Control of cloud cavitating flow around hydrofoils using local active oscillatory surfaces

Partial cavity oscillation is characterized by large-scale cavity shedding and intense pressure pulsations, causing severe damage to hydraulic machines. An incompressible homogeneous two-phase mixture numerical model is employed to investigate the effect of local active oscillatory surfaces on cavitating flows. The surfaces are positioned close to the cavity closure and simulated using an oscillatory velocity boundary to encumber the re-entrant jets. The results show that at high oscillation frequencies, the cavity shedding frequency synchronizes with the excitation frequency, indicating the presence of a lock-in mechanism. Meanwhile, the mean value and the fluctuation amplitude of the vapor volume are significantly reduced, indicating that the cavitation intensity and unsteady behaviors have been effectively weakened by the local active oscillation. Additionally, the high-pressure pulsation region diminishes, and the maximum pulsation amplitude declines. A simplified model manifests that the total vaporization and condensation rates of the entire domain exhibit a periodic variation in response to pressure pulsations. The dynamic mode decomposition (DMD) analysis reveals that small vortices shed from the main flow and dissipate under the influence of local oscillation. This study demonstrates that local active oscillatory surfaces are effective in inhibiting cloud cavitation.