Due to its scientific significance and practical applications, the common natural phenomena of drops impacting on inclined surfaces have attracted extensive attention. Previous research has primarily reported the distinct morphology and dynamic behavior of drops impacting on inclined superhydrophobic surfaces compared to the impact on the horizontal scenarios. One distinguished feature of drop impingement on inclined surfaces is the asymmetric shapes of the drop, which accounts for different underlying physics compared to the impacts on horizontal surfaces. However, the impact forces exerted by the inclined surface during impingement have remained unknown. In this study, we present a direct measurement of the normal impact force of drops on inclined superhydrophobic surfaces using a high-precision force sensor. We observe the temporal evolution of the force and identify two peak forces occurring during the spreading and retraction stages, respectively. Our findings lie on investigating the variation of these two peak forces with the normal Weber number, based on scaling arguments. We reveal that the asymmetrical morphology of the drop must be taken into account especially in the scenarios of large impact velocities and large tilt angles to revise the theoretical model of the second peak force. The physics reported in this work sheds new light on the impingement of drops.

中文翻译：

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液滴落在倾斜的超疏水表面上的冲击力


由于其科学意义和实际应用，水滴撞击倾斜表面的常见自然现象引起了广泛关注。以前的研究主要报道了与对水平场景的影响相比，液滴撞击倾斜超疏水表面的独特形态和动态行为。液滴撞击倾斜表面的一个显著特征是液滴的不对称形状，与水平表面的冲击相比，这解释了不同的基本物理特性。然而，倾斜表面在撞击过程中施加的冲击力仍然未知。在这项研究中，我们提出了一种使用高精度力传感器直接测量液滴在倾斜的超疏水表面上的法向冲击力的方法。我们观察力的时间演变，并分别确定了在扩张和收缩阶段发生的两个峰值力。我们的发现在于基于缩放参数研究这两个峰值力与正常韦伯数的变化。我们揭示了必须考虑液滴的不对称形态，尤其是在大冲击速度和大倾斜角的情况下，以修正第二峰值力的理论模型。这项工作中报告的物理学为液滴的撞击提供了新的视角。