Lee Duck-Gyu, Kim Ho-Young
School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744, Korea.
Langmuir. 2008 Jan 1;24(1):142-5. doi: 10.1021/la702437c. Epub 2007 Nov 14.
When a water drop hits a superhydrophobic solid surface, it bounces off the substrate like an elastic ball. Here we show that when a tiny superhydrophobic solid sphere impacts with water, it can bounce off the free surface just as it impacts with an elastic membrane. The motion of a sinking sphere is analytically calculated by solving a potential flow whose free boundary is determined by the Young-Laplace equation. To find conditions under which the solid sphere should sink, bounce off, or oscillate upon impact with water, we construct simple scaling laws which are shown to agree well with experimentally found boundaries between the distinct impact behaviors in a regime map based on dimensionless parameters.
当一滴水撞击超疏水固体表面时，它会像弹性球一样从基底反弹。在这里我们表明，当一个微小的超疏水固体球体与水碰撞时，它可以像撞击弹性膜一样从自由表面反弹。通过求解一个自由边界由杨-拉普拉斯方程确定的势流，解析计算了下沉球体的运动。为了找到固体球体在与水碰撞时应该下沉、反弹或振荡的条件，我们构建了简单的比例定律，结果表明这些定律与基于无量纲参数的状态图中不同撞击行为之间通过实验发现的边界非常吻合。
