Droplet impact hydrodynamics on “V”-shaped valleys or grooves of variant wettability and geometric dimensions have been studied experimentally and probed theoretically. The groove geometry makes the hydrodynamics three-dimensional, as in addition to the droplet dynamics in the lateral direction, liquid jets are generated from the post-impact droplet along the axial direction of the groove. The effect of the impact Weber number (We) on the jet velocity, the non-dimensional spreading width (γ), and north-pole height (h*) has been studied. It has been observed that the inertial forces dominate over the surface forces for higher impact We and hence, the effect of wettability is not important. However, the wettability of the substrate has a significant role in lower impact We as recoiling of the droplet is observed for the impact on the superhydrophobic substrate in this case. It has been observed that the spreading width of the post-impact droplet decreases with the increase in groove steepness. The jetting hydrodynamics has been probed and instantaneously after the impact, the generated jets travel at high velocity, but quickly reduce to a steady value. Jet velocity is observed to increase with an increase in the hydrophobicity of the substrate as well as the impact We. A semi-analytical formalism has been proposed to predict the jet velocity evolution in terms of governing Weber (We) and capillary (Ca) numbers. The predictions from the proposed model are in good agreement with the experimental results.

中文翻译：

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润湿调制谷配置中的液滴碰撞和射流演化水动力

已经对“ V”形谷或不同润湿性和几何尺寸的凹槽上的液滴冲击流体动力学进行了实验研究并从理论上进行了探讨。凹槽的几何形状使流体力学具有三维性，因为除了沿横向方向的液滴动力学以外，还从碰撞后的液滴沿凹槽的轴向生成了液体射流。研究了冲击韦伯数（We）对射流速度，无量纲扩展宽度（γ）和北极高度（h *）的影响。据观察惯性力支配的表面力较高影响我们因此，润湿性的影响并不重要。然而，基材的润湿性在较低的冲击We中具有重要作用。因为在这种情况下观察到液滴的回卷对超疏水基材的影响。已经观察到，碰撞后液滴的铺展宽度随着凹槽陡度的增加而减小。已探究了射流的水动力，在撞击后立即产生的射流以高速行进，但迅速减小到稳定值。观察到喷射速度随着基材的疏水性以及冲击We的增加而增加。已经提出了一种半分析形式主义，以控制Weber来预测射流速度的演变（我们）和毛细管（Ca）数。该模型的预测结果与实验结果吻合良好。