Experimental Investigation on the Impact Behavior of Droplets on Inclined Grooving Surfaces.

An experimental study on the droplet impact behavior on the inclined grooving surface was performed by varying the Weber number () and inclined angles (θ) and groove spacing (). The results show that the droplet spreads in a wave-like manner as = 6.26, whereas it assumes a pancake-like morphology as = 41.6 and 81.4. As the Weber number achieves 81.4, inertia takes precedence, creating a bulge at the leading edge of the drop while leaving a thin trail of water at the back end. Two events in contraction are summarized: the stable contraction rate (SCR) and the sudden contraction trailing-edge event (SCTE). The SCR stage is characterized by a constant contraction velocity, which acts to minimize the droplet's surface area. The SCTE typically occurs at the moment when the trailing edge of the droplet begins to detach from the surface. Moreover, the increased inclination amplifies the asymmetry of the droplet's morphology while promoting the occurrence of SCTE. It is also observed that the increasing inclined angle reduces the contact time and grows the sliding length. As the Weber number increases, the droplet's sliding motion is promoted, then the contraction process transits to the stage of SCTE from SCR along with the trailing-edge acceleration phenomena, and finally the droplet turns from columnar rebound to stretched rebound and even stretch breakup. Furthermore, the wider groove spacing allows greater droplet expansion. The findings contribute to a more comprehensive understanding of droplet-surface interactions.