Formation of a Jet and Its Breakup into Drops in Liquid-Liquid Systems.

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The formation of an axisymmetric liquid jet when one Newtonian liquid is injected through an orifice into another immiscible Newtonian liquid, and its breakup into drops, is studied using direct numerical simulations. A front tracking/finite difference method is used to track unsteady motion of the liquid-liquid interface. Various combinations of the non-dimensional numbers are examined (Re=80, 160, and 320; We=5 and 8; Fr=4, 8, 32, and ∞ ) for constant ratios of density (ρc⁄ρj=1.25) and viscosity (μc⁄μj=1), where subscrips c and j denote continuous phase and jet, respectively. For all cases examined, the droplets break off due to capillary wave instability. Double-node breakup where two most-unstable waves become one drop, is often observed, because the vortical motions in the external fluid affect the breakup process unlike the breakup of a liquid jet in air. This is one of the reasons that a distribution of drop sizes is produced by the breakup and the averaged size of droplets differs from that predicted by linear stability theory.
日本学術会議「機械工学委員会・土木工学・建築学委員会合同IUTAM分科会」の論文