Acoustics and Soft Matter

By measuring the speed and attenuation of sound in a bubbly liquid, we can characterize the bubbles present (air volume fraction, typical size). An acoustic method offers the advantage of being applicable in opaque media, and enables real-time monitoring.

Reference: “Time-Resolved Ultrasonic Spectroscopy for Bubbles”, Valentin Leroy, Anatoliy Strybulevych, Tomohisa Norisuye, AIChE Journal (2017)

Ultrasound allows real-time monitoring of the aeration of a lubricating oil entrained by a rotating pinion. It has been shown that the oil formulation has a significant impact on the quantity of bubbles entrained, but also on the size of these bubbles, which explains the differences in de-aeration times observed in previous studies.

Reference : “Detailed characterization of aeration in lubricating oils by an ultrasonic approach”, Che Zhan, A. Saint-Jalmes, M. Receveur, H. El Bahi, F. Rondelez, V. Leroy, Tribology International (2022).

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When a superhydrophobic surface is immersed, a layer of air just a few microns thick is trapped. We have studied the response of this very flattened bubble to acoustic pulses ranging from simple echoes to cavitation with increasing intensity.

Reference : “Acoustic responses of underwater superhydrophobic surfaces subjected to an intense pulse“, Adrien Bussonnière, Qingxia Chad Liu, Peichun Amy Tsai, JFM 2023

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Heterogeneous cavitation relies on micro/nanobubbles trapped in defects and called nuclei. Until now, these bubbles were supposed to appear when the surfaces were immersed, but thanks to the use of a succession of thousands of acoustic pulses, we have shown that these nuclei can also regenerate spontaneously within the liquid.

Reference : “Cavitation Nuclei Regeneration in a Water-Particle Suspension“, Adrien Bussonnière, Qingxia Liu, Peichun Amy Tsai, Phys. Rev. Lett. 2020

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The existence of highly stable sub-micron bubbles has been reported, whereas theory predicts dissolution in milliseconds. Experiments generally rely on the optical contrast between the nanobubbles and the liquid, which opens up the possibility that the nano-objects detected are not gaseous, but arise from solid or liquid contamination. We proposed to use an acoustic method, sensitive to mechanical contrast.

Reference: “Investigating the existence of nanobubbles with ultrasound“, V. Leroy and T. Norisuye, ChemPhysChem (2016)

Acoustic transmission through an ordered plane of bubbles passes through a minimum at a frequency above the individual bubble resonance frequency. A simple model shows that this shift is due to multiple scattering within the bubble layer.

Reference: “Transmission of ultrasound through a single layer of bubbles”, V. Leroy, A. Strybulevych, M.G. Scanlon, and J.H. Page, Eur. Phys. J. E (2009)

Using the preceding analytical model, we show that acoustic absorption can be optimized by judiciously choosing the pitch of the bubble array as a function of the viscosity of the host medium. This revisits the theme of anechoic tiles used in underwater acoustics.

Reference : “Superabsorption of acoustic waves with bubble metascreens”, Valentin Leroy, Anatoliy Strybulevych, Maxime Lanoy, Fabrice Lemoult, Arnaud Tourin, and John H. Page, Phys. Rev. B (2015)

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It has been shown that the sound absorption performance of solid foams can be improved by the presence of thin membranes.

Reference : “Acoustic absorption of solid foams with thin membranes”, C. Gaulon, J. Pierre, C. Derec, L. Jaouen, F.-X. Bécot, F. Chevillotte, F. Elias, W. Drenckhan, and V. Leroy, Applied Physics Letters (2018)

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Acoustic metamaterials sometimes have a negative effective density. We propose a simple model to understand the origin of this phenomenon.

Reference: “A toy model for the effective density of acoustic metamaterials”, Juliette Pierre, Valentin Leroy and Benjamin Dollet, Proceedings of the Royal Society A (2022)

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