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MS.Thesis.Mansoor.Mustafa.pdf (5.24 MB)
ETD Abstract Container
Abstract Header
Investigation into Offset Streams for Jet Noise Reduction
Author Info
Mustafa, Mansoor
Permalink:
http://rave.ohiolink.edu/etdc/view?acc_num=osu1437477139
Abstract Details
Year and Degree
2015, Master of Science, Ohio State University, Aero/Astro Engineering.
Abstract
This effort investigates the near field behavior of two ideally-expanded subsonic dual-stream jets. One case implements a traditional symmetric, concentric dual-stream nozzle configuration while the other imposes an asymmetric, eccentric layout to model the behavior of an offset stream. The essence of an offset stream is to force an uneven azimuthal distribution of the secondary coflow and create an outside stream that varies in thickness. Past studies have shown a benefit in acoustic propagation in the direction of the thickest coflow and the present work further analyzes this phenomenon. A LES (Large Eddy Simulation) approach is implemented to run the simulations for both cases and a number of qualitative and quantitative analyses tools are used for post-processing. A reduction in the noise levels for the lower, thicker side of the eccentric nozzle is observed in comparison to the baseline concentric case. Examination of the mean flow behavior shows a shorter, thinner primary potential core for the offset case and a faster axial velocity decay rate. The asymmetric distribution of the coflow causes varying velocity profiles in the radial direction for the top and bottom regions and consequently produces unique flow features on either side. Lower levels of shear stress and slower decay rates lead to less turbulence production on the lower side of the eccentric nozzle. An investigation into the flow structures reveals lower vorticity and weaker convective structures on the bottom which influences propagation in that direction. Two-point correlation analysis reveals the presence of smaller turbulence scales in the lower, thicker portion of the eccentric case. This is further confirmed by an Empirical Mode Decomposition (EMD) study that shows lower frequency ranges dominate the concentric near field in comparison to the eccentric. The combination of these unique features demonstrate the principles behind the acoustic benefit of implementing offset stream flows in dual-stream nozzle configurations.
Committee
Datta Gaitonde (Advisor)
Mei Zhuang (Committee Member)
Subject Headings
Aerospace Engineering
Keywords
offset
;
noise reduction
;
jets
;
aerospace
;
aerodynamics
;
LES
;
computational simulation
;
jet noise
;
eccentric
;
concentric
;
dual-stream
;
nozzle
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Citations
Mustafa, M. (2015).
Investigation into Offset Streams for Jet Noise Reduction
[Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437477139
APA Style (7th edition)
Mustafa, Mansoor.
Investigation into Offset Streams for Jet Noise Reduction.
2015. Ohio State University, Master's thesis.
OhioLINK Electronic Theses and Dissertations Center
, http://rave.ohiolink.edu/etdc/view?acc_num=osu1437477139.
MLA Style (8th edition)
Mustafa, Mansoor. "Investigation into Offset Streams for Jet Noise Reduction." Master's thesis, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437477139
Chicago Manual of Style (17th edition)
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Document number:
osu1437477139
Download Count:
2,305
Copyright Info
© 2015, some rights reserved.
Investigation into Offset Streams for Jet Noise Reduction by Mansoor Mustafa is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.