Growth, oscillation and collapse of vortex cavitation bubbles

Choi, Jaehyug; Hsiao, Chao-Tsung; Chahine, Georges L.; Ceccio, Steven L.

doi:10.1017/s0022112008005430

Cited by 69 publications

(44 citation statements)

References 17 publications

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“…Alternatively, Gaussian vortex formulations were proposed by Choi and Ceccio (2007) and Choi et al (2009). These differed from the previous formulation with an additional parameter describing the azimuthal velocity at the cavity interface.…”

Section: Discussionmentioning

confidence: 99%

Flow field measurement around vortex cavitation

2015

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stage. These involve the smooth transport of vapor into the tip vortex, leading harmful implosions away from the propeller surface. The tip vortex cavity dynamics are not directly related to the propeller rotation rate. The excitation of this cavity often leads to high amplitude broadband pressure fluctuations between the fourth and seventh blade rate frequency (Wijngaarden et al. 2005).To better understand the sound production from vortex cavitation, a model for the waves on a tip vortex cavity was developed and was shown to be able to describe the interface dynamics in detail (Pennings et al. 2015). As a result, a condition could be predicted where a cavity resonance frequency could be amplified to produce high amplitude sound, as reported by Maines and Arndt (1997).The part that remains to be validated is a vortex model for the cavity size and cavity angular velocity. It has been shown that a Lamb-Oseen vortex model poorly estimates the cavity size as a function of cavitation number (Pennings et al. 2015). It is possible that overestimation of the vortex peak azimuthal velocity could have led to an overestimation of the cavity size. The main goal of the present study was to configure a simple low-order vortex model, to serve as an input into a vortex cavity wave dynamics model, to describe the tip vortex resonance frequency. It is based on the following steps.1. Model the tip vortex velocity field without cavitation (further referred to as wetted vortex) 2. Model the cavity size as a function of cavitation number based on wetted vortex properties 3. Show the difference in velocity field around a wetted and cavitating vortex 4. Obtain the cavity angular velocity value that gives the best correlation to the tip vortex cavity resonance frequency Abstract Models for the center frequency of cavitatingvortex induced pressure-fluctuations, in a flow around propellers, require knowledge of the vortex strength and vapor cavity size. For this purpose, stereoscopic particle image velocimetry (PIV) measurements were taken downstream of a fixed half-wing model. A high spatial resolution is required and was obtained via correlation averaging. This reduces the interrogation area size by a factor of 2-8, with respect to conventional PIV measurements. Vortex wandering was accounted for by selecting PIV images for a given vortex position, yielding sufficient data to obtain statistically converged and accurate results, both with and without a vapor-filled vortex core. Based on these results, the loworder Proctor model was applied to describe the tip vortex velocity outside the viscous core, and the cavity size as a function of cavitation number. The flow field around the vortex cavity shows, in comparison with a flow field without cavitation, a region of retarded flow. This layer around the cavity interface is similar to the viscous core of a vortex without cavitation.

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Section: Discussionmentioning

confidence: 99%

Flow field measurement around vortex cavitation

2015

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“…The condition of zero shear stress results in a small region of solid-body rotation near the cavity. The present formulation is different from the Gaussian vortex formulations proposed by Choi & Ceccio (2007) and Choi et al (2009) who introduce an additional parameter that describes the azimuthal velocity at the cavity interface. The formulation for the azimuthal velocity of the cavitating vortex still needs to be validated by detailed flow field measurements.…”

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confidence: 83%

Dynamics of isolated vortex cavitation

et al. 2015

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The dynamic behaviour of vortex cavitation on marine propellers may cause inboard noise and vibration, but is not well understood. The main goal of the present study is to experimentally analyse the dynamics of an isolated tip vortex cavity generated at the tip of a wing of elliptical planform. Detailed high-speed video shadowgraphy was used to determine the cavity deformations in combination with force and sound measurements. The cavity deformations can be divided in different modes, each of which show a distinct dispersion relation between frequency and wavenumber. The dispersion relations show good agreement with an analytical formulation. Finally, experimental support is given to the hypothesis that the resonance frequency of the cavity volume variation is related to a zero group velocity.

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“…Similarly, [25] demonstrated possible fragmentation of the vortex core so as to increase the vorticity at the core centre. Finally, the strong interaction observed between vortex properties and bubble dynamics [26], the coupling of radial and axial growth of bubbles trapped in vortices [27] and the interaction between shear (or normal strain) flow and bubble volume change [28] form a tremendously complex flow field inside an injector nozzle, where dynamic changes in the behaviour of vortices and vapour bubbles strongly affect the emerging fuel spray. Highly transient flow phenomena caused by the fast needle response times, give rise to formation of vortical structures and therefore, to string cavitation [8].…”

Section: Introductionmentioning

confidence: 99%