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Sound radiation from a high speed axial flow fan due to the inlet turbulence quadrupole interactionA formula is obtained for the total acoustic power spectra radiated out the front of the fan as a function of frequency. The formula involves the design parameters of the fan as well as the statistical properties of the incident turbulence. Numerical results are calculated for values of the parameters in the range of interest for quiet fans tested at the Lewis Research Center. As in the dipole analysis, when the turbulence correlation lengths become equal to the interblade spacing, the predicted spectra exhibit peaks around the blade passing frequency and its harmonics. There has recently been considerable conjecture about whether the stretching of turbulent eddies as they enter a stationary fan could result in the inlet turbulence being the dominant source of pure tones from nontranslating fans. The results of the current analysis show that, unless the turbulent eddies become quite elongated, this noise source contributes predominantly to the broadband spectrum.
Document ID
19740017421
Acquisition Source
Legacy CDMS
Document Type
Other - NASA Technical Note (TN)
Authors
Goldstein, M. E. (NASA Lewis Research Center Cleveland, OH, United States)
Rosenbaum, B. M. (NASA Lewis Research Center Cleveland, OH, United States)
Albers, L. U. (NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 3, 2013
Publication Date
June 1, 1974
Subject Category
Aerodynamics
Report/Patent Number
E-7741
NASA-TN-D-7667
Accession Number
74N25534
Funding Number(s)
PROJECT: RTOP 501-04
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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