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- Title
Drop impact entrapment of bubble rings.
- Authors
Thoraval, M.-J.; Takehara, K.; Etoh, T. G.; Thoroddsen, S. T.
- Abstract
We use ultra-high-speed video imaging to look at the initial contact of a drop impacting on a liquid layer. We observe experimentally the vortex street and the bubble-ring entrapments predicted numerically, for high impact velocities, by Thoraval et al. (Phys. Rev. Lett., vol. 108, 2012, article 264506). These dynamics mainly occur within $50~\mathrm{\mu} \mathrm{s} $ after the first contact, requiring imaging at 1 million f.p.s. For a water drop impacting on a thin layer of water, the entrapment of isolated bubbles starts through azimuthal instability, which forms at low impact velocities, in the neck connecting the drop and pool. For Reynolds number $Re$ above ${\sim }12\hspace{0.167em} 000$, up to 10 partial bubble rings have been observed at the base of the ejecta, starting when the contact is ${\sim }20\hspace{0.167em} \% $ of the drop size. More regular bubble rings are observed for a pool of ethanol or methanol. The video imaging shows rotation around some of these air cylinders, which can temporarily delay their breakup into micro-bubbles. The different refractive index in the pool liquid reveals the destabilization of the vortices and the formation of streamwise vortices and intricate vortex tangles. Fine-scale axisymmetry is thereby destroyed. We show also that the shape of the drop has a strong influence on these dynamics.
- Subjects
BUBBLES; MICROBUBBLES; ROTATIONAL motion (Rigid dynamics); FLUID dynamics; DIFFERENTIABLE dynamical systems
- Publication
Journal of Fluid Mechanics, 2013, Vol 724, p234
- ISSN
0022-1120
- Publication type
Article
- DOI
10.1017/jfm.2013.147