How Chevrons Decrease Broadband Jet Noise in Cruise.
Gutmark, Ephraim J. and Rask, Olaf R. and Michel, Ulf (2007) How Chevrons Decrease Broadband Jet Noise in Cruise. In: 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference) (AIAA-2007-3611). 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), AIAA Papers (AIAA-2007-3611), 2007-05-21 - 2007-05-23, Rome, Italy.
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Broadband shock noise is reduced because chevrons increase the shear-layer thickness between the flight stream and the jet. It is shown experimentally and with results of a theory of Michalke that this is directly related to a reduction of the axial variation of the pressure amplitudes in the mean flow field of the jet. Since broadband shock noise is the result of an interaction between the turbulence in a jet and the axial variation of the mean flow field the chevrons yield a reduced noise emission. The effects of chevrons on the sound emission from nozzles operating at underexpanded conditions are demonstrated with experimental results. In a cruise condition with a flight Mach number 0.85, the chevron nozzle yields a lower broadband shock noise. It is shown experimentally as well as with the theory of Michalke that chevrons reduce the shock cell spacing, which explains the higher frequencies for broadband shock noise.
|Document Type:||Conference or Workshop Item (Paper)|
|Title:||How Chevrons Decrease Broadband Jet Noise in Cruise.|
|Date:||21 May 2007|
|Journal or Publication Title:||13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference)|
|In ISI Web of Science:||No|
|Series Name:||AIAA Papers|
|Keywords:||Broadband shock noise, chevrons, nozzle serrations, supersonic jets, cabin noise reduction, shear layer thickness|
|Event Title:||13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), AIAA Papers (AIAA-2007-3611)|
|Event Location:||Rome, Italy|
|Event Type:||international Conference|
|Event Dates:||2007-05-21 - 2007-05-23|
|Organizer:||ASSOCIAZIONE ITALIANA DI AERONAUTICA E ASTRONAUTICA|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Aeronautics|
|HGF - Program Themes:||L VU - Air Traffic and Environment|
|DLR - Research area:||Aeronautics|
|DLR - Program:||L VU - Air Traffic and Environment|
|DLR - Research theme (Project):||L - Quiet Air Traffic (old)|
|Institutes and Institutions:||Institute of Propulsion Technology > Engine Acoustic|
|Deposited By:||Prof. Dr.-Ing. Ulf Michel|
|Deposited On:||21 Jun 2007|
|Last Modified:||27 Apr 2009 13:50|
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