Assessment of Cavitating Flow Aggressiveness on a Hydrofoil: Experimental and Numerical Approaches

Carrat, Jean-Bastien; Patella, Régiane Fortes; Franc, Jean-Pierre

doi:10.1115/fedsm2017-69187

Cited by 7 publications

(13 citation statements)

References 11 publications

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“…Other methods to distinguish individual events include conventional pressure sensors (Franc et al 2011) and polyvinylidene fluoride (PVDF) sensors that are thin piezoelectric pressure sensors (Hujer et al 2015;Momma and Lichtarowicz 1995;Wang and Chen 2007;Carrat et al 2017;Arndt et al 1997). Notably, the measurements by Hujer et al (2015) and Franc et al (2011), which were carried out in the same tunnel, provided exponential cumulative distributions similar to the results extracted from AE signals of this study.…”

Section: Introductionsupporting

confidence: 53%

Estimation of Cavitation Pit Distributions by Acoustic Emission

et al. 2020

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Cavitation erosion in hydraulic machinery, such as in turbines and pumps, often leads to significant reduction of the service life of the affected components, with serious consequences for their maintenance costs and operation efficiency. In this study, the potential contribution of acoustic emission (AE) measurements to the assessment of cavitation damage is evaluated from experiments in a cavitation tunnel. Stainless steel samples were exposed to cavitation and damage was characterized from pitting tests carried out on mirror-polished samples. The pits were measured using an optical profilometer and cavitation damage was characterized by pit diameter distribution. In parallel, AE time signal was measured directly from behind the samples. A dedicated signal-processing technique was developed in order to identify each burst in the AE signal and determine its amplitude. The AE amplitude distribution compares well with PVDF and pressure sensor measurements from literature. It is concluded that AE signal analysis can be used to monitor the formation of pits without visual examination of the damaged surface. This provides a basis for possible future applications of nonintrusive cavitation erosion monitoring in hydraulic machines, provided the findings remain true in a more complex environment.

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Section: Introductionsupporting

confidence: 53%

Estimation of Cavitation Pit Distributions by Acoustic Emission

et al. 2020

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“…3(b) for t=0.0725 s. It is calculated for every frame and provides the space-time diagram of the mean gray level shown in Fig 3(c). This kind of analyses allows estimating the maximum cavity length and the shedding frequency for different cavitating conditions [12]. In Fig 3(c), the maximum cavity length is indicated by red arrows.…”

Section: Hydrofoil Geometry and Experimental Set-upmentioning

confidence: 99%

“…The upstream cavitation number fluctuates during unsteady calculations and a numerical mean value of σ is estimated from simulations to carry out comparisons with experiments. Several calculations were performed in previous work [12] considering different flow conditions. Detailed physical analyses concerning cavity dynamics were presented and the cavitating flow simulations were validated by comparisons with experimental data obtained mainly from high speed videos.…”

Section: Cfd Simulationsmentioning

confidence: 99%

“…The numerical computation of impact load spectra [9] requires to resolve individual vapour structures and the shock waves induced by their collapse, which is often challenging in terms of computational resources. Simpler approaches such as [12] were also developed that do not seek to capture the dynamics of the smaller vapour structures responsible for cavitation erosion but are based on the computation of the void fraction field. This is the technique used in the present paper which is more widely discussed in Section 5.…”

Section: Introductionmentioning

confidence: 99%

“…The cavitating flow on the hydrofoil studied in this paper was thoroughly investigated from a joint numerical and experimental analysis. A detailed description of the cavity dynamics was carried out and results concerning the cavity length evolution, the shedding frequencies and corresponding Strouhal numbers were presented in [12]. In this paper, the focus is given to experimental and numerical evaluations of cavitation aggressiveness.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experimental and Numerical Investigation of the Erosive Potential of a Leading Edge Cavity

Carrat¹,

Patella²,

Franc³

2019

IJFMS

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This paper presents a joint experimental and numerical analysis of the erosive potential of an unsteady cavity that develops at the leading edge of a two-dimensional hydrofoil and periodically sheds vapour clouds. From an experimental viewpoint, the erosive potential was characterized by pressure pulse height spectra. The hydrofoil was equipped with eight pressure sensors made of PVDF piezoelectric film that allowed the measurement of flow aggressiveness at different locations along the hydrofoil chord. It was shown that the mean peak rate over a large number of cavity pulsations exhibits a maximum at a distance from the leading edge close to the maximum cavity length. Moreover, the increase in flow aggressiveness caused by an increase in flow velocity can be explained by an increase in both amplitude and frequency of impact loads. From a numerical viewpoint, the unsteady Reynolds averaged Navier-Stokes (RANS) equations were solved using a modified k-ε RNG turbulence model together with a homogeneous cavitation model within a two-dimensional approach. Flow aggressiveness was estimated from the Lagrangian derivative of the computed void fraction that allows identifying the regions of collapse of vapour structures. Three different critical regions from an erosive viewpoint were numerically identified. Apart from the region of collapse of the shed cloud (which was not instrumented in the present study), the computations showed a maximum of aggressiveness around the maximum cavity length as found experimentally. Another region of high aggressiveness closer to the leading edge and associated to the upward movement of the re-entrant jet was predicted by the present numerical model but not confirmed experimentally, which probably shows the limitation of a two-dimensional approach.

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Numerical simulation of cavitating flows: comparison between two-fluid and homogeneous approaches

Ferhat

Leclercq

Patella

et al. 2022

IOP Conf. Ser.: Earth Environ. Sci.

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The paper presents a new two-phase flow approach to simulate unsteady cavitating flows. The study applied the in-house code neptune_cfd, which allows two-fluid modelling of liquid-vapor flows [1]. The code solves the ensemble-averaged equations of mass, momentum and energy conservation for each phase (liquid and vapour) for a total of six conservation equations. The equations system requires closure laws for the interfacial terms that represent the mass, momentum and energy transfers occurring between the liquid and vapor phases. An original approach is implemented by using an energy-source term based on the difference between the local enthalpy and its saturation value. 2D and 3D simulations are carried out for a NACA 65−012 hydrofoil with an angle of attack of 6°, a cavity length of 40% of the hydrofoil chord and different flow velocities. The methodology to obtain the cavity length and the main frequency of its periodic behavior is presented. Then the numerical results are compared with those previously obtained by a homogeneous approach [2] and with the available experimental data [3]. The quantitative predictions of the hydrodynamic characteristics (i.e. cavitation sigma number, cavity length, shedding frequency and cavity shape) obtained from two-phase flow modeling appear in better accordance with experimental data.

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Assessment of Cavitating Flow Aggressiveness on a Hydrofoil: Experimental and Numerical Approaches

Cited by 7 publications

References 11 publications

Estimation of Cavitation Pit Distributions by Acoustic Emission

Estimation of Cavitation Pit Distributions by Acoustic Emission

Experimental and Numerical Investigation of the Erosive Potential of a Leading Edge Cavity

Numerical simulation of cavitating flows: comparison between two-fluid and homogeneous approaches

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