Drop impact on cylindrical substrates is more common than on flat substrates in many natural and engineering settings. Quantifying the transient impact force in drop-cylinder collisions is, therefore, crucial for understanding drop dynamics on curved substrates and for applications, such as icing mitigation, heat-transfer enhancement, and erosion reduction. Here, we experimentally investigate the transient impact force and morphological evolution of water drops impacting superhydrophobic cylinders, using a piezoelectric force sensor synchronized with high-speed imaging. The cylinder diameter ranges from 2 mm, which is comparable to the drop diameter of 2.05 mm, up to the flat-surface limit, while the Weber number varies from 4.5 to 102.2. Our results show that, on both flat and cylindrical superhydrophobic substrates, the impact force exhibits two distinct peaks. For the first peak, we find that at low Weber numbers the dynamics are governed by the combined effects of inertia and surface tension, while the influence of curvature remains weak. As the Weber number increases, the dependence of the first peak on curvature becomes increasingly pronounced. Based on the scaling analysis, we establish a quantitative relationship between the normalized first peak and the ratio of cylinder diameter to drop diameter. In contrast, the second peak is highly sensitive to curvature at low Weber numbers. The singular Worthington jet that forms on flat surfaces and cylinders with large diameter is suppressed on cylinders with small diameter due to the strongly asymmetric interfacial evolution. Consequently, the second peak decreases significantly as the cylinder diameter is reduced.
Chen et al. (Sun,) studied this question.