Transition time of a bouncing drop

Abstract

Contact time of bouncing drops is one of the most essential parameters to quantify the water repellency of surfaces. Generally, the contact time on superhydrophobic surfaces is known to be Weber number independent. Here, we probe an additional characteristic time, transition time, inherent in water drops impacting on superhydrophobic surfaces, marking a switch from a predominantly lateral motion to an axial motion. Systematic experiments and numerical simulations show that the transition time is also Weber number independent and accounts for half the contact time. Additionally, we identify a Weber-independent partition of volume at the maximum spreading state between the rim and the lamella and show that the latter contains 1/4 of the total volume of the drop.