Numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise

The sound generated by high speed trains can be exacerbated by the presence of trackside structures. Tunnels are the principal structures that have a strong influence on the noise produced by trains. A train entering a tunnel causes air to flow in and out of the tunnel portal, forming a monopole...

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Main Author: Zagadou, Franck
Language:en_US
Published: Boston University 2021
Subjects:
Online Access:https://hdl.handle.net/2144/42324
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spelling ndltd-bu.edu-oai-open.bu.edu-2144-423242021-03-30T05:01:47Z Numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise Zagadou, Franck Finite Difference method Helmholtz equation Aerospace and mechanical engineering The sound generated by high speed trains can be exacerbated by the presence of trackside structures. Tunnels are the principal structures that have a strong influence on the noise produced by trains. A train entering a tunnel causes air to flow in and out of the tunnel portal, forming a monopole source of low frequency sound ["infrasound"] whose wavelength is large compared to the tunnel diameter. For the compact case, when the tunnel diameter is small, incompressible flow theory can be used to compute the Green's function that determines the monopole sound. However, when the infrasound is "shielded" from the far field by a large "flange" at the tunnel portal, the problem of calculating the sound produced in the far field is more complex. In this case, the monopole contribution can be calculated in a first approximation in terms of a modified Compact Green's function, whose properties are determined by the value at the center of a. disk (modelling the flange) of a diffracted potential produced by a thin circular disk. In this thesis this potential is calculated numerically. The scattering of sound by a thin circular disk is investigated using the Finite Difference Method applied to the three dimensional Helmholtz equation subject to appropriate boundary conditions on the disk. The solution is also used to examine the unsteady force acting on the disk. 2021-03-26T17:50:16Z 2021-03-26T17:50:16Z 2002 Thesis/Dissertation https://hdl.handle.net/2144/42324 en_US This work is being made available in OpenBU by permission of its author, and is available for research purposes only. All rights are reserved to the author. Boston University
collection NDLTD
language en_US
sources NDLTD
topic Finite Difference method
Helmholtz equation
Aerospace and mechanical engineering
spellingShingle Finite Difference method
Helmholtz equation
Aerospace and mechanical engineering
Zagadou, Franck
Numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise
description The sound generated by high speed trains can be exacerbated by the presence of trackside structures. Tunnels are the principal structures that have a strong influence on the noise produced by trains. A train entering a tunnel causes air to flow in and out of the tunnel portal, forming a monopole source of low frequency sound ["infrasound"] whose wavelength is large compared to the tunnel diameter. For the compact case, when the tunnel diameter is small, incompressible flow theory can be used to compute the Green's function that determines the monopole sound. However, when the infrasound is "shielded" from the far field by a large "flange" at the tunnel portal, the problem of calculating the sound produced in the far field is more complex. In this case, the monopole contribution can be calculated in a first approximation in terms of a modified Compact Green's function, whose properties are determined by the value at the center of a. disk (modelling the flange) of a diffracted potential produced by a thin circular disk. In this thesis this potential is calculated numerically. The scattering of sound by a thin circular disk is investigated using the Finite Difference Method applied to the three dimensional Helmholtz equation subject to appropriate boundary conditions on the disk. The solution is also used to examine the unsteady force acting on the disk.
author Zagadou, Franck
author_facet Zagadou, Franck
author_sort Zagadou, Franck
title Numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise
title_short Numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise
title_full Numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise
title_fullStr Numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise
title_full_unstemmed Numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise
title_sort numerical analysis of acoustic scattering by a thin circular disk, with application to train-tunnel interaction noise
publisher Boston University
publishDate 2021
url https://hdl.handle.net/2144/42324
work_keys_str_mv AT zagadoufranck numericalanalysisofacousticscatteringbyathincirculardiskwithapplicationtotraintunnelinteractionnoise
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