Effects of leading-edge protuberances on cavitation, induced noise and hydrodynamic performances of three-dimensional hydrofoils

By incorporating leading-edge (L-E) protuberances inspired by humpback whale flippers, this study enhances hydrodynamic performance, mitigates cavitation effects and develops efficient models to minimise noise emissions in aquatic systems. Experimental and numerical simulations are conducted on four semi-elliptical NACA 16020 three-dimensional (3-D) hydrofoils, including a baseline hydrofoil and three modified versions featuring sinusoidal L-E alterations. These alterations encompass amplitudes of 2 %, wavelengths of 8.33 % and 4.1667 % of the mean chord length (C), and wavenumbers of 12 and 6. Experimental analysis encompassing both cavitational and non-cavitational regimes at varying attack angles revealed significant relationships between the hydrodynamic performance and partial sheet cavitation. Hydrodynamic force analysis shows that hydrofoils with L-E protuberances generate elevated lift at moderate and high angles of attack (AOA) in cavitating and non-cavitating conditions. Under lower-severity cavitating conditions, models with L-E protuberances exhibit no significant reduction in sound pressure level. In contrast, at higher severity, the presence of L-E protuberances effectively reduces the flow-induced noise, with partial cavities covering 30 %–50 % of the chord. Numerical simulations were conducted to investigate the turbulent kinetic energy (TKE) distribution and the presence of counter-rotating vortices on each protuberance. The results reveal a significantly enhanced TKE around the trough area and the presence of counter-rotating vortices at each protuberance peak. The more realistic asymmetric design performed better than the other modifications regarding hydrodynamic force, whereas the symmetric model with wavelengths of 8.33 % excelled at cavitation and noise suppression. Therefore, this study offers promising avenues for advancing hydrofoil design in diverse engineering domains.