Dynamics of drop formation, growth and pinching phenomena from a submerged nozzle

Drop formation is studied through a comprehensive experimentation, injecting different lighter fluids in an immiscible liquid, over a range of velocities, from submerged nozzles of four different diameters. The process involves a number of unique interfacial developments, namely inception and growth, neck for-mation and pinching, drop departure, etc. The study emphasizes on the dynamical aspects like shape oscillation on the nozzle tip, neck radius fluctuation, length variation of the leading edge (L-v) etc. At a low flow rate, the retractile motion of the remnant mass is found responsible for shape alteration. The process of drop pinching exhibits radial fluctuation of the neck and depends on both flow rate and viscosity. Moreover, in an unconfined system, drops may be generated with increased frequency within the limit of the dripping regime while keeping L-v approximately unchanged. Different regimes of drop formation have also been identified. (C) 2021 Elsevier Ltd. All rights reserved.