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10342644
High Speed Flight 69 - 101
Description
Aeronautical Engineering (M11 Mind Maps) Mind Map on High Speed Flight 69 - 101, created by Kenzie Evans on 13/09/2017.
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aeronautical engineering
m11 mind maps
Mind Map by
Kenzie Evans
, updated more than 1 year ago
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Created by
Kenzie Evans
over 7 years ago
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Resource summary
High Speed Flight 69 - 101
Three Speed Regions
Subsonic
Transonic
Supersonic
Subsonic Region
All speeds around the aircraft are below the speed of sound
Air is incompressible at low speed
Transonic Region
Some speeds around the aircraft are below speed of sound, other are above
Supersonic Region
All speeds around aircraft are higher than the speed of sound
Small changes in pressure and almost no change in density
Air becomes compressible
Shock waves produced
Large pressure and density changes
Low Speed
Sound waves move ahead of the object
Airflow immediately ahead of object is influenced by forward moving pressure field
Acts as 'pressure warning' to the leading edge and there is a change of flow direction ahead of leading edge
Above the Speed of Sound
Airflow ahead of object is not influenced by pressure field
Sound waves can't move ahead of the object
Approaching speed of sound: compression wave forms
Changes in velocity, pressure and density take place suddenly and sharply
Airflow ahead of object receives no pressure warning because the air particles are suddenly forced out of the way by the shock wave
Mach
Subsonic: <0.8 Mach
Transonic: 0.8 - 1.2 Mach
Supersonic: 1.2 - 5.0 Mach
Critical Mach Number
Highest Mach number we can have without supersonic airflow
Boundary between subsonic and transonic flight
When exceeded, an area of supersonic airflow is created
Local Mach number of the wing will be higher than aircraft speed
Wing profile accelerates airflow over the upper surface
Normal shock wave takes place at Mach 1.2
Leads to large increase in static pressure behind wave
Strong shockwave causes boundary layer to have too little energy to withstand increase in static pressure
Flow separation
Reduced lift
As flight Mach number reaches 1, areas of supersonic flow increase
Shock waves move closer to trailing edge
Bow Wave
Forms at leading edge when flight exceeds speed of sound
Has a detached normal shockwave region with an area of subsonic flow behind wave and oblique shock wave regions
SUpersonic flow behind the wave
If speed increased to a higher supersonic value
Detached normal shock portion of the bow wave moves closer to trailing edge
Wave Drag
Portion of total drag due to shock waves
Two ways to reduce
Vortex Generators
Produce a vortex which energises the boundary layer
Reduces flow separation
Produces oblique shock wave inside supersonic airflow
Reduced airspeed behind oblique shockwave produces smaller normal shockwave
Reduces wave drag
Increase parasite drag slightly
'Area Rule'
Swept Wing Effect
Wings designed to carry weight and house fuel tanks
If profile is 1.5m thick and chord length 10m, thickness is 0.15 or 15%
Profile thickness = actual thickness/chord length
Most modern jets have sweep angle of 30 degrees
Reduces thickness more and increases critical Mach number
Variable Sweep Angle
Allows improvement at low speed where thicker chord to length ratio makes for greater lift for take-off and landing
And high speed flight where fully swept position has greater critical speed
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