TY - JOUR
T1 - Early azimuthal instability during drop impact
AU - Li, E. Q.
AU - Thoraval, M. J.
AU - Marston, J. O.
AU - Thoroddsen, S. T.
N1 - Funding Information:
The work reported herein was funded by King Abdullah University of Science and Technology (KAUST) under grant URF/1/2621-01-01. E.Q.L. acknowledges the Thousand Young Talents Program of China, the National Natural Science Foundation of China (grants nos 11772327, 11642019 and 11621202) and Fundamental Research Funds for the Central Universities (grant no. WK2090050041). M.-J.T. acknowledges the financial support from the National Natural Science Foundation of China (grant nos 11542016 and 11702210) and the 111 project (B18040). M.-J.T. is also supported by the Cyrus Tang Foundation through the Tang Scholar program, and by the Thousand Young Talents Program of China. We thank W. Chan and K. Taylor at Specialized Imaging for their assistance.
Publisher Copyright:
© 2018 Cambridge University Press.
PY - 2018/8/10
Y1 - 2018/8/10
N2 - When a drop impacts on a liquid surface its bottom is deformed by lubrication pressure and it entraps a thin disc of air, thereby making contact along a ring at a finite distance from the centreline. The outer edge of this contact moves radially at high speed, governed by the impact velocity and bottom radius of the drop. Then at a certain radial location an ejecta sheet emerges from the neck connecting the two liquid masses. Herein, we show the formation of an azimuthal instability at the base of this ejecta, in the sharp corners at the two sides of the ejecta. They promote regular radial vorticity, thereby breaking the axisymmetry of the motions on the finest scales. The azimuthal wavenumber grows with the impact Weber number, based on the bottom curvature of the drop, reaching over 400 streamwise streaks around the periphery. This instability occurs first at Reynolds numbers of ∼7000, but for larger is overtaken by the subsequent axisymmetric vortex shedding and their interactions can form intricate tangles, loops or chains.
AB - When a drop impacts on a liquid surface its bottom is deformed by lubrication pressure and it entraps a thin disc of air, thereby making contact along a ring at a finite distance from the centreline. The outer edge of this contact moves radially at high speed, governed by the impact velocity and bottom radius of the drop. Then at a certain radial location an ejecta sheet emerges from the neck connecting the two liquid masses. Herein, we show the formation of an azimuthal instability at the base of this ejecta, in the sharp corners at the two sides of the ejecta. They promote regular radial vorticity, thereby breaking the axisymmetry of the motions on the finest scales. The azimuthal wavenumber grows with the impact Weber number, based on the bottom curvature of the drop, reaching over 400 streamwise streaks around the periphery. This instability occurs first at Reynolds numbers of ∼7000, but for larger is overtaken by the subsequent axisymmetric vortex shedding and their interactions can form intricate tangles, loops or chains.
KW - capillary flows
KW - drops and bubbles
KW - interfacial flows (free surface)
UR - http://www.scopus.com/inward/record.url?scp=85048811892&partnerID=8YFLogxK
U2 - 10.1017/jfm.2018.383
DO - 10.1017/jfm.2018.383
M3 - Article
AN - SCOPUS:85048811892
VL - 848
SP - 821
EP - 835
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
SN - 0022-1120
ER -