Electrohydrodynamic instabilities at liquid interfaces continue to defy our intuition, from the pioneering work of Taylor (Proc. R. Soc. Lond. A, vol. 280, issue 1382, 1964, pp. 383-397) on conical tips of electrified droplets to a recent numerical study by Wagoner et al. (J. Fluid Mech., vol. 904, 2020, R4). The problem studied by Wagoner et al. (2020) consists of a droplet immersed in a more conducting and more dielectric liquid medium, in a strong electrical field. When the droplet is more viscous than the outer medium, the droplet develops a biconcave shape which might eventually evolve to a torus shape (or doughnut). In contrast, when the droplet is less viscous, it adopts a lenticular shape and emits a thin fluid sheet from its equator which in turn breaks up into droplets. These droplets form a ring of satellites around the original droplet, which justifies its appellation 'Saturnian droplet'. The numerical simulations bring light to this complex phenomenon and confirm the robustness of the leaky-dielectric framework (Melcher & Taylor, Annu. Rev. Fluid Mech., vol. 1, 1969, pp. 111-146).
- drops and bubbles
- electrohydrodynamic effects