78th Annual Meeting of the APS Division of Fluid Dynamics (Nov 23 — 25, 2025)

P038: Broken water, like broken glass

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Cavitation in a thin layer of water looks like broken glass. A 4.5-inch-diameter steel piston initially rests on a transparent plate of polycarbonate in water. The strike of a hammer accelerates the piston away from the plate with a magnitude on the order of 1000 g. The sudden acceleration induces a severe pressure drop in the thin liquid layer initiating the growth of vaporous cavitation bubbles as shown in the first image on the bottom right. As the wall-bounded bubbles expand, the piston and plate squish the bubbles into pancake-like shapes (second image). Continued growth causes the bubbles to push into each other forming thin polygonal vapor bubbles separated by liquid filaments (third and main images). With the bubbles forming shards and the liquid filaments forming cracks the combined effect is reminiscent of happy childhood days when playing with a ball near a window got a little out of hand.