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Diffusion multiple résonante des ondes ultrasonores dans des milieux désordonnés

Abstract : Complex physical phenomena study, such as resonant multiple scattering of waves, requireswell calibrated model systems. During this study, we suggest the use of resonant emulsions tostudy ultrasonic waves transport in strongly resonant disordered media. Emulsions components(uorinated oil droplets in a water-based gel) were selected for both their weak absorptionand propensity to generate strong Mie-type resonances. Fluid kind of those systems allowsfurthermore in situ acoustic _eld probing.First, we theoretically describe acoustic waves propagation in resonant emulsions. Dropletsresonance modes are calculated just as multiple scattering of an acoustic wave by a disorderedpopulation of identical objects. Then, micro-uidic technics used to make such model systemsare described as well as acoustic devices designed for both coherent and incoherent waves characterization.For diluted emulsions, our experimental observations of both the ballistic propagation ofcoherent wave and di_usive transport of averaged intensity are well described by independentscattering approximations. Energy velocity estimation of multiple scattered waves allows thenan original link between pioneering works in optics and acoustics.Finally, when scatterers concentration increases, previous approximations fail. We thus observefurther complex phenomena, which arise from scatterers interactions, such as\sub-di_usive"transport of averaged intensity suggesting attractive prospects for Anderson localization study.
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Submitted on : Friday, December 22, 2017 - 4:15:07 PM
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  • HAL Id : tel-01671808, version 1

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Benoit Tallon. Diffusion multiple résonante des ondes ultrasonores dans des milieux désordonnés. Autre [cond-mat.other]. Université de Bordeaux, 2017. Français. ⟨NNT : 2017BORD0784⟩. ⟨tel-01671808⟩

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