Wetting Effect on Torricelli’s Law

Jets at the exit of the tank for similar conditions except wetting; hole radius = 1.75 mm; initial height = 10 cm. From hydrophilic to hydrophobic plate: (a) Glass, (b) Plexiglas, (c) Hydrophobic-glass. Left side: Zoom in of the jets at the hole exit to display the meniscus profiles for the different wetting conditions (i.e. the small ring of fluid that forms around the outside of the hole), one notices these menisci are different. Photo J. Ferrand? - Make a hole in the bottom of a tank filled with a non-viscous fluid (e.g. water), the liquid it contains will flow out. How quickly the tank empties depends on the shape of the tank, the size of the hole, and, importantly, the initial amount of liquid (the rate at which the tank drains decreases as it gets emptier).