Aerodynamically Generated Sound and Subsonic Aerodynamics
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1979
- Accession Number
- ADA209920
Entities
People
- H. S. Ribner
Organizations
- University of Toronto