Dynamic characteristics of droplets impacting an inclined wall based on a front-tracking method

Abstract

In the current study, the dynamic characteristics of droplets impacting a hydrophilic/hydrophobic inclined wall are investigated using the front-tracking method. The morphological and kinematic features of the droplets are examined across various contact angles (θ), low Weber numbers (We≤10), and inclination angles (α). A sequence of events, including deposition, spreading, contraction, rebound, and subsequent re-spreading, is observed when a droplet impacts a hydrophobic wall, according to the results. The droplet exhibits both a small dimensionless spreading area (A*) and significant fluctuation, along with a noticeable slip on the wall. As We increases, the spread and rebound effects become more pronounced, and the slipping velocity also increases. As α increases, the slipping velocity becomes greater, and both A* and the dimensionless tangential spreading diameter (β) decrease. When a droplet impacts a hydrophilic wall, continuous deposition, spreading, and a subtle slip with inconspicuous rebound are observed. As We increases, A* expands at an accelerating rate. Furthermore, the wetting effect of hydrophilic surfaces on droplets cannot be overlooked. Consequently, it also shows that as α increases, there is a larger diffusion range along the wall with a longer diffusion film and a larger β. Such behaviors stand in contrast to a droplet impacting a hydrophobic wall.