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An Investigation of the Sound Generated by an Axisymmetric Jet Interacting with a Diffuser
Final rept. 15 Nov 1979-15 Jan 1980
TENNESSEE UNIV SPACE INST TULLAHOMA
Pagination or Media Count:
A study of the sound generated by the interaction of an axisymmetric exhaust jet with a constant area circular diffuser has been carried out. The results of the investigation show that the acoustic field produced by the jet diffuser interaction is quite different from that generated by the jet alone. The variation of overall sound power with changes in the geometric and fluid dynamic parameters indicates a complex interplay between the sound sources, shielding, and acoustic feedback. For certain test configurations, intense discrete frequency tones occur that are, in many cases, 20 dB or more above the broad-band noise. The test results indicate that the smallest ratio of diffuser diameter to nozzle diameter tested D sub dD sub n 1.43 with the diffuser entrance located less than 0.5 nozzle diameters from the nozzle produced the lowest sound power for all velocities tested. Tests with two different-sized nozzles scale factor 2 indicate that standard acoustic scaling laws are adequate to extrapolate the results to full-scale conditions.
APPROVED FOR PUBLIC RELEASE