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Fluid Dynamics Seminar

Monday, Oct. 24, 2010, 4:00 PM
Cullimore Lecture Hall, Room 611
New Jersey Institute of Technology

Capillary breakup in viscous fluids: surface-tension driven flow and the effect of surfactant or electric fields

Qiming Wang

Dept. Mathematical Sciences, NJIT

Abstract

Capillary pinchoff of a viscous thread immersed in another viscous fluid is investigated numerically and theoretically. Previous direct simulation of equal-viscosity case (Lister & Stone PF vol 10, #11 1998) show asymptotic self-similar regime prior to breakup. Present study will show some progress in the case of unequal viscosities. Self-similar behaviors can still be found for moderate viscosity ratios and cases of large viscosity contrast become subtle. The capability in capturing the nonlinear dynamics of possible long-wave models is also discussed. Interfacial dynamics becomes more complicated when surfactant (or electric field) is present, which changes the stability of the system by altering the stress balances at the free interface. Tip-streaming is identified numerically with insoluble surfactant and a few other results considering leaky-dielectric (as well as perfectly conducting) liquid threads are presented showing changes of the dynamics near breakup.