78th Annual Meeting of the APS Division of Fluid Dynamics (Nov 23 — 25, 2025)

V036: Plucking Droplets

When a stretched wire is impulsively plucked, transverse oscillations propagate along its length, driving complex interactions with any attached droplets. In this study, we investigate the dynamics of a droplet placed on a taut wire subjected to plucking, an event reminiscent of natural scenarios such as raindrops detaching from grass blades after a sudden breeze. High-speed imaging reveals that immediately following the upward motion of the wire, the droplet stretches to form a thin sheet bounded by rims. A capillary wave develops on the sheet, which expands vertically and contracts laterally, leading to rim collision and the emergence of a single jet. This jet elongates, detaches from the wire, and fragments into smaller secondary droplets. The breakup is governed by an interplay between upward inertia and pump-like flow, counteracted by capillary retraction forces. At reduced wire speeds, breakup is delayed: the sheet thickens, capillary waves vanish, and capillary retraction dominates. Droplets of varying properties further highlight distinct stretching and breakup dynamics. For an aqueous SDS solution (surface tension ≈ 32 mN/m), release is unexpectedly delayed due to a markedly different initial droplet shape. A glycerin-water mixture (≈25 cSt) produces a smoother, longer jet without capillary wave formation, as viscous dissipation suppresses instabilities. A shear-thinning viscoelastic fluid (zero-stress viscosity ≈20 cSt) exhibits even greater jet elongation, delayed detachment, and pronounced oscillations, with capillary waves re-emerging due to shear-thinning effects. These results highlight how inertia, surface tension, viscosity, and viscoelasticity collectively govern impulsive droplet release from wires, offering new insights into instability-driven breakup and natural droplet transport.