Cavitating flow around a scaled-down model of guide vanes of a high-pressure turbine

Timoshevskiy, Mikhail V.; Churkin, Sergey; Kravtsova, Aleksandra Yu.; Pervunin, Konstantin S.; Маркович, Д. М.; Hanjalić, K.

doi:10.1016/j.ijmultiphaseflow.2015.09.014

Cited by 35 publications

(21 citation statements)

References 17 publications

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“…There is also a third mechanism, the side-entrant jet ( Foeth et al, 2008;Ji et al, 2013;Peng et al, 2016 ), which is associated with the part of the re-entrant flow that has a strong spanwise velocity component such as in hydrofoils. Decaix and Goncalves (2013) reported on the presence of an oblique mode of the cavity oscillations and Timoshevskiy et al (2016) concluded that the oblique mode of sheet cavity oscillations associated with the development of the spanwise instability exists for all test objects independent of their shape. Because of the similarity between the side-entrant jet to the re-entrant jet, the side-entrant jet is not discussed in further detail.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of partial cavitation in an axisymmetric converging-diverging nozzle

Jahangir

Hogendoorn

Poelma

2018

International Journal of Multiphase Flow

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Partial cavitation dynamics in an axisymmetric converging-diverging nozzle are investigated experimentally. Shadowgraphy is used to visualize and analyze different cavitation regimes. These regimes are generated by changing the global static pressure and flow velocity independently. Cloud cavitation is the most interesting and complex regime, because the shedding of vapor clouds is caused by two different mechanisms: the re-entrant jet mechanism and the bubbly shock mechanism. The dynamics are investigated using a position-time diagram. Using such a diagram we show that for cavitation number σ > 0.95 the cavity shedding is caused by the re-entrant jet mechanism, and for σ < 0.75 the mechanism responsible for periodic cavity shedding is the bubbly shock mechanism. Both mechanisms are observed in the transition region, 0.75 < σ < 0.95. The shedding frequencies, expressed as Strouhal numbers, collapse on a single curve when plotted against the cavitation number, except for the transition region. The re-entrant jet mechanism is a pressure gradient driven phenomenon, which is caused by a temporary stagnation point at the cavity front. This leads to stick-slip behavior of the cavity. In the bubbly shock regime, a shock wave is induced by a collapse of the previously shedded vapor bubbles downstream of the venturi, which triggers the initiation of the detachment of the growing cavity. The propagation velocity of the shock wave is quantified both in the liquid and the mixture phase by means of the position-time diagram.

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Section: Introductionmentioning

confidence: 99%

Dynamics of partial cavitation in an axisymmetric converging-diverging nozzle

Jahangir

Hogendoorn

Poelma

2018

International Journal of Multiphase Flow

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“…The experiments were carried out using the cavitation rig at the Institute of Thermophysics SB RAS, described in detail in [9]. The test object was a reduced model of the Francis turbine guide vane with a chord length 𝐶 = 100 mm and a maximum thickness 𝐻 max = 0.2149𝐶, described in detail in [10]. The hydrofoil was installed at an angle of attack 𝛼 = 9°.…”

Section: Methodsmentioning

confidence: 99%

Statistical analysis of vapor distribution in a cavitation flow based on an ensemble of instantaneous liquid velocity fields

Severin

Timoshevskiy

Ilyushin

et al. 2021

J. Phys.: Conf. Ser.

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A new method was developed for statistical analysis of ensembles of instantaneous velocity fields measured by PIV in liquid (continuous phase) to determine the distribution of the vapor phase in cavitating flow. The method is based on two main principles: the absence of tracers used for PIV measurements in vapor, and the statistical independence of individual measurements. This allowed establishing an exponential dependence of repeatability of the vapor phase at a certain point of a cavitating flow. Compliance with this theoretical law was verified using the Pearson chi-square test. All theoretical distributions were divided into several groups depending on the time-averaged local vapor content calculated over the entire ensemble of realizations and the probability of a single event. As a result, dimensions of the stationary part of an attached cavity and the place of detachments of cloud cavities from the hydrofoil surface were determined using the new method of statistical analysis for an unsteady cloud cavitation regime.

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“…Here, we consider a cavitating flow around the 2D symmetric hydrofoil section mimicking a guide vane of a Francis turbine (Timoshevskiy et al 2016) that was installed in the test channel of the cavitation tunnel in Kutateladze Institute of Thermophysics SB RAS (Kravtsova et al 2014). Its chord length C = 100 mm and aspect ratio is 0.8 (Fig.…”

Section: Piv Approachmentioning

confidence: 99%

Distribution of probability of the vapor phase occurrence in a cavitating flow based on the concentration of PIV tracers in liquid

2021

Self Cite

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We present a new method of extracting information on average vapor distribution in a cavitating flow based on statistical processing of PIV data for a liquid phase. For this, vectors on instantaneous velocity fields are analyzed over the entire statistical ensemble of instantaneous realizations considering their status: valid-vectors that passed validation procedures, outliers-the ones with incorrect values, out-of-flow-those calculated on insufficient number of seeding particles (tracers), masked-they correspond to unilluminated flow regions. The suggested approach is based on the two basic principles: absence of the tracers in the vapor phase and statistical independence of the successive measurements. The case study is performed for a cavitating 2D symmetric hydrofoil under unsteady cloud cavitation conditions with regular shedding of large-scale cloud cavities. Comparing statistical distribution laws in different flow regions makes it possible to recognize the stable sheet cavity and its pulsating part and determine the location of cloud cavity detachments. This approach for PIV data analysis is shown to be an effective tool to characterize time-averaged distribution of the dispersed phase in cavitating flow based merely on velocity measurements for the liquid phase. Using it allows one to substantially reduce consumption of computational resources and save time when investigating the structure of cavitating flows, limiting to standard PIV measurements in liquid. This method can be also applied to analyze the structure of other types of dispersed two-phase flows.

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Cavitating flow around a scaled-down model of guide vanes of a high-pressure turbine

Cited by 35 publications

References 17 publications

Dynamics of partial cavitation in an axisymmetric converging-diverging nozzle

Dynamics of partial cavitation in an axisymmetric converging-diverging nozzle

Statistical analysis of vapor distribution in a cavitation flow based on an ensemble of instantaneous liquid velocity fields

Distribution of probability of the vapor phase occurrence in a cavitating flow based on the concentration of PIV tracers in liquid

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