Shedding of multiple sessile droplets by an airflow

Abstract

Shedding of multiple sessile droplets by an airflow in triangle, square, reversed triangle, and diamond arrangements is examined. The interaction of the flow around the sessile droplets is found to be influenced by the type of the arrangement and the spacing of the sessile droplets in each arrangement. Consequently, the minimum airflow velocity required to shed the droplet (Ucr) also changes. Water droplets of 5 and 10 μl were used on both hydrophilic and hydrophobic surfaces in a laminar airflow. In general, at the minimum spacing, the highest increase in Ucr for the upstream droplet(s) (compared with that for a single droplet) was observed for the triangle arrangement (∼40%), followed by the diamond, reversed triangle, and square arrangements. Increasing the spacing resulted in a reduction of the Ucr for all the arrangements, except for the square arrangement where increasing the spacing does not show a substantial change in Ucr. Neither the size of the droplets nor the wettability of the substrate was found to significantly affect the amount of the change in the Ucr.