Phase-field model for the pinchoff of liquid-liquid jets

Understanding pinchoff in a liquid-liquid jet is one of the fundamental problems in the physics of fluid. Pinchoff has a wide variety of applications, such as in ink-jet printers. We have need a phase-field model to numerically investigate the breakup of a forced liquid jet into drops in immiscible liquid-liquid systems. In the phase-field model, the classical sharp interface between the two immiscible fluids is represented by a transition region of small, but finite, width. Across this width the composition of one of the two fluids changes continuously. The phase-field method can deal with topological transitions, such as breakup and reconnection, smoothly without ad-hoc "cut and connect" or smoothing procedures. We found the numerical results for the pinchoff of liquidliquid jets with surface tension to be in good agreement with experimental data. In particular, we investigated the axial velocities and the vorticity structures around the jet neck before and after pinchoff.