Drop impact

A 0.86-mm drop of silicone oil with 1.3 times the viscosity of water hitting a solid surface at 2.47 m/s and breaking up into a splash.

A DROP falling onto a surface may either spread in a smooth blob or splash and disintegrate into smaller droplets, but the factors determining which of these two outcomes occurs are not entirely clear. Guillaume Riboux and Jose Manuel Gordillo of the University of Seville in Spain used high-speed cameras to film droplets of different liquids as they fell onto a solid surface at varying speed. The analysis of the experiments allowed the researchers to derive criteria to predict when a drop will splash. They concluded that the gas surrounding the droplet played a crucial role because it determined the aerodynamic lift that propelled the sheet of impacting liquid upwards until it ruptured. The work has been published in the latest issue of Physical Review Letters. The model may find a wide range of applications, for example, a formula that predicts whether splashing will occur could help make inkjet printing accurate and smooth. According to Gordillo, the work could also help in reducing the spread of plant infections because it could allow researchers to calculate the minimum plant spacing needed to avoid bacterial transfer resulting from raindrop splashes.