These images show the structure of the noise field of a propeller of
unit radius. The vertical line shows one half of the propeller. The
noise was calculated for the fourth harmonic of a four bladed
propeller. Because of the very large variation in acoustic pressure
p throughout the field, the quantity shown here is actually
sign(p)log(|p|). The variation in the field is shown for
two blade tip Mach numbers (Mtip) and three flight
Mach numbers (Mfl) which correspond to zero, takeoff
and cruise velocities. Flight is from left to right in each case (flow
is from right to left). More details of the results and the
calculation method can be found in
Carley, M., 1999, Sound
radiation from propellers in forward flight, Journal of Sound and
Vibration, 225(2):353-374, also available online to
IDEAL subscribers.
Carley, M., 2000, Propeller noise fields, Journal of Sound and
Vibration, 233(2):255-277, also available online
to
IDEAL subscribers
The method has recently been extended to the case of rotors at incidence and some sample results are available. At present I am working on extending the method to handle ducted rotors.
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| Mtip=0.7, Mfl=0 | Mtip=1.05, Mfl=0 |
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| Mtip=0.7, Mfl=0.2 | Mtip=1.05, Mfl=0.2 |
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| Mtip=0.7, Mfl=0.7 | Mtip=1.05, Mfl=0.8 |