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Supersonic air flow due to solid-liquid impact
Stephan Gekle1, Ivo R Peters, José Manuel Gordillo
1Department of Applied Physics and J. M. Burgers Centre for Fluid Dynamics, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
Physical Review Letters
|April 7, 2010
Summary
When an object hits a liquid, a high-speed air jet is ejected from the collapsing cavity. This air jet reaches supersonic speeds, behaving like a nozzle formed by the shrinking liquid cavity.
Area of Science:
- Fluid Dynamics
- Acoustics
- Physics of Liquids
Background:
- Impact of solid objects on liquids generates liquid jets via cavity collapse.
- The dynamics of the air within the collapsing cavity remain less understood.
Purpose of the Study:
- To investigate the generation and characteristics of air jets during solid-object-liquid impacts.
- To analyze the conditions under which these air jets achieve supersonic speeds.
Main Methods:
- High-speed visualization experiments using smoke particles.
- Multiscale numerical simulations of the impact process.
Main Results:
- A high-speed air jet is expelled from the collapsing impact cavity.
- Supersonic air jet speeds are achieved at cavity diameters just over 1 mm.
- The air flow structure mimics compressible flow through a nozzle.
Conclusions:
- The rapid collapse of liquid impact cavities can generate supersonic air jets.
- The liquid cavity acts as a transient, time-varying nozzle for the air flow.
- This phenomenon offers insights into high-speed gas dynamics in liquid environments.
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