Naghavi Seyed Ataollah, Czerski Helen
Department of Mechanical Engineering, University College London, London, United Kingdom.
J Acoust Soc Am. 2018 Jun;143(6):3563. doi: 10.1121/1.5041260.
An antibubble is an unusual object: a submerged water drop encapsulated in a thin shell of air that is stable underwater for 10-100 s. They are often thought of as the inverse of a soap bubble because they are a spherical shell of air in water in contrast to a shell of water in air. Antibubbles may be formed when water droplets impact the surface of surfactant-covered water, within a limited range of drop radius and drop impact velocity. In this paper, the range of drop size and impact velocity over which large antibubbles (radius 1-3 mm) are generated by the impact of falling drops is characterised, and the relationship of these parameters to the size of the antibubble formed is shown. Measurements of the two acoustical signals that may be produced as an antibubble is formed by drop impact are reported, and their relationship to the antibubble radius and shell thickness is established. Acoustical measurements taken are interpreted in the context of a modified Rayleigh-Plesset equation that provides a good fit to the frequency data for air shells greater than 100 μm in thickness. However, these results highlight the need for future work on the damping mechanisms associated with these larger antibubbles.
一个被薄空气壳包裹的水下液滴，能在水下稳定存在10到100秒。它们常被认为是肥皂泡的对立面，因为与空气中的水壳相反，它们是水中的空气球壳。当水滴在有限的液滴半径和液滴撞击速度范围内撞击覆盖有表面活性剂的水面时，可能会形成反气泡。在本文中，表征了下落液滴撞击产生大反气泡（半径1 - 3毫米）时的液滴尺寸和撞击速度范围，并展示了这些参数与所形成反气泡尺寸的关系。报告了液滴撞击形成反气泡时可能产生的两种声学信号的测量结果，并建立了它们与反气泡半径和壳厚度的关系。所进行的声学测量结果在一个修正的瑞利 - 普列赛方程的背景下进行了解释，该方程能很好地拟合厚度大于100微米的空气壳的频率数据。然而，这些结果凸显了未来对与这些较大反气泡相关的阻尼机制开展研究的必要性。
