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A method is presented to determine significant frequencies of oscillations of cavitation structures from high-speed camera recordings of a flow around a 2-D hydrofoil. The top view of the suction side of an NACA 2412 hydrofoil is studied in a transparent test section of a cavitation tunnel for selected cloud cavitation regimes with strong oscillations induced by the leading-edge cavity shedding. The ability of the method to accurately determine the dominant oscillation frequencies is confirmed by pressure measurements. The method can resolve subtle flow characteristics that are not visible to the naked eye. The method can be used for noninvasive experimental studies of oscillations in cavitating flows with adequate visual access when pressure measurements are not available or when such measurements would disturb the flow.

A method is presented to determine significant frequencies of oscillations of cavitation structures from high-speed camera recordings of a flow around a 2-D hydrofoil. The top view of the suction side of an NACA 2412 hydrofoil is studied in a transparent test section of a cavitation tunnel for selected cloud cavitation regimes with strong oscillations induced by the leading-edge cavity shedding. The ability of the method to accurately determine the dominant oscillation frequencies is confirmed by pressure measurements. The method can resolve subtle flow characteristics that are not visible to the naked eye. The method can be used for noninvasive experimental studies of oscillations in cavitating flows with adequate visual access when pressure measurements are not available or when such measurements would disturb the flow.

The paper attempts to assess the erosive potential of cavitation bubbles in unsteady flow of liquid over a prismatic hydrofoil using two-way coupling of the URANS and the Rayleigh-Plesset equations. The erosive potential of the cavitating flow is evaluated from the energy dissipated during the collapses of imploding cavitation bubbles near the solid surface of the hydrofoil. The bubbles are assumed spherical and the phase slip is neglected. Bubble fission is modelled using a simple break-up model. The interaction between bubbles is considered by superposing the pressure change due to pressure waves generated by collapsing bubbles and propagated in the computational domain over the local pressure in the liquid (external to the bubble). The rate of erosion of the solid material is not studied in this work. The flow is analysed using the in-house three-dimensional solver for unsteady turbulent flow with bubble dynamics. The results are demonstrated on the NACA 2412 hydrofoil with the incidence angle of 8 degrees and the cavitation number 1.37, which corresponds to the regime of oscillating partial cavity with periodic shedding of bubble cloud downstream of the cavity.

Our objective is a better understanding of the role of physical properties of real fluids in the thermodynamics of cavitation in impure water. An extension to the classical homogenous nucleation theory suitable for mixtures is presented in attempt to address the discrepancy between the theoretical predictions and practical observations of cavitation rates in water at normal temperatures. The extension takes into account the non-equilibrium (dissipative) effects involved in nuclei formation through a substance dependent correction coefficient to be determined experimentally. The theory of thermodynamic fluctuations is applied to derive the work of formation of a bubble nucleus. The value of the correction coefficient is estimated using preliminary experimental data from a convergent-divergent nozzle. An application of the results to the numerical prediction of the cavitation zones in a radial-flow water pump is shown.