title: Role of the channel geometry on the bubble pinch-off in flow-focusing devices.
abstract: The formation of bubbles by flow focusing of a gas and a liquid in a rectangular channel is shown to depend strongly on the channel aspect ratio. Bubble breakup consists in a slow linear 2D collapse of the gas thread, ending in a fast 3D pinch-off. The 2D collapse is predicted to be stable against perturbations of the gas-liquid interface, whereas the 3D pinch-off is unstable, causing bubble polydispersity. During 3D pinch-off, a scaling w_(m) approximately tau(1/3) between the neck width w_(m) and the time tau before breakup indicates that breakup is driven by the inertia of both gas and liquid, not by capillarity.
authors.affiliation: Physics of Fluids, University of Twente, Enschede, The Netherlands. benjamin.dollet@univ-rennes1.fr
authors.forename: Benjamin
authors.initials: B
authors.lastname: Dollet
authors.forename: Wim
authors.initials: W
authors.lastname: van Hoeve
authors.forename: Jan-Paul
authors.initials: JP
authors.lastname: Raven
authors.forename: Philippe
authors.initials: P
authors.lastname: Marmottant
authors.forename: Michel
authors.initials: M
authors.lastname: Versluis