Hanging Liquids

A horizontal filament of viscous liquid hanging between two plates stretches under gravity. The photo above is a composite showing the stretching of a single thread over several time steps. The fluid forms a catenary, the same shape as a hanging chain or cable when supported only at its ends. This behavior is confined to viscous filaments of sufficient length and diameter. Short and thin filaments instead form a U-shape with a thin horizontal filament joined to two thicker vertical threads. This difference in shape occurs due to the drainage of the liquid along the filament’s length. If the viscous thread begins to fall before surface tension drains the fluid from the center toward the ends, then a catenary of essentially uniform diameter forms. If instead the liquid drains before falling, the non-uniform U-shape is observed. (Photo credit: M. Le Merrer et al.)

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