Accession Number:

ADA209920

Title:

Aerodynamically Generated Sound and Subsonic Aerodynamics

Descriptive Note:

Final scientific rept.

Corporate Author:

TORONTO UNIV DOWNSVIEW (ONTARIO) INST FOR AEROSPACE STUDIES

Personal Author(s):

Report Date:

1979-01-01

Pagination or Media Count:

18.0

Abstract:

Jet noise diagnostics were performed by cross-correlating the suspected source terms e.g., rates of turbulent momentum flux with the effect they produce. To eliminate the possibility of spurious noise, the source terms were measured with a laser doppler velocimeter and correlated with the far field jet noise microphone signal. Source distribution over slices of jet inferred therefrom are, unexpectedly, somewhat pear-shaped. Spectra predicted from measured cross-spectral densities are compatible with corresponding spectra extracted from far field intensities and with theory. Experimental studies of unorthodox concepts for shielding jet noise were carried out. Only modes attenuation of the park jet noise was found with a family of half-round sugar scoop shields e.g., 5-6 PNdB when scaled to a full size engine, owing largely to edge noise from jet interference. Another shielding concept involved extending the effective length of the sugar scoops by means of a hot refractive layer array of flames. Marginal increases in shielding were found. Keywords Jet aircraft noise Sonic boom Aeroacoustics Thunder Blast waves Noise reduction Canada.

Subject Categories:

  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE