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NEW ACOUSTIC AND AERODYNAMIC PHENOMENA DUE TO NON-UNIFORM ROTATION OF PROPELLERS

Yin, Jianping and Ahmed, Syed R. and Dobrzynski, Werner (1999) NEW ACOUSTIC AND AERODYNAMIC PHENOMENA DUE TO NON-UNIFORM ROTATION OF PROPELLERS. Journal of Sound and Vibration, 225 (1), pp. 171-187. ISSN 0022-460x

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Abstract

A study is reported of the influence of non-uniform rotation--which is inherent to piston engine driven propellers--on the aerodynamics and aeroacoustics of multi-blade propellers by numerical simulation. The combination of aerodynamic predictions with a 3-D unsteady free wake panel method and aeroacoustic predictions based on Farassat's Formulation 1A of the Ffowcs Williams and Hawkings equation is used to achieve this goal. The numerical results show that non-uniform rotation has a significant influence on propeller aerodynamics and can lead to an increase in the generated noise. In case of a mismatch between the periodicity of the non-uniformity and the basic blade passage frequency, additional harmonics ("subharmonics'') are generated. For a periodicity coincidence, the effects are masked due to an overlapping of the frequencies. The level of such subharmonics may be high enough to increase the overall A-weighted noise. The azimuthal directivity of the of the propeller noise remains no longer axisymmetric, and changes to a wave-like harmonic variation. The number of undulations per revolution depends on the order of the non-uniformity and is not related to the number of propeller blades. The polar directivity pattern also changes substantially from that known for uniform rotation. A frequency domain analysis of the unsteady pressure distribution shows that the subharmonics perceived at space-fixed location are not due to an aerodynamic or acoustic interaction but rather the consequence of a motion geometry or Doppler effect.

Item URL in elib:https://elib.dlr.de/19958/
Document Type:Article
Title:NEW ACOUSTIC AND AERODYNAMIC PHENOMENA DUE TO NON-UNIFORM ROTATION OF PROPELLERS
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Yin, JianpingUNSPECIFIEDUNSPECIFIED
Ahmed, Syed R.UNSPECIFIEDUNSPECIFIED
Dobrzynski, WernerUNSPECIFIEDUNSPECIFIED
Date:1999
Journal or Publication Title:Journal of Sound and Vibration
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:Yes
Volume:225
Page Range:pp. 171-187
ISSN:0022-460x
Status:Published
Keywords:Unsteady panel method, aerodynamics of propellers, non-uniform rotation, pressure time history, acoustic spectrum
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:L VU - Air Traffic and Environment (old)
DLR - Research area:Aeronautics
DLR - Program:L VU - Air Traffic and Environment
DLR - Research theme (Project):L - Quiet Air Traffic (old)
Location: Braunschweig
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Technical Acoustics
Deposited By: Yin, Dr.-Ing. Jianping
Deposited On:05 Dec 2005
Last Modified:27 Apr 2009 04:44

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