Satellite droplet formation by unstable binary drop collisions

The formation of satellite droplets by stretching separation in unstable binary collisions of equal-sized drops is investigated. Based on data from detailed experiments on the formation and breakup of ligaments in off-center collisions with appreciable impact parameter, the process of satellite droplet formation is modeled. The experiments are carried out using two streams of monodisperse drops of various liquids. Drop sizes and velocities, and dimensions of ligaments and sizes of satellites are formed after unstable off-center collisions are measured with an image-processing technique. The model represents the physics of the collisions by functions of nondimensional characteristic numbers. The functions are determined using the experimental data. The experiments are well reproduced by the model, which reveals the importance of both the drop size and the liquid viscosity for the formation of the satellites.