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Taylor-Culick retractions and the influence of the surroundings

When a freely suspended liquid film ruptures, it retracts spontaneously under the action of surface tension. If the film is surrounded by air, the retraction velocity is known to approach the constant Taylor-Culick velocity. However, when surrounded by an external viscous medium, the dissipation within that medium dictates the magnitude of the retraction velocity. In the present work, we study the retraction of a liquid (water) film in a viscous oil ambient (\emph{two-phase} Taylor-Culick retractions), and that sandwiched between air and a viscous oil (\emph{three-phase} Taylor-Culick retractions). In the latter case, the experimentally-measured retraction velocity is observed to have a weaker dependence on the viscosity of the oil phase as compared to the configuration where the water film is surrounded completely by oil. Numerical simulations indicate that this weaker dependence arises from the localization of viscous dissipation near the three-phase contact line. The speed of retraction only depends on the viscosity of the surrounding medium and not on that of the film. From the experiments and the numerical simulations, we reveal unprecedented regimes for the scaling of the Weber number $We_f$ of the film (based on its retraction velocity) or the capillary number $Ca_s$ of the surroundings vs. the Ohnesorge number $Oh_s$ of the surroundings in the regime of large viscosity of the surroundings ($Oh_s \gg 1$), namely $We_f \sim Oh_s^{-2}$ and $Ca_s \sim Oh_s^{0}$ for the two-phase Taylor-Culick configuration, and $We_f \sim Oh_s^{-1}$ and $Ca_s \sim Oh_s^{1/2}$ for the three-phase Taylor-Culick configuration.