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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/313

Title: Thermoacoustically induced and acoustically driven flows and heat transfer in enclosures
Authors: Aktas, Murat K.
Keywords: Mechanical engineering;Acoustical engineering;Sound-waves
Issue Date: 14-Jun-2004
Abstract: In this study, the behavior of acoustic waves induced by thermal and mechanical effects and the interaction of these waves with flow fields and rigid walls were investigated. The study focuses on two important effects of the acoustic-fluid dynamic interactions. These effects are termed as ‘thermoacoustic convection’ and ‘acoustic streaming’ and are analyzed using computational and experimental techniques. The generation and the short-time behavior of thermoacoustic waves in compressible gas-filled two-dimensional enclosures were investigated first. The vertical walls of the enclosure were heated or cooled to generate the thermoacoustic waves. The numerical solutions were obtained by employing a flux corrected transport (FCT) algorithm for the Euler equations and by coupling these to the viscous and diffusive terms of the fully compressible form of Navier-Stokes equations. When a vertical wall temperature is rapidly changed, the resulting waves induce remarkable pressure-induced flows in the enclosure. The long time effects of the thermoacoustic wave motion on the developing natural convection were studied next. The strength of the pressure waves associated with the thermoacoustic effect and the resulting flow patterns were found to be strongly correlated to the rapidity of the wall heating process. The interactions of mechanically driven acoustic waves with in a viscous fluid were studied next. A standing wave field in a two-dimensional enclosure was created by the vibration of one side wall of the enclosure. The interaction of this wave field with the solid boundaries leads to the production of Schlichting (inner) and Rayleigh (outer) type acoustic streaming flow patterns in the enclosure. The effect of the enclosure height and the amount of maximum wall displacement for vibratory motion were studied primarily. These parameters play significant role in the characteristics of the resulting flow structures. It is found that the streaming patterns vary strongly with a change of the standing acoustic wave form from ‘harmonic wave profile’ to ‘sharp shock wave’ type profile. The formation of streaming in an air filled acoustic chamber was also investigated experimentally. The computationally predicted results demonstrate qualitative agreement with the measured pressure values and the visualized streaming flow structures in the experiments.
URI: http://dspace.library.drexel.edu/handle/1860/313
Appears in Collections:Drexel Theses and Dissertations

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