Numerical analysis of cavitation-induced noise characteristics in hydrofoils using finite element acoustic method and spherical cavity radiation theory

A volumetric pulsation accompanied by significant noise arises from the initial generation, development, and collapse of cavitation bubbles, profoundly impacting the stability and noise level of turbomachinery. This paper introduces a numerical simulation approach to study cavitation-induced noise on a NACA0015 hydrofoil, employing the acoustic finite element method and spherical cavity radiation theory. Validation of the Detached Eddy Simulation (DES) method is conducted by comparing it with high-speed photography results and pressure variations on the hydrofoil surface. The cavitating flow evolution, pressure pulsation characteristics, and vortex dynamics are analysed in conjunction with experimental observations. Subsequent numerical simulations of cavitation-induced noise are carried out from two perspectives: neglecting and considering the volumetric pulsation of bubbles. Results demonstrate the accuracy of the DES method in predicting the cavitating flow evolution. Notably, both solving methods for cavitation-induced noise yield relatively precise outcomes. The distribution of stretching terms in the vorticity transport equation closely resembles the Q distribution. Particularly, significant stretching-straining terms around the cavitation region notably influence vorticity generation. Following cavitation onset, the suction surface and trailing edge of the hydrofoil emerge as primary sound sources. Moreover, the total sound pressure level due to bubble volume pulsation radiation noise is approximately 17 dB higher than when neglecting bubble volume pulsation, underscoring the monopole noise radiated by bubble volume pulsation as the primary noise source in the cavitation flow field.