Drop fragmentation due to hole formation during Leidenfrost impact

Drop impacts on a smooth plate heated above the Leidenfrost temperature are investigated in the range of large Weber number. Liquid fragmentation due to the rupture of the expanding lamella during the impact-by hole nucleation and subsequent growth-is studied. Control of this rupturing process is achieved experimentally through the use of single model-defects attached to the substrate which act as an initiating spots for the hole formation, whereas the liquid does not contact the substrate. Overall, the lamella rupture is shown to take place above a critical impact velocity, the value of which decreases with increasing defect size. Comparing this rupture mechanism to classical splash, it is shown to be the relevant fragmentation phenomenon below a critical ratio between drop (R-0) and defect (d) sizes of R-0/d <= 40. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3553277]