Bionic leading-edge protuberances and hydrofoil cavitation

Cavitation is a challenging and complex phenomenon in hydraulic machineries such as pumps, turbines, and marine propellers. The shedding and collapse of the cavitation cloud are responsible for hydraulic instability. Recently, the modified wavy leading-edge hydrofoil has attracted considerable attention for passive cavitation control. To reduce hydrofoil cavitation, the leading-edge protuberances of humpback whale flippers were introduced in hydrofoil modification, and its effect on the cavitation flow was investigated in the present study. First, a sinusoidal modification method for the leading-edge of the hydrofoil was adopted. The lift and drag coefficients, cavitation morphology, and flow characteristics of the basic and bionic hydrofoils were numerically calculated using the large eddy simulation method, and the accuracy of the numerical model was verified via comparison with available experimental results. Then, the wavelengths (0.25C, 0.5C) and amplitudes (0.05C, 0.12C) of the leading-edge protuberances were varied to study the effects of the structural parameters on the cavitation. The results indicated that the wavy leading-edge can improve the lift-drag characteristics, restrain the hydrofoil cavitation, and reduce the cavitation volume by approximately 30%. Reducing the wavelength and increasing the amplitude help restrain the instability of cavitation shedding. Increasing the amplitude can reduce the pressure amplitude by approximately 60%, significantly reduce the cavitation volume, and enhance the cavitation suppression.