Document Type

Miscellaneous

Journal/Book Title/Conference

Physics of Fluids

Volume

27

Issue

9

Publisher

American Institute of Physics

Publication Date

2015

Abstract

Despite the scholarly fascination with water entry of spheres for well over a century,1 we present a new observation, namely, the crown-buckling instability. This instability is characterized by striations appearing near the top of the crown walls just prior to the surface seal, as shown in Fig. 1(a). The crown wall collapses inward due to the pressure differential across the wall created by the moving air in the wake of the sphere and surface tension within the crown. Since the rate of collapse is faster than that at which fluid drains out from the neck region, fluid collects into the striations and the crown buckles. The wall is slightly thicker along these striations than in between where the films are more susceptible to air flow and get drawn inward into the crown interior, thereby developing into bag-like structures (Figs. 1(a) and 1(b)) that ultimately atomize, causing a fine spray inside the crown. Under atmospheric conditions, this typically occurs within 5 ms after impact.

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