Gorin Benjamin, Di Mauro Gabrielle, Bonn Daniel, Kellay Hamid
Van der Waals Zeeman Institute, University of Amsterdam,1018 XE Amsterdam, The Netherlands.
Laboratoire Ondes et Matière d'Aquitaine, Université de Bordeaux, 33400 Talence, France.
Langmuir. 2022 Mar 1;38(8):2608-2613. doi: 10.1021/acs.langmuir.1c03288. Epub 2022 Feb 18.
Droplet impacts are common in many applications such as coating, spraying, or printing; understanding how droplets spread after impact is thus of utmost importance. Such impacts may occur with different velocities on a variety of substrates. The fluids may also be non-Newtonian and thus possess different rheological properties. How the different properties such as surface roughness and wettability, droplet viscosity, and rheology as well as interfacial properties affect the spreading dynamics of the droplets and the eventual drop size after impact are unresolved questions. Most recent work focuses on the maximum spreading diameter after impact and uses scaling laws to predict this. In this paper, we show that a proper rescaling of the spreading dynamics with the maximum radius attained by the drop and the impact velocity leads to a unique single and thus universal curve for the variation of diameter versus time. The validity of this universal functional shape is validated for different liquids with different rheological properties as well as substrates with different wettabilities. This universal function agrees with a recent model that proposes a closed set of differential equations for the spreading dynamics of droplets.
液滴撞击在许多应用中都很常见，如涂层、喷涂或印刷；因此，了解液滴撞击后如何扩散至关重要。这种撞击可能以不同速度发生在各种基材上。流体也可能是非牛顿流体，因此具有不同的流变特性。诸如表面粗糙度和润湿性、液滴粘度、流变学以及界面特性等不同特性如何影响液滴的扩散动力学以及撞击后的最终液滴尺寸，仍是未解决的问题。最近的研究工作主要集中在撞击后的最大扩散直径，并使用标度律来预测这一数值。在本文中，我们表明，用液滴达到的最大半径和撞击速度对扩散动力学进行适当的重新标度，会得到一条独特的单一且通用的曲线，用于表示直径随时间的变化。对于具有不同流变特性的不同液体以及具有不同润湿性的基材，这种通用函数形状的有效性得到了验证。这个通用函数与最近一个为液滴扩散动力学提出一组封闭微分方程的模型一致。
