Collisions of viscous droplets Available to Purchase

From industrial food and drug processing to car and jet engines, the interactions between small liquid droplets have a surprisingly large effect on our lives. Wherever they occur, the interactions are complex—involving multiple phases and multiple time and length scales. And as shown in the figure, collisions can have different outcomes, including reflexive separation (left), stretching separation (right), and coalescence (center). Although numerical, theoretical, and experimental efforts over the past few decades have explored the underlying fluid dynamics, a detailed understanding, especially concerning the role of viscous forces, has yet to emerge. For water droplets, viscous forces are usually much less relevant than surface tension, but in spray drying and other industrial applications they can be substantial and lead to significant energy loss as the droplets merge and deform. To better understand the effect of droplet viscosity, a team of Dutch researchers led by Hans Kuipers (Eindhoven University of...