单液滴撞击超疏水冷表面的反弹及破碎行为

对直径2.8 mm的液滴撞击冷表面的动态行为进行快速可视化观测，对比研究单液滴撞击普通冷表面以及超疏水冷表面的动力学特性，同时对初始撞击速度以及冷表面温度对液滴动态演化行为的影响进行了对比分析。实验结果表明：与液滴撞击普通冷表面（温度-25~-5℃）发生瞬时冻结沉积相比，液滴撞击超疏水冷表面时均未发生冻结，而且伴随铺展、回缩、反弹以及破碎行为；撞击速度越大，普通冷表面上液滴铺展因子越大，而且液滴越易冻结。液滴低速（We≤76）撞击超疏水冷表面会发生反弹现象，但速度对液滴最大铺展时间无影响；液滴高速（We≥115）撞击超疏水冷表面后会产生明显液指，而且破碎为多组卫星液滴。此外，冷表面温度仅影响液滴反弹高度，对液滴最大铺展因子以及液滴铺展时间影响较小。结果表明超疏水表面可显著抑制液滴撞击冷表面的瞬时冻结沉积。

Rebounding and splashing behavior of single water droplet impacting on cold superhydrophobic surface

Dynamic behavior of a single water droplet with 2.8 mm in diameter impacting on cold surface was visually observed by high speed camera, the evolutional characteristics of water droplet impacting on cold superhydrophobic and bare aluminum surfaces were comparatively studied. Besides, the effect of initial impacting velocity and cold surface temperatures on the dynamic behavior of water droplet on cold surface were analyzed. The experimental result showed that compared with the instantly freezing of water droplet impacting on cold bare aluminum surface, the water droplet impacting on cold superhydrophobic surface (-25—-5℃) can not freeze along with spreading, retraction, rebound and smash behaviors. The higher the impacting velocity is, the bigger the spreading factor is and the more easily the water droplet freezes on cold bare aluminum surface. Moreover, rebounding behavior can be found when droplet impacts on the superhydrophobic surface with a low speed (We≤76) and velocity has no effect on the maximum spreading time. Also, obvious droplet fingers will appear and can be fragmented into many satellite droplets as droplet impacts on cold superhydrophobic surface with a high speed (We≥115). In addition, cold surface temperature has obvious effect on rebounding height but has little effect on the spreading factor and spreading time. The results indicate that the superhydrophobic surface can prevent the water droplet effectively from freezing instantly as the droplet impacts on cold surface.