77th Annual Meeting of the APS Division of Fluid Dynamics (November 24, 2024 — November 26, 2024)

P2692828: Two instabilities in one liquid sheet

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Authors

• Sandip Dighe, King Abdullah Univ of Sci & Tech (KAUST)
• Hrishikesh Gadgil, Department of Aerospace Engineering, Indian Institute of Technology, Bombay, Mumbai, Maharashtra, India
• Tadd Truscott, King Abdullah University of Science and Technology

DOI: https://doi.org/10.1103/APS.DFD.2024.GFM.P2692828

Two cylindrical liquid jets (dia = 1 mm) of a glycerol-water mixture (80/20) impinge at 90º to one another, creating a thin liquid sheet bordered by a thick rim. Classical fish-bone shapes (sheet-thread-droplet) are formed where the rim instability is driven by Rayleigh-Plateau type mechanisms. Here we also see fish-bone shapes occurring for similar reasons. However, the waves on the sheet are formed by small imbalances between the two jet velocities (natural pipe driven oscillation), rather than the traditional Kelvin-Helmholtz instability. Our stroboscopic photograph of the sheet reveals that both of these instabilities can coexist within a narrow range of operating conditions. The breakup of the liquid sheet (lower down) is caused by the combined instability of spatially growing waves. The liquid sheet breaks down mainly through the growth of bounded waves. These waves eventually break, forming long threads at the bottom of the sheet, which further disintegrate into droplets due to the Rayleigh-Plateau instability of threads.