A solid rapidly pushed into a liquid, of viscosity η, at velocityU entrains surrounding air along with its moving surface. Using high-speed interferometry we find a robust characteristic structure of the entrained air layer: there is a thin-thick alternation of gap thickness in the transverse direction and this feature occurs both in wetting and de-wetting. In the thin regions we find that the gap thickness scales approximately as (ηU)0.5. We present a model using the assumption that the velocity profile is robust to thickness fluctuations that gives a good quantitative estimate of this gap thickness. This is in contrast to the Landau-Levich analysis which had previously been assumed applicable to this problem.This work was primarily supported by the University of Chicago MRSEC, funded by the National Science Foundation under Award Number DMR-1420709 and by NSF Grand DMR-1404841.
APS March Meeting Abstracts
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