title: Cavity ripples observed during the impact of solid objects into liquids.
abstract: We report the experimental observation of a well-defined rippling of the air cavity entrained by a rapidly moving solid object entering the free surface of a liquid (water or ethanol). The ripples are fixed in the lab frame, and begin just after the pinch-off (deep seal) of the cavity, simultaneous with the acoustic emission. This acoustic resonance corresponds approximately to the Minnaert frequency for volume oscillations of the bubble. We present an irrotational model which explains the ripples as a spatial rectification of these volume oscillations by the surface of the moving object.
authors.affiliation: W.G. Pritchard Laboratories, Department of Mathematics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Torben
authors.initials: T
authors.lastname: Grumstrup
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Keller
authors.forename: Andrew
authors.initials: A
authors.lastname: Belmonte