Air-cushioning effect and Kelvin-Helmholtz instability before the slamming of a disk on water

Utkarsh Jain*, Anaïs Gauthier, Detlef Lohse, Devaraj van der Meer

*Corresponding author for this work

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Abstract

The macroscopic dynamics of a droplet impacting a solid is crucially determined by the intricate air dynamics occurring at the vanishingly small length scale between droplet and substrate prior to direct contact. Here we investigate the inverse problem, namely, the role of air for the impact of a horizontal flat disk onto a liquid surface, and find an equally significant effect. Using an in-house experimental technique, we measure the free surface deflections just before impact, with a precision of a few micrometers. Whereas stagnation pressure pushes down the surface in the center, we observe a liftup under the edge of the disk, which sets in at a later stage, and which we show to be consistent with a Kelvin-Helmholtz instability of the water-air interface.
Original languageEnglish
Article numberL042001
JournalPhysical review fluids
Volume6
Issue number4
DOIs
Publication statusPublished - 29 Apr 2021

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