Unsteady pressure fluctuation characteristics in the process of breakup and shedding of sheet/cloud cavitation

Wang, Changchang; Huang, Biao; Wang, Guoyu; Zhang, Mindi; Ding, Nan

doi:10.1016/j.ijheatmasstransfer.2017.06.005

Cited by 79 publications

(21 citation statements)

References 53 publications

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“…Consequently, compressibility is frequently ignored in flow with Mach number. However, the present study as well as other preliminary investigations (Egerer et al, 2014;Wang et al, 2017;Zhang et al, 2017) confirm that flow with low Mach number may involve flow dynamics closely correlated with density fluctuation. Claims such as that a redefinition is required for compressible flow are obviously an overstatement, even though the traditional notion is at variance with the findings of the present research.…”

Section: Re-examination Of Compressibility/compressible Flowsupporting

confidence: 83%

“…It leads to a secondary growth and detachment of sheet cavity. A similar phenomenon is observed in the case of a Venturi-tube (C. Wang, Huang, Wang, Zhang, & Ding, 2017) and submerged circular nozzle (Stanley, Barber, & Rosengarten, 2014), where the pressure propagation produces discontinuity in vapor distribution. The Mach number in the non-cavitating region is less than 0.1.…”

Section: Introductionsupporting

confidence: 68%

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Comparison of compressible and incompressible numerical methods in simulation of a cavitating jet through a poppet valve

Yuan

Jun

Liu

2018

Engineering Applications of Computational Fluid Mechanics

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The regime of compressible flow generally refers to the super/subsonic case. However, several remarkable cases with low Mach number could not be appropriately described with the incompressible method. It is a similar case for a cavitating jet inside a poppet valve. In order to comprehensively address the discrepancy between incompressible and compressible methods, both non-cavitating and cavitating cases are performed in experiment and calculation based on OpenFOAM. Experiment reveals a transition in flow pattern in both non-cavitating and cavitating flow. For example, for 0.7 mm openness and 30-degree poppet angle, transition happens at approximately 29 and 27 bar pressure drop for the two cases, respectively. In general, results from the compressible method exhibit better agreement with experiment regarding both flow performance and flow structure. By contrast, the incompressible method could not provide an accurate description for the transition process under the applied flow condition. A series of studies are carried out with emphasis on such discrepancy. Firstly, the deviation in flow performance is addressed based on velocity profile and turbulence level. Secondly, the disparity in flow structure is illustrated and the mechanism for cavitation inception is discussed, which combined provide an interpretation of the deficiency of the incompressible method. Thirdly, different inlet boundary conditions are applied, and the results confirm the independence of deficiency of the incompressible method for inlet fluctuation. Finally, a re-examination is proposed concerning traditional notion of compressible flow as well as the applicability of incompressible numerical method.

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Section: Re-examination Of Compressibility/compressible Flowsupporting

confidence: 83%

Section: Introductionsupporting

confidence: 68%

Comparison of compressible and incompressible numerical methods in simulation of a cavitating jet through a poppet valve

Yuan

Jun

Liu

2018

Engineering Applications of Computational Fluid Mechanics

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“…Arndt et al (2001); Reisman et al (1998). Converging-diverging geometries have been investigated experimentally by Ganesh et al (2016); Jahangir et al (2018); Wang et al (2017); Wu et al (2017) and recently by compressible numerical simulations (Budich et al, 2018). For shock initiated shedding, one observes an upstream moving bubbly shock rather than a re-entrant jet.…”

Section: Introductionmentioning

confidence: 99%

Investigation of condensation shocks and re-entrant jet dynamics in a cavitating nozzle flow by Large-Eddy Simulation

