Title page for ETD etd-12072005-113549


Type of Document Dissertation
Author Ravetta, Patricio A
URN etd-12072005-113549
Title LORE Approach for Phased Array Measurements and Noise Control of Landing Gears
Degree PhD
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Burdisso, Ricardo A. Committee Chair
Ng, Fai Committee Co-Chair
Johnson, Martin E. Committee Member
Khorrami, Mehdi Committee Member
Stoker, Robert Committee Member
Wicks, Alfred L. Committee Member
Keywords
  • Noise Control Devices
  • Aeroacoustics
  • Beamforming
  • Deconvolution
  • Phased Array
  • Landing Gear Noise
Date of Defense 2005-11-28
Availability unrestricted
Abstract
A novel concept in noise control devices for landing gears is presented. These devices consist of elastic membranes creating a fairing around the major noise sources. The purpose of these devices is to reduce wake interactions and to hide components from the flow, thus, reducing the noise emission. The design of these fairings was focused on the major noise sources identified in a 777 main landing gear. To find the major noise sources, an extensive noise source identification process was performed using phased arrays. To this end, phased array technologies were developed and a 26%-scale 777 main landing gear model was tested at the Virginia Tech Stability Wind Tunnel.

Since phased array technologies present some issues leading to misinterpretation of results and inaccuracy in determining actual levels, a new approach to the deconvolution of acoustic sources has been developed. The goal of this post-processing is to "simplify" the beamforming output by suppressing the sidelobes and reducing the sources mainlobe to a small number of points that accurately identify the noise sources position and their actual levels. To this end, the beamforming output is modeled as a superposition of "complex" point spread functions and a nonlinear system of equations is posted. Such system is solved using a new 2-step procedure. In the first step an approximated linear problem is solved, while in the second step an optimization is performed over the nonzero values obtained in the previous step. The solution to this system of equations renders the sources position and amplitude. The technique is called: noise source Localization and Optimization of Array Results (LORE). Numerical simulations as well as sample experimental results are shown for the proposed post-processing.

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