Vortex dynamics and pressure fluctuations during cavitating flow over a pitching hydrofoil: a numerical investigation

Pitching hydrofoils are essential for studying cavitating flows with moving boundaries, where the coupling of motion-induced unsteadiness and phase change affects operational stability. This study investigates the cavitation-vortex interaction, pressure fluctuations, and hydrodynamic characteristics of a pitching Clark-Y hydrofoil using large eddy simulation and a mass-transfer cavitation model. Numerical predictions of cavitation patterns and cavity areas show high agreement with experimental data. Results indicate that the lift coefficient exhibits two distinct stages: large-amplitude and small-amplitude fluctuations. In the large-amplitude stage, three characteristic lift patterns are identified, influenced by cavity scale, shedding modes, and vortex structures. During this stage, dominant pressure fluctuation frequencies at the trailing and leading edges are 50 Hz and 30 Hz, respectively. In the small-amplitude stage, which comprises linear and nonlinear phases, the lift peaks and amplitudes decrease. While the trailing-edge dominant frequency remains 50 Hz, the leading-edge frequencies increase significantly. These findings elucidate the transient mechanisms of unsteady cavitation, providing a theoretical foundation for optimizing the performance and stability of complex hydraulic machinery.