Droplet impact and penetration on series of parallel tubes

Impact and penetration of a liquid droplet on a substrate having a line of parallel capillary openings drilled along its thickness is experimentally studies. Different regimes of droplet penetration are identified. At low impact velocities, the droplet impacts on the substrate, spreads, and penetrates into the substrate mainly due to the capillary action in each tubular hole. At higher impact velocities, the droplet impacts on the substrate, spreads and penetrates due to the droplet inertia, and then penetrates further due to the capillary action. Threshold velocities for liquid penetration into capillary tubes are identified. Two penetration regimes, capillary and inertia driven regimes, have been studied extensively for a range of parameters related to droplet impact on a line of parallel capillary openings. Index Terms—Droplet impact, parallel capillary tubes, penetration, liquid spread