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On the Relevance of Convection Effects for a Laser-Generated Sound Source

Rossignol, Karl-Stéphane and Delfs, Jan Werner and Boden, Fritz (2015) On the Relevance of Convection Effects for a Laser-Generated Sound Source. 21st AIAA/CEAS Aeroacoustics Conference, Dallas, USA.

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Abstract

A laser-generated sound source is used to generate a nearly omni-directional sound field. This sound field is investigated experimentally to reveal its characteristics as a function of the surrounding medium mean velocity. It is found that the sound source approximately has monopole character when generated in a stagnant medium. Increas- ing the surrounding flow velocity leads to a positive Doppler-shift combined with a convective amplification for an observer downstream of the source while the reverse is observed upstream of the source. The laser sound source behaves therefore as a convected point heat source in a uniform flow. A solution of the convected wave equa- tion for a moving point heat source in a uniform subsonic flow is derived, providing a closed-form description of the source and appropriate scaling parameters for exper- imental results. The derived theoretical model enables the determination of the heat release function resulting from the laser energy deposition in the medium and associ- ated to the measured far-field pressure pulses. An implementation of the heat release function in CAA codes is straigthforward, making numerical replication of shielding tests with the laser sound source possible.

Item URL in elib:https://elib.dlr.de/100145/
Document Type:Conference or Workshop Item (Speech)
Title:On the Relevance of Convection Effects for a Laser-Generated Sound Source
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Rossignol, Karl-Stéphanekarl-stephane.rossignol (at) dlr.deUNSPECIFIED
Delfs, Jan Wernerjan.delfs (at) dlr.deUNSPECIFIED
Boden, Fritzfritz.boden (at) dlr.deUNSPECIFIED
Date:2015
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:Aeroacoustic, Sound source, Laser, Noise Shielding, Wind tunnel testing
Event Title:21st AIAA/CEAS Aeroacoustics Conference
Event Location:Dallas, USA
Event Type:international Conference
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Flight Physics
Location: Braunschweig , Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Technical Acoustics
Institute of Aerodynamics and Flow Technology > Experimental Methods
Deposited By: Rossignol, Karl-Stephane
Deposited On:09 Dec 2015 13:46
Last Modified:10 May 2016 23:36

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