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Vibrations of and sound radiating from some periodic structures under convected loading

Vibrations of and sound radiating from some periodic structures under convected loading
Vibrations of and sound radiating from some periodic structures under convected loading
This thesis deals with the forced, vibrations of infinite periodically supported beams, orthogonally stiffened plates and ring stiffened cylindrical shells excited by random convected loadings. The sound power radiated under these conditions is also dealt with. The stiffened structures are represented by uniform beams, plates or shells on periodically spaced elastic supports which represent stiffener-skin interaction forces and moments. The available literature on the response of stiffened structures is first reviewed. A special infinite series of space harmonics is then evolved and employed to obtain the response of infinite stiffened beams, plates and cylindrical shells to spatial and temporal harmonic loadings. The coefficients of this series are determined by applying the principle of virtual work. The series is shown to be satisfactorily converging so that only a limited number of terms need be included for an actual solution of a reasonable accuracy. The method easily predicts and explains the sound radiation by structures excited by loadings convected at subsonic convection velocities. The terms in the series contributing to this radiation can be easily identified with the help of a simple diagram included in the thesis. The response to boundary layer pressure field has been obtained by analysing this field into a wave length frequency spectrum and then numerically integrating the response due to each wave length component. The low wave numbers in the spectrum are important for sound power radiated by the structure especially at subsonic convection velocities of loading. An experiment has been carried out to determine the sound power radiated by an orthogonally stiffened damped panel representative of aircraft construction under excitation by acoustic plane waves. A satisfactory agreement has been obtained between experimental and theoretical results.
University of Southampton
Pujara, K.K.
9e442185-d597-478e-b72c-d2dd7407e861
Pujara, K.K.
9e442185-d597-478e-b72c-d2dd7407e861
Mead, D.J.
40b88582-f349-4478-b0b2-c562ae425cfd

Pujara, K.K. (1970) Vibrations of and sound radiating from some periodic structures under convected loading. University of Southampton, Institute of Sound and Vibration Research, Doctoral Thesis, 259pp.

Record type: Thesis (Doctoral)

Abstract

This thesis deals with the forced, vibrations of infinite periodically supported beams, orthogonally stiffened plates and ring stiffened cylindrical shells excited by random convected loadings. The sound power radiated under these conditions is also dealt with. The stiffened structures are represented by uniform beams, plates or shells on periodically spaced elastic supports which represent stiffener-skin interaction forces and moments. The available literature on the response of stiffened structures is first reviewed. A special infinite series of space harmonics is then evolved and employed to obtain the response of infinite stiffened beams, plates and cylindrical shells to spatial and temporal harmonic loadings. The coefficients of this series are determined by applying the principle of virtual work. The series is shown to be satisfactorily converging so that only a limited number of terms need be included for an actual solution of a reasonable accuracy. The method easily predicts and explains the sound radiation by structures excited by loadings convected at subsonic convection velocities. The terms in the series contributing to this radiation can be easily identified with the help of a simple diagram included in the thesis. The response to boundary layer pressure field has been obtained by analysing this field into a wave length frequency spectrum and then numerically integrating the response due to each wave length component. The low wave numbers in the spectrum are important for sound power radiated by the structure especially at subsonic convection velocities of loading. An experiment has been carried out to determine the sound power radiated by an orthogonally stiffened damped panel representative of aircraft construction under excitation by acoustic plane waves. A satisfactory agreement has been obtained between experimental and theoretical results.

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Published date: 1970
Organisations: University of Southampton

Identifiers

Local EPrints ID: 52177
URI: http://eprints.soton.ac.uk/id/eprint/52177
PURE UUID: 3b7c6c1c-333c-43d1-a01d-531531d73fb5

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Date deposited: 26 Aug 2008
Last modified: 15 Mar 2024 10:26

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Contributors

Author: K.K. Pujara
Thesis advisor: D.J. Mead

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