Experimental aero-acoustic assessment of swirling flows for drag applications

The need for quiet drag technologies stems from stricter requirements for and growing demand of low-noise aircraft. The research presented in this thesis regards the use of swirling exhaust flows capable of generating pressure drag quietly by establishing a steady streamwise vortex. The simple concept of a so called swirl tube, a ducted set of stationary turning vanes, was implemented to experimentally assess the aerodynamic and aero-acoustic behavior of swirling flows. A modular design was chosen for the model-scale wind-tunnel test article based on a full-scale diameter of 1.2 m to allow for the wind-tunnel testing of different swirl angles, including both stable swirling configurations and cases exhibiting vortex breakdown. Analyses of both aerodynamic and aero-acoustic test results indicate that highly swirling stable flows obtain maximum drag coefficients greater than 0.8 +0.04 referenced to inlet area with full-scale overall sound pressure level (OASPL) of 42 dBA ±2 dBA, validating the working hypothesis that swirling flows can generate drag quietly. An advanced deconvolution approach for the mapping of acoustic sources (DAMAS), previously developed at the NASA Langley Research Center, was used to identify and to quantify quadrupole- and turbulent scattering-type noise sources in stable swirling flow cases, radiating from the downstream exhaust core and nacelle trailing edge regions, respectively.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Mobed, Darius Darayes

Advisor dc:contributor.advisor

• Zoltan S. Spakovszky.

• Aeronautics and Astronautics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/38650

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/38650