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Bulles d'air dans l'eau : couplage d'oscillateurs harmoniques et excitation paramétrique

Abstract : A gas bubble in a liquid is a major acoustic source. For example, air bubbles created by the swirls of a river are responsible for the characteristic sound of these flows. In 1933, Minnaert proposed a simple harmonic oscillator model to describe the oscillations of an air bubble in water. The first part of this work is devoted to the study of this particular oscillator, which can be seen as a water mass fastened on an air spring, and to the coupling between several of such oscillators. We present an original experimental device allowing to catch one or several bubbles, with a net, in order to study this system response to an acoustic excitation. The originality of our theoretical approach consists in considering the cloud of N bubbles as a system of coupled harmonic oscillators with N degrees of freedom, what amounts to neglect the degrees of freedom associated with water compressibility. This model properly accounts for the main observations: resonance peaks at low frequencies and strong attenuation for higher frequencies. The extension of the model to the case of propagation in an infinite medium is also presented. In the second part, the study of bubble parametric excitation is tackled. We develop an original formalism, based on Glauber variables, convenient to study the non-linear behavior of an oscillator. A parenthesis on a model system (two coupled pendula) permits to validate experimentally this formalism. Finally, we show that with the parametric excitation of a bubble one can obtain a phase conjugation phenomenon. This mechanism could be turned to account to realize bubbles echoes, in a way similar to spins echoes used in MRI.
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https://tel.archives-ouvertes.fr/tel-00007437
Contributor : Valentin Leroy <>
Submitted on : Wednesday, November 17, 2004 - 11:43:22 AM
Last modification on : Wednesday, December 9, 2020 - 3:11:55 PM
Long-term archiving on: : Friday, April 2, 2010 - 9:06:33 PM

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  • HAL Id : tel-00007437, version 1

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Valentin Leroy. Bulles d'air dans l'eau : couplage d'oscillateurs harmoniques et excitation paramétrique. Acoustique [physics.class-ph]. Université Paris-Diderot - Paris VII, 2004. Français. ⟨tel-00007437⟩

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