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A Noise Reduction Study on Flow-Permeable Trailing-Edges

Herr, Michaela (2007) A Noise Reduction Study on Flow-Permeable Trailing-Edges. In: CD Proceedings ODAS 2007. 8th ONERA-DLR Aerospace Symposium (ODAS), 2007-10-17 - 2007-10-19, Göttingen, Germany.



This paper summarizes the results of an experimental study on flow-permeable comb-type trailing-edges which have the potential to effectively reduce turbulent boundary-layer trailing-edge noise. Basic design rules are presented with respect to a future use of such devices as suitable add-on solutions for a wide range of technical applications. These are e.g. the high-lift devices of current passenger aircraft, the blades of cooling fans or wind turbines which represent strong trailing-edge noise radiators. The noise reduction potential of several trailing-edge modifications, applied on a flat plate and on a two-dimensional NACA0012-like airfoil, was measured by a directional microphone in the open-jet anechoic Aeroacoustic Wind Tunnel Braunschweig. Additional knowledge of the incident boundary-layer flow properties was gained by application of hot-wire anemometry and unsteady surface pressure measurements. Within the range of parameters tested so far, comb design optimization appears mainly determined by geometric details of the comb itself than being dependent on specifics of the incident flow. Comb devices show the same (velocity)^5-scaling behaviour of farfield trailing-edge noise intensity as solid edges, however, on a significantly reduced level (-2 to -10 dB), and based on a constant scaling length. A minimum device length (in the order of the turbulent boundary-layer thickness or more) and a narrow slit width (of about the viscous sublayer thickness) were identified as the major design requirements. Flexibility of the comb material was found beneficial, but not essential to achieve a noise reduction.

Item URL in elib:https://elib.dlr.de/52821/
Document Type:Conference or Workshop Item (Speech, Paper)
Title:A Noise Reduction Study on Flow-Permeable Trailing-Edges
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Date:October 2007
Journal or Publication Title:CD Proceedings ODAS 2007
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
EditorsEmailEditor's ORCID iD
Keywords:Trailing-Edge Noise, Noise Reduction, Trailing-Edge Brushes, Comb-Type Trailing-Edges, Slit Trailing-Edges. Flow-Permeable Edge-Modifications, Elliptic Mirror, Directional Microphone Measurements, Airframe Noise
Event Title:8th ONERA-DLR Aerospace Symposium (ODAS)
Event Location:Göttingen, Germany
Event Type:international Conference
Event Dates:2007-10-17 - 2007-10-19
HGF - Research field:Aeronautics, Space and Transport
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: Herr, Michaela
Deposited On:26 Mar 2009
Last Modified:31 Jul 2019 19:21

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