A study of bubble generation for constant gas-flux condition by single
-nozzle injection in a coflowing liquid is reported. Focusing on singl
e-bubble generation in the dynamic and bubbly flow regime, the onset c
ondition for bubble coalescence is investigated The role of various fo
rces involved in the bubble formation process is studied and an overal
l force balance describing bubble dynamics is developed Gas-momentum f
lux and buoyancy in normal gravity enhance, while the surface-tension
force at the nozzle rim inhibits bubble detachment. On the other hand,
liquid drag and inertia can act both as attaching or detaching forces
, depending on the relative velocity of the bubble with respect to the
surrounding liquid. Predictions of the theoretical model compare well
with the present reduced-gravity experiment and available normal-grav
ity experiments. Effects of the fluid properties, injection geometry,
and flow conditions on bubble size are investigated.