Air film stability underneath a drop is crucial for drop contact dynamics upon impact. An unstable film leads to the drop contacting the surface and subsequent spreading or splashing. Apart from previously reported film and kink contact modes, here we present the experimental evidence for a dimple failure mode of an air film, driven by a thin film instability when a drop impacts onto an atomically smooth surface. The dimple failure occurs beyond the inertial-capillary timescale and is initiated when the dimple inverts at the drop's central axis. For the same impact Weber number, the dimple failure observed in low-viscosity drops is absent at a higher viscosity, due to damping of capillary waves.

中文翻译：

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薄膜不稳定性驱动的凹坑模式，在跌落在光滑表面上的过程中导致气膜失效

跌落下的气膜稳定性对于撞击后的跌落接触动力学至关重要。不稳定的薄膜会导致液滴接触表面并随后扩散或飞溅。除了先前报道的薄膜和扭结接触模式之外，在这里，我们还提供了空气膜的酒窝破坏模式的实验证据，该液滴模式由液滴撞击原子光滑表面时的薄膜不稳定性驱动。酒窝失效发生在惯性毛细管时间范围之外，并在酒窝在液滴的中心轴上反转时引发。对于相同的冲击韦伯数，由于毛细管波的阻尼，在较高粘度下不存在在低粘度液滴中观察到的酒窝破坏。