Role of the channel geometry on the bubble pinch-off in flow-focusing devices.
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.
Dollet
Benjamin
B
Physics of Fluids, University of Twente, Enschede, The Netherlands. benjamin.dollet@univ-rennes1.fr
van Hoeve
Wim
W
Raven
Jan-Paul
JP
Marmottant
Philippe
P
Versluis
Michel
M