The post-impact dynamics of drop rebound on inclined hydrophobic surfaces of various wettabilities

Abstract

In this work, the post-impact drop motions of the rebound regime on inclined hydrophobic surfaces are investigated using a numerical technique. The effects of impact velocity (com.elsevier.xml.ani.Math@bc6a3de = 0.5-1.5 m/s), drop diameter (com.elsevier.xml.ani.Math@430e365b = 1.0-2.5 mm), surface wettability (com.elsevier.xml.ani.Math@11324c97 = 120°-160°), and inclined angle (com.elsevier.xml.ani.Math@7c97fb78 = 0°-80°) on the post-impact regimes, contact time (com.elsevier.xml.ani.Math@42716f67) and spreading time (com.elsevier.xml.ani.Math@707f259c), nondimensionalized maximum spreading diameter (com.elsevier.xml.ani.Math@73aa89f0), and drop displacement prior to the rebound (com.elsevier.xml.ani.Math@30a5e0c6) are examined and analyzed, some of which exhibit markedly different outcomes at com.elsevier.xml.ani.Math@79e6abe2 = 80° compared to com.elsevier.xml.ani.Math@703c2287 60°. It has been discovered that the rebound regime occurs in most impact conditions at com.elsevier.xml.ani.Math@577ec079 = 160° and 140° but transitions to sliding for all com.elsevier.xml.ani.Math@4842a980 = 80° cases at com.elsevier.xml.ani.Math@437a2d1 = 120°. When com.elsevier.xml.ani.Math@158e80ca 60°, com.elsevier.xml.ani.Math@34d2f70a and com.elsevier.xml.ani.Math@698156b9 of com.elsevier.xml.ani.Math@50995072 = 160° and 140° are very close and hardly affected by com.elsevier.xml.ani.Math@3170027b and com.elsevier.xml.ani.Math@12b9c9f8, which are generally smaller than those of com.elsevier.xml.ani.Math@71ee7188 = 80°, resulting from the rapid decline of the normal impact velocity that diminishes drop deformation and prolongs drop sliding motion. com.elsevier.xml.ani.Math@6b6eb507 is barely influenced by com.elsevier.xml.ani.Math@5abc01cb but increases with com.elsevier.xml.ani.Math@616e56d and com.elsevier.xml.ani.Math@4f6a616 and decreases when com.elsevier.xml.ani.Math@1a2eed02 increases owing to a greater normal inertial force. com.elsevier.xml.ani.Math@20a605d5 generally increases with com.elsevier.xml.ani.Math@11aab121com.elsevier.xml.ani.Math@20dd6314, and com.elsevier.xml.ani.Math@4df6ccf0 but with different mechanisms. More importantly, the nondimensionalized parameters com.elsevier.xml.ani.Math@5d6ef036com.elsevier.xml.ani.Math@19097103, and com.elsevier.xml.ani.Math@528764f5 are found to scale with the normal or tangential Weber numbers according to the power law, while the exponents vary with com.elsevier.xml.ani.Math@296da319 and com.elsevier.xml.ani.Math@3281942