KAUST DepartmentClean Combustion Research Center
High-Speed Fluids Imaging Laboratory
Mechanical Engineering Program
Office of the VP
Physical Science and Engineering (PSE) Division
KAUST Grant NumberURF/1/2621-01-01
Online Publication Date2018-06-13
Print Publication Date2018-08
Permanent link to this recordhttp://hdl.handle.net/10754/630502
MetadataShow full item record
AbstractWhen 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.
CitationLi EQ, Thoraval M-J, Marston JO, Thoroddsen ST (2018) Early azimuthal instability during drop impact. Journal of Fluid Mechanics 848: 821–835. Available: http://dx.doi.org/10.1017/jfm.2018.383.
SponsorsThe 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.
PublisherCambridge University Press (CUP)
JournalJournal of Fluid Mechanics