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Transonic and Subsonic flight (incompressible air flow (centre of pressure…
Transonic and Subsonic flight
incompressible air flow
the compressibility becomes significant at higher speeds
subsonic flow
supersonic flow
with supersonic flow, the air decreasing velocity, increasing density and pressure
centre of pressure
in subsonic flight, as the separation point moves forward, the centre of pressure moves forward
in transonic flight, the pressure behind the shock-waves is higher and there is a reduction in velocity. this moves the centre of pressure rearward, towards the trailing edge, leading to control reversal
critical mach number
the CMN or (Mcrit) of an aircraft is the lowest mach number at which the airflow over some point of an aircraft reaches the speed of sound but does not exceed it
the drag divergence mach number
he mach number at which the aerodynamic drag on an aerofoil or airframe increases rapidly
usually higher than the Mcrit
transonic flow
speed of sound
the speed of sound is proportional to the square root of the absolute temperature (ISA) in kelvin (Ka)
the LSS (the local speed of sound) can be calculated via: LSS = 39 x root [absolute temperature]
Supersonic flow
mach numbers: subsonic < mach 0.75, transonic flow mach 0.75 - mach 1.2, supersonic flow mach 1.2 - 5.0, hypersonic flow > mach 5.0.
shockwave
oblique shock waves
Bow shock waves
Normal shock waves
calculating the mach cone and angle
designs to alleviate Transonic problems
