The University of Minnesota Twin Cities did the pioneering study. It was published in Nature Communications, and it could help engineers do what? To design better, more erosion-resistant materials. To do that, they studied how water droplets erode rocks.
how do they accomplish this?
The pressure created by the impact of liquid droplets on surfaces was measured. This phenomenon has only been studied visually. It is well known that slowly dripping water droplets can erode surfaces over time. How does something seemingly soft and fluid impact hard surfaces so much?
“There’s a saying that ‘dripping water hollows out stone,'” Xiang Cheng explained in a statement. He is lead author of the paper and a professor at the University of Minnesota. “You can’t help but ask yourself questions. ‘Why does the impact of the fall cause any damage?’ That question is what motivated our research.”
Drop impact was only analyzed visually with high-speed cameras. The new technique is called high-speed stress microscopy. It measures the force, stress and pressure beneath liquid droplets as they strike surfaces.
Water pumps
what did they discover? That the force exerted by a drop actually spreads out with the impinging drop. It is not concentrated at the center of the drop. The speed at which the droplet spreads out exceeds the speed of sound for short periods. And this generates a ripple impact across the surface. Each droplet behaves like a small bomb, releasing its impact energy explosively.
Knowing how water droplets erode rocks is helpful. Engineers could design more erosion-resistant surfaces. Cheng plans to expand this research to study different textures and materials change the amount of force created by liquid droplets.
“We could reduce the amount of shear stress from the droplets. And design special surfaces that can mitigate the stress.”
