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Noise Reduction and Flow Characteristics in Asymmetric Dual-Stream Jets

Shupe, Rebecca S. (2007) Noise Reduction and Flow Characteristics in Asymmetric Dual-Stream Jets. Masters thesis, University of California, Irvine. http://resolver.caltech.edu/CaltechAUTHORS:20091105-161716840

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Abstract

This research effort is motivated by the advent of asymmetric nozzle concepts for directional suppression of jet noise from turbofan engines. The specific method addressed is the fan flow deflection (FFD) technique, whereby aerodynamic devices deflect downward the fan stream of the turbofan exhaust and thus create an asymmetry in the plume of the jet exiting an otherwise coaxial nozzle. The asymmetry reduces jet noise emissions in downward and sideward directions affecting airport communities. Flow field and acoustic measurements were conducted to understand what flow quantities are affected by the departure from symmetry and how their changes impact noise emission. The experiments were complemented by computations that included the effect of forward flight. It is found that FFD reduces the radial gradients of mean velocity, the turbulent kinetic energy, and the Reynolds stress on the underside of the jet. A preliminary correlation between downward velocity gradient and downward sound emission indicates that velocity gradient reduction is an important ingredient for noise suppression using FFD. Further, a correlation between the maximum radial gradient of the axial velocity component and peak turbulent kinetic energy was obtained. In an additional related aspect of this work, the effect of baseline nozzle geometry on efficacy of methods that create jet asymmetry was studied. A phenomenological investigation between nozzles with parallel exit flow lines and converging exit flow lines was conducted. Jets with uniformly reduced radial gradients below the centerplane were found to be acoustically superior to jet plumes with focused or narrow gradient reduction.


Item Type:Thesis (Masters)
Additional Information:Portions of Chapters 3&5 © 2006 Dimitri Papamoschou All other materials © 2007 Rebecca Shupe Thesis Committee: Professor Dimitri Papamoschou, Chair Professor William A. Sirignano Professor Feng Liu
Funders:
Funding AgencyGrant Number
NASA Glenn Research CenterNAG-3-2345
NASA Graduate Student Researchers Program (GSRP) FellowshipUNSPECIFIED
Mechanical and Aerospace Engineering Departmental Fellowship (Graduate Assistance in Areas of National Need (GAANN) program)UNSPECIFIED
Record Number:CaltechAUTHORS:20091105-161716840
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20091105-161716840
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16596
Collection:CaltechAUTHORS
Deposited By: Rebecca Shupe
Deposited On:16 Nov 2009 20:58
Last Modified:26 Dec 2012 11:32

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