What is it about?
Water usually carries gas in solution as well as contaminating agents that form stable gaseous nuclei on bounding surfaces or on particles, decisive for its tensile strength. A model of skin-stabilized gaseous nuclei in diffusion balance on solid-water interfaces is presented, and it is used to interpret experiments of cavitation inception, generated by transient pulses of tensile stress.
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Why is it important?
The shift from water being a single phase liquid to being a bubbly two-phase medium at tensile stressing is named cavitation. It occurs in hydraulic systems, e.g. ship propellers, water turbines, valves, ultrasonic cleaning devices, when suddenly the pressure drops to negative values, but the level of stressing demanded depends on the cavitation nuclei present. This level varies from almost zero to hundreds of atmospheres. Cavitation is crucial for the hydraulic performance of components exposed to cavitation, but unfortunately, our knowledge of the nuclei governing the transition is at best qualitative. This work presents a new model of the cavitation nuclei, and it explains satisfactorily experimental cavitation inception, generated in simple controlled experiments.
Perspectives
The experimental work in this paper was produced first, but publication required that theoretical support was presented along. It led to the development of a full model - and it turned out to explain the experimental results surprisingly well. The model seems to show the road for further research.
Dr Knud Aage Mørch
Danmarks Tekniske Universitet
Read the Original
This page is a summary of: Cavitation nuclei in water exposed to transient pressures, Journal of Fluid Mechanics, April 2015, Cambridge University Press,
DOI: 10.1017/jfm.2015.185.
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