%0 Journal Article
%T Free radially expanding liquid sheet in air: time- and space-resolved measurement of the thickness field
%+ Laboratoire Charles Coulomb (L2C)
%A Vernay, Clara
%A Ramos, Laurence
%A Ligoure, Christian
%Z accepted for publication in Journal of Fluid Mechanics. Réf Journal: J. Fluid Mech. (2015), vol. 764, pp. 428-444
%< avec comité de lecture
%Z L2C:14-258
%@ 0022-1120
%J Journal of Fluid Mechanics
%I Cambridge University Press (CUP)
%V 764
%P 428-444
%8 2015
%D 2015
%Z 1412.3930
%R 10.1017/jfm.2014.714
%Z Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft]
%Z Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn]Journal articles
%X The collision of a liquid drop against a small target results in the formation of a thin liquid sheet that extends radially until it reaches a maximum diameter. The subsequent retraction is due to the air-liquid surface tension. We have used a time- and space-resolved technique to measure the thickness field of this class of liquid sheet, based on the grey level measurement of the image of a dyed liquid sheet recorded using a fast camera. This method enables a precise measurement of the thickness in the range $(10-450) \, \mathrm{\mu m}$, with a temporal resolution equal to that of the camera. We have measured the evolution with time since impact, $t$, and radial position, $r$, of the thickness, $h(r,t)$, for various drop volumes and impact velocities. Two asymptotic regimes for the expansion of the sheet are evidenced. The scalings of the thickness with $t$ and $r$ measured in the two regimes are those that were predicted in \citet{Rozhkov2004} fort the short-time regime and \citet{Villermaux2011} for the long time regime, but never experimentally measured before. Interestingly, our experimental data also evidence the existence of a maximum of the film thickness $h_{\rm{max}}(r)$ at a radial position $r_{\rm{h_{max}}}(t)$ corresponding to the crossover of these two asymptotic regimes. The maximum moves with a constant velocity of the order of the drop impact velocity, as expected theoretically. Thanks to our visualization technique, we also evidence an azimuthal thickness modulation of the liquid sheets.
%G English
%L hal-01104008
%U https://hal.science/hal-01104008
%~ CNRS
%~ L2C
%~ MIPS
%~ UNIV-MONTPELLIER
%~ UM-2015-2021