Inner Structure of Cloud Cavity on a Foil Section.

Kawanami, Yasutaka; Kato, Hiroharu; Yamaguchi, Hideyo; Maeda, Masatsugu; Nakasumi, Shogo

doi:10.1299/jsmeb.45.655

Cited by 37 publications

(21 citation statements)

References 11 publications

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“…Thus it must extend to walls of the flow area or form a closed path. In most cases the cavitation cloud will form a cylindrical vortex which turns into a horseshoe vortex (see Kawanami et al 2002). The horseshoe vortex is excited by two mechanisms: the first is a dynamic mechanism which acts by increasing the ambient pressure and the second, which is a kinematic mechanism, acts by stretching the vortex ring as indicated by Buttenbender & Pelz (2012).…”

Section: Sheet and Cloud Cavitationmentioning

confidence: 99%

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The transition from sheet to cloud cavitation

2017

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Recent studies indicate that the transition from sheet to cloud cavitation depends on both cavitation number and Reynolds number. In the present paper this transition is investigated analytically and a physical model is introduced. In order to include the entire process, the model consists of two parts, a model for the growth of the sheet cavity and a viscous film flow model for the so-called re-entrant jet. The models allow the calculation of the length of the sheet cavity for given nucleation rates and initial nuclei radii and the spreading history of the viscous film. By definition, the transition occurs when the re-entrant jet reaches the point of origin of the sheet cavity, implying that the cavity length and the penetration length of the re-entrant jet are equal. Following this criterion, a stability map is derived showing that the transition depends on a critical Reynolds number which is a function of cavitation number and relative surface roughness. A good agreement was found between the model-based calculations and the experimental measurements. In conclusion, the presented research shows the evidence of nucleation and bubble collapse for the growth of the sheet cavity and underlines the role of wall friction for the evolution of the re-entrant jet.

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Section: Sheet and Cloud Cavitationmentioning

confidence: 99%

“…The cavitation cloud is then carried downstream by the fluid flow and collapses. Lange & Bruin (1997), Kjeldsen, Arndt & Effertz (2000) and Kawanami et al (2002) also made important contributions to the study of this complex phenomenon.…”

Section: P F Pelz T Keil and T F Großmentioning

confidence: 99%

The transition from sheet to cloud cavitation

2017

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“…Boorsma and Whitworth [8] and van Rijsbergen et al [1] related the structures to the acoustic emission signals and suggested that the orientation of the shock wave should be considered. Large scale primary spanwise vortices were studied by Pereira et al [9] and Kawanami et al [10], who observed their development by stereography and holography, respectively. They have shown that the focusing of the collapse could play a role in the aggressiveness of erosion.…”

Section: Introductionmentioning

confidence: 99%

On the mechanisms of cavitation erosion – Coupling high speed videos to damage patterns

Dular

Petkovšek

2015

Experimental Thermal and Fluid Science

106

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“…They found the convection velocity of the cloud to be much lower than the free-stream speed. Kawanami et al (2002) used laser holography to study the structure of a cloud shed from a hydrofoil and estimated the bubble size distribution. Measurements of the re-entrant flow underneath the cavity using electrical impedance probes was done by Pham, Larrarte & Fruman (1999) and George, Iyer & Ceccio (2000).…”

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confidence: 99%

Bubbly shock propagation as a mechanism for sheet-to-cloud transition of partial cavities

2016

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Partial cavitation in the separated region forming from the apex of a wedge is examined to reveal the flow mechanism responsible for the transition from stable sheet cavity to periodically shedding cloud cavitation. High-speed visualization and time-resolved X-ray densitometry measurements are used to examine the cavity dynamics, including the time-resolved void-fraction fields within the cavity. The experimentally observed time-averaged void-fraction profiles are compared to an analytical model employing free-streamline theory. From the instantaneous void-fraction flow fields, two distinct shedding mechanisms are identified. The classically described re-entrant flow in the cavity closure is confirmed as a mechanism for vapour entrainment and detachment that leads to intermittent shedding of smaller-scale cavities. But, with a sufficient reduction in cavitation number, large-scale periodic cloud shedding is associated with the formation and propagation of a bubbly shock within the high void-fraction bubbly mixture in the separated cavity flow. When the shock front impinges on flow at the wedge apex, a large cloud is pinched off. For periodic shedding, the speed of the front in the laboratory frame is of the order of half the free-stream speed. The features of the observed condensation shocks are related to the average and dynamic pressure and void fraction using classical one-dimensional jump conditions. The sound speed of the bubbly mixture is estimated to determine the Mach number of the cavity flow. The transition from intermittent to transitional to strongly periodic shedding occurs when the average Mach number of the cavity flow exceeds that required for the generation of strong shocks.

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Inner Structure of Cloud Cavity on a Foil Section.

Cited by 37 publications

References 11 publications

The transition from sheet to cloud cavitation

The transition from sheet to cloud cavitation

On the mechanisms of cavitation erosion – Coupling high speed videos to damage patterns

Bubbly shock propagation as a mechanism for sheet-to-cloud transition of partial cavities

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