Oscillations couplées de microbulles sous champ ultrasonore et conséquences hydrodynamiques

Abstract : The pulsation properties of air bubbles under ultrasound have received much attention since the development of sonoporation and contrast agents. Spherical bubbles are well known to induce streaming when excited by ultrasound.We report in this manuscript the acoustic vibration of microbubbles confined between the two walls of a microfluidic channel. These bubbles exhibit a volumetric pulsation at low intensities of ultrasound, superimposed with a parametric surface mode for higher intensities of the pressure field. Because the channel walls are elastic, the bubble pulsation leads to the generation of Rayleigh waves at the channel wall interface. The bubble coupling induced by these surface waves has hydrodynamic consequences. In fact, a neighbouring bubble will create a translation mode of the bubble, in addition to its volumetric pulsation. It gives rise to a long-range mixed-mode streaming. The Rayleigh waves lead also to a self-organization of the bubbles in a network. In order to study the collective effects of these bubble networks in a controlled manner, bubble positions were fixed by capillarity on micropits. Conditions for an amplification or a synchronization of the bubble pulsations are sought in order to develop new bubble metamaterials.
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Flore Mekki-Berrada. Oscillations couplées de microbulles sous champ ultrasonore et conséquences hydrodynamiques. Dynamique des Fluides [physics.flu-dyn]. Université Grenoble Alpes, 2015. Français. ⟨NNT : 2015GREAY069⟩. ⟨tel-01458915⟩

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