Investigation of cavitation and vapor shedding mechanisms in a Venturi nozzle

Brunhart, Maxwell; Soteriou, Celia; Gavaises, Manolis; Karathanassis, Ioannis K.; Koukouvinis, Phoevos; Jahangir, Saad; Poelma, Christian

doi:10.1063/5.0015487

Cited by 52 publications

(13 citation statements)

References 36 publications

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“…More specifically, it was found that LES can offer a better performance in the prediction of the intermittent vortices compared with RANS. Thanks to the latest works of the research groups at the Swiss Federal Institute of Technology of Lausanne [25][26][27][28], the Technical University of Munich [29][30][31], the Chalmers University of Technology [32][33][34], the Delft University of Technology [35] and the University of London [36][37][38], great progress has been made in the simulation of cavitation in vortical flows with LES. These works have increased the understanding of the cavitation effects on vortices/eddies dynamic behavior, ranging from the large scales to the intermittent ones.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of the Cavitation Effects on the Vortex Shedding from a Hydrofoil with Blunt Trailing Edge

Chen

Geng

Escaler

2020

Fluids

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Vortex cavitation can appear in the wake flow of hydrofoils, inducing unwanted consequences such as vibrations or unstable behaviors in hydraulic machinery and systems. To investigate the cavitation effects on hydrofoil vortex shedding, a numerical investigation of the flow around a 2D NACA0009 with a blunt trailing edge at free caviation conditions and at two degrees of cavitation developments has been carried out by means of the Zwart cavitation model and the LES WALE turbulence model which permits predicting the laminar to turbulent transition of the boundary layers. To analyze the dynamic behavior of the vortex shedding process and the coherent structures, two identification methods based on the Eulerian and Lagrangian reference frames have been applied to the simulated unsteady flow field. It is found that the cavitation occurrence in the wake significantly changes the main vortex shedding characteristics including the morphology of the vortices, the vortex formation length, the effective height of the near wake flow and the shedding frequency. The numerical results predict that the circular shape of the vortices changes to an elliptical one and that the vortex shedding frequency is significantly increased under cavitation conditions. The main reason for the frequency increase seems to be the reduction in the transverse separation between the upper and lower rows of vortices induced by the increase in the vortex formation length.

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Section: Introductionmentioning

confidence: 99%

Numerical Investigation of the Cavitation Effects on the Vortex Shedding from a Hydrofoil with Blunt Trailing Edge

Chen

Geng

Escaler

2020

Fluids

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“…The cavitation status is defined by the pressure recovery number κ, which can be calculated by P 1 , P 2 and P v , the expression is depicted as equation 3 [22,20,23].…”

Section: Experiments Setupmentioning

confidence: 99%

A Venturi tube design for studying travelling bubble cavitation

Zuo

2022

J. Phys.: Conf. Ser.

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Travelling bubble cavitation always appears in forms of nearly spherical travelling bubbles. These bubbles grow from the freestream/surface nuclei in the low-pressure region in the flow channel. As the inception of travelling bubble cavitation is very sensitive to the boundary layer flow, attached cavitation would be likely to appear simultaneously if the flow is not well-controlled. In this study, based on the interaction between cavitation inception and boundary layer, a Venturi tube for studying travelling bubble cavitation is designed with the aid of a computational fluid dynamics (CFD) approach. The flow channel of this Venturi tube is composed of an inlet straight pipe (10 mm × 10 mm square), a contraction section, a throat section (5 mm × 5 mm square) and two diffuser sections (diffuser 1 and diffuser 2). For visualization convenience, each cross section of the Venturi tube is square. From CFD results, no flow separation occurs near the throat section and the adverse pressure gradient is relatively small, which indicates attached cavitation may not occur. The manufactured Venturi tube is installed in a blow-down type tunnel and tested with Reynolds number at roughly 3 - 3.75 × 104 and the pressure recovery number at 2.95 - 4.41. The velocity of the Venturi inlet varies from about 6 m/s to 7.5 m/s. Experiment results shows travelling bubble cavitation can be generated successfully and pure travelling bubble cavitation inception is achieved in this Venturi tube. The formation of travelling bubbles is recorded by a Phantom VEO 710L high-speed camera with framing rate of 24000 fps.

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“…Knapp demonstrated the development of a liquid re-entrant jet for the first time. Brunhart et al 28 have proven that there are two vapor-shedding mechanisms under cavitation conditions: re-entry flow and condensation shock through simulation and experiment. Long 29 reported that a liquid–vapor mixing shockwave is also observed under the operating-limit cavitation stage in jet pumps.…”

Section: Introductionmentioning

confidence: 99%

Research on Noise-Induced Characteristics of Unsteady Cavitation of a Jet Pump

2022

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The dynamic cavitation characteristics of normal-temperature water flowing through a transparent jet pump under different cavitation conditions were experimentally studied by adjusting the pressure ratio. The common results are presented at different pressure ratios, including the temporal and spatial changes of the pressure and noise, together with the visual observation of the cavitation unsteady behaviors using a high-speed camera. The analyses on the measured data and images reveal that the cavitation cloud is generated by periodic oscillations of the jet traveling pressure wave and the bubble traveling pressure wave. The oscillation of the two kinds of interface waves is caused by the collapse of the bubbles, which is the main mechanism of the bubble cloud shedding. As the pressure ratio increases, the maximum length of the jet cloud and bubble cloud linearly decreases, while their oscillation frequency increases gradually. Combined with the cavitation-cloud visualization data and noise frequency analysis, it is proposed that the strong impact between the jet traveling pressure wave and the bubble traveling pressure wave is the main cause of noise. Specially, the acoustic pressure reaches the maximum when the oscillation frequency of the jet traveling pressure wave is the same as that of the bubble traveling pressure wave. Also, the jet traveling pressure wave has a great influence on the migration of bubbles in the cavity. The results can provide guidance for the optimal operating condition in cavitation applications such as jet aerator and quantitative addition.

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Investigation of cavitation and vapor shedding mechanisms in a Venturi nozzle

Cited by 52 publications

References 36 publications

Numerical Investigation of the Cavitation Effects on the Vortex Shedding from a Hydrofoil with Blunt Trailing Edge

Numerical Investigation of the Cavitation Effects on the Vortex Shedding from a Hydrofoil with Blunt Trailing Edge

A Venturi tube design for studying travelling bubble cavitation

Research on Noise-Induced Characteristics of Unsteady Cavitation of a Jet Pump

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