The Synergistic Reduction of the Contact Time in the Droplet Impact on a Moving Ridge Surface.

The contact time of the droplet impacting on solid surfaces can be markedly reduced by 40% to 50% by breaking the symmetric behaviors with the help of the surface structures and motion, which is crucial to diverse applications involving anti-icing, anti-erosion, self-cleaning, etc. Herein, it is interesting to note that the contact time can be further decreased up to 60% on a moving ridge surface because of corresponding synergy, inspired by flying insects or wind-dispersal seeds. In the present work, the synergistic mechanisms of the reduction in contact time have been revealed by analyzing the 3 basic features, called Leaf-type, Ear-type, and Butterfly-type, according to their morphological and dynamical behaviors. Therefore, a universal theoretical model has arrived by introducing normal and tangential Weber numbers, beyond previous descriptions. Importantly, our study discovers a generalized scaling law of -0.52 between the contact time and new composite Weber number ( ), which is feasible to stationary and moving surfaces, suggesting that the limit reduction rate on a moving ridge surface tends to 78%. The present work provides an insight to optimize the corresponding application efficiency by coupling the surface structure and motion.