Can shock waves on helicopter rotors generate noise? - A study of the quadrupole sourceAn analysis has previously established that local shock surfaces attached to helicopter rotor blades moving at high subsonic speeds are potent noise generators; in pursuit of this insight, a novel formulation is presented for the prediction of the noise of a deformable shock, whose area changes as a function of the azimuthal position of the blade. The derivation of this formulation has its basis in a mapping of the moving shock to a time-independent region. In virtue of this mapping, the implementation of the main result on a computer becomes straightforward enough for incorporation into the available rotor-noise prediction code. A problem illustrating the importance of rotor shocks in the generation of high-intensity noise is presented.
Document ID
19910032600
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Farassat, F. (NASA Langley Research Center Hampton, VA, United States)
Tadghighi, H. (McDonnell Douglas Helicopter Co. Mesa, AZ, United States)