Measurement of the Bubbly Flow Beneath Partial Attached Cavities Using Electrical Impedance Probes

George, D. L.; Iyer, Claudia O.; Ceccio, Steven L.

doi:10.1115/1.483237

Cited by 23 publications

(14 citation statements)

References 7 publications

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“…Subsequent studies have demonstrated that inception involves intermittent and short-lived attachment of travelling bubble cavitation to the surface near the minimum pressure point (Blake, Wolpert & Geib 1977; Ceccio & Brennen 1991; De Chizelle, Ceccio & Brennen 1995; Li & Ceccio 1996; Laberteaux et al. 1998; George, Iyer & Ceccio 2000). The important role of boundary layers was discussed first by Arakeri & Acosta (1973).…”

Section: Introductionmentioning

confidence: 99%

On the mechanisms that sustain the inception of attached cavitation

2020

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Section: Introductionmentioning

confidence: 99%

On the mechanisms that sustain the inception of attached cavitation

2020

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“…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). Callenaere et al (2001) measured the thickness of the re-entrant jet using acoustic probes and found shedding to be dependent on the jet thickness, with thicker re-entrant jets resulting in shedding.…”

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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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“…For the current study the complex part of the mixture impedance is assumed to be negligible since o" w >> 2 1rfFL e,, where a." is the conductivity of water (-3.5 IuS cm), f is the input frequency (-10 kHz), FL is the non-dimensionalized permittivity of the water (-80), and e, is the permittivity of a vacuum (8.85x10-2 F m -) (George et al, 2000). The real part of the mixture impedance (i.e.…”

Section: Near-wall Void Fraction Analysismentioning

confidence: 99%

High Reynolds Number Micro-Bubble and Polymer Drag Reduction Experiments

Ceccio¹,

Dowling²,

Perlin³

et al. 2008

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Background: This effort was a continuation of the joint ONR and DARPA programs of the PI and Co-PI's initiated as part of the DARPA Friction Drag Reduction Program (ATO/TTO). The purpose of the investigation was to examine the physics and engineering of friction drag reduction methods for turbulent boundary layers (TBL) found in hydrodynamic flows. Three methods of friction drag reduction (FDR) were examined:" Polymer Drag Reduction-solutions containing extensible, long-chain molecules ' are injected into a TBL. The polymer molecules interact with the underlying turbulent flow and lead to a reduction of the correlated velocity fluctuations and, hence, a reduction of the turbulent transport of momentum across the TBL. This leads to local drag reduction of up to -70% for a TBL flow over smooth surfaces compared to a flow without polymer injection.* Micro-bubble Drag Reduction-air is injected into the TBL with the aim of producing a large volume of small bubbles in the near-wall region of the TBL. The presence of the bubbles reduces the bulk density of the fluid near the wall and possibly alters the turbulent velocity fluctuations. These effects can combine to locally reduce the friction drag over 80%." Air Layer Drag Reduction-air is injected into the TBL with the aim of creating a stable gas layer of very high void fraction (> 80% void fraction), separating the liquid flow from the solid surface. This results in friction drag reductions of over 80% compared to the friction drag of an unmodified TBL. DISTRIBUTION STATEMENT A 20080131 272 Approved for Public ReleaseDistribution UnlimitedThese FDR methods have been studied for some time on the laboratory scale, yielding a great deal of information on their engineering potential and underlying methods. However, the flow physics responsible for FDR does not easily scale from the laboratory to full-scale hydrodynamic applications. Hence, our effort focused on conducting a series of experiments at both large size scales and high Reynolds numbers in order to further explore the flow physics and practicality of these FDR methods.Our experiments were performed on a canonical TBL flow formed on a flat plate, zeropressure gradient boundary layer. The maximum length of the test model was -10 m, and the maximum velocity of the flow was -20 m/s, making the Reynolds number based on maximum length -200 million. Our experiments were conducted in the William B.Morgan Large Cavitation Channel (LCC), owed and operated by the Naval Surface Warfare Center-Carderock Division of the U. S. Navy.During this portion of our research program, three rounds of testing in the LCC were conducted:* Phase III (Polymer FDR) * Phase IV (MBDR/ALDR) * Phase V (Polymer FDR).Two additional rounds of testing were conducted under the first portion of ONR and DARPA support: Phase I was a baseline test of the model, and Phase II was on MBDR. Also, a portion of Phase V was devoted to examining the influence of roughness on Polymer FDR and ALDR. This portion of the effort was supported under DARPA contract "...

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Measurement of the Bubbly Flow Beneath Partial Attached Cavities Using Electrical Impedance Probes

Cited by 23 publications

References 7 publications

On the mechanisms that sustain the inception of attached cavitation

On the mechanisms that sustain the inception of attached cavitation

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

High Reynolds Number Micro-Bubble and Polymer Drag Reduction Experiments

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