| Abstract: |
| The Instability and breakup of a fluid thread of low viscosity immersed in highly viscous exterior fluid at low Reynolds number is studied. With an aim to better understand the pinch-off dynamics, we use slender body theory, numerical simulations and experimental studies to investigate the effect of surfactant on the necking and eventual breakup. Evolution equations are derived using long wavelength approximations. These one dimensional partial differential equations are solved numerically for given initial interface and surfactant concentration. It is found that the presence of surfactant at the interface retards the pinch-off process. Surface diffusion and solubility of surfactant are found to have significant influence on the instability of the thread. It is found that greater diffusion of surfactant causes the thread to pinch faster. Results of the long wavelength model are also compared against the numerical simulations of the full problem. The solution of the full problem shows similar behavior to the simplified model. The experimental results support the prediction of theoretical model that the presence of surfactant slows down the pinch-off process. |
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