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Published on: February 17, 2019
Cavity ripples observed during the impact of solid objects into liquids
Torben Grumstrup1, Joseph B Keller, Andrew Belmonte
1W.G. Pritchard Laboratories, Department of Mathematics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Physical Review Letters
|October 13, 2007
Summary
Rapidly moving objects create fixed ripples on liquid surfaces. This phenomenon, linked to acoustic resonance and bubble oscillations, is explained by a new irrotational model.
Area of Science:
- Fluid dynamics
- Acoustics
- Surface physics
Background:
- Objects entering liquids create air cavities.
- Cavity dynamics influence acoustic emissions.
- Surface tension and object motion are key factors.
Purpose of the Study:
- To experimentally observe and model the rippling of air cavities formed by moving objects.
- To understand the relationship between cavity pinch-off, acoustic emission, and surface ripples.
- To develop a theoretical framework for the observed phenomenon.
Main Methods:
- Experimental observation of air cavity formation and surface dynamics.
- High-speed imaging of object-liquid interaction.
- Acoustic emission measurement.
- Development of an irrotational fluid dynamics model.
Main Results:
- Observed well-defined, lab-frame-fixed ripples on the air cavity surface.
- Ripples initiate at cavity pinch-off, coinciding with acoustic emission.
- Acoustic resonance frequency approximates the Minnaert frequency.
- The irrotational model successfully explains ripple formation via spatial rectification of volume oscillations.
Conclusions:
- The study reveals a novel fluid dynamics phenomenon: fixed ripples on entrained air cavities.
- Acoustic resonance plays a crucial role in the formation of these surface patterns.
- The proposed model provides a theoretical basis for understanding the interaction between cavity dynamics and surface geometry.
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