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Nonspherical dynamics and microstreaming of a wall-attached microbubble
Published online by Cambridge University Press: 31 January 2022
Abstract
Acoustic microstreaming is a nonlinear response of a fluid that undergoes high-amplitude acoustic stimulation and tends to viscously absorb it. The present experimental study investigates the generation of acoustic microstreaming induced by an oscillating wall-attached bubble undergoing nonspherical shape modes. From a microscope top view, the formation of particular flow signatures is explored for the main classes of spherical harmonics $Y_{nm}(\theta, \phi )$: zonal ($m = 0 < n$), sectoral ($n = m > 0$) and tesseral ($0 < m < n$) oscillation. The microstreaming induced by a bubble animated by a sectoral mode alone reveals a pattern characterized by a $4n$-lobe flower shape. Tesseral modes give rise to 4m-lobe flower-shaped patterns. Finally, when sectoral and zonal modes coexist, two kinds of pattern stand out: $2n$-lobe flower shape and $n$-pointed star shape. The preferential emergence of one or another streaming pattern is discussed on the basis of the amplitude and phase shift between both shape modes.
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References
REFERENCES
Fauconnier et al. supplementary movie 1
High frame rate top-view visualization of the dynamics of a bubble animated by a zonal mode of degree n=4. Recording frame rate: 67065 images/s. Visualization frame rate: 20 images/s.
Fauconnier et al. supplementary movie 2
Low frame rate top-view visualization of the microstreaming induced by a bubble animated by a zonal mode of degree n=4. Recording frame rate: 2000 images/s. Visualization frame rate: 20 images/s.
Fauconnier et al. supplementary movie 3
High frame rate top-view visualization of the dynamics of a bubble animated by a sectoral mode of degree n=4. Recording frame rate: 67065 images/s. Visualization frame rate: 20 images/s.
Fauconnier et al. supplementary movie 4
Low frame rate top-view visualization of the microstreaming induced by a bubble animated by a sectoral mode of degree n=4. Recording frame rate: 2000 images/s. Visualization frame rate: 20 images/s.
Fauconnier et al. supplementary movie 5
High frame rate top-view visualization of the dynamics of a bubble animated by a tesseral mode of order m=1. Recording frame rate: 67065 images/s. Visualization frame rate: 20 images/s.
Fauconnier et al. supplementary movie 6
Low frame rate top-view visualization of the microstreaming induced by a bubble animated by a tesseral mode of order m=1. Recording frame rate: 2000 images/s. Visualization frame rate: 20 images/s.
Fauconnier et al. supplementary movie 7
High frame rate top-view visualization of the dynamics of a bubble simultaneously animated by a zonal and a sectoral mode of degree n=3. Recording frame rate: 67065 images/s. Visualization frame rate: 20 images/s.
Fauconnier et al. supplementary movie 8
Low frame rate top-view visualization of the microstreaming induced by a bubble simultaneously animated by a zonal and a sectoral mode of degree n=3. Recording frame rate: 2000 images/s. Visualization frame rate: 20 images/s.
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