Use of cross-correlation measurements to investigate noise generating regions of a real jet engine and a model jetCross-correlations are reported of the jet static pressure fluctuations (as measured with a B and K microphone fitted with a nose cone), with the far-field radiated sound pressure. These measurements were made for various probe positions and a large number of far-field positions (at various angles). In addition, the tests were run for a number of different jet exit velocities. The measured, normalized cross-correlation functions vary between 0.004 and 0.155. These values depend upon the angular position of the far-field microphone, the jet exit Mach number, and the position of the probe. In addition, the cross-correlation technique was employed to study the symmetry of the far-field radiated sound about the jet axis. Third-octave analyses of both the probe signal and the far-field radiated sound were made. This is the first time correlation measurements have been made on a jet engine. In addition, a report is given on an extensive noise survey of a model jet. The correlations are related to sound source functions and jet source regions are discussed.
Document ID
19740014537
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Meecham, W. C. (California Univ. Los Angeles, CA, United States)
Hurdle, P. M. (California Univ. Los Angeles, CA, United States)