Statistical structure of the velocity field in cavitating flow around a 2D hydrofoil

• Published in: The International journal of heat and fluid flow 2020-10, Vol.85, p.108646, Article 108646
• Main Authors: Timoshevskiy, Mikhail V., Ilyushin, Boris B., Pervunin, Konstantin S.
• Format: Article
• Language: English
• Subjects: Flow separation; Hydrofoil; PIV measurements; Probability density function (PDF); Recirculation zone; Sheet/cloud cavities; Skewness and excess; Turbulence structure; Turbulent kinetic energy; Two-mode statistical distribution; Unsteady cloud cavitation; Velocity fields
• ISSN: 0142-727X; 1879-2278
• DOI: 10.1016/j.ijheatfluidflow.2020.108646

•Analysis of basic statistical information on velocity fields in cavitating flow.•Modification of flow statistical structure in case of unsteady cloud cavitation.•Two-mode distribution of PDF of velocity fluctuations for unsteady cloud cavitation.•Different behaviors of the mean and most probable velocities with flow speed-up. Transformation of flow turbulence structure with cavitation occurrence, determination of the flow conditions favorable for nucleation of cavitation bubbles, influence of the statistical structure of turbulence on this process and the inverse effect of cavitation on the flow dynamics are challenging problems in modern fluid mechanics. The paper reports on the results of statistical processing of the velocity fields measured by a PIV technique in cavitating flow over a 2D symmetric hydrofoil for four flow conditions, starting from a cavitation-free regime and finishing by unsteady cloud cavitation. We analyze basic information on the statistical structure of velocity fluctuations in the form of histograms and Q-Q diagrams along with profiles of the mean velocity and turbulent kinetic energy. The research reveals that the flow turbulence pattern and distributions of turbulent fluctuations change significantly with the cavitation development. Under unsteady cloud cavitation conditions, the probability density function of the fluctuating velocity has a two-mode distribution, which indicates switching of two alternating flow conditions in a region above the hydrofoil aft part due to periodic passing of cavitation clouds. Behaviors of the mean and most probable velocities unexpectedly appear to be different with a monotonous increase of the incoming flow velocity. This finding must be caused by modification of the skewness coefficient of the fluctuating velocity.