Cavitation inception noise excited by a tip leakage vortex with various gap sizes: A Eulerian–Lagrangian investigation

In this paper, the noise characteristics of tip leakage vortex cavitation (TLVC) inception are numerically investigated using a previously developed hybrid Eulerian–Lagrangian model [Wang et al., “Numerical investigation of how gap size influences tip leakage vortex cavitation inception using a Eulerian–Lagrangian method,” Phys. Fluids 35, 012113 (2023).] and the porous Ffowcs-Williams and Hawkings analogy method. A gap size significantly affects the far-field noise, which is louder for large gaps than small gaps, and for high-frequency band than low- and medium-frequency bands. Wavelet and theoretical analyses show that the main broadband noise source is the multiple collapses of cavitating bubbles and that the noise intensity is positively related to the maximum bubble radius. The maximum bubble radius depends on the unsteady pressure evolution at the TLV center, where the mean pressure is mainly influenced by the tip leakage velocity and the pressure fluctuation results from the boundary layer roll-up. This paper reveals the hydroacoustic mechanism of TLVC inception, which can provide insight into noise reduction techniques.