Cavitation nuclei in water exposed to transient pressures

Andersen, A.; Mørch, Knud Aage

doi:10.1017/jfm.2015.185

Cited by 16 publications

(26 citation statements)

References 36 publications

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“…Based on the large number of observations discussed above, a model of skin-stabilized interfacial cavitation nuclei was [36]. In this model, the cavitation nuclei are supposed to be the same shape as the very flat surface nanobubbles found by AFM (see figure 7a), i.e.…”

Section: Model Of a Skin-stabilized Interfacial Cavitation Nucleusmentioning

confidence: 99%

“…(c) At subsequent exposure to tensile stress it expands and loses tensile strength over time by diffusion of gas. (Reproduced with permission from [36].…”

Section: ð4:2þmentioning

confidence: 99%

“…Andersen & Mørch [36,39] produced pulsed pressurization by dropping their water-filled container onto a steel block, producing a compressive pulse (C-pulse) of maximum intensity about 3-4 bar centrally at the bottom and of duration 1.1 or 1.7 ms, followed by a tensile tail. During pressurization strong approximately 11 kHz resonance oscillations were superposed on the basic compressive pulse (figure 13a).…”

Section: Experiments On Pulse Pressurization Of Interfacial Cavitatiomentioning

confidence: 99%

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Cavitation inception from bubble nuclei

Mørch¹

2015

Interface Focus.

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The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure–time history of the water. A recent model and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes.

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Section: Model Of a Skin-stabilized Interfacial Cavitation Nucleusmentioning

confidence: 99%

“…(c) At subsequent exposure to tensile stress it expands and loses tensile strength over time by diffusion of gas. (Reproduced with permission from [36].…”

Section: ð4:2þmentioning

confidence: 99%

Section: Experiments On Pulse Pressurization Of Interfacial Cavitatiomentioning

confidence: 99%

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Cavitation inception from bubble nuclei

Mørch¹

2015

Interface Focus.

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“…After the reflection of the initial compression wave a tensile stress wave is generated in the medium and when the local tensile strength is larger than the strength of the material, small defects present in the solid structure are activated in a process similar to that of cavitation in liquids when the pressure falls below Blake's threshold. [17][18][19][20][21][22] In this context, spallation refers to the ejection or vaporization of a material from the target in response to an impact. In liquids, the impact of a projectile flying across a vessel full of liquid is known to induce the formation of bubbles and its latter collapse.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the collapse of bubbles after the impact of a piston on a liquid free surface

et al. 2017

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We describe a novel technique based on the impact of a piston on a liquid confined in a vessel. Pressure measurements reveal that strong pressure variations (up to 100 atmospheres) with a rich content of frequencies are efficiently transmitted to the liquid. High-speed camera visualizations show that pre-existing millimetric bubbles always collapse during the first instants of the impact whereas the behavior of submillimetric bubbles depends on the features of the pressure evolution in the system. In addition to the impact velocity, the amount of * Corresponding author: fuster@dalembert.upmc.fr 1 gas/vapor trapped between the piston and the liquid's surface plays an important role on how pressure evolves. Only when negative pressure occurs bubbles grow significantly and collapse. The violent collapse of bubbles promote turbulence and mixing at very small length-scales which renders this technique interesting to intensify processes limited by heat and mass diffusion.

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“…Knapp, Daily & Hammitt 1970;Franc & Michel 2004). Recent studies about nuclei on hydrophobic surfaces (Bremond et al 2005;Borkent et al 2009), skin-stabilised surface nuclei (Andersen & Mørch 2015), the activation of roughness elements that serve as nucleation spots (van Rijsbergen & van Terwisga 2011), vapour-bubble nucleation in Rayleigh-Bénard turbulence (Guzman et al 2016), vapour bubbles and the role of non-condensable gas (Prosperetti 2017), and the broad field of nano-bubbles (Lohse & Zhang 2015) underline the importance of research on cavitation nuclei as well as on (micro-and nano-) bubbles.…”

Section: Harvey Nucleimentioning

confidence: 99%

Diffusion-driven nucleation from surface nuclei in hydrodynamic cavitation

Groß

Pelz

2017

J. Fluid Mech.

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Investigations about the role of nuclei and nucleation for the inception and formation of cavitation have been part of cavitation research since Harvey et al. (J. Cell. Physiol., vol. 24 (1), 1944, pp. 1-22) postulated the existence of gas filled crevices on surfaces and particles in liquids. In a supersaturated liquid, surface nuclei produce small gas bubbles due to mass transfer of gas or themselves work as weak spots in the liquid that are necessary for a phase change under technically relevant static pressures. Although various theories and models about nuclei and nucleation have found their way into standard literature, there is a lack of experimentally validated theories that describe the process of diffusion-driven nucleation in hydrodynamic cavitation. In order to close this gap we give new theoretical insights into the physics of this nucleation mechanism at technically relevant low supersaturations validated with extensive experimental results. The nucleation rate, the number of produced bubbles per second, is proportional to the supersaturation of the liquid and shows a nonlinear dependence on the shear rate at the surface nucleus. A model for the Strouhal number as dimensionless nucleation rate is derived allowing the estimation of nucleation rates from surface nuclei in hydrodynamic cavitation. The model provides three asymptotes, being a function of Péclet number, Weber number, the supersaturation of the liquid ζ and gas solubility Λ for three different detachment mechanisms, Sr ∝ ζ ΛWe n Pe 1/3 with n = 1/3, 3/4, 1. The theoretical findings are in good agreement with experimental results, leading to a new assessment of the role of diffusion in cavitating flows.

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Cavitation nuclei in water exposed to transient pressures

Cited by 16 publications

References 36 publications

Cavitation inception from bubble nuclei

Cavitation inception from bubble nuclei

Investigation of the collapse of bubbles after the impact of a piston on a liquid free surface

Diffusion-driven nucleation from surface nuclei in hydrodynamic cavitation

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