Transient evolution of cavitation flow structures and induced noise characteristics of a hydrofoil

Cavitation flow is a complex fluid phenomenon involving phase change, which is widely observed in equipment, such as ship propellers, pumps, and valves. The issues it induces, including cavitation erosion, noise, and vibration, directly affect the performance and safety of the equipment. To reveal the complex cavitation flow and the induced noise characteristics, this study investigates the unsteady cavitation flow field and evolution behavior of a NACA0015 hydrofoil using large eddy simulation and the Lagrangian coherent structure methods. Furthermore, the flow noise characteristics induced by cavitation development are analyzed based on Lighthill's acoustic analogy theory. The research finds that reverse jet of the wake vortex is the primary cause of the detachment of attached vortices on the suction surface. The three-dimensional cavitation flow field clearly captures detachment process of the attached cavitation vortex on the suction surface resulting from the reverse jet of the wake vortex. Finite-time Lyapunov exponent analysis shows that the detachment of vortex structures near the wall occurs later than that of those farther from the wall, leading to the formation of a U-shaped cavity. Cavitation causes a sharp increase in the overall noise, with cavitation noise attenuating more rapidly along the flow direction. The distribution of acoustic sources highly coincides with the cavitation region.