The oscillation characteristics of a single droplet after normal collision with smooth surfaces are numerically investigated by using volume of fluid (VOF) method. An adaptive mesh refinement technique is used to guarantee the high computational accuracy of the interaction between the falling liquid droplet and the solid surface. The results of VOF simulations are consonant with the previously reported experiments. The effects of seven key issues on the oscillation characteristics of a liquid droplet advancing/recoiling onto both hydrophilic and hydrophobic surfaces are studied quantitatively with the help of dimensionless wetting length, average amplitude ratio and average oscillation period. These issues include impact velocity, contact angle, slip length, surface tension, droplet density, liquid viscosity and droplet diameter. Especially, surface and interface effects gradually become a primary factor that controls the droplet behavior as droplet size is reduced, and therefore the oscillation concerning micrometer-size droplet may be damped more rapidly. The presented study can contribute to provide more insight into the wetting kinetics of droplet collision, the interface interaction between the liquid droplet and the solid surface, and the oscillation features of the droplet spreading/receding after droplet impact.

使用流体体积（VOF）方法数值研究了单个液滴在与光滑表面正常碰撞后的振荡特性。自适应网格细化技术用于保证下落液滴与固体表面相互作用的高计算精度。VOF 模拟的结果与先前报道的实验一致。借助无量纲润湿长度、平均振幅比和平均振荡周期，定量研究了七个关键问题对液滴在亲水和疏水表面上前进/反冲的振荡特性的影响。这些问题包括冲击速度、接触角、滑移长度、表面张力、液滴密度、液体粘度和液滴直径。尤其，随着液滴尺寸的减小，表面和界面效应逐渐成为控制液滴行为的主要因素，因此有关微米尺寸液滴的振荡可以更快地衰减。所提出的研究有助于更深入地了解液滴碰撞的润湿动力学、液滴与固体表面之间的界面相互作用以及液滴撞击后液滴扩散/后退的振荡特征。