Two-phase flow structure of sheet cavitation

Stutz, Benoı̂t; Reboud, Jean-Luc

doi:10.1063/1.869505

Cited by 142 publications

(69 citation statements)

References 26 publications

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“…Void fraction distribution measurements within a Venturi flow were performed by Stutz & Reboud (1997a) and Stutz & Reboud (1997b). Using optical probes, they measured the conditionally averaged void fraction and the liquid-phase flow velocity of cloud 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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confidence: 99%

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

2016

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“…Un dispositif de mesure locale par bisonde optique a été déve-loppé afin de pouvoir étudier les écoulements diphasiques au sein des poches de cavitation [9] …”

Section: Mesures Au Sein Des éCoulements Diphasiquesunclassified

Etude expérimentale des débits de vaporisation dans les poches de cavitation

Stutz¹,

Reboud²

1997

La Houille Blanche

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“…The exact mechanisms of cavitating flow with complex characteristics have been identified across multiple experiences (Reisman et al 1998, Chen et al 2010, Tomov et al 2016, Stutz and Reboud, 1997and Zhang et al 2015.…”

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confidence: 99%

Numerical Study of Unsteady Cavitating Flows around a Hydrofoil

Taher

Kanfoudi

Ennouri

et al. 2017

JAFM

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In this paper, we report the results of a numerical investigation on unsteady cavitating flows around a circular leading edge (CLE) hydrofoil. The objective of this study is to properly predict the appearance of cavitation pocket, its development and its detachment causing adverse effects on industrial systems such as microscopic plastic deformations at the solid walls. For this reason it is very important to study the influence of turbulence models on simulation results. We present a closing of the hydrodynamic equation system by a transport equation of an active scalar (volume fraction of the vapor phase) with a source terms. The Computational Fluid Dynamics (CFD) code used is ANSYS CFX. Before comparing the capability of the different turbulent models to predict unsteady behavior of cavitating flow along the hydrofoil, the study of the influence of the mesh resolution was performed in cavitating condition. This investigation was performed, on CLE hydrofoil, by monitoring the influence of for progressively finer meshes on the values of the drag CD and lift CL coefficients. Moreover, a study of the influence of the normal dimensionless distance to the wall (y+) was carried out on the hydrofoil surface. For the unsteady flow, a comparison of different turbulence models with the experiment leads to study the interaction of these models with the vapor pocket (detachment and collapse of vapor pocket). Two turbulence models were tested in this study: modified k-ε model and large eddy simulation (LES). In the present work, the predictions of velocity and pressure evolutions in the vicinity of the hydrofoil are compared to experimental data.

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Two-phase flow structure of sheet cavitation

Abstract: Development of a wall shear stress integral measurement and analysis system for two-phase flow boundary layers Rev.

Cited by 142 publications

References 26 publications

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

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

Etude expérimentale des débits de vaporisation dans les poches de cavitation

Numerical Study of Unsteady Cavitating Flows around a Hydrofoil

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