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Abstract
Cavitation, a transient and dynamic phenomenon, significantly impacts the characteristics and performance of hydrofoils across various applications, necessitating effective passive control strategies. This study employs transient numerical simulations to investigate the effectiveness of passive controllers of varying sizes in managing cavitation and explores their subsequent impact on the performance of a cambered NACA 4412 (base) hydrofoil with fixed trailing edge modifications. Here NACA stands for National Advisory Committee for Aeronautics. The passive controllers tested are arc-shaped pimples with radii of 2 mm, 1 mm, and 0.5 mm, strategically placed on the suction surface of the cambered section with a circular trailing edge of 0.5 mm radius. These hydrofoils are referred to as pimpled R1, pimpled R2, and pimpled R3. The investigation covers sheet and cloud cavitation regimes at cavitation numbers ranging from 0.92 to 1.6, with an angle of attack of 8°. The study evaluates the effectiveness of different sizes of passive controllers in controlling cavitation and their impact on hydrofoil performance, including transient cavity evolution, total and time-averaged cavity volumes, and hydrodynamic performance parameters, both qualitatively and quantitatively. The numerical simulations were conducted using a realizable κ-ϵ turbulence model and the Zwart Gerber-Belamri (ZGB) cavitation model. The accuracy of these numerical predictions has been validated against available experimental results, showing strong agreement. The results demonstrate that all hydrofoils with passive controllers exhibit improved cavitation control compared to the NACA4412(base) hydrofoil in all cavitating regimes. Among the tested pimples, R1 significantly reduces transient cavity evolution, time-averaged cavity volume, and cavity length, while also achieving the lowest drag coefficient (Cd). Although R2 and R3 also show improvements, R1 proves to be the most effective. However, the enhanced cavitation control and drag reduction associated with R1 are accompanied by a cost of reduced lift coefficient (Cl), with R1 exhibiting the lowest lift performance.
