Periodic jetting and monodisperse jet drops from oblique gas injection
Periodic jetting and monodisperse jet drops from oblique gas injection
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倾斜气体注入产生的周期性喷射和单分散射流滴
DOI：
10.1103/physreve.96.013112
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发表时间：
2017
影响因子：
2.4
通讯作者：
Bird, James C.
中科院分区：
文献类型：
--
作者：
McRae, Oliver;Gaillard, Antoine;Bird, James C.
当空气在靠近气液界面的吸管或管中吹入时，通常会观察到两种行为之一：液体表面出现一个小凹痕，或者是疯狂的溅射气泡、波浪和喷雾。在这里，我们报告并描述了当受限空气射流以一定角度进入界面时可能产生的中间状态。这种状态是振荡的，具有明显的特征频率，可以形成周期性的角度射流，可以分解成单分散的气溶胶。造成这种高度周期性的潜在机制还没有被很好地理解。在这里，我们让一束连续的气体流过靠近液体表面的管子，在系统地调整各种参数时，从光学和声学上观察液-气界面的变形。我们证明开尔文-亥姆霍兹不稳定性是由气体形成的空腔内产生波的原因。惯性、重力和毛细力都能形成空腔，并控制这些气体诱导的空腔波的频率和振幅。扑动腔将波聚焦成一系列周期性喷流，这些喷流可以在瑞利高原不稳定后分解成液滴。我们提出了缩放论点来合理化驱动该系统的基频，以及约束周期制度的条件。这些频率和条件与我们的实验结果比较好。
When air is blown in a straw or tube near an air-liquid interface, typically one of two behaviors is observed: a dimple in the liquid's surface, or a frenzy of sputtering bubbles, waves, and spray. Here we report and characterize an intermediate regime that can develop when a confined air jet enters the interface at an angle. This regime is oscillatory with a distinct characteristic frequency and can develop periodic angled jets that can break up into monodisperse aerosols. The underlying mechanisms responsible for this highly periodic regime are not well understood. Here we flow a continuous stream of gas through a tube near a liquid surface, observing both optically and acoustically the deformation of the liquid-air interface as various parameters are systematically adjusted. We show that the Kelvin-Helmholtz instability is responsible for the inception of waves within a cavity formed by the gas. Inertia, gravity, and capillary forces both shape the cavity and govern the frequency and amplitude of these gas-induced cavity waves. The flapping cavity focuses the waves into a series of periodic jets that can break up into droplets following the Rayleigh-Plateau instability. We present scaling arguments to rationalize the fundamental frequencies driving this system, as well as the conditions that bound the periodic regime. These frequencies and conditions compare well with our experimental results.