Theoretical Modeling of High‐Speed Helicopter Impulsive Noise
- 1 January 1979
- journal article
- Published by AHS International dba Vertical Flight Society in Journal of the American Helicopter Society
- Vol. 24 (1) , 10-19
- https://doi.org/10.4050/jahs.24.1.10
Abstract
A simple theoretical model of high‐speed helicopter impulsive noise, based on the Ffowcs Williams and Hawkings theoretical formulation, is developed. The model depends primarily on the large scale features of the rotor's aerodynamic flow field. For acoustic radiation near the rotor's tip‐path‐plane, monopole, dipole, and quadrupole sources all contribute—with the monopole term dominating for high subsonic advancing tip Mach numbers ( Mat). Predicted pulse shapes show good agreement with experimental data below Mat = 0.9 and poor agreement above. Predicted peak amplitudes show generally poor agreement, becoming worse as Mat approaches 1.0. Several methods of improving theory‐data correlation are suggested.Keywords
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