Bioinspired Drag Reduction of Cavities Induced by Janus Nanostructure Interfaces on Hydrophobic Spheres Plunging into Water with a Low Speed

Form drag of the blunt object occurs from pressure difference due to physical dimensions obstructing and altering flow fluid. The innovative approach form reduction is realized by changing shape a streamlined body introducing cavity. construction superhydrophobic interfaces widely considered as best solution for cavity, because water prevented penetrating space between nanoscale structures, leading Cassie–Baxter wetting regime then splashing outward. Here, Janus nanostructure coating on hydrophobic spheres, it found that position (impacting direction) coverage ratio (r) nanostructures, accurately manipulate performance film sphere surface. When faces upward, detached thin develops splash crown only if r increases 1/3 or even above. Correspondingly, remaining open aperture aids in increasing subsequent air entrainment, an air-entrainment cavity trapped However, downward, tiny region nanostructures (r ≤ 1/8) can help liquid directly develop into