Propeller Acoustics Research (Isolated Airfoil Noise).
Final rept. 1 Oct 71-30 Jun 75,
AIR FORCE AERO PROPULSION LAB WRIGHT-PATTERSON AFB OHIO
Pagination or Media Count:
This report describes the development of a quiet, free jet wind tunnel for aero-acoustic research on isolated airfoils. Analytical expressions are developed for boundary layer noise, noise due to upstream turbulence, and shed vortex noise. Preliminary experimental tests were conducted to determine airfoil noise levels due to upstream turbulence and shed vortices. The results are in good agreement with the analytical predictions. Pure tone components are present in the acoustic spectra, verifying the findings of recent investigators. The theories of Tam and Fink are briefly reviewed. Tone frequencies determined during the preliminary tests agree well with the prediction model of Fink. The report presents a brief technical plan outlining additional research required. The objectives of the recommended program are to clearly define both the broadband and pure tone mechanisms of isolated airfoil noise, to define the effects of rotation on these mechanisms through static model propeller testing and finally to assess the effects of forward flight through quiet wind tunnel testing. Author
- Fluid Mechanics