10342644
Description
Mind Map by Kenzie Evans, updated more than 1 year ago
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Created by Kenzie Evans
over 6 years ago
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High Speed Flight 69 - 101
- Three Speed Regions
- Subsonic
- Transonic
- Supersonic
- Subsonic
- Subsonic Region
- All speeds around the aircraft are below the speed of sound
- Air is incompressible at low speed
- Air is incompressible at low speed
- All speeds around the aircraft are below the speed of sound
- Transonic Region
- Some speeds around the aircraft are below speed of sound, other are above
- 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
- Large pressure and density changes
- All speeds around aircraft are higher than the speed of sound
- 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
- Acts as 'pressure warning' to the leading edge and there is a change of flow direction ahead of leading edge
- Sound waves move ahead of the object
- Above the Speed of Sound
- Airflow ahead of object is not influenced by pressure field
- Sound waves can't move ahead of the object
- 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
- Airflow ahead of object is not influenced by pressure field
- Mach
- Subsonic: <0.8 Mach
- Transonic: 0.8 - 1.2 Mach
- Supersonic: 1.2 - 5.0 Mach
- Subsonic: <0.8 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
- Wing profile accelerates airflow over the upper surface
- Local Mach number of the wing will be higher than aircraft speed
- 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
- Reduced lift
- Flow separation
- Leads to large increase in static pressure behind wave
- As flight Mach number reaches 1, areas of supersonic flow increase
- Shock waves move closer to trailing edge
- 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
- 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
- Detached normal shock portion of the bow wave moves closer to trailing edge
- Forms at leading edge when flight exceeds speed of sound
- Highest Mach number we can have without supersonic airflow
- 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
- Reduces flow separation
- Produces oblique shock wave inside supersonic airflow
- Reduced airspeed behind oblique shockwave produces smaller normal shockwave
- Reduces wave drag
- Reduces wave drag
- Reduced airspeed behind oblique shockwave produces smaller normal shockwave
- Increase parasite drag slightly
- Produce a vortex which energises the boundary layer
- 'Area Rule'
- Vortex Generators
- Portion of total drag due to shock waves
- 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
- Profile thickness = actual thickness/chord length
- Most modern jets have sweep angle of 30 degrees
- Reduces thickness more and increases critical Mach number
- 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
- And high speed flight where fully swept position has greater critical speed
- Allows improvement at low speed where thicker chord to
length ratio makes for greater lift for take-off and landing
- Wings designed to carry weight and house fuel tanks
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