Droplet impact on a miscible liquid film finds several applications in scientific and engineering problems. Here, we report that how pre-existing perturbations of a target liquid film, in the form of surface waves, change the impact dynamics and splashing phenomena. For this purpose, we release dyed water droplets and study droplet impact dynamics on a wavy water film, where the waves atop the liquid film are generated by imposing low-frequency two-dimensional (2D) lateral (horizontal) vibrations on glass substrates. Methylene blue-dyed droplet was employed to facilitate the observation of the details of mixing phenomenon given its importance in some applications such as casting homogeneous thin-film coatings. The results are compared with the impact on a quiescent/smooth liquid surface. Splashing is found to be more pronounced for the wavy surface given the additional energy imparted by vibrations and waves. An increase in the crown diameter is also observed for the vibrated wavy liquid film. It is observed that mixing is enhanced significantly in the presence of vibrations and surface waves. The interaction between the pre-existing surface waves and the waves formed after the droplet impact is also studied.

中文翻译：

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多轴横向振动下液滴对波浪形液膜的冲击

液滴对混溶液膜的影响在科学和工程问题中具有多种应用。在这里，我们报告了目标液膜的预先存在的扰动，以表面波的形式，如何改变冲击动力学和飞溅现象。为此，我们释放染色的水滴并研究波浪状水膜上的水滴撞击动力学，其中液膜顶部的波是通过在玻璃基板上施加低频二维 (2D) 横向（水平）振动来产生的。考虑到混合现象在某些应用（例如铸造均匀薄膜涂层）中的重要性，使用亚甲蓝染色液滴来促进观察混合现象的细节。将结果与对静止/光滑液体表面的影响进行比较。考虑到振动和波浪赋予的额外能量，波浪表面的飞溅更为明显。对于振动的波浪形液膜，也观察到冠部直径的增加。观察到在存在振动和表面波的情况下混合显着增强。还研究了预先存在的表面波与液滴撞击后形成的波之间的相互作用。