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A broadband method for liner impedance eduction in the presence of a mean flow

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URI: http://hdl.handle.net/2042/57722
Title: A broadband method for liner impedance eduction in the presence of a mean flow
Author: Troian, Renata; Dragna, Didier; Bailly, Christophe; Galland, Marie-Annick,
Abstract: In this study, a broadband impedance eduction method is developed to identify the surface impedance of acoustic liners, mounted in the walls of aircraft engine nacelles, from measurements on a test rig. A numerical model of an acoustic liner under a grazing flow is undertaken by considering finite-difference time-domain simulations and the Euler equations for the acoustic propagation. A broadband impedance model is used to prescribe time-domain boundary conditions. The impedance eduction procedure is established using an multiobjective optimization with the genetic algorithm NSGA-II. The pressure is measured at six positions in the duct for each considered frequency. The present methodology is validated by comparison with benchmark data provided by NASA.
Subject: impedance eduction; acoustic propagation; finite difference time domain modeling; broadband impedance model; multiobjective optimization
Publisher: AFM, Association Française de Mécanique
Date: 2015

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