Light shed on shedding droplets

If you’ve ever been on an airplane, you have reason to appreciate new research on the shedding of droplets. Razzagh et al. studied how multiple droplets on a surface are affected by airflow by studying the droplets’ size and arrangement. Their results may help improve anti-icing of airplanes, and are important in myriad other applications.

“We have indirectly been able to probe the effect of the flow field around sessile droplets as relates to droplet removal, for the first time” said co-author Alidad Amirfazli. “We found the size of the droplets and the surface wettability didn’t have a significant effect on the shedding, which was unexpected.”

Previous work has studied suspended droplets, as well as single drops placed on a surface. However until now, work had not looked at how aerodynamic drag affects arrangements of multiple droplets on a surface, which is essential for understanding real-life applications.

The authors placed water droplets on a surface in a wind tunnel in square, diamond, equilateral triangle, and reverse-equilateral triangle formations. The size and spacing of the droplets were varied, as well as the surface material. The results found a triangle shape required the maximum airflow velocity to shed the droplets from the surface. Simulations helped understand further details of the flow and provide explanation of the results.

Knowing how multiple droplets can be best removed from a surface has a wide range of applications, such as airplane anti-icing, improving fuel cell performance, and removing impurities in biological samples. The authors plan to continue working with the particle image velocimetry to better understand their results.

Source: “Shedding of multiple sessile droplets by an airflow,” by A. Razzagh, S. A. Banitabaie, and A. Amirfazli, Physics of Fluids (2018). The article can be accessed at https://doi.org/10.1063/1.5039443 .