Rotor noise due to atmospheric turbulence ingestion. II - Aeroacoustic results

A computer program for the prediction of noise due to the turbulence of inflow to a propeller or helicopter rotor is extended to the case of nonisotropic turbulence, on the basis of a combined mean flow contraction model and rapid distortion theory. The mean flow distortion is noted to stretch the turbulence, decreasing the velocities along the principal axis of the stretching. In the case of a principal stretching axis lying close to the rotor axis, the distortion acts to decrease the upwash velocities of the rotor: thereby decreasing the noise from levels associated with isotropic turbulence. Acoustic energies are calculated at observer location for several cases, and compared to the turbulence energy as affected by the contraction.

[1]  A. R. George,et al.  Broadband rotor noise analyses , 1984 .

[2]  R. Mani.  Noise due to interaction of inlet turbulence with isolated stators and rotors , 1971 .

[3]  G. Batchelor,et al.  THE EFFECT OF RAPID DISTORTION OF A FLUID IN TURBULENT MOTION , 1954 .

[4]  A. R. George,et al.  High-Frequency Broadband Rotor Noise , 1977 .

[5]  R. K. Amiet,et al.  Noise of a model helicopter rotor due to ingestion of isotropic turbulence , 1982 .

[6]  B. Mugridge.  Sound radiation from aerofoils in turbulent flow , 1970 .

[7]  Rotor noise due to atmospheric turbulence ingestion. I - Fluid mechanics , 1990 .

[8]  R. Amiet.  Acoustic radiation from an airfoil in a turbulent stream , 1975 .

[9]  E. Greitzer,et al.  Helicopter rotor noise due to ingestion of atmospheric turbulence , 1986 .

[10]  D. Hanson.  Measurements of static inlet turbulence , 1975 .

[11]  R. K. Amiet,et al.  Acoustic radiation and surface pressure characteristics of an airfoil due to incident turbulence , 1976 .

[12]  M. V. Lowson,et al.  The sound field for singularities in motion , 1965, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[13]  A. R. George,et al.  Broadband and discrete frequency radiation from subsonic rotors , 1974 .

[14]  H. Ribner,et al.  Spectrum of turbulence in a contracting stream , 1953 .

[15]  A. R. George,et al.  HELICOPTER NOISE: STATE-OF-THE-ART , 1978 .

[16]  R. K. Amiet,et al.  Noise Produced by Turbulent Flow into a Propeller or Helicopter Rotor , 1976 .

[17]  R. H. Schlinker,et al.  Progress in rotor broadband noise research , 1983 .

[18]  A. Love.  A treatise on the mathematical theory of elasticity , 1892 .

[19]  R. K. Amiet.  Noise due to rotor-turbulence interaction , 1978 .

[20]  I. J. Sharland.  Sources of noise in axial flow fans , 1964 .