Trummler

Schmidt

Adams

2020

International Journal of Multiphase Flow

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Cloud cavitation is related to an intrinsic instability where clouds are shed periodically. The shedding process is initiated either by the motion of a liquid re-entrant jet or a condensation shock. Cloud cavitation in nozzles interacts with the flow field in the nozzle, the mass flow and the spray break-up, and causes erosion damage. For nozzle geometries cloud shedding and the associated processes have not yet been studied in detail.In this paper, we investigate the process of cloud cavitation shedding, the re-entrant jet and condensation shocks in a scaled-up generic step nozzle with injection into gas using implicit Large-Eddy Simulations (LES). For modeling of the cavitating liquid we employ a barotropic equilibrium cavitation model, embedded in a homogeneous multi-component mixture model. Full compressibility of all components is taken into account to resolve the effects of collapsing vapor structures.We carry out simulations of two operating points exhibiting different cavitation regimes. The time-resolved, three-dimensional simulation results cover several shedding cycles and provide deeper insight into the flow field. Our results show that at lower cavitation numbers, shedding is initiated by condensation shocks, which has not yet been reported for nozzle flows with a constant crosssection. We analyze the cavitation dynamics and the shedding cycles of both operating points. Based on our observations we propose modifications to established schematics of the cloud shedding process. Additionally, we analyze the near-wall upstream flow in and underneath the vapor sheet and possible driving mechanism behind the formation of the re-entrant jet.

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“…Besides, the y + of the medium mesh is nearly 1 for most of the hydrofoil surface. The definition of y + can be written as Equation (15). According to the previous comments for a valid LES method [37,44], a medium mesh with about 3.5 million nodes was selected as the final grid.…”

Section: Numerical Methods and Validationmentioning

confidence: 99%

“…Ganesh et al [14] conducted a series of experiments and found that the formation and propagation of a bubbly shock wave could cause large-scale shedding of an attached cavity at a small enough cavitation number. Wang [15] also indicated that a bubbly shock wave can cause void fraction discontinuity in sheet/cloud cavitating flows in a convergent-divergent channel. Actually, the mechanism of the re-entrant jet-induced shedding is typical, and widely studied by many researchers.…”

Section: Introductionmentioning

confidence: 99%

Large Eddy Simulation of Turbulent Attached Cavitating Flows around Different Twisted Hydrofoils

Chen²,

Yang

et al. 2018

Energies

Self Cite

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In this paper, the turbulent attached cavitating flows around two different twisted hydrofoils, named as NACA0009 and Clark-y, are studied numerically, with emphasis on cavity shedding dynamic behavior and the turbulence flow structures. The computational method of large eddy simulation (LES) coupled with a homogeneous cavitation model is applied and assessed by previous experimental data. It was found that the predicted results were in good agreement with that of the experiment. The unsteady cavity morphology of the two hydrofoils undergoes a similar quasi-periodic process, but has different shedding dynamic behavior. The scale of the U-type shedding structures forming on the suction surface of NACA0009 is larger than that of Clark-y. This phenomenon is also present in the iso-surface distributions of Q-criterion. Otherwise, the time-averaged cavity morphology is dramatically different for the two hydrofoils, and it is found that the attached location of the cavity is closely related to the hydrofoil geometry. The time fluctuation of the lift force coefficients is affected significantly by the cavity shedding dynamics. Compared with NACA0009, the lift force of Clark-y shows more fluctuation, due to its complicated shedding behavior. Further analysis of the turbulent structure indicates that the more violent shedding behaviors can induce higher levels of turbulence velocity fluctuations.

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Unsteady pressure fluctuation characteristics in the process of breakup and shedding of sheet/cloud cavitation

Cited by 79 publications

References 53 publications

Comparison of compressible and incompressible numerical methods in simulation of a cavitating jet through a poppet valve

Comparison of compressible and incompressible numerical methods in simulation of a cavitating jet through a poppet valve

Investigation of condensation shocks and re-entrant jet dynamics in a cavitating nozzle flow by Large-Eddy Simulation

Large Eddy Simulation of Turbulent Attached Cavitating Flows around Different Twisted Hydrofoils

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