/2 x p x v^2
Dynamic pressure = 1/2 x density x velocity squared
Dynamic pressure can also be referred to as what?
Indicated airspeed (pitot pressure)
Describe the point of stagnation
When the speed of the airflow falls to zero and static pressure is equal to total pressure.
No dynamic pressure means there is no flow
In an Venturi tube what are the air pressures doing at the inlet?
Dynamic pressure (q) is low
Static pressure (p) is high
Velocity (V) is low
In an Venturi tube what are the air pressures doing at the narrowest point of the tube?
Dynamic pressure (q) is high
Static pressure (p) is low
Velocity (V) is high
Static pressure reduces as velocity and dynamic pressure increase into the narrow duct
In an Venturi tube what are the air pressures doing at the diffuser outlet of the tube?
Dynamic pressure (q) reduces
Static pressure (p) increases
Velocity (V) reduces
How is the Venturi tube theory affected as the airflow reaches the speed of sound?
The pressures at the inlet, narrow point and outlet are the opposite
What is the relationship between dynamic and static pressure with the introduction of an aerofoil into the airflow?
Wing upper surface will have higher dynamic pressure and lower static pressure, wing lower surface has unchanged static pressure.
How does an aerofoil create lift?
The difference in static pressure between lower and upper surface. Higher static below trying to move towards upper surface lower static pressure creates the lift. (HIGH PRESSURE MOVING TO LOW)
What is the chord of an aerofoil?
A straight line connecting leading edge and trailing edge
What is camber of a aerofoil?
Mean camber line is a line drawn equidistant between upper and lower surfaces of the profile
Typically 5% located 45% aft of leading edge
What is the fineness ratio?
Maximum thickness or depth expressed as a percentage of the chord
Typically 18% located 30% aft of leading edge
What is aspect ratio?
Ratio between length and average width of the surface
AR = wing span ^2
——————-
Wing area (mean wing chord)
At normal cruising airspeed with a small positive angle of attack, where is the CP positioned on the wing/chord line?
Approximately 25% back from the leading edge on the chord line
For most aerofoils what is considered the maximum AOA?
15-18 degrees
What type of drag are wing tip vortices?
Induced drag formed by spanwise flow
Profile/Parasitic/Form Drag is reduced by what?
Streamlining
How does induced drag react with an increase in altitude?
It increases, as density decreases more lift required thus more induced drag
How is the thrust to weight ratio calculated?
Ratio = thrust / weight
In the aerodynamic resultant, which direction does lift always act?
Perpendicular to relative wind
Wing loading equation?
Wing loading = weight / wing area
With a rectangular wing shape which stalls first tip or root?
Root stalls first (most desirable)
With a swept wing, at what point does the wing stall? Root or tip?
Wing tip first
What term describes the speed at which shock waves begin to form?
Critical Mach number - Mcrit
With reference to the drag curves, at the point where induced drag and form/parasitic drag meet is know by what acronym?
Vmd (minimum drag)
At lower speed, how does it affect AOA and induced drag?
At lower speeds more lift required, higher angle of attack and thus more induced drag
At higher speed, how does it affect AOA and induced drag?
At higher speeds, less lift required to be produced thus less induced drag meaning higher efficiency
How does induced drag change with increases in altitude?
Induced drag increases as more lift is required at altitude assuming constant speed
What is the Magnus effect?
A cylinder in free stream air with added mechanical clockwise rotation produces net lift
Air over the upper edge is accelerate, air beneath the cylinder is slowed
What is the Magnus effect?
A cylinder in free stream air with added mechanical clockwise rotation produces net lift
What is the coefficient of lift equation?
Lift = Cl x 1/2 p x v^2 x A
If anything after the = increases lift and drag increase
Wing loading equation?
Wing loading = weight
—————
Wing area
Which of the following best describes load factor?
Ratio of lift to drag
Ration of weight to wing area
Ratio of lift to weight during maneuvers
Ratio of lift to weight during manoeuvres
LF = lift in a turn
—————-
Weight
Stall speed is defined as what?
The minimum airspeed at which an aircraft can maintain level flight.
The speed below which the wings cannot generate enough lift to support the weight
What happens to an aircraft’s stall speed as weight increases?
Stall speed decreases
Stall speed increases
Stall speed remains the same
Stall speed increases. The minimum speed required to maintain lift is raised with added weight
