Oblique Collisions Between Wetted Particles

Wetted collisions appear in nature in examples such as pollen capture, landslides, and avalanche flow. Furthermore, wetted collisions have industrial applications in granulation, coagulation, and water filtration. Previous experiments, with two wetted particles (head-on collisions) or particle wall collisions (head-on or oblique), exhibited two outcomes: bounce or stick. In this paper, new experimental results from oblique particle-particle collisions are presented. Here, a new outcome has been observed; namely, after two, wetted particles collide and form an agglomerate, the particles first stick and rotate (through a significantly larger angle than in a bounce outcome), and then separate. Therefore, instead of two outcomes, three outcomes are possible: bounce, stick, and stick-separate. An experimental regime map of the outcomes is presented along with a physical interpretation of the results via a consideration of elastohydrodynamics and rotational motion.