Multitude of dimple shapes can produce singular jets during the collapse of immiscible drop-impact craters. (10th December 2020)

• Record Type: Journal Article
• Authors: Yang, Zi Qiang; Tian, Yuan Si; Thoroddsen, S. T.
• Is Part Of: Journal of fluid mechanics. Volume 904(2020)
• Publication Date: 2020-12-10
• Subjects: breakup/coalescence; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2020.694
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract: Abstract : We study singular jets from the collapse of drop-impact craters, when the drop and pool are of different immiscible liquids. The fastest jets emerge from a dimple at the bottom of the rebounding crater, when no bubble is pinched off. The parameter space is considerably more complex than for identical liquids, revealing intricate compound-dimple shapes. In contrast to the universal capillary–inertial drop pinch-off regime, where the neck radius scales as $R\sim t^{2/3}$, for a purely inertial air dimple the collapse has $R \sim t^{1/2}$ . The bottom dimple dynamics is not self-similar but possesses memory effects, being sensitive to initial and boundary conditions. Sequence of capillary waves can therefore mould the air dimple into different collapse shapes, such as bamboo-like and telescopic forms. The finest jets are only $12\ \mathrm {\mu }\textrm {m}$ in diameter and the normalized jetting speeds are up to one order of magnitude larger than for jets from bursting bubbles. We study the cross-over between the two power laws approaching the singularity. The singular jets show the earliest cross-over into the inertial regime. The fastest jets can pinch off a toroidal micro-bubble from the cusp at the base of the jet.