Droplet impact on a spinning surface has been observed in different industries and plays an important role in the performance of industrial systems. In the current study, the dynamics of water droplet impact on a hydrophilic spinning disk is investigated. An experimental setup is designed in a way that droplet diameter, impact velocity, disk rotational speed, and location of impact are precisely controlled. While the droplet diameter is fixed in the present study, other mentioned parameters are changed and their effects on the droplet behavior are discussed. High-speed imaging is used to record the droplet dynamics under various operating conditions. It is demonstrated that after impact, droplet spreads on the surface due to a high adhesion between water and the hydrophilic substrate. It is indicated that the wetted area is a function of time, impact velocity, disk rotational speed, and centrifugal acceleration. Furthermore, depending on the mentioned parameters, different phenomena such as rivulet formation, fingering, and detachment of secondary droplet(s) are observed. In the angular direction, in general, the wetted length increases as time passes. However, in the radial direction, the droplet first spreads on the surface and reaches a maximum value, and then recedes until a plateau is attained. At this instant, a bulk of liquid, which is called wave in this study, moves radially outward from the inner boundary of the droplet toward its outer boundary due to the effect of centrifugal force. Once the wave reaches the outer boundary, depending on its size and momentum, fingers or rivulets are formed, and small droplet(s) may detach. The process is analyzed comprehensively, and different empirical correlations for wetted lengths in radial and angular directions, secondary droplet formation, number of fingers, the onset of fingering, and wave velocity are developed.

中文翻译：

---

铝旋转盘上的液滴撞击动力学

液滴对纺丝表面的影响已在不同行业中观察到，并且在工业系统的性能中起着重要作用。在目前的研究中，研究了水滴对亲水旋转盘的影响动力学。实验装置的设计方式可以精确控制液滴直径、冲击速度、圆盘旋转速度和冲击位置。虽然在本研究中液滴直径是固定的，但其他提到的参数发生了变化，并讨论了它们对液滴行为的影响。高速成像用于记录各种操作条件下的液滴动力学。结果表明，撞击后，由于水和亲水性基材之间的高附着力，液滴会在表面扩散。表明润湿面积是时间的函数，冲击速度、圆盘转速和离心加速度。此外, 根据上述参数, 观察到不同的现象, 如小流形成、指法和二次液滴的脱离。在角度方向上，通常润湿长度随着时间的推移而增加。然而，在径向上，液滴首先在表面扩散并达到最大值，然后后退直至达到平台。此时，由于离心力的作用，大量液体（在本研究中称为波）从液滴的内边界向外边界径向向外移动。一旦波到达外边界，根据其大小和动量，会形成指状或小溪，小液滴可能会分离。过程分析的很全面，