Fudge Ben D, Cimpeanu Radu, Antkowiak Arnaud, Castrejón-Pita J Rafael, Castrejón-Pita Alfonso A
Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, United Kingdom.
Mathematics Institute, University of Warwick, Coventry CV4 7AL, United Kingdom; Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom; Department of Mathematics, Imperial College London, London SW7 2AZ, United Kingdom.
J Colloid Interface Sci. 2023 Jul;641:585-594. doi: 10.1016/j.jcis.2023.03.040. Epub 2023 Mar 17.
Droplet impact onto liquid pools is a canonical scenario relevant to numerous natural phenomena and industrial processes. However, despite their ubiquity, multi-fluid systems with the drop and pool consisting of different liquids are far less well understood. Our hypothesis is that the post-impact dynamics greatly depends on the pool-to-droplet viscosity ratioμ/μ, which we explore over a range of six orders of magnitude using a combination of experiments and theoretical approaches (mathematical modelling and direct numerical simulation). Our findings indicate that in this scenario the splashing threshold and the composition of the ejecta sheet are controlled by the viscosity ratio. We uncover that increasing the pool viscosity decreases the splashing threshold for high viscosity pools (μ/μ≳35) when the splash comes from the droplet. By contrast, for low viscosity pools, the splash sheet comes from the pool and increasing the pool viscosity increases the splashing threshold. Surprisingly, there are conditions for which no splashing is observed under the conditions attainable in our laboratory. Furthermore, considering the interface velocity together with asymptotic arguments underlying the generation of the ejecta has allowed us to understand meaningful variations in the pressure during impact and rationalise the observed changes in the splashing threshold.
液滴撞击液池是一种与众多自然现象和工业过程相关的典型场景。然而，尽管它们无处不在，但由不同液体组成的液滴和液池的多流体系统却远未得到充分理解。我们的假设是，撞击后的动力学很大程度上取决于液池与液滴的粘度比μ/μ，我们使用实验和理论方法（数学建模和直接数值模拟）相结合的方式，在六个数量级的范围内对其进行了探索。我们的研究结果表明，在这种情况下，飞溅阈值和喷射薄片的组成由粘度比控制。我们发现，当飞溅来自液滴时，对于高粘度液池（μ/μ≳35），增加液池粘度会降低飞溅阈值。相比之下，对于低粘度液池，飞溅薄片来自液池，增加液池粘度会提高飞溅阈值。令人惊讶的是，在我们实验室可达到的条件下，存在未观察到飞溅的情况。此外，考虑界面速度以及喷射产生背后的渐近论据，使我们能够理解撞击过程中压力的有意义变化，并合理解释观察到的飞溅阈值变化。
