Gradient Nonwettability\nControls Water-Film Flowing\nFeatures

The flow of the water film on solid surface depended\non the film\nReynolds number and wind speed. Moreover, environmental factors had\nan impact on the flow process. This study explored how surface wettability\nimpacts the stability and detachment of water film under varying conditions.\nSuperhydrophobic surface played a critical role in speeding up the\ndetachment of water film, especially under conditions of strong wind\nand specific flow dynamics, such as a wind speed of 19 m/s and a Reynolds\nnumber of 83. The efficiency in water removal was due to a combination\nof forces: capillary action, which pulls the water into smaller areas,\nreduced surface tension, and decreased adhesion between the liquid\nand surface. These factors worked together to shrink the area of contact,\nallowing the film to break and detach more easily. The findings suggested\nthat enhancing nonwettability can improve water removal efficiency,\nwith potential applications in fields like aerospace. Furthermore,\nadditional trials across varying wind speeds and Reynolds numbers\nconsistently supported the superior performance of superhydrophobic\nsurface in driving rapid water-film detachment. To advance this effect,\na gradient nonwetting surface was introduced, specifically engineered\nwithin the superhydrophobic regime, to amplify the velocity of film\nseparation. This design innovation leveraged variations in surface\nenergy across the gradient, which fostered directional water-film\nmovement and accelerated detachment. A comprehensive analysis of the\nunderlying physical mechanisms further elucidated its potential in\nenhancing water-shedding applications across a range of environmental\nconditions.