An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise from a High-Speed Propeller

An Experimental Investigation of the Effect of Boundary Layer Refraction on the Noise from a High-Speed Propeller
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Total Pages: 34
Release: 2018-08-16
Genre:
ISBN: 9781725626317

Models of supersonic propellers were previously tested for acoustics in the Lewis 8- by 6-Foot Wind Tunnel using pressure transducers mounted in the tunnel ceiling. The boundary layer on the tunnel ceiling is believed to refract some of the propeller noise away from the measurement transducers. Measurements were made on a plate installed in the wind tunnel which had a thinner boundary layer than the ceiling boundary layer. The plate was installed in two locations for comparison with tunnel ceiling noise data and with fuselage data taken on the NASA Dryden Jetstar airplane. Analysis of the data indicates that the refraction increases with: increasing boundary layer thickness; increasing free stream Mach number; increasing frequency; and decreasing sound radiation angle (toward the inlet axis). At aft radiation angles greater than about 100 deg there was little or no refraction. Comparisons with the airplane data indicated that not only is the boundary layer thickness important but also the shape of the velocity profile. Comparisons with an existing two-dimensional theory, using an idealized shear layer to approximate the boundary layer, showed that the theory and data had the same trends. Analysis of the data taken in the tunnel at two different distances from the propeller indicates a decay with distance in the wind tunnel at high Mach numbers but the decay at low Mach numbers is not as clear. Dittmar, J. H. and Burns, R. J. and Leciejewski, D. J. Glenn Research Center NASA-TM-83764, E-2257, NAS 1.15:83764 RTOP 535-03-12...

Scientific and Technical Aerospace Reports

Scientific and Technical Aerospace Reports
Author:
Publisher:
Total Pages: 456
Release: 1995
Genre: Aeronautics
ISBN:

Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Monthly Catalog of United States Government Publications

Monthly Catalog of United States Government Publications
Author: United States. Superintendent of Documents
Publisher:
Total Pages:
Release: 1985
Genre: Government publications
ISBN:

February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index

NASA SP.

NASA SP.
Author:
Publisher:
Total Pages: 138
Release: 1988
Genre: Aeronautics
ISBN: