8.2 Airflow Around A Body Flashcards
What is static pressure
Stationary
What is dynamic pressure
1/2 p x v2
What is Bernoulli’s theorem
Total pressure = Static + dynamic
What is a jet outlet
When diameter decreases and speed increases
What is a diffuser outlet
When diameter increases and speed decreases
What is a Venturi tube
Airflow increases when it narrows
What is the boundary layer
Is the layer of fluid density above the surface of the skin
It is retarded air
What is laminar flow
When particles in fluid all flow parallel to one another
This is desirable as less drag so more fuel efficient and high lift
Flow over the leading edge
What is turbulent flow
High pressure in turbulent air
There is more friction drag
High aot cause greater amounts of turbulent flow
What is free stream airflow
Air above boundary layer that is unaffected by friction
What is relative airflow
Direction of airflow with respect to moving body
Where is transition point of laminar flow
Max thickness and lowest pressure where flow separates
What is upwash
Air flowing towards the wing will flow upwards to the low pressure upper surface of the wing
What is downwash
The fluid flow returns to its original state
What do door gutters help with
Reflect upwash and downwash
What are vortices
Are circular patterns of rotating air behind a wing
Goes clockwise at left wing tip
Anti-clockwise at right
What is the camber line
Line that is equidistant from the upper and lower surface
Mid line between top and bottom surface
What is chord line
Line between the leading and trailing edge
Low speed profile has max camber 5% 45% aft leading egdge
What is finess ratio
Max thickness of a section expressed as a percentage
What is aspect ratio
Ratio of wing length to width
High ar = low drag
Low ar = high drag
What is washin wings
Angle of incedence is greater at wing tip than wing root
Aerodynamically twisted wings are washin
What is wash out wings
Angle of incedence is greater at the root than the wing tip
These are geometrically twisted
What is the mean aerodynamic chord
Average chord length of a tapered or swept wing
Centre or lift and centre of pressure act here
What is the angle of attack
Angle between relative wind and relative chord line
What is angle of incedence
Angle between the chord line and aircraft centre line
What are the wing shapes
Elliptical entire wing stalls
Rectangular root stall first nose down
Swept back tip stall first nose up
Why are wings swept back
To reduce critical Mach number
What is induced drag
Downwards flow of the wing tip vortice inside the span
What is form drag
Caused by differences in pressure between leading and trailing edge
What is friction drag
Inversely proportional to form drag
What is interference drag
Turbulence in airflow caused by sharp corners
Fairings used to counteract
How is lift generated
Air circulating around the aerofoil by the Magnus effect
What is glide ratio
Highest lift to lowest drag at a certain aoa 4 degreees
