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

P041: The Pinching Sound

Authors
  • Ziqiang Yang, King Abdullah University of Science and Technology
  • Yuansi Tian , University of Science and Technology of China
  • Er Qiang Li , Department of Modern Mechanics, University of Science and Technology of China , Hefei 230027, China
  • Sigurdur T. Thoroddsen , King Abdullah University of Science and Technology

Based on the study of immiscible liquid drop-impact craters, we investigate the acoustic signature of dual pinch-off events. Through high-speed imaging at 5 million fps synchronized with hydrophone recordings, we capture the precise moment of bubble detachment. The complex dimple collapse produces two distinct pinch-off events, each generating characteristic pressure waves (x-axis unit μs, y-axis unit Pa). By mapping the acoustic signal to visual frames, we accurately determine the exact timing of each pinch-off (marked by red dots on the acoustic curve), resolving previous controversies in the literature. The first acoustic peak corresponds to the initial neck rupture, while the second marks the secondary pinch-off at the top region. This direct correlation between visual and acoustic data provides unprecedented insight into the bubble dynamics responsible for underwater sound of rain.

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