Kooij Stefan, Astefanei Alina, Corthals Garry L, Bonn Daniel
Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, Amsterdam, 1098 XH, The Netherlands.
Van t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, Amsterdam, 1098 XH, The Netherlands.
Sci Rep. 2019 Apr 16;9(1):6128. doi: 10.1038/s41598-019-42599-8.
In many applications where small, similar-sized droplets are needed, ultrasonic nebulizers are employed. Little is known about the mechanism of nebulization, for example about what determines the median droplet size. Even less understood, is the droplet size distribution, which is often simply fitted with a log-normal distribution or assumed to be very narrow. We perform the first systematic study of droplet size distributions for different nebulizer technologies, showing that these distributions can be very well fitted with distributions found for sprays, where the size distribution is completely determined by the corrugation of ligaments and the distribution of ligament sizes. In our case, breakup is believed to be due to pinch-off of Faraday instabilities. The droplet size distribution is then set by the distribution of wavelengths of the standing capillary waves and the roughness of the pinch-off ligaments. We show that different nebulizer technologies produce different size distributions, which we relate to (variation in) wavelengths of the waves that contribute to the droplet formation. We further show that the median droplet size scales with the capillary wavelength, with a proportionality constant that depends only slightly on the type of nebulizer, despite order-of-magnitude differences in other parameters.
在许多需要小尺寸、大小相似液滴的应用中，会使用超声雾化器。关于雾化机制，例如什么决定了液滴的中位尺寸，人们了解甚少。对于液滴尺寸分布更是知之甚少，其通常只是简单地拟合为对数正态分布，或者被假定为非常窄。我们首次对不同雾化器技术的液滴尺寸分布进行了系统研究，结果表明这些分布可以很好地拟合喷雾的分布，在喷雾中，尺寸分布完全由韧带的波纹和韧带尺寸的分布决定。在我们的案例中，破裂被认为是由于法拉第不稳定性的夹断。然后，液滴尺寸分布由驻波毛细波的波长分布和夹断韧带的粗糙度决定。我们表明，不同的雾化器技术会产生不同的尺寸分布，我们将其与促成液滴形成的波的（变化的）波长联系起来。我们进一步表明，液滴的中位尺寸与毛细波长成比例，比例常数仅略微依赖于雾化器的类型，尽管其他参数存在数量级差异。
