Silencing performance and aeroacoustic-structural responese of flexible panel silencer

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Silencing performance and aeroacoustic-structural responese of flexible panel silencer

 

Author: Li, Ka Hin
Title: Silencing performance and aeroacoustic-structural responese of flexible panel silencer
Degree: M.Sc.
Year: 2015
Subject: Noise control.
Acoustical engineering.
Vibration.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Mechanical Engineering
Pages: xii, 69 leaves : illustrations (some color) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2819455
URI: http://theses.lib.polyu.edu.hk/handle/200/8207
Abstract: Flexible panel installation in rigid ducts is proposed for attenuating duct noise. When there is a wave propagating in a flexible duct segment, panels respond by vibrating. The vibration further generates acoustic waves thereby altering the original pressure field in the duct. This phenomenon is utilized to control duct noise. The mechanism involves coupling between flow dynamics, acoustics and panel structural dynamics, which three factors are inter-related to each other. This study aims to find the panel responses and the following aeroacoustic responses, which contributes to different silencing performance.Simulation is conducted in a two-dimensional rigid duct with two flush-mounted flexible panels installed opposite each other. Simulation is carried out by a time domain methodology. The study is divided into two parts: one is the simulation on the duct with a monotonic acoustic source in the inlet. Six panel lengths are investigated in the absence of mean flow and at subsonic mean flow speed. The second is a simulation in a duct with a specific panel length. The investigation is carried under four different mean flow speeds.In the first part, two types of panel responses and following acoustic response leading to good and poor silencing effect are contrasted.The effect of mean flow on the panel flexural waves is investigated. In the second part, the silencing effect by frequency is found. The panel vibration characteristics are discussed by the modal velocity amplitude and the flexural wave characteristics according to their frequency and wavenumber. The acoustic responses are illustrated by the amplitude and phase responses of the downstream propagating re-radiated wave.

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