Date of Award

Spring 2007

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Aerospace Engineering

Committee Director

Osama Kandil

Committee Member

Oktay Baysal

Committee Member

Brett Newman

Call Number for Print

Special Collections; LD4331.E535 H55 2007

Abstract

The transonic aerodynamic and low-speed acoustic characteristics of an advanced, Over-the-Wing Nacelle (OWN), subsonic transport configuration are assessed. The cruise aerodynamics of the OWN were analyzed using both inviscid Euler and viscous Navier-Stokes CFD. Results of the assessments are compared to a similar configuration with a more traditional Under-the-Wing Nacelle (UWN) installation and a similar reference Wing-Body Qualitative observations and quantitative drag computations are made for the three configurations at a cruise Mach number of0.78, an approximate altitude of35,000-ft, and a CL, of 0.44. It was found that the OWN's novel inboard wing channel design is effective in producing favorable leading-edge suction but that the overall drag, compared to the UWN, is higher by 32 counts (1 count= 0.0001 CD), which amounts to 9.6% lower LID. Possible sources of this drag excess are examined. CFD solutions were also obtained for several transonic Mach numbers to assess the drag rise characteristics of the three configurations. Results showed that the OWN experiences a much milder drag rise than the UWN.

It was also desired to assess the OWN's capability to shield engine exhaust noise with its wing. Computer codes were written to calculate insertion loss of engine noise sources through the OWN's wing and reflection of engine noise sources off of the UWN's wing by using 2-D barrier diffraction and ray reflection methods. Results showed that sources close to the nozzle exit experienced significant attenuation on the OWN and modest amplification on the UWN. A community noise study was then performed that used the shielding and reflection data. An aircraft noise model was constructed using NASA's Aircraft Noise Prediction Program. Source noise levels were predicted and ground noise levels were computed. Results showed that the total aircraft cumulative noise reduction of the OWN, compared with the UWN, was 6.1-EPNdB over the cutback and approach FAR-36 noise certification points. Sound Exposure Levels were also computed for the configurations along a line of ground observers underneath the flight track. Results showed modest noise reductions for the OWN compared to the UWN.

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DOI

10.25777/pw3z-yp68

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