Revealing insights into hydrodynamic noise induced by different cavitating flows around a hydrofoil

Cavitation-induced noise hazards in marine environments have raised significant concerns. This paper presents a study on the flow noise generated by cavitating flow around a model-scale NACA66 hydrofoil, utilizing the permeable acoustic analogy method. Through Large Eddy Simulation and the Schnerr-Sauer cavitation model, the study captures the cavitation flow pattern, aligning with experimental observations. The research conducts a detailed analysis of the monopole and dipole noise components, providing insights into their characteristics under different cavitation conditions (cavitation number σ  = 0.60, 0.83, 1.29, and 1.44). The results revealed a noteworthy trend where the proportion of the dipole component increases as the cavitation number σ decreases. Furthermore, the study uncovered the mechanism behind monopole noise induction in unsteady cavitating flows, offering insights into different types of sound impulse sources associated with cavitation collapse. Particularly, the collapse of clouds during secondary shedding is identified as a significant source of highly intense impulses, surpassing the levels observed in other cavitation flow stages. Additionally, deeper exploration demonstrated the co-action of vortex stretching and dilatation, contributing to the enhanced deformation, breakdown, and condensation of vapor structures, consequently significantly accelerating the collapse process.