Fauconnier Maxime, Béra Jean-Christophe, Inserra Claude
LabTAU, INSERM, Centre Léon Bérard, Université Lyon, F-69003 Lyon, France.
Phys Rev E. 2020 Sep;102(3-1):033108. doi: 10.1103/PhysRevE.102.033108.
When excited at sufficiently high acoustic pressures, a wall-attached bubble may exhibit asymmetric nonspherical modes. These vibration modes can be decomposed over the set of spherical harmonics Y_{nm}(θ,ϕ) for a degree n and order m. We experimentally capture the time-resolved dynamics of asymmetric bubble oscillations in a top-view configuration. A spatiotemporal modal analysis is performed and allowed recovering the set of zonal (m=0), tesseral (0<m<n), and sectoral (m=n) spherical harmonics that develop at the bubble interface. The analysis of the surface instability thresholds reveals that the frequencies of asymmetric modes differ from the standard Lamb spectrum. In addition, the nondegeneracy of asymmetric modes for a given degree n is evidenced by noncompletely overlapping resonance bands. Finally, the coexistence between zonal and sectoral modes is analyzed through their modal interaction, amplitude interplay and relation of phase, as well as their geometric compatibility.
当在足够高的声压下激发时，附着在壁上的气泡可能会呈现非对称非球形模态。这些振动模态可以在度数为(n)、阶数为(m)的球谐函数(Y_{nm}(θ,ϕ))集合上进行分解。我们通过顶视图配置实验捕获了非对称气泡振荡随时间变化的动力学过程。进行了时空模态分析，并能够恢复在气泡界面处发展的带状（(m = 0)）、田字形（(0 < m < n)）和扇形（(m = n)）球谐函数集合。对表面不稳定性阈值的分析表明，非对称模态的频率不同于标准的兰姆谱。此外，给定度数(n)的非对称模态的非简并性通过不完全重叠的共振带得到证明。最后，通过带状模态和扇形模态之间的模态相互作用、振幅相互作用和相位关系以及它们的几何兼容性，分析了它们的共存情况。
