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Experimental analysis on unsteady characteristics of sheet/cloud cavitating Venturi flow under the effect of dissolved air

Malekshah Emad Hasani, Wróblewski Włodzimierz, Bochon Krzysztof, Majkut Mirosław, Rusin Krzysztof

Archives of Thermodynamics

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2022

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Vol. 43, no 3

63--84

EN

The highly dynamic and unsteady characteristics of the cavitating flow cause many negative effects such as erosion, noise and vibration. Also, in the real application, it is inevitable to neglect the dissolved air in the water, although it is usually neglected in the previous works to reduce the complexity. The novelty of the present work is analysing the impact of dissolved air on the average/unsteady characteristics of Venturi flow by conducting sets of experimental tests. For this purpose, two different amounts of dissolved air at five pressure levels (i.e. five different sets of cavitation numbers) were considered in the study of cavitating flow inside a Venturi nozzle. The fast Fourier transform analysis of pressure fluctuations proved that the shedding frequency reduces almost by 50% to 66%, depending on the case, with adding the amount of dissolved air. However, the reduction of 14% to 25% is achieved by the vibration transducers. On the other hand, the cavity enlarges as well as bubbly flow is observed in the test chamber at a higher level of dissolved air. Furthermore, it is observed that the re-entrant jet, as the main reason for the cavity detachment, is more effective for the detachment process in cases with a lower level of dissolved air, where the re-entrant jet front penetrates more toward the leading edge.

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LES numerical study on in–injector cavitating flow

Pyszczek R., Kapusta Ł. J., Teodorczyk A.

Journal of Power Technologies

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2017

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Vol. 97, nr 1

52--60

EN

In this paper a computational study on hexane flow in a fuel injector is presented. Large Eddy Simulation (LES) was used to capture the turbulent patterns present in the flow. The main aim was to investigate the cavitation phenomenon and its interaction with turbulence as well as the influence of injection pressure and backpressure on fuel mass flow and flow conditions. Analysis of the approach to define the outlet boundary conditions in terms of convergence time and fluid mass outflow oscillations formed a crucial part of the study. Numerical simulations were performed with AVL Fire CFD (Computational Fluid Dynamics) software. The Euler-Euler approach and multifluid model for multiphase flow modelling were applied. Injector needle movement was included in the simulation. Results show that the additional volumes attached to the nozzle outlets improved the convergence of the simulations and reduced mass outflow oscillations. Fuel mass flow at the outlets was dependent on inlet pressure, position of the needle and backpressure, while the influence of backpressure on fuel mass flow was negligible. The presence of the vapor phase at the exit of the nozzles did not affect average fuel mass flow. All the simulations showed interaction between the gaseous phase distribution and the turbulence of the flow.

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Validation of Numerical Simulations of Cavitating Flow in Convergent-Divergent Nozzle

Niedźwiedzka A., Lipiński S.

Measurement Automation Monitoring

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2016

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Vol. 62, No. 10

329--332

EN

In the article, validation of results of numerical simulations of cavitating flow in a convergent-divergent nozzle is presented. In validation, a new optoelectronic system is used in order to extract the changes in the bubbles volume fraction of the mixture in freely specified cross-sections. Three homogeneous models (Schnerr and Sauer, Singhal et al. and Zwart et al.) are analysed. The assessment of usefulness of the new system in experimental measurements of cavitation is the main aim of the article. Looking for new opportunities to replace image analysis, which is a traditional validation method in numerical simulations of cavitating flows, is motivation for the research. The results obtained with the use of the system show a good agreement with the simulation’s results for the two chosen cross-sections. The described optoelectronic system gives promising results and can be regarded as an alternative to traditional validation methods in the cavitation research area.

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Modelowanie kawitacji przy opływie profilu z zastosowaniem zmiennej liczby kawitacji

Homa D., Wróblewski W.

Modelowanie Inżynierskie

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2015

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T. 24, nr 55

42--49

PL

W artykule przedstawiono modelowanie przepływu z kawitacją w przypadku opływu wokół profilu hydraulicznego. Liczba kawitacja została dobrana w taki sposób, by zaobserwować różne typy struktur kawitacyjnych. Użyto modelu wielofazowego typu one–fluid oraz założono izotermiczność przepływu. Do zamodelowania powstawania fazy gazowej użyto modelu Schnerr & Sauer. Ze względu na niestacjonarność zjawiska zastosowano symulacje typu transient. Porównano wyniki symulacji z danymi eksperymentalnymi dla różnych typów kawitacji. Przeanalizowano rozkłady udziału objętościowego pary w punktach monitorujących wzdłuż profilu oraz okresy zmian struktur kawitacyjnych. Do symulacji użyto profilu ClarkY. Obliczenia przeprowadzono z użyciem kodu OpenFoam z wykorzystaniem solvera interPhaseChangeFoam.

EN

The paper concerns cavitation modelling in case of flow over a hydrofoil. Cavitation number was set to the values that enable to observe different types of cavitation. Multiphase model of one-fluid type was used and isothermal flow was assumed. To simulate vapor volume transport the Schnerr & Sauer model was used. As the investigated phenomenon is unsteady transient type of calculation was used. The calculation results for different cavitation types were compared with the available experimental data. The distribution of vapor volume fraction in monitor points over the foil as well as changes in the frequency of cavitation structures were analysed. The simulation was run on ClarkY foil. The calculations were performed using OpenFoam open source code with interPhaseChangeFoam solver.

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Modelowanie przepływu kawitacyjnego w maszynach hydraulicznych

Janczak M.

Górnictwo Odkrywkowe

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2010

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R. 51, nr 3

279-283

PL

W artykule przedstawiono wyniki symulacji numerycznych modelowania przepływu kawitacyjnego w wybranych maszynach hydraulicznych. Zaprezentowano wpływ przyjętego sposobu prowadzenia obliczeń i stopnia uwzględnienia współpracujących z elementem roboczym, nieruchomych elementów przepływowych, na rozkład pola przepływu, w tym udział fazy gazowo-parowej i kształt charakterystyk kawitacyjnych oraz ich zbieżność z wynikami badań doświadczalnych.

EN

This paper describes the results of numerical investigations of the cavitating flow through the stage of a multistage pump and an cocial inducer. Both steady and unsteady modeling through the impeller and the stator were made. The numerical results were compared with the real ones. The influence of simplification modeling to obtain cavitation clouds in the inducer was demonstrated and the best settings for modeling in order to get high convergence of results were shown.