NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Due to the lapse in federal government funding, NASA is not updating this website. We sincerely regret this inconvenience.

Back to Results
Directivity and trends of noise generated by a propeller in a wakeAn experimental study of the effects on far-field propeller noise of a pylon wake interaction was conducted with a scale model of a single-rotation propeller in a low-speed anechoic wind tunnel. A detailed mapping of the noise directivity was obtained at 10 test conditions covering a wide range of propeller power landings at several subsonic tip speeds. Two types of noise penalties were investigated-pulser and spacing. The pusher noise penalty is the difference in the average overall sound pressure level, OASPL, for pusher and tractor installations. (In a pusher installation, the propeller disk is downstream of a pylon or another aerodynamic surface.) The spacing noise penalty is the difference in the average OASPL for different distances between the pylon trailing edge and the propeller. The variations of these noise penalties with axial, or flyover, angle theta and circumferential angle phi are presented, and the trends in these noise penalties with tip Mach number and power loading are given for selected values of theta and phi. The circumferential directivity of the noise from a pusher installation showed that the addition noise due to the interaction of the pylon wake with the propeller had a broad peak over a wide range of circumferential angles approximately perpendicular to the pylon with a sharp minimum 90 deg. to the pylon for the majority of cases tested. The variation of the pusher noise penalty with theta had a minimum occurring near the propeller plane and maximum values of as much as 20 dB occurring toward the propeller axes. The magnitude of the pusher noise penalty generally decreased as propeller tip Mach number or power loading was increased.
Document ID
19860021869
Acquisition Source
Legacy CDMS
Document Type
Technical Publication (TP)
Authors
Block, P. J. W.
(NASA Langley Research Center Hampton, VA, United States)
Gentry, C. L., Jr.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 5, 2013
Publication Date
September 1, 1986
Subject Category
Acoustics
Report/Patent Number
L-16131
NASA-TP-2609
NAS 1.60:2609
Report Number: L-16131
Report Number: NASA-TP-2609
Report Number: NAS 1.60:2609
Accession Number
86N31341
Funding Number(s)
PROJECT: RTOP 535-03-11-02
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
No Preview Available